From 7a55125f2935b72c30f0e44bff38220ffb8feb76 Mon Sep 17 00:00:00 2001 From: mikemccand Date: Tue, 3 Jun 2014 14:43:52 -0400 Subject: [PATCH 1/2] add CHMV8 --- .../java/jsr166e/ConcurrentHashMapV8.java | 6312 +++++++++++++++++ src/main/java/jsr166e/CountedCompleter.java | 753 ++ src/main/java/jsr166e/ForkJoinPool.java | 3345 +++++++++ src/main/java/jsr166e/ForkJoinTask.java | 1557 ++++ .../java/jsr166e/ForkJoinWorkerThread.java | 125 + src/main/java/jsr166e/ThreadLocalRandom.java | 199 + .../common/lucene/uid/Versions.java | 5 +- .../concurrent/ConcurrentCollections.java | 18 +- .../common/util/concurrent/KeyedLock.java | 5 +- 9 files changed, 12314 insertions(+), 5 deletions(-) create mode 100644 src/main/java/jsr166e/ConcurrentHashMapV8.java create mode 100644 src/main/java/jsr166e/CountedCompleter.java create mode 100644 src/main/java/jsr166e/ForkJoinPool.java create mode 100644 src/main/java/jsr166e/ForkJoinTask.java create mode 100644 src/main/java/jsr166e/ForkJoinWorkerThread.java create mode 100644 src/main/java/jsr166e/ThreadLocalRandom.java diff --git a/src/main/java/jsr166e/ConcurrentHashMapV8.java b/src/main/java/jsr166e/ConcurrentHashMapV8.java new file mode 100644 index 0000000000000..4008c3104bfa8 --- /dev/null +++ b/src/main/java/jsr166e/ConcurrentHashMapV8.java @@ -0,0 +1,6312 @@ + +// Rev 1.121 copied from http://gee.cs.oswego.edu/cgi-bin/viewcvs.cgi/jsr166/src/jsr166e/ConcurrentHashMapV8.java?view=markup + +/* + * Written by Doug Lea with assistance from members of JCP JSR-166 + * Expert Group and released to the public domain, as explained at + * http://creativecommons.org/publicdomain/zero/1.0/ + */ + +package jsr166e; + +import jsr166e.ForkJoinPool; + +import java.io.ObjectStreamField; +import java.io.Serializable; +import java.lang.reflect.ParameterizedType; +import java.lang.reflect.Type; +import java.util.AbstractMap; +import java.util.Arrays; +import java.util.Collection; +import java.util.Comparator; +import java.util.ConcurrentModificationException; +import java.util.Enumeration; +import java.util.HashMap; +import java.util.Hashtable; +import java.util.Iterator; +import java.util.Map; +import java.util.NoSuchElementException; +import java.util.Set; +import java.util.concurrent.ConcurrentMap; +import java.util.concurrent.atomic.AtomicReference; +import java.util.concurrent.atomic.AtomicInteger; +import java.util.concurrent.locks.LockSupport; +import java.util.concurrent.locks.ReentrantLock; + +/** + * A hash table supporting full concurrency of retrievals and + * high expected concurrency for updates. This class obeys the + * same functional specification as {@link java.util.Hashtable}, and + * includes versions of methods corresponding to each method of + * {@code Hashtable}. However, even though all operations are + * thread-safe, retrieval operations do not entail locking, + * and there is not any support for locking the entire table + * in a way that prevents all access. This class is fully + * interoperable with {@code Hashtable} in programs that rely on its + * thread safety but not on its synchronization details. + * + *

Retrieval operations (including {@code get}) generally do not + * block, so may overlap with update operations (including {@code put} + * and {@code remove}). Retrievals reflect the results of the most + * recently completed update operations holding upon their + * onset. (More formally, an update operation for a given key bears a + * happens-before relation with any (non-null) retrieval for + * that key reporting the updated value.) For aggregate operations + * such as {@code putAll} and {@code clear}, concurrent retrievals may + * reflect insertion or removal of only some entries. Similarly, + * Iterators and Enumerations return elements reflecting the state of + * the hash table at some point at or since the creation of the + * iterator/enumeration. They do not throw {@link + * ConcurrentModificationException}. However, iterators are designed + * to be used by only one thread at a time. Bear in mind that the + * results of aggregate status methods including {@code size}, {@code + * isEmpty}, and {@code containsValue} are typically useful only when + * a map is not undergoing concurrent updates in other threads. + * Otherwise the results of these methods reflect transient states + * that may be adequate for monitoring or estimation purposes, but not + * for program control. + * + *

The table is dynamically expanded when there are too many + * collisions (i.e., keys that have distinct hash codes but fall into + * the same slot modulo the table size), with the expected average + * effect of maintaining roughly two bins per mapping (corresponding + * to a 0.75 load factor threshold for resizing). There may be much + * variance around this average as mappings are added and removed, but + * overall, this maintains a commonly accepted time/space tradeoff for + * hash tables. However, resizing this or any other kind of hash + * table may be a relatively slow operation. When possible, it is a + * good idea to provide a size estimate as an optional {@code + * initialCapacity} constructor argument. An additional optional + * {@code loadFactor} constructor argument provides a further means of + * customizing initial table capacity by specifying the table density + * to be used in calculating the amount of space to allocate for the + * given number of elements. Also, for compatibility with previous + * versions of this class, constructors may optionally specify an + * expected {@code concurrencyLevel} as an additional hint for + * internal sizing. Note that using many keys with exactly the same + * {@code hashCode()} is a sure way to slow down performance of any + * hash table. To ameliorate impact, when keys are {@link Comparable}, + * this class may use comparison order among keys to help break ties. + * + *

A {@link Set} projection of a ConcurrentHashMapV8 may be created + * (using {@link #newKeySet()} or {@link #newKeySet(int)}), or viewed + * (using {@link #keySet(Object)} when only keys are of interest, and the + * mapped values are (perhaps transiently) not used or all take the + * same mapping value. + * + *

This class and its views and iterators implement all of the + * optional methods of the {@link Map} and {@link Iterator} + * interfaces. + * + *

Like {@link Hashtable} but unlike {@link HashMap}, this class + * does not allow {@code null} to be used as a key or value. + * + *

ConcurrentHashMapV8s support a set of sequential and parallel bulk + * operations that are designed + * to be safely, and often sensibly, applied even with maps that are + * being concurrently updated by other threads; for example, when + * computing a snapshot summary of the values in a shared registry. + * There are three kinds of operation, each with four forms, accepting + * functions with Keys, Values, Entries, and (Key, Value) arguments + * and/or return values. Because the elements of a ConcurrentHashMapV8 + * are not ordered in any particular way, and may be processed in + * different orders in different parallel executions, the correctness + * of supplied functions should not depend on any ordering, or on any + * other objects or values that may transiently change while + * computation is in progress; and except for forEach actions, should + * ideally be side-effect-free. Bulk operations on {@link java.util.Map.Entry} + * objects do not support method {@code setValue}. + * + *

+ * + *

These bulk operations accept a {@code parallelismThreshold} + * argument. Methods proceed sequentially if the current map size is + * estimated to be less than the given threshold. Using a value of + * {@code Long.MAX_VALUE} suppresses all parallelism. Using a value + * of {@code 1} results in maximal parallelism by partitioning into + * enough subtasks to fully utilize the {@link + * ForkJoinPool#commonPool()} that is used for all parallel + * computations. Normally, you would initially choose one of these + * extreme values, and then measure performance of using in-between + * values that trade off overhead versus throughput. + * + *

The concurrency properties of bulk operations follow + * from those of ConcurrentHashMapV8: Any non-null result returned + * from {@code get(key)} and related access methods bears a + * happens-before relation with the associated insertion or + * update. The result of any bulk operation reflects the + * composition of these per-element relations (but is not + * necessarily atomic with respect to the map as a whole unless it + * is somehow known to be quiescent). Conversely, because keys + * and values in the map are never null, null serves as a reliable + * atomic indicator of the current lack of any result. To + * maintain this property, null serves as an implicit basis for + * all non-scalar reduction operations. For the double, long, and + * int versions, the basis should be one that, when combined with + * any other value, returns that other value (more formally, it + * should be the identity element for the reduction). Most common + * reductions have these properties; for example, computing a sum + * with basis 0 or a minimum with basis MAX_VALUE. + * + *

Search and transformation functions provided as arguments + * should similarly return null to indicate the lack of any result + * (in which case it is not used). In the case of mapped + * reductions, this also enables transformations to serve as + * filters, returning null (or, in the case of primitive + * specializations, the identity basis) if the element should not + * be combined. You can create compound transformations and + * filterings by composing them yourself under this "null means + * there is nothing there now" rule before using them in search or + * reduce operations. + * + *

Methods accepting and/or returning Entry arguments maintain + * key-value associations. They may be useful for example when + * finding the key for the greatest value. Note that "plain" Entry + * arguments can be supplied using {@code new + * AbstractMap.SimpleEntry(k,v)}. + * + *

Bulk operations may complete abruptly, throwing an + * exception encountered in the application of a supplied + * function. Bear in mind when handling such exceptions that other + * concurrently executing functions could also have thrown + * exceptions, or would have done so if the first exception had + * not occurred. + * + *

Speedups for parallel compared to sequential forms are common + * but not guaranteed. Parallel operations involving brief functions + * on small maps may execute more slowly than sequential forms if the + * underlying work to parallelize the computation is more expensive + * than the computation itself. Similarly, parallelization may not + * lead to much actual parallelism if all processors are busy + * performing unrelated tasks. + * + *

All arguments to all task methods must be non-null. + * + *

jsr166e note: During transition, this class + * uses nested functional interfaces with different names but the + * same forms as those expected for JDK8. + * + *

This class is a member of the + * + * Java Collections Framework. + * + * @since 1.5 + * @author Doug Lea + * @param the type of keys maintained by this map + * @param the type of mapped values + */ +public class ConcurrentHashMapV8 extends AbstractMap + implements ConcurrentMap, Serializable { + private static final long serialVersionUID = 7249069246763182397L; + + /** + * An object for traversing and partitioning elements of a source. + * This interface provides a subset of the functionality of JDK8 + * java.util.Spliterator. + */ + public static interface ConcurrentHashMapSpliterator { + /** + * If possible, returns a new spliterator covering + * approximately one half of the elements, which will not be + * covered by this spliterator. Returns null if cannot be + * split. + */ + ConcurrentHashMapSpliterator trySplit(); + /** + * Returns an estimate of the number of elements covered by + * this Spliterator. + */ + long estimateSize(); + + /** Applies the action to each untraversed element */ + void forEachRemaining(Action action); + /** If an element remains, applies the action and returns true. */ + boolean tryAdvance(Action action); + } + + // Sams + /** Interface describing a void action of one argument */ + public interface Action { void apply(A a); } + /** Interface describing a void action of two arguments */ + public interface BiAction { void apply(A a, B b); } + /** Interface describing a function of one argument */ + public interface Fun { T apply(A a); } + /** Interface describing a function of two arguments */ + public interface BiFun { T apply(A a, B b); } + /** Interface describing a function mapping its argument to a double */ + public interface ObjectToDouble { double apply(A a); } + /** Interface describing a function mapping its argument to a long */ + public interface ObjectToLong { long apply(A a); } + /** Interface describing a function mapping its argument to an int */ + public interface ObjectToInt {int apply(A a); } + /** Interface describing a function mapping two arguments to a double */ + public interface ObjectByObjectToDouble { double apply(A a, B b); } + /** Interface describing a function mapping two arguments to a long */ + public interface ObjectByObjectToLong { long apply(A a, B b); } + /** Interface describing a function mapping two arguments to an int */ + public interface ObjectByObjectToInt {int apply(A a, B b); } + /** Interface describing a function mapping two doubles to a double */ + public interface DoubleByDoubleToDouble { double apply(double a, double b); } + /** Interface describing a function mapping two longs to a long */ + public interface LongByLongToLong { long apply(long a, long b); } + /** Interface describing a function mapping two ints to an int */ + public interface IntByIntToInt { int apply(int a, int b); } + + + /* + * Overview: + * + * The primary design goal of this hash table is to maintain + * concurrent readability (typically method get(), but also + * iterators and related methods) while minimizing update + * contention. Secondary goals are to keep space consumption about + * the same or better than java.util.HashMap, and to support high + * initial insertion rates on an empty table by many threads. + * + * This map usually acts as a binned (bucketed) hash table. Each + * key-value mapping is held in a Node. Most nodes are instances + * of the basic Node class with hash, key, value, and next + * fields. However, various subclasses exist: TreeNodes are + * arranged in balanced trees, not lists. TreeBins hold the roots + * of sets of TreeNodes. ForwardingNodes are placed at the heads + * of bins during resizing. ReservationNodes are used as + * placeholders while establishing values in computeIfAbsent and + * related methods. The types TreeBin, ForwardingNode, and + * ReservationNode do not hold normal user keys, values, or + * hashes, and are readily distinguishable during search etc + * because they have negative hash fields and null key and value + * fields. (These special nodes are either uncommon or transient, + * so the impact of carrying around some unused fields is + * insignificant.) + * + * The table is lazily initialized to a power-of-two size upon the + * first insertion. Each bin in the table normally contains a + * list of Nodes (most often, the list has only zero or one Node). + * Table accesses require volatile/atomic reads, writes, and + * CASes. Because there is no other way to arrange this without + * adding further indirections, we use intrinsics + * (sun.misc.Unsafe) operations. + * + * We use the top (sign) bit of Node hash fields for control + * purposes -- it is available anyway because of addressing + * constraints. Nodes with negative hash fields are specially + * handled or ignored in map methods. + * + * Insertion (via put or its variants) of the first node in an + * empty bin is performed by just CASing it to the bin. This is + * by far the most common case for put operations under most + * key/hash distributions. Other update operations (insert, + * delete, and replace) require locks. We do not want to waste + * the space required to associate a distinct lock object with + * each bin, so instead use the first node of a bin list itself as + * a lock. Locking support for these locks relies on builtin + * "synchronized" monitors. + * + * Using the first node of a list as a lock does not by itself + * suffice though: When a node is locked, any update must first + * validate that it is still the first node after locking it, and + * retry if not. Because new nodes are always appended to lists, + * once a node is first in a bin, it remains first until deleted + * or the bin becomes invalidated (upon resizing). + * + * The main disadvantage of per-bin locks is that other update + * operations on other nodes in a bin list protected by the same + * lock can stall, for example when user equals() or mapping + * functions take a long time. However, statistically, under + * random hash codes, this is not a common problem. Ideally, the + * frequency of nodes in bins follows a Poisson distribution + * (http://en.wikipedia.org/wiki/Poisson_distribution) with a + * parameter of about 0.5 on average, given the resizing threshold + * of 0.75, although with a large variance because of resizing + * granularity. Ignoring variance, the expected occurrences of + * list size k are (exp(-0.5) * pow(0.5, k) / factorial(k)). The + * first values are: + * + * 0: 0.60653066 + * 1: 0.30326533 + * 2: 0.07581633 + * 3: 0.01263606 + * 4: 0.00157952 + * 5: 0.00015795 + * 6: 0.00001316 + * 7: 0.00000094 + * 8: 0.00000006 + * more: less than 1 in ten million + * + * Lock contention probability for two threads accessing distinct + * elements is roughly 1 / (8 * #elements) under random hashes. + * + * Actual hash code distributions encountered in practice + * sometimes deviate significantly from uniform randomness. This + * includes the case when N > (1<<30), so some keys MUST collide. + * Similarly for dumb or hostile usages in which multiple keys are + * designed to have identical hash codes or ones that differs only + * in masked-out high bits. So we use a secondary strategy that + * applies when the number of nodes in a bin exceeds a + * threshold. These TreeBins use a balanced tree to hold nodes (a + * specialized form of red-black trees), bounding search time to + * O(log N). Each search step in a TreeBin is at least twice as + * slow as in a regular list, but given that N cannot exceed + * (1<<64) (before running out of addresses) this bounds search + * steps, lock hold times, etc, to reasonable constants (roughly + * 100 nodes inspected per operation worst case) so long as keys + * are Comparable (which is very common -- String, Long, etc). + * TreeBin nodes (TreeNodes) also maintain the same "next" + * traversal pointers as regular nodes, so can be traversed in + * iterators in the same way. + * + * The table is resized when occupancy exceeds a percentage + * threshold (nominally, 0.75, but see below). Any thread + * noticing an overfull bin may assist in resizing after the + * initiating thread allocates and sets up the replacement array. + * However, rather than stalling, these other threads may proceed + * with insertions etc. The use of TreeBins shields us from the + * worst case effects of overfilling while resizes are in + * progress. Resizing proceeds by transferring bins, one by one, + * from the table to the next table. However, threads claim small + * blocks of indices to transfer (via field transferIndex) before + * doing so, reducing contention. A generation stamp in field + * sizeCtl ensures that resizings do not overlap. Because we are + * using power-of-two expansion, the elements from each bin must + * either stay at same index, or move with a power of two + * offset. We eliminate unnecessary node creation by catching + * cases where old nodes can be reused because their next fields + * won't change. On average, only about one-sixth of them need + * cloning when a table doubles. The nodes they replace will be + * garbage collectable as soon as they are no longer referenced by + * any reader thread that may be in the midst of concurrently + * traversing table. Upon transfer, the old table bin contains + * only a special forwarding node (with hash field "MOVED") that + * contains the next table as its key. On encountering a + * forwarding node, access and update operations restart, using + * the new table. + * + * Each bin transfer requires its bin lock, which can stall + * waiting for locks while resizing. However, because other + * threads can join in and help resize rather than contend for + * locks, average aggregate waits become shorter as resizing + * progresses. The transfer operation must also ensure that all + * accessible bins in both the old and new table are usable by any + * traversal. This is arranged in part by proceeding from the + * last bin (table.length - 1) up towards the first. Upon seeing + * a forwarding node, traversals (see class Traverser) arrange to + * move to the new table without revisiting nodes. To ensure that + * no intervening nodes are skipped even when moved out of order, + * a stack (see class TableStack) is created on first encounter of + * a forwarding node during a traversal, to maintain its place if + * later processing the current table. The need for these + * save/restore mechanics is relatively rare, but when one + * forwarding node is encountered, typically many more will be. + * So Traversers use a simple caching scheme to avoid creating so + * many new TableStack nodes. (Thanks to Peter Levart for + * suggesting use of a stack here.) + * + * The traversal scheme also applies to partial traversals of + * ranges of bins (via an alternate Traverser constructor) + * to support partitioned aggregate operations. Also, read-only + * operations give up if ever forwarded to a null table, which + * provides support for shutdown-style clearing, which is also not + * currently implemented. + * + * Lazy table initialization minimizes footprint until first use, + * and also avoids resizings when the first operation is from a + * putAll, constructor with map argument, or deserialization. + * These cases attempt to override the initial capacity settings, + * but harmlessly fail to take effect in cases of races. + * + * The element count is maintained using a specialization of + * LongAdder. We need to incorporate a specialization rather than + * just use a LongAdder in order to access implicit + * contention-sensing that leads to creation of multiple + * CounterCells. The counter mechanics avoid contention on + * updates but can encounter cache thrashing if read too + * frequently during concurrent access. To avoid reading so often, + * resizing under contention is attempted only upon adding to a + * bin already holding two or more nodes. Under uniform hash + * distributions, the probability of this occurring at threshold + * is around 13%, meaning that only about 1 in 8 puts check + * threshold (and after resizing, many fewer do so). + * + * TreeBins use a special form of comparison for search and + * related operations (which is the main reason we cannot use + * existing collections such as TreeMaps). TreeBins contain + * Comparable elements, but may contain others, as well as + * elements that are Comparable but not necessarily Comparable for + * the same T, so we cannot invoke compareTo among them. To handle + * this, the tree is ordered primarily by hash value, then by + * Comparable.compareTo order if applicable. On lookup at a node, + * if elements are not comparable or compare as 0 then both left + * and right children may need to be searched in the case of tied + * hash values. (This corresponds to the full list search that + * would be necessary if all elements were non-Comparable and had + * tied hashes.) On insertion, to keep a total ordering (or as + * close as is required here) across rebalancings, we compare + * classes and identityHashCodes as tie-breakers. The red-black + * balancing code is updated from pre-jdk-collections + * (http://gee.cs.oswego.edu/dl/classes/collections/RBCell.java) + * based in turn on Cormen, Leiserson, and Rivest "Introduction to + * Algorithms" (CLR). + * + * TreeBins also require an additional locking mechanism. While + * list traversal is always possible by readers even during + * updates, tree traversal is not, mainly because of tree-rotations + * that may change the root node and/or its linkages. TreeBins + * include a simple read-write lock mechanism parasitic on the + * main bin-synchronization strategy: Structural adjustments + * associated with an insertion or removal are already bin-locked + * (and so cannot conflict with other writers) but must wait for + * ongoing readers to finish. Since there can be only one such + * waiter, we use a simple scheme using a single "waiter" field to + * block writers. However, readers need never block. If the root + * lock is held, they proceed along the slow traversal path (via + * next-pointers) until the lock becomes available or the list is + * exhausted, whichever comes first. These cases are not fast, but + * maximize aggregate expected throughput. + * + * Maintaining API and serialization compatibility with previous + * versions of this class introduces several oddities. Mainly: We + * leave untouched but unused constructor arguments refering to + * concurrencyLevel. We accept a loadFactor constructor argument, + * but apply it only to initial table capacity (which is the only + * time that we can guarantee to honor it.) We also declare an + * unused "Segment" class that is instantiated in minimal form + * only when serializing. + * + * Also, solely for compatibility with previous versions of this + * class, it extends AbstractMap, even though all of its methods + * are overridden, so it is just useless baggage. + * + * This file is organized to make things a little easier to follow + * while reading than they might otherwise: First the main static + * declarations and utilities, then fields, then main public + * methods (with a few factorings of multiple public methods into + * internal ones), then sizing methods, trees, traversers, and + * bulk operations. + */ + + /* ---------------- Constants -------------- */ + + /** + * The largest possible table capacity. This value must be + * exactly 1<<30 to stay within Java array allocation and indexing + * bounds for power of two table sizes, and is further required + * because the top two bits of 32bit hash fields are used for + * control purposes. + */ + private static final int MAXIMUM_CAPACITY = 1 << 30; + + /** + * The default initial table capacity. Must be a power of 2 + * (i.e., at least 1) and at most MAXIMUM_CAPACITY. + */ + private static final int DEFAULT_CAPACITY = 16; + + /** + * The largest possible (non-power of two) array size. + * Needed by toArray and related methods. + */ + static final int MAX_ARRAY_SIZE = Integer.MAX_VALUE - 8; + + /** + * The default concurrency level for this table. Unused but + * defined for compatibility with previous versions of this class. + */ + private static final int DEFAULT_CONCURRENCY_LEVEL = 16; + + /** + * The load factor for this table. Overrides of this value in + * constructors affect only the initial table capacity. The + * actual floating point value isn't normally used -- it is + * simpler to use expressions such as {@code n - (n >>> 2)} for + * the associated resizing threshold. + */ + private static final float LOAD_FACTOR = 0.75f; + + /** + * The bin count threshold for using a tree rather than list for a + * bin. Bins are converted to trees when adding an element to a + * bin with at least this many nodes. The value must be greater + * than 2, and should be at least 8 to mesh with assumptions in + * tree removal about conversion back to plain bins upon + * shrinkage. + */ + static final int TREEIFY_THRESHOLD = 8; + + /** + * The bin count threshold for untreeifying a (split) bin during a + * resize operation. Should be less than TREEIFY_THRESHOLD, and at + * most 6 to mesh with shrinkage detection under removal. + */ + static final int UNTREEIFY_THRESHOLD = 6; + + /** + * The smallest table capacity for which bins may be treeified. + * (Otherwise the table is resized if too many nodes in a bin.) + * The value should be at least 4 * TREEIFY_THRESHOLD to avoid + * conflicts between resizing and treeification thresholds. + */ + static final int MIN_TREEIFY_CAPACITY = 64; + + /** + * Minimum number of rebinnings per transfer step. Ranges are + * subdivided to allow multiple resizer threads. This value + * serves as a lower bound to avoid resizers encountering + * excessive memory contention. The value should be at least + * DEFAULT_CAPACITY. + */ + private static final int MIN_TRANSFER_STRIDE = 16; + + /** + * The number of bits used for generation stamp in sizeCtl. + * Must be at least 6 for 32bit arrays. + */ + private static int RESIZE_STAMP_BITS = 16; + + /** + * The maximum number of threads that can help resize. + * Must fit in 32 - RESIZE_STAMP_BITS bits. + */ + private static final int MAX_RESIZERS = (1 << (32 - RESIZE_STAMP_BITS)) - 1; + + /** + * The bit shift for recording size stamp in sizeCtl. + */ + private static final int RESIZE_STAMP_SHIFT = 32 - RESIZE_STAMP_BITS; + + /* + * Encodings for Node hash fields. See above for explanation. + */ + static final int MOVED = -1; // hash for forwarding nodes + static final int TREEBIN = -2; // hash for roots of trees + static final int RESERVED = -3; // hash for transient reservations + static final int HASH_BITS = 0x7fffffff; // usable bits of normal node hash + + /** Number of CPUS, to place bounds on some sizings */ + static final int NCPU = Runtime.getRuntime().availableProcessors(); + + /** For serialization compatibility. */ + private static final ObjectStreamField[] serialPersistentFields = { + new ObjectStreamField("segments", Segment[].class), + new ObjectStreamField("segmentMask", Integer.TYPE), + new ObjectStreamField("segmentShift", Integer.TYPE) + }; + + /* ---------------- Nodes -------------- */ + + /** + * Key-value entry. This class is never exported out as a + * user-mutable Map.Entry (i.e., one supporting setValue; see + * MapEntry below), but can be used for read-only traversals used + * in bulk tasks. Subclasses of Node with a negative hash field + * are special, and contain null keys and values (but are never + * exported). Otherwise, keys and vals are never null. + */ + static class Node implements Map.Entry { + final int hash; + final K key; + volatile V val; + volatile Node next; + + Node(int hash, K key, V val, Node next) { + this.hash = hash; + this.key = key; + this.val = val; + this.next = next; + } + + public final K getKey() { return key; } + public final V getValue() { return val; } + public final int hashCode() { return key.hashCode() ^ val.hashCode(); } + public final String toString(){ return key + "=" + val; } + public final V setValue(V value) { + throw new UnsupportedOperationException(); + } + + public final boolean equals(Object o) { + Object k, v, u; Map.Entry e; + return ((o instanceof Map.Entry) && + (k = (e = (Map.Entry)o).getKey()) != null && + (v = e.getValue()) != null && + (k == key || k.equals(key)) && + (v == (u = val) || v.equals(u))); + } + + /** + * Virtualized support for map.get(); overridden in subclasses. + */ + Node find(int h, Object k) { + Node e = this; + if (k != null) { + do { + K ek; + if (e.hash == h && + ((ek = e.key) == k || (ek != null && k.equals(ek)))) + return e; + } while ((e = e.next) != null); + } + return null; + } + } + + /* ---------------- Static utilities -------------- */ + + /** + * Spreads (XORs) higher bits of hash to lower and also forces top + * bit to 0. Because the table uses power-of-two masking, sets of + * hashes that vary only in bits above the current mask will + * always collide. (Among known examples are sets of Float keys + * holding consecutive whole numbers in small tables.) So we + * apply a transform that spreads the impact of higher bits + * downward. There is a tradeoff between speed, utility, and + * quality of bit-spreading. Because many common sets of hashes + * are already reasonably distributed (so don't benefit from + * spreading), and because we use trees to handle large sets of + * collisions in bins, we just XOR some shifted bits in the + * cheapest possible way to reduce systematic lossage, as well as + * to incorporate impact of the highest bits that would otherwise + * never be used in index calculations because of table bounds. + */ + static final int spread(int h) { + return (h ^ (h >>> 16)) & HASH_BITS; + } + + /** + * Returns a power of two table size for the given desired capacity. + * See Hackers Delight, sec 3.2 + */ + private static final int tableSizeFor(int c) { + int n = c - 1; + n |= n >>> 1; + n |= n >>> 2; + n |= n >>> 4; + n |= n >>> 8; + n |= n >>> 16; + return (n < 0) ? 1 : (n >= MAXIMUM_CAPACITY) ? MAXIMUM_CAPACITY : n + 1; + } + + /** + * Returns x's Class if it is of the form "class C implements + * Comparable", else null. + */ + static Class comparableClassFor(Object x) { + if (x instanceof Comparable) { + Class c; Type[] ts, as; Type t; ParameterizedType p; + if ((c = x.getClass()) == String.class) // bypass checks + return c; + if ((ts = c.getGenericInterfaces()) != null) { + for (int i = 0; i < ts.length; ++i) { + if (((t = ts[i]) instanceof ParameterizedType) && + ((p = (ParameterizedType)t).getRawType() == + Comparable.class) && + (as = p.getActualTypeArguments()) != null && + as.length == 1 && as[0] == c) // type arg is c + return c; + } + } + } + return null; + } + + /** + * Returns k.compareTo(x) if x matches kc (k's screened comparable + * class), else 0. + */ + @SuppressWarnings({"rawtypes","unchecked"}) // for cast to Comparable + static int compareComparables(Class kc, Object k, Object x) { + return (x == null || x.getClass() != kc ? 0 : + ((Comparable)k).compareTo(x)); + } + + /* ---------------- Table element access -------------- */ + + /* + * Volatile access methods are used for table elements as well as + * elements of in-progress next table while resizing. All uses of + * the tab arguments must be null checked by callers. All callers + * also paranoically precheck that tab's length is not zero (or an + * equivalent check), thus ensuring that any index argument taking + * the form of a hash value anded with (length - 1) is a valid + * index. Note that, to be correct wrt arbitrary concurrency + * errors by users, these checks must operate on local variables, + * which accounts for some odd-looking inline assignments below. + * Note that calls to setTabAt always occur within locked regions, + * and so in principle require only release ordering, not + * full volatile semantics, but are currently coded as volatile + * writes to be conservative. + */ + + @SuppressWarnings("unchecked") + static final Node tabAt(Node[] tab, int i) { + return (Node)U.getObjectVolatile(tab, ((long)i << ASHIFT) + ABASE); + } + + static final boolean casTabAt(Node[] tab, int i, + Node c, Node v) { + return U.compareAndSwapObject(tab, ((long)i << ASHIFT) + ABASE, c, v); + } + + static final void setTabAt(Node[] tab, int i, Node v) { + U.putObjectVolatile(tab, ((long)i << ASHIFT) + ABASE, v); + } + + /* ---------------- Fields -------------- */ + + /** + * The array of bins. Lazily initialized upon first insertion. + * Size is always a power of two. Accessed directly by iterators. + */ + transient volatile Node[] table; + + /** + * The next table to use; non-null only while resizing. + */ + private transient volatile Node[] nextTable; + + /** + * Base counter value, used mainly when there is no contention, + * but also as a fallback during table initialization + * races. Updated via CAS. + */ + private transient volatile long baseCount; + + /** + * Table initialization and resizing control. When negative, the + * table is being initialized or resized: -1 for initialization, + * else -(1 + the number of active resizing threads). Otherwise, + * when table is null, holds the initial table size to use upon + * creation, or 0 for default. After initialization, holds the + * next element count value upon which to resize the table. + */ + private transient volatile int sizeCtl; + + /** + * The next table index (plus one) to split while resizing. + */ + private transient volatile int transferIndex; + + /** + * Spinlock (locked via CAS) used when resizing and/or creating CounterCells. + */ + private transient volatile int cellsBusy; + + /** + * Table of counter cells. When non-null, size is a power of 2. + */ + private transient volatile CounterCell[] counterCells; + + // views + private transient KeySetView keySet; + private transient ValuesView values; + private transient EntrySetView entrySet; + + + /* ---------------- Public operations -------------- */ + + /** + * Creates a new, empty map with the default initial table size (16). + */ + public ConcurrentHashMapV8() { + } + + /** + * Creates a new, empty map with an initial table size + * accommodating the specified number of elements without the need + * to dynamically resize. + * + * @param initialCapacity The implementation performs internal + * sizing to accommodate this many elements. + * @throws IllegalArgumentException if the initial capacity of + * elements is negative + */ + public ConcurrentHashMapV8(int initialCapacity) { + if (initialCapacity < 0) + throw new IllegalArgumentException(); + int cap = ((initialCapacity >= (MAXIMUM_CAPACITY >>> 1)) ? + MAXIMUM_CAPACITY : + tableSizeFor(initialCapacity + (initialCapacity >>> 1) + 1)); + this.sizeCtl = cap; + } + + /** + * Creates a new map with the same mappings as the given map. + * + * @param m the map + */ + public ConcurrentHashMapV8(Map m) { + this.sizeCtl = DEFAULT_CAPACITY; + putAll(m); + } + + /** + * Creates a new, empty map with an initial table size based on + * the given number of elements ({@code initialCapacity}) and + * initial table density ({@code loadFactor}). + * + * @param initialCapacity the initial capacity. The implementation + * performs internal sizing to accommodate this many elements, + * given the specified load factor. + * @param loadFactor the load factor (table density) for + * establishing the initial table size + * @throws IllegalArgumentException if the initial capacity of + * elements is negative or the load factor is nonpositive + * + * @since 1.6 + */ + public ConcurrentHashMapV8(int initialCapacity, float loadFactor) { + this(initialCapacity, loadFactor, 1); + } + + /** + * Creates a new, empty map with an initial table size based on + * the given number of elements ({@code initialCapacity}), table + * density ({@code loadFactor}), and number of concurrently + * updating threads ({@code concurrencyLevel}). + * + * @param initialCapacity the initial capacity. The implementation + * performs internal sizing to accommodate this many elements, + * given the specified load factor. + * @param loadFactor the load factor (table density) for + * establishing the initial table size + * @param concurrencyLevel the estimated number of concurrently + * updating threads. The implementation may use this value as + * a sizing hint. + * @throws IllegalArgumentException if the initial capacity is + * negative or the load factor or concurrencyLevel are + * nonpositive + */ + public ConcurrentHashMapV8(int initialCapacity, + float loadFactor, int concurrencyLevel) { + if (!(loadFactor > 0.0f) || initialCapacity < 0 || concurrencyLevel <= 0) + throw new IllegalArgumentException(); + if (initialCapacity < concurrencyLevel) // Use at least as many bins + initialCapacity = concurrencyLevel; // as estimated threads + long size = (long)(1.0 + (long)initialCapacity / loadFactor); + int cap = (size >= (long)MAXIMUM_CAPACITY) ? + MAXIMUM_CAPACITY : tableSizeFor((int)size); + this.sizeCtl = cap; + } + + // Original (since JDK1.2) Map methods + + /** + * {@inheritDoc} + */ + public int size() { + long n = sumCount(); + return ((n < 0L) ? 0 : + (n > (long)Integer.MAX_VALUE) ? Integer.MAX_VALUE : + (int)n); + } + + /** + * {@inheritDoc} + */ + public boolean isEmpty() { + return sumCount() <= 0L; // ignore transient negative values + } + + /** + * Returns the value to which the specified key is mapped, + * or {@code null} if this map contains no mapping for the key. + * + *

More formally, if this map contains a mapping from a key + * {@code k} to a value {@code v} such that {@code key.equals(k)}, + * then this method returns {@code v}; otherwise it returns + * {@code null}. (There can be at most one such mapping.) + * + * @throws NullPointerException if the specified key is null + */ + public V get(Object key) { + Node[] tab; Node e, p; int n, eh; K ek; + int h = spread(key.hashCode()); + if ((tab = table) != null && (n = tab.length) > 0 && + (e = tabAt(tab, (n - 1) & h)) != null) { + if ((eh = e.hash) == h) { + if ((ek = e.key) == key || (ek != null && key.equals(ek))) + return e.val; + } + else if (eh < 0) + return (p = e.find(h, key)) != null ? p.val : null; + while ((e = e.next) != null) { + if (e.hash == h && + ((ek = e.key) == key || (ek != null && key.equals(ek)))) + return e.val; + } + } + return null; + } + + /** + * Tests if the specified object is a key in this table. + * + * @param key possible key + * @return {@code true} if and only if the specified object + * is a key in this table, as determined by the + * {@code equals} method; {@code false} otherwise + * @throws NullPointerException if the specified key is null + */ + public boolean containsKey(Object key) { + return get(key) != null; + } + + /** + * Returns {@code true} if this map maps one or more keys to the + * specified value. Note: This method may require a full traversal + * of the map, and is much slower than method {@code containsKey}. + * + * @param value value whose presence in this map is to be tested + * @return {@code true} if this map maps one or more keys to the + * specified value + * @throws NullPointerException if the specified value is null + */ + public boolean containsValue(Object value) { + if (value == null) + throw new NullPointerException(); + Node[] t; + if ((t = table) != null) { + Traverser it = new Traverser(t, t.length, 0, t.length); + for (Node p; (p = it.advance()) != null; ) { + V v; + if ((v = p.val) == value || (v != null && value.equals(v))) + return true; + } + } + return false; + } + + /** + * Maps the specified key to the specified value in this table. + * Neither the key nor the value can be null. + * + *

The value can be retrieved by calling the {@code get} method + * with a key that is equal to the original key. + * + * @param key key with which the specified value is to be associated + * @param value value to be associated with the specified key + * @return the previous value associated with {@code key}, or + * {@code null} if there was no mapping for {@code key} + * @throws NullPointerException if the specified key or value is null + */ + public V put(K key, V value) { + return putVal(key, value, false); + } + + /** Implementation for put and putIfAbsent */ + final V putVal(K key, V value, boolean onlyIfAbsent) { + if (key == null || value == null) throw new NullPointerException(); + int hash = spread(key.hashCode()); + int binCount = 0; + for (Node[] tab = table;;) { + Node f; int n, i, fh; + if (tab == null || (n = tab.length) == 0) + tab = initTable(); + else if ((f = tabAt(tab, i = (n - 1) & hash)) == null) { + if (casTabAt(tab, i, null, + new Node(hash, key, value, null))) + break; // no lock when adding to empty bin + } + else if ((fh = f.hash) == MOVED) + tab = helpTransfer(tab, f); + else { + V oldVal = null; + synchronized (f) { + if (tabAt(tab, i) == f) { + if (fh >= 0) { + binCount = 1; + for (Node e = f;; ++binCount) { + K ek; + if (e.hash == hash && + ((ek = e.key) == key || + (ek != null && key.equals(ek)))) { + oldVal = e.val; + if (!onlyIfAbsent) + e.val = value; + break; + } + Node pred = e; + if ((e = e.next) == null) { + pred.next = new Node(hash, key, + value, null); + break; + } + } + } + else if (f instanceof TreeBin) { + Node p; + binCount = 2; + if ((p = ((TreeBin)f).putTreeVal(hash, key, + value)) != null) { + oldVal = p.val; + if (!onlyIfAbsent) + p.val = value; + } + } + } + } + if (binCount != 0) { + if (binCount >= TREEIFY_THRESHOLD) + treeifyBin(tab, i); + if (oldVal != null) + return oldVal; + break; + } + } + } + addCount(1L, binCount); + return null; + } + + /** + * Copies all of the mappings from the specified map to this one. + * These mappings replace any mappings that this map had for any of the + * keys currently in the specified map. + * + * @param m mappings to be stored in this map + */ + public void putAll(Map m) { + tryPresize(m.size()); + for (Map.Entry e : m.entrySet()) + putVal(e.getKey(), e.getValue(), false); + } + + /** + * Removes the key (and its corresponding value) from this map. + * This method does nothing if the key is not in the map. + * + * @param key the key that needs to be removed + * @return the previous value associated with {@code key}, or + * {@code null} if there was no mapping for {@code key} + * @throws NullPointerException if the specified key is null + */ + public V remove(Object key) { + return replaceNode(key, null, null); + } + + /** + * Implementation for the four public remove/replace methods: + * Replaces node value with v, conditional upon match of cv if + * non-null. If resulting value is null, delete. + */ + final V replaceNode(Object key, V value, Object cv) { + int hash = spread(key.hashCode()); + for (Node[] tab = table;;) { + Node f; int n, i, fh; + if (tab == null || (n = tab.length) == 0 || + (f = tabAt(tab, i = (n - 1) & hash)) == null) + break; + else if ((fh = f.hash) == MOVED) + tab = helpTransfer(tab, f); + else { + V oldVal = null; + boolean validated = false; + synchronized (f) { + if (tabAt(tab, i) == f) { + if (fh >= 0) { + validated = true; + for (Node e = f, pred = null;;) { + K ek; + if (e.hash == hash && + ((ek = e.key) == key || + (ek != null && key.equals(ek)))) { + V ev = e.val; + if (cv == null || cv == ev || + (ev != null && cv.equals(ev))) { + oldVal = ev; + if (value != null) + e.val = value; + else if (pred != null) + pred.next = e.next; + else + setTabAt(tab, i, e.next); + } + break; + } + pred = e; + if ((e = e.next) == null) + break; + } + } + else if (f instanceof TreeBin) { + validated = true; + TreeBin t = (TreeBin)f; + TreeNode r, p; + if ((r = t.root) != null && + (p = r.findTreeNode(hash, key, null)) != null) { + V pv = p.val; + if (cv == null || cv == pv || + (pv != null && cv.equals(pv))) { + oldVal = pv; + if (value != null) + p.val = value; + else if (t.removeTreeNode(p)) + setTabAt(tab, i, untreeify(t.first)); + } + } + } + } + } + if (validated) { + if (oldVal != null) { + if (value == null) + addCount(-1L, -1); + return oldVal; + } + break; + } + } + } + return null; + } + + /** + * Removes all of the mappings from this map. + */ + public void clear() { + long delta = 0L; // negative number of deletions + int i = 0; + Node[] tab = table; + while (tab != null && i < tab.length) { + int fh; + Node f = tabAt(tab, i); + if (f == null) + ++i; + else if ((fh = f.hash) == MOVED) { + tab = helpTransfer(tab, f); + i = 0; // restart + } + else { + synchronized (f) { + if (tabAt(tab, i) == f) { + Node p = (fh >= 0 ? f : + (f instanceof TreeBin) ? + ((TreeBin)f).first : null); + while (p != null) { + --delta; + p = p.next; + } + setTabAt(tab, i++, null); + } + } + } + } + if (delta != 0L) + addCount(delta, -1); + } + + /** + * Returns a {@link Set} view of the keys contained in this map. + * The set is backed by the map, so changes to the map are + * reflected in the set, and vice-versa. The set supports element + * removal, which removes the corresponding mapping from this map, + * via the {@code Iterator.remove}, {@code Set.remove}, + * {@code removeAll}, {@code retainAll}, and {@code clear} + * operations. It does not support the {@code add} or + * {@code addAll} operations. + * + *

The view's {@code iterator} is a "weakly consistent" iterator + * that will never throw {@link ConcurrentModificationException}, + * and guarantees to traverse elements as they existed upon + * construction of the iterator, and may (but is not guaranteed to) + * reflect any modifications subsequent to construction. + * + * @return the set view + */ + public KeySetView keySet() { + KeySetView ks; + return (ks = keySet) != null ? ks : (keySet = new KeySetView(this, null)); + } + + /** + * Returns a {@link Collection} view of the values contained in this map. + * The collection is backed by the map, so changes to the map are + * reflected in the collection, and vice-versa. The collection + * supports element removal, which removes the corresponding + * mapping from this map, via the {@code Iterator.remove}, + * {@code Collection.remove}, {@code removeAll}, + * {@code retainAll}, and {@code clear} operations. It does not + * support the {@code add} or {@code addAll} operations. + * + *

The view's {@code iterator} is a "weakly consistent" iterator + * that will never throw {@link ConcurrentModificationException}, + * and guarantees to traverse elements as they existed upon + * construction of the iterator, and may (but is not guaranteed to) + * reflect any modifications subsequent to construction. + * + * @return the collection view + */ + public Collection values() { + ValuesView vs; + return (vs = values) != null ? vs : (values = new ValuesView(this)); + } + + /** + * Returns a {@link Set} view of the mappings contained in this map. + * The set is backed by the map, so changes to the map are + * reflected in the set, and vice-versa. The set supports element + * removal, which removes the corresponding mapping from the map, + * via the {@code Iterator.remove}, {@code Set.remove}, + * {@code removeAll}, {@code retainAll}, and {@code clear} + * operations. + * + *

The view's {@code iterator} is a "weakly consistent" iterator + * that will never throw {@link ConcurrentModificationException}, + * and guarantees to traverse elements as they existed upon + * construction of the iterator, and may (but is not guaranteed to) + * reflect any modifications subsequent to construction. + * + * @return the set view + */ + public Set> entrySet() { + EntrySetView es; + return (es = entrySet) != null ? es : (entrySet = new EntrySetView(this)); + } + + /** + * Returns the hash code value for this {@link Map}, i.e., + * the sum of, for each key-value pair in the map, + * {@code key.hashCode() ^ value.hashCode()}. + * + * @return the hash code value for this map + */ + public int hashCode() { + int h = 0; + Node[] t; + if ((t = table) != null) { + Traverser it = new Traverser(t, t.length, 0, t.length); + for (Node p; (p = it.advance()) != null; ) + h += p.key.hashCode() ^ p.val.hashCode(); + } + return h; + } + + /** + * Returns a string representation of this map. The string + * representation consists of a list of key-value mappings (in no + * particular order) enclosed in braces ("{@code {}}"). Adjacent + * mappings are separated by the characters {@code ", "} (comma + * and space). Each key-value mapping is rendered as the key + * followed by an equals sign ("{@code =}") followed by the + * associated value. + * + * @return a string representation of this map + */ + public String toString() { + Node[] t; + int f = (t = table) == null ? 0 : t.length; + Traverser it = new Traverser(t, f, 0, f); + StringBuilder sb = new StringBuilder(); + sb.append('{'); + Node p; + if ((p = it.advance()) != null) { + for (;;) { + K k = p.key; + V v = p.val; + sb.append(k == this ? "(this Map)" : k); + sb.append('='); + sb.append(v == this ? "(this Map)" : v); + if ((p = it.advance()) == null) + break; + sb.append(',').append(' '); + } + } + return sb.append('}').toString(); + } + + /** + * Compares the specified object with this map for equality. + * Returns {@code true} if the given object is a map with the same + * mappings as this map. This operation may return misleading + * results if either map is concurrently modified during execution + * of this method. + * + * @param o object to be compared for equality with this map + * @return {@code true} if the specified object is equal to this map + */ + public boolean equals(Object o) { + if (o != this) { + if (!(o instanceof Map)) + return false; + Map m = (Map) o; + Node[] t; + int f = (t = table) == null ? 0 : t.length; + Traverser it = new Traverser(t, f, 0, f); + for (Node p; (p = it.advance()) != null; ) { + V val = p.val; + Object v = m.get(p.key); + if (v == null || (v != val && !v.equals(val))) + return false; + } + for (Map.Entry e : m.entrySet()) { + Object mk, mv, v; + if ((mk = e.getKey()) == null || + (mv = e.getValue()) == null || + (v = get(mk)) == null || + (mv != v && !mv.equals(v))) + return false; + } + } + return true; + } + + /** + * Stripped-down version of helper class used in previous version, + * declared for the sake of serialization compatibility + */ + static class Segment extends ReentrantLock implements Serializable { + private static final long serialVersionUID = 2249069246763182397L; + final float loadFactor; + Segment(float lf) { this.loadFactor = lf; } + } + + /** + * Saves the state of the {@code ConcurrentHashMapV8} instance to a + * stream (i.e., serializes it). + * @param s the stream + * @throws java.io.IOException if an I/O error occurs + * @serialData + * the key (Object) and value (Object) + * for each key-value mapping, followed by a null pair. + * The key-value mappings are emitted in no particular order. + */ + private void writeObject(java.io.ObjectOutputStream s) + throws java.io.IOException { + // For serialization compatibility + // Emulate segment calculation from previous version of this class + int sshift = 0; + int ssize = 1; + while (ssize < DEFAULT_CONCURRENCY_LEVEL) { + ++sshift; + ssize <<= 1; + } + int segmentShift = 32 - sshift; + int segmentMask = ssize - 1; + @SuppressWarnings("unchecked") Segment[] segments = (Segment[]) + new Segment[DEFAULT_CONCURRENCY_LEVEL]; + for (int i = 0; i < segments.length; ++i) + segments[i] = new Segment(LOAD_FACTOR); + s.putFields().put("segments", segments); + s.putFields().put("segmentShift", segmentShift); + s.putFields().put("segmentMask", segmentMask); + s.writeFields(); + + Node[] t; + if ((t = table) != null) { + Traverser it = new Traverser(t, t.length, 0, t.length); + for (Node p; (p = it.advance()) != null; ) { + s.writeObject(p.key); + s.writeObject(p.val); + } + } + s.writeObject(null); + s.writeObject(null); + segments = null; // throw away + } + + /** + * Reconstitutes the instance from a stream (that is, deserializes it). + * @param s the stream + * @throws ClassNotFoundException if the class of a serialized object + * could not be found + * @throws java.io.IOException if an I/O error occurs + */ + private void readObject(java.io.ObjectInputStream s) + throws java.io.IOException, ClassNotFoundException { + /* + * To improve performance in typical cases, we create nodes + * while reading, then place in table once size is known. + * However, we must also validate uniqueness and deal with + * overpopulated bins while doing so, which requires + * specialized versions of putVal mechanics. + */ + sizeCtl = -1; // force exclusion for table construction + s.defaultReadObject(); + long size = 0L; + Node p = null; + for (;;) { + @SuppressWarnings("unchecked") K k = (K) s.readObject(); + @SuppressWarnings("unchecked") V v = (V) s.readObject(); + if (k != null && v != null) { + p = new Node(spread(k.hashCode()), k, v, p); + ++size; + } + else + break; + } + if (size == 0L) + sizeCtl = 0; + else { + int n; + if (size >= (long)(MAXIMUM_CAPACITY >>> 1)) + n = MAXIMUM_CAPACITY; + else { + int sz = (int)size; + n = tableSizeFor(sz + (sz >>> 1) + 1); + } + @SuppressWarnings("unchecked") + Node[] tab = (Node[])new Node[n]; + int mask = n - 1; + long added = 0L; + while (p != null) { + boolean insertAtFront; + Node next = p.next, first; + int h = p.hash, j = h & mask; + if ((first = tabAt(tab, j)) == null) + insertAtFront = true; + else { + K k = p.key; + if (first.hash < 0) { + TreeBin t = (TreeBin)first; + if (t.putTreeVal(h, k, p.val) == null) + ++added; + insertAtFront = false; + } + else { + int binCount = 0; + insertAtFront = true; + Node q; K qk; + for (q = first; q != null; q = q.next) { + if (q.hash == h && + ((qk = q.key) == k || + (qk != null && k.equals(qk)))) { + insertAtFront = false; + break; + } + ++binCount; + } + if (insertAtFront && binCount >= TREEIFY_THRESHOLD) { + insertAtFront = false; + ++added; + p.next = first; + TreeNode hd = null, tl = null; + for (q = p; q != null; q = q.next) { + TreeNode t = new TreeNode + (q.hash, q.key, q.val, null, null); + if ((t.prev = tl) == null) + hd = t; + else + tl.next = t; + tl = t; + } + setTabAt(tab, j, new TreeBin(hd)); + } + } + } + if (insertAtFront) { + ++added; + p.next = first; + setTabAt(tab, j, p); + } + p = next; + } + table = tab; + sizeCtl = n - (n >>> 2); + baseCount = added; + } + } + + // ConcurrentMap methods + + /** + * {@inheritDoc} + * + * @return the previous value associated with the specified key, + * or {@code null} if there was no mapping for the key + * @throws NullPointerException if the specified key or value is null + */ + public V putIfAbsent(K key, V value) { + return putVal(key, value, true); + } + + /** + * {@inheritDoc} + * + * @throws NullPointerException if the specified key is null + */ + public boolean remove(Object key, Object value) { + if (key == null) + throw new NullPointerException(); + return value != null && replaceNode(key, null, value) != null; + } + + /** + * {@inheritDoc} + * + * @throws NullPointerException if any of the arguments are null + */ + public boolean replace(K key, V oldValue, V newValue) { + if (key == null || oldValue == null || newValue == null) + throw new NullPointerException(); + return replaceNode(key, newValue, oldValue) != null; + } + + /** + * {@inheritDoc} + * + * @return the previous value associated with the specified key, + * or {@code null} if there was no mapping for the key + * @throws NullPointerException if the specified key or value is null + */ + public V replace(K key, V value) { + if (key == null || value == null) + throw new NullPointerException(); + return replaceNode(key, value, null); + } + + // Overrides of JDK8+ Map extension method defaults + + /** + * Returns the value to which the specified key is mapped, or the + * given default value if this map contains no mapping for the + * key. + * + * @param key the key whose associated value is to be returned + * @param defaultValue the value to return if this map contains + * no mapping for the given key + * @return the mapping for the key, if present; else the default value + * @throws NullPointerException if the specified key is null + */ + public V getOrDefault(Object key, V defaultValue) { + V v; + return (v = get(key)) == null ? defaultValue : v; + } + + public void forEach(BiAction action) { + if (action == null) throw new NullPointerException(); + Node[] t; + if ((t = table) != null) { + Traverser it = new Traverser(t, t.length, 0, t.length); + for (Node p; (p = it.advance()) != null; ) { + action.apply(p.key, p.val); + } + } + } + + public void replaceAll(BiFun function) { + if (function == null) throw new NullPointerException(); + Node[] t; + if ((t = table) != null) { + Traverser it = new Traverser(t, t.length, 0, t.length); + for (Node p; (p = it.advance()) != null; ) { + V oldValue = p.val; + for (K key = p.key;;) { + V newValue = function.apply(key, oldValue); + if (newValue == null) + throw new NullPointerException(); + if (replaceNode(key, newValue, oldValue) != null || + (oldValue = get(key)) == null) + break; + } + } + } + } + + /** + * If the specified key is not already associated with a value, + * attempts to compute its value using the given mapping function + * and enters it into this map unless {@code null}. The entire + * method invocation is performed atomically, so the function is + * applied at most once per key. Some attempted update operations + * on this map by other threads may be blocked while computation + * is in progress, so the computation should be short and simple, + * and must not attempt to update any other mappings of this map. + * + * @param key key with which the specified value is to be associated + * @param mappingFunction the function to compute a value + * @return the current (existing or computed) value associated with + * the specified key, or null if the computed value is null + * @throws NullPointerException if the specified key or mappingFunction + * is null + * @throws IllegalStateException if the computation detectably + * attempts a recursive update to this map that would + * otherwise never complete + * @throws RuntimeException or Error if the mappingFunction does so, + * in which case the mapping is left unestablished + */ + public V computeIfAbsent(K key, Fun mappingFunction) { + if (key == null || mappingFunction == null) + throw new NullPointerException(); + int h = spread(key.hashCode()); + V val = null; + int binCount = 0; + for (Node[] tab = table;;) { + Node f; int n, i, fh; + if (tab == null || (n = tab.length) == 0) + tab = initTable(); + else if ((f = tabAt(tab, i = (n - 1) & h)) == null) { + Node r = new ReservationNode(); + synchronized (r) { + if (casTabAt(tab, i, null, r)) { + binCount = 1; + Node node = null; + try { + if ((val = mappingFunction.apply(key)) != null) + node = new Node(h, key, val, null); + } finally { + setTabAt(tab, i, node); + } + } + } + if (binCount != 0) + break; + } + else if ((fh = f.hash) == MOVED) + tab = helpTransfer(tab, f); + else { + boolean added = false; + synchronized (f) { + if (tabAt(tab, i) == f) { + if (fh >= 0) { + binCount = 1; + for (Node e = f;; ++binCount) { + K ek; V ev; + if (e.hash == h && + ((ek = e.key) == key || + (ek != null && key.equals(ek)))) { + val = e.val; + break; + } + Node pred = e; + if ((e = e.next) == null) { + if ((val = mappingFunction.apply(key)) != null) { + added = true; + pred.next = new Node(h, key, val, null); + } + break; + } + } + } + else if (f instanceof TreeBin) { + binCount = 2; + TreeBin t = (TreeBin)f; + TreeNode r, p; + if ((r = t.root) != null && + (p = r.findTreeNode(h, key, null)) != null) + val = p.val; + else if ((val = mappingFunction.apply(key)) != null) { + added = true; + t.putTreeVal(h, key, val); + } + } + } + } + if (binCount != 0) { + if (binCount >= TREEIFY_THRESHOLD) + treeifyBin(tab, i); + if (!added) + return val; + break; + } + } + } + if (val != null) + addCount(1L, binCount); + return val; + } + + /** + * If the value for the specified key is present, attempts to + * compute a new mapping given the key and its current mapped + * value. The entire method invocation is performed atomically. + * Some attempted update operations on this map by other threads + * may be blocked while computation is in progress, so the + * computation should be short and simple, and must not attempt to + * update any other mappings of this map. + * + * @param key key with which a value may be associated + * @param remappingFunction the function to compute a value + * @return the new value associated with the specified key, or null if none + * @throws NullPointerException if the specified key or remappingFunction + * is null + * @throws IllegalStateException if the computation detectably + * attempts a recursive update to this map that would + * otherwise never complete + * @throws RuntimeException or Error if the remappingFunction does so, + * in which case the mapping is unchanged + */ + public V computeIfPresent(K key, BiFun remappingFunction) { + if (key == null || remappingFunction == null) + throw new NullPointerException(); + int h = spread(key.hashCode()); + V val = null; + int delta = 0; + int binCount = 0; + for (Node[] tab = table;;) { + Node f; int n, i, fh; + if (tab == null || (n = tab.length) == 0) + tab = initTable(); + else if ((f = tabAt(tab, i = (n - 1) & h)) == null) + break; + else if ((fh = f.hash) == MOVED) + tab = helpTransfer(tab, f); + else { + synchronized (f) { + if (tabAt(tab, i) == f) { + if (fh >= 0) { + binCount = 1; + for (Node e = f, pred = null;; ++binCount) { + K ek; + if (e.hash == h && + ((ek = e.key) == key || + (ek != null && key.equals(ek)))) { + val = remappingFunction.apply(key, e.val); + if (val != null) + e.val = val; + else { + delta = -1; + Node en = e.next; + if (pred != null) + pred.next = en; + else + setTabAt(tab, i, en); + } + break; + } + pred = e; + if ((e = e.next) == null) + break; + } + } + else if (f instanceof TreeBin) { + binCount = 2; + TreeBin t = (TreeBin)f; + TreeNode r, p; + if ((r = t.root) != null && + (p = r.findTreeNode(h, key, null)) != null) { + val = remappingFunction.apply(key, p.val); + if (val != null) + p.val = val; + else { + delta = -1; + if (t.removeTreeNode(p)) + setTabAt(tab, i, untreeify(t.first)); + } + } + } + } + } + if (binCount != 0) + break; + } + } + if (delta != 0) + addCount((long)delta, binCount); + return val; + } + + /** + * Attempts to compute a mapping for the specified key and its + * current mapped value (or {@code null} if there is no current + * mapping). The entire method invocation is performed atomically. + * Some attempted update operations on this map by other threads + * may be blocked while computation is in progress, so the + * computation should be short and simple, and must not attempt to + * update any other mappings of this Map. + * + * @param key key with which the specified value is to be associated + * @param remappingFunction the function to compute a value + * @return the new value associated with the specified key, or null if none + * @throws NullPointerException if the specified key or remappingFunction + * is null + * @throws IllegalStateException if the computation detectably + * attempts a recursive update to this map that would + * otherwise never complete + * @throws RuntimeException or Error if the remappingFunction does so, + * in which case the mapping is unchanged + */ + public V compute(K key, + BiFun remappingFunction) { + if (key == null || remappingFunction == null) + throw new NullPointerException(); + int h = spread(key.hashCode()); + V val = null; + int delta = 0; + int binCount = 0; + for (Node[] tab = table;;) { + Node f; int n, i, fh; + if (tab == null || (n = tab.length) == 0) + tab = initTable(); + else if ((f = tabAt(tab, i = (n - 1) & h)) == null) { + Node r = new ReservationNode(); + synchronized (r) { + if (casTabAt(tab, i, null, r)) { + binCount = 1; + Node node = null; + try { + if ((val = remappingFunction.apply(key, null)) != null) { + delta = 1; + node = new Node(h, key, val, null); + } + } finally { + setTabAt(tab, i, node); + } + } + } + if (binCount != 0) + break; + } + else if ((fh = f.hash) == MOVED) + tab = helpTransfer(tab, f); + else { + synchronized (f) { + if (tabAt(tab, i) == f) { + if (fh >= 0) { + binCount = 1; + for (Node e = f, pred = null;; ++binCount) { + K ek; + if (e.hash == h && + ((ek = e.key) == key || + (ek != null && key.equals(ek)))) { + val = remappingFunction.apply(key, e.val); + if (val != null) + e.val = val; + else { + delta = -1; + Node en = e.next; + if (pred != null) + pred.next = en; + else + setTabAt(tab, i, en); + } + break; + } + pred = e; + if ((e = e.next) == null) { + val = remappingFunction.apply(key, null); + if (val != null) { + delta = 1; + pred.next = + new Node(h, key, val, null); + } + break; + } + } + } + else if (f instanceof TreeBin) { + binCount = 1; + TreeBin t = (TreeBin)f; + TreeNode r, p; + if ((r = t.root) != null) + p = r.findTreeNode(h, key, null); + else + p = null; + V pv = (p == null) ? null : p.val; + val = remappingFunction.apply(key, pv); + if (val != null) { + if (p != null) + p.val = val; + else { + delta = 1; + t.putTreeVal(h, key, val); + } + } + else if (p != null) { + delta = -1; + if (t.removeTreeNode(p)) + setTabAt(tab, i, untreeify(t.first)); + } + } + } + } + if (binCount != 0) { + if (binCount >= TREEIFY_THRESHOLD) + treeifyBin(tab, i); + break; + } + } + } + if (delta != 0) + addCount((long)delta, binCount); + return val; + } + + /** + * If the specified key is not already associated with a + * (non-null) value, associates it with the given value. + * Otherwise, replaces the value with the results of the given + * remapping function, or removes if {@code null}. The entire + * method invocation is performed atomically. Some attempted + * update operations on this map by other threads may be blocked + * while computation is in progress, so the computation should be + * short and simple, and must not attempt to update any other + * mappings of this Map. + * + * @param key key with which the specified value is to be associated + * @param value the value to use if absent + * @param remappingFunction the function to recompute a value if present + * @return the new value associated with the specified key, or null if none + * @throws NullPointerException if the specified key or the + * remappingFunction is null + * @throws RuntimeException or Error if the remappingFunction does so, + * in which case the mapping is unchanged + */ + public V merge(K key, V value, BiFun remappingFunction) { + if (key == null || value == null || remappingFunction == null) + throw new NullPointerException(); + int h = spread(key.hashCode()); + V val = null; + int delta = 0; + int binCount = 0; + for (Node[] tab = table;;) { + Node f; int n, i, fh; + if (tab == null || (n = tab.length) == 0) + tab = initTable(); + else if ((f = tabAt(tab, i = (n - 1) & h)) == null) { + if (casTabAt(tab, i, null, new Node(h, key, value, null))) { + delta = 1; + val = value; + break; + } + } + else if ((fh = f.hash) == MOVED) + tab = helpTransfer(tab, f); + else { + synchronized (f) { + if (tabAt(tab, i) == f) { + if (fh >= 0) { + binCount = 1; + for (Node e = f, pred = null;; ++binCount) { + K ek; + if (e.hash == h && + ((ek = e.key) == key || + (ek != null && key.equals(ek)))) { + val = remappingFunction.apply(e.val, value); + if (val != null) + e.val = val; + else { + delta = -1; + Node en = e.next; + if (pred != null) + pred.next = en; + else + setTabAt(tab, i, en); + } + break; + } + pred = e; + if ((e = e.next) == null) { + delta = 1; + val = value; + pred.next = + new Node(h, key, val, null); + break; + } + } + } + else if (f instanceof TreeBin) { + binCount = 2; + TreeBin t = (TreeBin)f; + TreeNode r = t.root; + TreeNode p = (r == null) ? null : + r.findTreeNode(h, key, null); + val = (p == null) ? value : + remappingFunction.apply(p.val, value); + if (val != null) { + if (p != null) + p.val = val; + else { + delta = 1; + t.putTreeVal(h, key, val); + } + } + else if (p != null) { + delta = -1; + if (t.removeTreeNode(p)) + setTabAt(tab, i, untreeify(t.first)); + } + } + } + } + if (binCount != 0) { + if (binCount >= TREEIFY_THRESHOLD) + treeifyBin(tab, i); + break; + } + } + } + if (delta != 0) + addCount((long)delta, binCount); + return val; + } + + // Hashtable legacy methods + + /** + * Legacy method testing if some key maps into the specified value + * in this table. This method is identical in functionality to + * {@link #containsValue(Object)}, and exists solely to ensure + * full compatibility with class {@link java.util.Hashtable}, + * which supported this method prior to introduction of the + * Java Collections framework. + * + * @param value a value to search for + * @return {@code true} if and only if some key maps to the + * {@code value} argument in this table as + * determined by the {@code equals} method; + * {@code false} otherwise + * @throws NullPointerException if the specified value is null + */ + @Deprecated public boolean contains(Object value) { + return containsValue(value); + } + + /** + * Returns an enumeration of the keys in this table. + * + * @return an enumeration of the keys in this table + * @see #keySet() + */ + public Enumeration keys() { + Node[] t; + int f = (t = table) == null ? 0 : t.length; + return new KeyIterator(t, f, 0, f, this); + } + + /** + * Returns an enumeration of the values in this table. + * + * @return an enumeration of the values in this table + * @see #values() + */ + public Enumeration elements() { + Node[] t; + int f = (t = table) == null ? 0 : t.length; + return new ValueIterator(t, f, 0, f, this); + } + + // ConcurrentHashMapV8-only methods + + /** + * Returns the number of mappings. This method should be used + * instead of {@link #size} because a ConcurrentHashMapV8 may + * contain more mappings than can be represented as an int. The + * value returned is an estimate; the actual count may differ if + * there are concurrent insertions or removals. + * + * @return the number of mappings + * @since 1.8 + */ + public long mappingCount() { + long n = sumCount(); + return (n < 0L) ? 0L : n; // ignore transient negative values + } + + /** + * Creates a new {@link Set} backed by a ConcurrentHashMapV8 + * from the given type to {@code Boolean.TRUE}. + * + * @return the new set + * @since 1.8 + */ + public static KeySetView newKeySet() { + return new KeySetView + (new ConcurrentHashMapV8(), Boolean.TRUE); + } + + /** + * Creates a new {@link Set} backed by a ConcurrentHashMapV8 + * from the given type to {@code Boolean.TRUE}. + * + * @param initialCapacity The implementation performs internal + * sizing to accommodate this many elements. + * @return the new set + * @throws IllegalArgumentException if the initial capacity of + * elements is negative + * @since 1.8 + */ + public static KeySetView newKeySet(int initialCapacity) { + return new KeySetView + (new ConcurrentHashMapV8(initialCapacity), Boolean.TRUE); + } + + /** + * Returns a {@link Set} view of the keys in this map, using the + * given common mapped value for any additions (i.e., {@link + * Collection#add} and {@link Collection#addAll(Collection)}). + * This is of course only appropriate if it is acceptable to use + * the same value for all additions from this view. + * + * @param mappedValue the mapped value to use for any additions + * @return the set view + * @throws NullPointerException if the mappedValue is null + */ + public KeySetView keySet(V mappedValue) { + if (mappedValue == null) + throw new NullPointerException(); + return new KeySetView(this, mappedValue); + } + + /* ---------------- Special Nodes -------------- */ + + /** + * A node inserted at head of bins during transfer operations. + */ + static final class ForwardingNode extends Node { + final Node[] nextTable; + ForwardingNode(Node[] tab) { + super(MOVED, null, null, null); + this.nextTable = tab; + } + + Node find(int h, Object k) { + // loop to avoid arbitrarily deep recursion on forwarding nodes + outer: for (Node[] tab = nextTable;;) { + Node e; int n; + if (k == null || tab == null || (n = tab.length) == 0 || + (e = tabAt(tab, (n - 1) & h)) == null) + return null; + for (;;) { + int eh; K ek; + if ((eh = e.hash) == h && + ((ek = e.key) == k || (ek != null && k.equals(ek)))) + return e; + if (eh < 0) { + if (e instanceof ForwardingNode) { + tab = ((ForwardingNode)e).nextTable; + continue outer; + } + else + return e.find(h, k); + } + if ((e = e.next) == null) + return null; + } + } + } + } + + /** + * A place-holder node used in computeIfAbsent and compute + */ + static final class ReservationNode extends Node { + ReservationNode() { + super(RESERVED, null, null, null); + } + + Node find(int h, Object k) { + return null; + } + } + + /* ---------------- Table Initialization and Resizing -------------- */ + + /** + * Returns the stamp bits for resizing a table of size n. + * Must be negative when shifted left by RESIZE_STAMP_SHIFT. + */ + static final int resizeStamp(int n) { + return Integer.numberOfLeadingZeros(n) | (1 << (RESIZE_STAMP_BITS - 1)); + } + + /** + * Initializes table, using the size recorded in sizeCtl. + */ + private final Node[] initTable() { + Node[] tab; int sc; + while ((tab = table) == null || tab.length == 0) { + if ((sc = sizeCtl) < 0) + Thread.yield(); // lost initialization race; just spin + else if (U.compareAndSwapInt(this, SIZECTL, sc, -1)) { + try { + if ((tab = table) == null || tab.length == 0) { + int n = (sc > 0) ? sc : DEFAULT_CAPACITY; + @SuppressWarnings("unchecked") + Node[] nt = (Node[])new Node[n]; + table = tab = nt; + sc = n - (n >>> 2); + } + } finally { + sizeCtl = sc; + } + break; + } + } + return tab; + } + + /** + * Adds to count, and if table is too small and not already + * resizing, initiates transfer. If already resizing, helps + * perform transfer if work is available. Rechecks occupancy + * after a transfer to see if another resize is already needed + * because resizings are lagging additions. + * + * @param x the count to add + * @param check if <0, don't check resize, if <= 1 only check if uncontended + */ + private final void addCount(long x, int check) { + CounterCell[] as; long b, s; + if ((as = counterCells) != null || + !U.compareAndSwapLong(this, BASECOUNT, b = baseCount, s = b + x)) { + CounterHashCode hc; CounterCell a; long v; int m; + boolean uncontended = true; + if ((hc = threadCounterHashCode.get()) == null || + as == null || (m = as.length - 1) < 0 || + (a = as[m & hc.code]) == null || + !(uncontended = + U.compareAndSwapLong(a, CELLVALUE, v = a.value, v + x))) { + fullAddCount(x, hc, uncontended); + return; + } + if (check <= 1) + return; + s = sumCount(); + } + if (check >= 0) { + Node[] tab, nt; int n, sc; + while (s >= (long)(sc = sizeCtl) && (tab = table) != null && + (n = tab.length) < MAXIMUM_CAPACITY) { + int rs = resizeStamp(n); + if (sc < 0) { + if ((sc >>> RESIZE_STAMP_SHIFT) != rs || sc == rs + 1 || + sc == rs + MAX_RESIZERS || (nt = nextTable) == null || + transferIndex <= 0) + break; + if (U.compareAndSwapInt(this, SIZECTL, sc, sc + 1)) + transfer(tab, nt); + } + else if (U.compareAndSwapInt(this, SIZECTL, sc, + (rs << RESIZE_STAMP_SHIFT) + 2)) + transfer(tab, null); + s = sumCount(); + } + } + } + + /** + * Helps transfer if a resize is in progress. + */ + final Node[] helpTransfer(Node[] tab, Node f) { + Node[] nextTab; int sc; + if (tab != null && (f instanceof ForwardingNode) && + (nextTab = ((ForwardingNode)f).nextTable) != null) { + int rs = resizeStamp(tab.length); + while (nextTab == nextTable && table == tab && + (sc = sizeCtl) < 0) { + if ((sc >>> RESIZE_STAMP_SHIFT) != rs || sc == rs + 1 || + sc == rs + MAX_RESIZERS || transferIndex <= 0) + break; + if (U.compareAndSwapInt(this, SIZECTL, sc, sc + 1)) { + transfer(tab, nextTab); + break; + } + } + return nextTab; + } + return table; + } + + /** + * Tries to presize table to accommodate the given number of elements. + * + * @param size number of elements (doesn't need to be perfectly accurate) + */ + private final void tryPresize(int size) { + int c = (size >= (MAXIMUM_CAPACITY >>> 1)) ? MAXIMUM_CAPACITY : + tableSizeFor(size + (size >>> 1) + 1); + int sc; + while ((sc = sizeCtl) >= 0) { + Node[] tab = table; int n; + if (tab == null || (n = tab.length) == 0) { + n = (sc > c) ? sc : c; + if (U.compareAndSwapInt(this, SIZECTL, sc, -1)) { + try { + if (table == tab) { + @SuppressWarnings("unchecked") + Node[] nt = (Node[])new Node[n]; + table = nt; + sc = n - (n >>> 2); + } + } finally { + sizeCtl = sc; + } + } + } + else if (c <= sc || n >= MAXIMUM_CAPACITY) + break; + else if (tab == table) { + int rs = resizeStamp(n); + if (sc < 0) { + Node[] nt; + if ((sc >>> RESIZE_STAMP_SHIFT) != rs || sc == rs + 1 || + sc == rs + MAX_RESIZERS || (nt = nextTable) == null || + transferIndex <= 0) + break; + if (U.compareAndSwapInt(this, SIZECTL, sc, sc + 1)) + transfer(tab, nt); + } + else if (U.compareAndSwapInt(this, SIZECTL, sc, + (rs << RESIZE_STAMP_SHIFT) + 2)) + transfer(tab, null); + } + } + } + + /** + * Moves and/or copies the nodes in each bin to new table. See + * above for explanation. + */ + private final void transfer(Node[] tab, Node[] nextTab) { + int n = tab.length, stride; + if ((stride = (NCPU > 1) ? (n >>> 3) / NCPU : n) < MIN_TRANSFER_STRIDE) + stride = MIN_TRANSFER_STRIDE; // subdivide range + if (nextTab == null) { // initiating + try { + @SuppressWarnings("unchecked") + Node[] nt = (Node[])new Node[n << 1]; + nextTab = nt; + } catch (Throwable ex) { // try to cope with OOME + sizeCtl = Integer.MAX_VALUE; + return; + } + nextTable = nextTab; + transferIndex = n; + } + int nextn = nextTab.length; + ForwardingNode fwd = new ForwardingNode(nextTab); + boolean advance = true; + boolean finishing = false; // to ensure sweep before committing nextTab + for (int i = 0, bound = 0;;) { + Node f; int fh; + while (advance) { + int nextIndex, nextBound; + if (--i >= bound || finishing) + advance = false; + else if ((nextIndex = transferIndex) <= 0) { + i = -1; + advance = false; + } + else if (U.compareAndSwapInt + (this, TRANSFERINDEX, nextIndex, + nextBound = (nextIndex > stride ? + nextIndex - stride : 0))) { + bound = nextBound; + i = nextIndex - 1; + advance = false; + } + } + if (i < 0 || i >= n || i + n >= nextn) { + int sc; + if (finishing) { + nextTable = null; + table = nextTab; + sizeCtl = (n << 1) - (n >>> 1); + return; + } + if (U.compareAndSwapInt(this, SIZECTL, sc = sizeCtl, sc - 1)) { + if ((sc - 2) != resizeStamp(n) << RESIZE_STAMP_SHIFT) + return; + finishing = advance = true; + i = n; // recheck before commit + } + } + else if ((f = tabAt(tab, i)) == null) + advance = casTabAt(tab, i, null, fwd); + else if ((fh = f.hash) == MOVED) + advance = true; // already processed + else { + synchronized (f) { + if (tabAt(tab, i) == f) { + Node ln, hn; + if (fh >= 0) { + int runBit = fh & n; + Node lastRun = f; + for (Node p = f.next; p != null; p = p.next) { + int b = p.hash & n; + if (b != runBit) { + runBit = b; + lastRun = p; + } + } + if (runBit == 0) { + ln = lastRun; + hn = null; + } + else { + hn = lastRun; + ln = null; + } + for (Node p = f; p != lastRun; p = p.next) { + int ph = p.hash; K pk = p.key; V pv = p.val; + if ((ph & n) == 0) + ln = new Node(ph, pk, pv, ln); + else + hn = new Node(ph, pk, pv, hn); + } + setTabAt(nextTab, i, ln); + setTabAt(nextTab, i + n, hn); + setTabAt(tab, i, fwd); + advance = true; + } + else if (f instanceof TreeBin) { + TreeBin t = (TreeBin)f; + TreeNode lo = null, loTail = null; + TreeNode hi = null, hiTail = null; + int lc = 0, hc = 0; + for (Node e = t.first; e != null; e = e.next) { + int h = e.hash; + TreeNode p = new TreeNode + (h, e.key, e.val, null, null); + if ((h & n) == 0) { + if ((p.prev = loTail) == null) + lo = p; + else + loTail.next = p; + loTail = p; + ++lc; + } + else { + if ((p.prev = hiTail) == null) + hi = p; + else + hiTail.next = p; + hiTail = p; + ++hc; + } + } + ln = (lc <= UNTREEIFY_THRESHOLD) ? untreeify(lo) : + (hc != 0) ? new TreeBin(lo) : t; + hn = (hc <= UNTREEIFY_THRESHOLD) ? untreeify(hi) : + (lc != 0) ? new TreeBin(hi) : t; + setTabAt(nextTab, i, ln); + setTabAt(nextTab, i + n, hn); + setTabAt(tab, i, fwd); + advance = true; + } + } + } + } + } + } + + /* ---------------- Conversion from/to TreeBins -------------- */ + + /** + * Replaces all linked nodes in bin at given index unless table is + * too small, in which case resizes instead. + */ + private final void treeifyBin(Node[] tab, int index) { + Node b; int n, sc; + if (tab != null) { + if ((n = tab.length) < MIN_TREEIFY_CAPACITY) + tryPresize(n << 1); + else if ((b = tabAt(tab, index)) != null && b.hash >= 0) { + synchronized (b) { + if (tabAt(tab, index) == b) { + TreeNode hd = null, tl = null; + for (Node e = b; e != null; e = e.next) { + TreeNode p = + new TreeNode(e.hash, e.key, e.val, + null, null); + if ((p.prev = tl) == null) + hd = p; + else + tl.next = p; + tl = p; + } + setTabAt(tab, index, new TreeBin(hd)); + } + } + } + } + } + + /** + * Returns a list on non-TreeNodes replacing those in given list. + */ + static Node untreeify(Node b) { + Node hd = null, tl = null; + for (Node q = b; q != null; q = q.next) { + Node p = new Node(q.hash, q.key, q.val, null); + if (tl == null) + hd = p; + else + tl.next = p; + tl = p; + } + return hd; + } + + /* ---------------- TreeNodes -------------- */ + + /** + * Nodes for use in TreeBins + */ + static final class TreeNode extends Node { + TreeNode parent; // red-black tree links + TreeNode left; + TreeNode right; + TreeNode prev; // needed to unlink next upon deletion + boolean red; + + TreeNode(int hash, K key, V val, Node next, + TreeNode parent) { + super(hash, key, val, next); + this.parent = parent; + } + + Node find(int h, Object k) { + return findTreeNode(h, k, null); + } + + /** + * Returns the TreeNode (or null if not found) for the given key + * starting at given root. + */ + final TreeNode findTreeNode(int h, Object k, Class kc) { + if (k != null) { + TreeNode p = this; + do { + int ph, dir; K pk; TreeNode q; + TreeNode pl = p.left, pr = p.right; + if ((ph = p.hash) > h) + p = pl; + else if (ph < h) + p = pr; + else if ((pk = p.key) == k || (pk != null && k.equals(pk))) + return p; + else if (pl == null) + p = pr; + else if (pr == null) + p = pl; + else if ((kc != null || + (kc = comparableClassFor(k)) != null) && + (dir = compareComparables(kc, k, pk)) != 0) + p = (dir < 0) ? pl : pr; + else if ((q = pr.findTreeNode(h, k, kc)) != null) + return q; + else + p = pl; + } while (p != null); + } + return null; + } + } + + /* ---------------- TreeBins -------------- */ + + /** + * TreeNodes used at the heads of bins. TreeBins do not hold user + * keys or values, but instead point to list of TreeNodes and + * their root. They also maintain a parasitic read-write lock + * forcing writers (who hold bin lock) to wait for readers (who do + * not) to complete before tree restructuring operations. + */ + static final class TreeBin extends Node { + TreeNode root; + volatile TreeNode first; + volatile Thread waiter; + volatile int lockState; + // values for lockState + static final int WRITER = 1; // set while holding write lock + static final int WAITER = 2; // set when waiting for write lock + static final int READER = 4; // increment value for setting read lock + + /** + * Tie-breaking utility for ordering insertions when equal + * hashCodes and non-comparable. We don't require a total + * order, just a consistent insertion rule to maintain + * equivalence across rebalancings. Tie-breaking further than + * necessary simplifies testing a bit. + */ + static int tieBreakOrder(Object a, Object b) { + int d; + if (a == null || b == null || + (d = a.getClass().getName(). + compareTo(b.getClass().getName())) == 0) + d = (System.identityHashCode(a) <= System.identityHashCode(b) ? + -1 : 1); + return d; + } + + /** + * Creates bin with initial set of nodes headed by b. + */ + TreeBin(TreeNode b) { + super(TREEBIN, null, null, null); + this.first = b; + TreeNode r = null; + for (TreeNode x = b, next; x != null; x = next) { + next = (TreeNode)x.next; + x.left = x.right = null; + if (r == null) { + x.parent = null; + x.red = false; + r = x; + } + else { + K k = x.key; + int h = x.hash; + Class kc = null; + for (TreeNode p = r;;) { + int dir, ph; + K pk = p.key; + if ((ph = p.hash) > h) + dir = -1; + else if (ph < h) + dir = 1; + else if ((kc == null && + (kc = comparableClassFor(k)) == null) || + (dir = compareComparables(kc, k, pk)) == 0) + dir = tieBreakOrder(k, pk); + TreeNode xp = p; + if ((p = (dir <= 0) ? p.left : p.right) == null) { + x.parent = xp; + if (dir <= 0) + xp.left = x; + else + xp.right = x; + r = balanceInsertion(r, x); + break; + } + } + } + } + this.root = r; + assert checkInvariants(root); + } + + /** + * Acquires write lock for tree restructuring. + */ + private final void lockRoot() { + if (!U.compareAndSwapInt(this, LOCKSTATE, 0, WRITER)) + contendedLock(); // offload to separate method + } + + /** + * Releases write lock for tree restructuring. + */ + private final void unlockRoot() { + lockState = 0; + } + + /** + * Possibly blocks awaiting root lock. + */ + private final void contendedLock() { + boolean waiting = false; + for (int s;;) { + if (((s = lockState) & ~WAITER) == 0) { + if (U.compareAndSwapInt(this, LOCKSTATE, s, WRITER)) { + if (waiting) + waiter = null; + return; + } + } + else if ((s & WAITER) == 0) { + if (U.compareAndSwapInt(this, LOCKSTATE, s, s | WAITER)) { + waiting = true; + waiter = Thread.currentThread(); + } + } + else if (waiting) + LockSupport.park(this); + } + } + + /** + * Returns matching node or null if none. Tries to search + * using tree comparisons from root, but continues linear + * search when lock not available. + */ + final Node find(int h, Object k) { + if (k != null) { + for (Node e = first; e != null; ) { + int s; K ek; + if (((s = lockState) & (WAITER|WRITER)) != 0) { + if (e.hash == h && + ((ek = e.key) == k || (ek != null && k.equals(ek)))) + return e; + e = e.next; + } + else if (U.compareAndSwapInt(this, LOCKSTATE, s, + s + READER)) { + TreeNode r, p; + try { + p = ((r = root) == null ? null : + r.findTreeNode(h, k, null)); + } finally { + Thread w; + int ls; + do {} while (!U.compareAndSwapInt + (this, LOCKSTATE, + ls = lockState, ls - READER)); + if (ls == (READER|WAITER) && (w = waiter) != null) + LockSupport.unpark(w); + } + return p; + } + } + } + return null; + } + + /** + * Finds or adds a node. + * @return null if added + */ + final TreeNode putTreeVal(int h, K k, V v) { + Class kc = null; + boolean searched = false; + for (TreeNode p = root;;) { + int dir, ph; K pk; + if (p == null) { + first = root = new TreeNode(h, k, v, null, null); + break; + } + else if ((ph = p.hash) > h) + dir = -1; + else if (ph < h) + dir = 1; + else if ((pk = p.key) == k || (pk != null && k.equals(pk))) + return p; + else if ((kc == null && + (kc = comparableClassFor(k)) == null) || + (dir = compareComparables(kc, k, pk)) == 0) { + if (!searched) { + TreeNode q, ch; + searched = true; + if (((ch = p.left) != null && + (q = ch.findTreeNode(h, k, kc)) != null) || + ((ch = p.right) != null && + (q = ch.findTreeNode(h, k, kc)) != null)) + return q; + } + dir = tieBreakOrder(k, pk); + } + + TreeNode xp = p; + if ((p = (dir <= 0) ? p.left : p.right) == null) { + TreeNode x, f = first; + first = x = new TreeNode(h, k, v, f, xp); + if (f != null) + f.prev = x; + if (dir <= 0) + xp.left = x; + else + xp.right = x; + if (!xp.red) + x.red = true; + else { + lockRoot(); + try { + root = balanceInsertion(root, x); + } finally { + unlockRoot(); + } + } + break; + } + } + assert checkInvariants(root); + return null; + } + + /** + * Removes the given node, that must be present before this + * call. This is messier than typical red-black deletion code + * because we cannot swap the contents of an interior node + * with a leaf successor that is pinned by "next" pointers + * that are accessible independently of lock. So instead we + * swap the tree linkages. + * + * @return true if now too small, so should be untreeified + */ + final boolean removeTreeNode(TreeNode p) { + TreeNode next = (TreeNode)p.next; + TreeNode pred = p.prev; // unlink traversal pointers + TreeNode r, rl; + if (pred == null) + first = next; + else + pred.next = next; + if (next != null) + next.prev = pred; + if (first == null) { + root = null; + return true; + } + if ((r = root) == null || r.right == null || // too small + (rl = r.left) == null || rl.left == null) + return true; + lockRoot(); + try { + TreeNode replacement; + TreeNode pl = p.left; + TreeNode pr = p.right; + if (pl != null && pr != null) { + TreeNode s = pr, sl; + while ((sl = s.left) != null) // find successor + s = sl; + boolean c = s.red; s.red = p.red; p.red = c; // swap colors + TreeNode sr = s.right; + TreeNode pp = p.parent; + if (s == pr) { // p was s's direct parent + p.parent = s; + s.right = p; + } + else { + TreeNode sp = s.parent; + if ((p.parent = sp) != null) { + if (s == sp.left) + sp.left = p; + else + sp.right = p; + } + if ((s.right = pr) != null) + pr.parent = s; + } + p.left = null; + if ((p.right = sr) != null) + sr.parent = p; + if ((s.left = pl) != null) + pl.parent = s; + if ((s.parent = pp) == null) + r = s; + else if (p == pp.left) + pp.left = s; + else + pp.right = s; + if (sr != null) + replacement = sr; + else + replacement = p; + } + else if (pl != null) + replacement = pl; + else if (pr != null) + replacement = pr; + else + replacement = p; + if (replacement != p) { + TreeNode pp = replacement.parent = p.parent; + if (pp == null) + r = replacement; + else if (p == pp.left) + pp.left = replacement; + else + pp.right = replacement; + p.left = p.right = p.parent = null; + } + + root = (p.red) ? r : balanceDeletion(r, replacement); + + if (p == replacement) { // detach pointers + TreeNode pp; + if ((pp = p.parent) != null) { + if (p == pp.left) + pp.left = null; + else if (p == pp.right) + pp.right = null; + p.parent = null; + } + } + } finally { + unlockRoot(); + } + assert checkInvariants(root); + return false; + } + + /* ------------------------------------------------------------ */ + // Red-black tree methods, all adapted from CLR + + static TreeNode rotateLeft(TreeNode root, + TreeNode p) { + TreeNode r, pp, rl; + if (p != null && (r = p.right) != null) { + if ((rl = p.right = r.left) != null) + rl.parent = p; + if ((pp = r.parent = p.parent) == null) + (root = r).red = false; + else if (pp.left == p) + pp.left = r; + else + pp.right = r; + r.left = p; + p.parent = r; + } + return root; + } + + static TreeNode rotateRight(TreeNode root, + TreeNode p) { + TreeNode l, pp, lr; + if (p != null && (l = p.left) != null) { + if ((lr = p.left = l.right) != null) + lr.parent = p; + if ((pp = l.parent = p.parent) == null) + (root = l).red = false; + else if (pp.right == p) + pp.right = l; + else + pp.left = l; + l.right = p; + p.parent = l; + } + return root; + } + + static TreeNode balanceInsertion(TreeNode root, + TreeNode x) { + x.red = true; + for (TreeNode xp, xpp, xppl, xppr;;) { + if ((xp = x.parent) == null) { + x.red = false; + return x; + } + else if (!xp.red || (xpp = xp.parent) == null) + return root; + if (xp == (xppl = xpp.left)) { + if ((xppr = xpp.right) != null && xppr.red) { + xppr.red = false; + xp.red = false; + xpp.red = true; + x = xpp; + } + else { + if (x == xp.right) { + root = rotateLeft(root, x = xp); + xpp = (xp = x.parent) == null ? null : xp.parent; + } + if (xp != null) { + xp.red = false; + if (xpp != null) { + xpp.red = true; + root = rotateRight(root, xpp); + } + } + } + } + else { + if (xppl != null && xppl.red) { + xppl.red = false; + xp.red = false; + xpp.red = true; + x = xpp; + } + else { + if (x == xp.left) { + root = rotateRight(root, x = xp); + xpp = (xp = x.parent) == null ? null : xp.parent; + } + if (xp != null) { + xp.red = false; + if (xpp != null) { + xpp.red = true; + root = rotateLeft(root, xpp); + } + } + } + } + } + } + + static TreeNode balanceDeletion(TreeNode root, + TreeNode x) { + for (TreeNode xp, xpl, xpr;;) { + if (x == null || x == root) + return root; + else if ((xp = x.parent) == null) { + x.red = false; + return x; + } + else if (x.red) { + x.red = false; + return root; + } + else if ((xpl = xp.left) == x) { + if ((xpr = xp.right) != null && xpr.red) { + xpr.red = false; + xp.red = true; + root = rotateLeft(root, xp); + xpr = (xp = x.parent) == null ? null : xp.right; + } + if (xpr == null) + x = xp; + else { + TreeNode sl = xpr.left, sr = xpr.right; + if ((sr == null || !sr.red) && + (sl == null || !sl.red)) { + xpr.red = true; + x = xp; + } + else { + if (sr == null || !sr.red) { + if (sl != null) + sl.red = false; + xpr.red = true; + root = rotateRight(root, xpr); + xpr = (xp = x.parent) == null ? + null : xp.right; + } + if (xpr != null) { + xpr.red = (xp == null) ? false : xp.red; + if ((sr = xpr.right) != null) + sr.red = false; + } + if (xp != null) { + xp.red = false; + root = rotateLeft(root, xp); + } + x = root; + } + } + } + else { // symmetric + if (xpl != null && xpl.red) { + xpl.red = false; + xp.red = true; + root = rotateRight(root, xp); + xpl = (xp = x.parent) == null ? null : xp.left; + } + if (xpl == null) + x = xp; + else { + TreeNode sl = xpl.left, sr = xpl.right; + if ((sl == null || !sl.red) && + (sr == null || !sr.red)) { + xpl.red = true; + x = xp; + } + else { + if (sl == null || !sl.red) { + if (sr != null) + sr.red = false; + xpl.red = true; + root = rotateLeft(root, xpl); + xpl = (xp = x.parent) == null ? + null : xp.left; + } + if (xpl != null) { + xpl.red = (xp == null) ? false : xp.red; + if ((sl = xpl.left) != null) + sl.red = false; + } + if (xp != null) { + xp.red = false; + root = rotateRight(root, xp); + } + x = root; + } + } + } + } + } + + /** + * Recursive invariant check + */ + static boolean checkInvariants(TreeNode t) { + TreeNode tp = t.parent, tl = t.left, tr = t.right, + tb = t.prev, tn = (TreeNode)t.next; + if (tb != null && tb.next != t) + return false; + if (tn != null && tn.prev != t) + return false; + if (tp != null && t != tp.left && t != tp.right) + return false; + if (tl != null && (tl.parent != t || tl.hash > t.hash)) + return false; + if (tr != null && (tr.parent != t || tr.hash < t.hash)) + return false; + if (t.red && tl != null && tl.red && tr != null && tr.red) + return false; + if (tl != null && !checkInvariants(tl)) + return false; + if (tr != null && !checkInvariants(tr)) + return false; + return true; + } + + private static final sun.misc.Unsafe U; + private static final long LOCKSTATE; + static { + try { + U = getUnsafe(); + Class k = TreeBin.class; + LOCKSTATE = U.objectFieldOffset + (k.getDeclaredField("lockState")); + } catch (Exception e) { + throw new Error(e); + } + } + } + + /* ----------------Table Traversal -------------- */ + + /** + * Records the table, its length, and current traversal index for a + * traverser that must process a region of a forwarded table before + * proceeding with current table. + */ + static final class TableStack { + int length; + int index; + Node[] tab; + TableStack next; + } + + /** + * Encapsulates traversal for methods such as containsValue; also + * serves as a base class for other iterators and spliterators. + * + * Method advance visits once each still-valid node that was + * reachable upon iterator construction. It might miss some that + * were added to a bin after the bin was visited, which is OK wrt + * consistency guarantees. Maintaining this property in the face + * of possible ongoing resizes requires a fair amount of + * bookkeeping state that is difficult to optimize away amidst + * volatile accesses. Even so, traversal maintains reasonable + * throughput. + * + * Normally, iteration proceeds bin-by-bin traversing lists. + * However, if the table has been resized, then all future steps + * must traverse both the bin at the current index as well as at + * (index + baseSize); and so on for further resizings. To + * paranoically cope with potential sharing by users of iterators + * across threads, iteration terminates if a bounds checks fails + * for a table read. + */ + static class Traverser { + Node[] tab; // current table; updated if resized + Node next; // the next entry to use + TableStack stack, spare; // to save/restore on ForwardingNodes + int index; // index of bin to use next + int baseIndex; // current index of initial table + int baseLimit; // index bound for initial table + final int baseSize; // initial table size + + Traverser(Node[] tab, int size, int index, int limit) { + this.tab = tab; + this.baseSize = size; + this.baseIndex = this.index = index; + this.baseLimit = limit; + this.next = null; + } + + /** + * Advances if possible, returning next valid node, or null if none. + */ + final Node advance() { + Node e; + if ((e = next) != null) + e = e.next; + for (;;) { + Node[] t; int i, n; // must use locals in checks + if (e != null) + return next = e; + if (baseIndex >= baseLimit || (t = tab) == null || + (n = t.length) <= (i = index) || i < 0) + return next = null; + if ((e = tabAt(t, i)) != null && e.hash < 0) { + if (e instanceof ForwardingNode) { + tab = ((ForwardingNode)e).nextTable; + e = null; + pushState(t, i, n); + continue; + } + else if (e instanceof TreeBin) + e = ((TreeBin)e).first; + else + e = null; + } + if (stack != null) + recoverState(n); + else if ((index = i + baseSize) >= n) + index = ++baseIndex; // visit upper slots if present + } + } + + /** + * Saves traversal state upon encountering a forwarding node. + */ + private void pushState(Node[] t, int i, int n) { + TableStack s = spare; // reuse if possible + if (s != null) + spare = s.next; + else + s = new TableStack(); + s.tab = t; + s.length = n; + s.index = i; + s.next = stack; + stack = s; + } + + /** + * Possibly pops traversal state. + * + * @param n length of current table + */ + private void recoverState(int n) { + TableStack s; int len; + while ((s = stack) != null && (index += (len = s.length)) >= n) { + n = len; + index = s.index; + tab = s.tab; + s.tab = null; + TableStack next = s.next; + s.next = spare; // save for reuse + stack = next; + spare = s; + } + if (s == null && (index += baseSize) >= n) + index = ++baseIndex; + } + } + + /** + * Base of key, value, and entry Iterators. Adds fields to + * Traverser to support iterator.remove. + */ + static class BaseIterator extends Traverser { + final ConcurrentHashMapV8 map; + Node lastReturned; + BaseIterator(Node[] tab, int size, int index, int limit, + ConcurrentHashMapV8 map) { + super(tab, size, index, limit); + this.map = map; + advance(); + } + + public final boolean hasNext() { return next != null; } + public final boolean hasMoreElements() { return next != null; } + + public final void remove() { + Node p; + if ((p = lastReturned) == null) + throw new IllegalStateException(); + lastReturned = null; + map.replaceNode(p.key, null, null); + } + } + + static final class KeyIterator extends BaseIterator + implements Iterator, Enumeration { + KeyIterator(Node[] tab, int index, int size, int limit, + ConcurrentHashMapV8 map) { + super(tab, index, size, limit, map); + } + + public final K next() { + Node p; + if ((p = next) == null) + throw new NoSuchElementException(); + K k = p.key; + lastReturned = p; + advance(); + return k; + } + + public final K nextElement() { return next(); } + } + + static final class ValueIterator extends BaseIterator + implements Iterator, Enumeration { + ValueIterator(Node[] tab, int index, int size, int limit, + ConcurrentHashMapV8 map) { + super(tab, index, size, limit, map); + } + + public final V next() { + Node p; + if ((p = next) == null) + throw new NoSuchElementException(); + V v = p.val; + lastReturned = p; + advance(); + return v; + } + + public final V nextElement() { return next(); } + } + + static final class EntryIterator extends BaseIterator + implements Iterator> { + EntryIterator(Node[] tab, int index, int size, int limit, + ConcurrentHashMapV8 map) { + super(tab, index, size, limit, map); + } + + public final Map.Entry next() { + Node p; + if ((p = next) == null) + throw new NoSuchElementException(); + K k = p.key; + V v = p.val; + lastReturned = p; + advance(); + return new MapEntry(k, v, map); + } + } + + /** + * Exported Entry for EntryIterator + */ + static final class MapEntry implements Map.Entry { + final K key; // non-null + V val; // non-null + final ConcurrentHashMapV8 map; + MapEntry(K key, V val, ConcurrentHashMapV8 map) { + this.key = key; + this.val = val; + this.map = map; + } + public K getKey() { return key; } + public V getValue() { return val; } + public int hashCode() { return key.hashCode() ^ val.hashCode(); } + public String toString() { return key + "=" + val; } + + public boolean equals(Object o) { + Object k, v; Map.Entry e; + return ((o instanceof Map.Entry) && + (k = (e = (Map.Entry)o).getKey()) != null && + (v = e.getValue()) != null && + (k == key || k.equals(key)) && + (v == val || v.equals(val))); + } + + /** + * Sets our entry's value and writes through to the map. The + * value to return is somewhat arbitrary here. Since we do not + * necessarily track asynchronous changes, the most recent + * "previous" value could be different from what we return (or + * could even have been removed, in which case the put will + * re-establish). We do not and cannot guarantee more. + */ + public V setValue(V value) { + if (value == null) throw new NullPointerException(); + V v = val; + val = value; + map.put(key, value); + return v; + } + } + + static final class KeySpliterator extends Traverser + implements ConcurrentHashMapSpliterator { + long est; // size estimate + KeySpliterator(Node[] tab, int size, int index, int limit, + long est) { + super(tab, size, index, limit); + this.est = est; + } + + public ConcurrentHashMapSpliterator trySplit() { + int i, f, h; + return (h = ((i = baseIndex) + (f = baseLimit)) >>> 1) <= i ? null : + new KeySpliterator(tab, baseSize, baseLimit = h, + f, est >>>= 1); + } + + public void forEachRemaining(Action action) { + if (action == null) throw new NullPointerException(); + for (Node p; (p = advance()) != null;) + action.apply(p.key); + } + + public boolean tryAdvance(Action action) { + if (action == null) throw new NullPointerException(); + Node p; + if ((p = advance()) == null) + return false; + action.apply(p.key); + return true; + } + + public long estimateSize() { return est; } + + } + + static final class ValueSpliterator extends Traverser + implements ConcurrentHashMapSpliterator { + long est; // size estimate + ValueSpliterator(Node[] tab, int size, int index, int limit, + long est) { + super(tab, size, index, limit); + this.est = est; + } + + public ConcurrentHashMapSpliterator trySplit() { + int i, f, h; + return (h = ((i = baseIndex) + (f = baseLimit)) >>> 1) <= i ? null : + new ValueSpliterator(tab, baseSize, baseLimit = h, + f, est >>>= 1); + } + + public void forEachRemaining(Action action) { + if (action == null) throw new NullPointerException(); + for (Node p; (p = advance()) != null;) + action.apply(p.val); + } + + public boolean tryAdvance(Action action) { + if (action == null) throw new NullPointerException(); + Node p; + if ((p = advance()) == null) + return false; + action.apply(p.val); + return true; + } + + public long estimateSize() { return est; } + + } + + static final class EntrySpliterator extends Traverser + implements ConcurrentHashMapSpliterator> { + final ConcurrentHashMapV8 map; // To export MapEntry + long est; // size estimate + EntrySpliterator(Node[] tab, int size, int index, int limit, + long est, ConcurrentHashMapV8 map) { + super(tab, size, index, limit); + this.map = map; + this.est = est; + } + + public ConcurrentHashMapSpliterator> trySplit() { + int i, f, h; + return (h = ((i = baseIndex) + (f = baseLimit)) >>> 1) <= i ? null : + new EntrySpliterator(tab, baseSize, baseLimit = h, + f, est >>>= 1, map); + } + + public void forEachRemaining(Action> action) { + if (action == null) throw new NullPointerException(); + for (Node p; (p = advance()) != null; ) + action.apply(new MapEntry(p.key, p.val, map)); + } + + public boolean tryAdvance(Action> action) { + if (action == null) throw new NullPointerException(); + Node p; + if ((p = advance()) == null) + return false; + action.apply(new MapEntry(p.key, p.val, map)); + return true; + } + + public long estimateSize() { return est; } + + } + + // Parallel bulk operations + + /** + * Computes initial batch value for bulk tasks. The returned value + * is approximately exp2 of the number of times (minus one) to + * split task by two before executing leaf action. This value is + * faster to compute and more convenient to use as a guide to + * splitting than is the depth, since it is used while dividing by + * two anyway. + */ + final int batchFor(long b) { + long n; + if (b == Long.MAX_VALUE || (n = sumCount()) <= 1L || n < b) + return 0; + int sp = ForkJoinPool.getCommonPoolParallelism() << 2; // slack of 4 + return (b <= 0L || (n /= b) >= sp) ? sp : (int)n; + } + + /** + * Performs the given action for each (key, value). + * + * @param parallelismThreshold the (estimated) number of elements + * needed for this operation to be executed in parallel + * @param action the action + * @since 1.8 + */ + public void forEach(long parallelismThreshold, + BiAction action) { + if (action == null) throw new NullPointerException(); + new ForEachMappingTask + (null, batchFor(parallelismThreshold), 0, 0, table, + action).invoke(); + } + + /** + * Performs the given action for each non-null transformation + * of each (key, value). + * + * @param parallelismThreshold the (estimated) number of elements + * needed for this operation to be executed in parallel + * @param transformer a function returning the transformation + * for an element, or null if there is no transformation (in + * which case the action is not applied) + * @param action the action + * @since 1.8 + */ + public void forEach(long parallelismThreshold, + BiFun transformer, + Action action) { + if (transformer == null || action == null) + throw new NullPointerException(); + new ForEachTransformedMappingTask + (null, batchFor(parallelismThreshold), 0, 0, table, + transformer, action).invoke(); + } + + /** + * Returns a non-null result from applying the given search + * function on each (key, value), or null if none. Upon + * success, further element processing is suppressed and the + * results of any other parallel invocations of the search + * function are ignored. + * + * @param parallelismThreshold the (estimated) number of elements + * needed for this operation to be executed in parallel + * @param searchFunction a function returning a non-null + * result on success, else null + * @return a non-null result from applying the given search + * function on each (key, value), or null if none + * @since 1.8 + */ + public U search(long parallelismThreshold, + BiFun searchFunction) { + if (searchFunction == null) throw new NullPointerException(); + return new SearchMappingsTask + (null, batchFor(parallelismThreshold), 0, 0, table, + searchFunction, new AtomicReference()).invoke(); + } + + /** + * Returns the result of accumulating the given transformation + * of all (key, value) pairs using the given reducer to + * combine values, or null if none. + * + * @param parallelismThreshold the (estimated) number of elements + * needed for this operation to be executed in parallel + * @param transformer a function returning the transformation + * for an element, or null if there is no transformation (in + * which case it is not combined) + * @param reducer a commutative associative combining function + * @return the result of accumulating the given transformation + * of all (key, value) pairs + * @since 1.8 + */ + public U reduce(long parallelismThreshold, + BiFun transformer, + BiFun reducer) { + if (transformer == null || reducer == null) + throw new NullPointerException(); + return new MapReduceMappingsTask + (null, batchFor(parallelismThreshold), 0, 0, table, + null, transformer, reducer).invoke(); + } + + /** + * Returns the result of accumulating the given transformation + * of all (key, value) pairs using the given reducer to + * combine values, and the given basis as an identity value. + * + * @param parallelismThreshold the (estimated) number of elements + * needed for this operation to be executed in parallel + * @param transformer a function returning the transformation + * for an element + * @param basis the identity (initial default value) for the reduction + * @param reducer a commutative associative combining function + * @return the result of accumulating the given transformation + * of all (key, value) pairs + * @since 1.8 + */ + public double reduceToDouble(long parallelismThreshold, + ObjectByObjectToDouble transformer, + double basis, + DoubleByDoubleToDouble reducer) { + if (transformer == null || reducer == null) + throw new NullPointerException(); + return new MapReduceMappingsToDoubleTask + (null, batchFor(parallelismThreshold), 0, 0, table, + null, transformer, basis, reducer).invoke(); + } + + /** + * Returns the result of accumulating the given transformation + * of all (key, value) pairs using the given reducer to + * combine values, and the given basis as an identity value. + * + * @param parallelismThreshold the (estimated) number of elements + * needed for this operation to be executed in parallel + * @param transformer a function returning the transformation + * for an element + * @param basis the identity (initial default value) for the reduction + * @param reducer a commutative associative combining function + * @return the result of accumulating the given transformation + * of all (key, value) pairs + * @since 1.8 + */ + public long reduceToLong(long parallelismThreshold, + ObjectByObjectToLong transformer, + long basis, + LongByLongToLong reducer) { + if (transformer == null || reducer == null) + throw new NullPointerException(); + return new MapReduceMappingsToLongTask + (null, batchFor(parallelismThreshold), 0, 0, table, + null, transformer, basis, reducer).invoke(); + } + + /** + * Returns the result of accumulating the given transformation + * of all (key, value) pairs using the given reducer to + * combine values, and the given basis as an identity value. + * + * @param parallelismThreshold the (estimated) number of elements + * needed for this operation to be executed in parallel + * @param transformer a function returning the transformation + * for an element + * @param basis the identity (initial default value) for the reduction + * @param reducer a commutative associative combining function + * @return the result of accumulating the given transformation + * of all (key, value) pairs + * @since 1.8 + */ + public int reduceToInt(long parallelismThreshold, + ObjectByObjectToInt transformer, + int basis, + IntByIntToInt reducer) { + if (transformer == null || reducer == null) + throw new NullPointerException(); + return new MapReduceMappingsToIntTask + (null, batchFor(parallelismThreshold), 0, 0, table, + null, transformer, basis, reducer).invoke(); + } + + /** + * Performs the given action for each key. + * + * @param parallelismThreshold the (estimated) number of elements + * needed for this operation to be executed in parallel + * @param action the action + * @since 1.8 + */ + public void forEachKey(long parallelismThreshold, + Action action) { + if (action == null) throw new NullPointerException(); + new ForEachKeyTask + (null, batchFor(parallelismThreshold), 0, 0, table, + action).invoke(); + } + + /** + * Performs the given action for each non-null transformation + * of each key. + * + * @param parallelismThreshold the (estimated) number of elements + * needed for this operation to be executed in parallel + * @param transformer a function returning the transformation + * for an element, or null if there is no transformation (in + * which case the action is not applied) + * @param action the action + * @since 1.8 + */ + public void forEachKey(long parallelismThreshold, + Fun transformer, + Action action) { + if (transformer == null || action == null) + throw new NullPointerException(); + new ForEachTransformedKeyTask + (null, batchFor(parallelismThreshold), 0, 0, table, + transformer, action).invoke(); + } + + /** + * Returns a non-null result from applying the given search + * function on each key, or null if none. Upon success, + * further element processing is suppressed and the results of + * any other parallel invocations of the search function are + * ignored. + * + * @param parallelismThreshold the (estimated) number of elements + * needed for this operation to be executed in parallel + * @param searchFunction a function returning a non-null + * result on success, else null + * @return a non-null result from applying the given search + * function on each key, or null if none + * @since 1.8 + */ + public U searchKeys(long parallelismThreshold, + Fun searchFunction) { + if (searchFunction == null) throw new NullPointerException(); + return new SearchKeysTask + (null, batchFor(parallelismThreshold), 0, 0, table, + searchFunction, new AtomicReference()).invoke(); + } + + /** + * Returns the result of accumulating all keys using the given + * reducer to combine values, or null if none. + * + * @param parallelismThreshold the (estimated) number of elements + * needed for this operation to be executed in parallel + * @param reducer a commutative associative combining function + * @return the result of accumulating all keys using the given + * reducer to combine values, or null if none + * @since 1.8 + */ + public K reduceKeys(long parallelismThreshold, + BiFun reducer) { + if (reducer == null) throw new NullPointerException(); + return new ReduceKeysTask + (null, batchFor(parallelismThreshold), 0, 0, table, + null, reducer).invoke(); + } + + /** + * Returns the result of accumulating the given transformation + * of all keys using the given reducer to combine values, or + * null if none. + * + * @param parallelismThreshold the (estimated) number of elements + * needed for this operation to be executed in parallel + * @param transformer a function returning the transformation + * for an element, or null if there is no transformation (in + * which case it is not combined) + * @param reducer a commutative associative combining function + * @return the result of accumulating the given transformation + * of all keys + * @since 1.8 + */ + public U reduceKeys(long parallelismThreshold, + Fun transformer, + BiFun reducer) { + if (transformer == null || reducer == null) + throw new NullPointerException(); + return new MapReduceKeysTask + (null, batchFor(parallelismThreshold), 0, 0, table, + null, transformer, reducer).invoke(); + } + + /** + * Returns the result of accumulating the given transformation + * of all keys using the given reducer to combine values, and + * the given basis as an identity value. + * + * @param parallelismThreshold the (estimated) number of elements + * needed for this operation to be executed in parallel + * @param transformer a function returning the transformation + * for an element + * @param basis the identity (initial default value) for the reduction + * @param reducer a commutative associative combining function + * @return the result of accumulating the given transformation + * of all keys + * @since 1.8 + */ + public double reduceKeysToDouble(long parallelismThreshold, + ObjectToDouble transformer, + double basis, + DoubleByDoubleToDouble reducer) { + if (transformer == null || reducer == null) + throw new NullPointerException(); + return new MapReduceKeysToDoubleTask + (null, batchFor(parallelismThreshold), 0, 0, table, + null, transformer, basis, reducer).invoke(); + } + + /** + * Returns the result of accumulating the given transformation + * of all keys using the given reducer to combine values, and + * the given basis as an identity value. + * + * @param parallelismThreshold the (estimated) number of elements + * needed for this operation to be executed in parallel + * @param transformer a function returning the transformation + * for an element + * @param basis the identity (initial default value) for the reduction + * @param reducer a commutative associative combining function + * @return the result of accumulating the given transformation + * of all keys + * @since 1.8 + */ + public long reduceKeysToLong(long parallelismThreshold, + ObjectToLong transformer, + long basis, + LongByLongToLong reducer) { + if (transformer == null || reducer == null) + throw new NullPointerException(); + return new MapReduceKeysToLongTask + (null, batchFor(parallelismThreshold), 0, 0, table, + null, transformer, basis, reducer).invoke(); + } + + /** + * Returns the result of accumulating the given transformation + * of all keys using the given reducer to combine values, and + * the given basis as an identity value. + * + * @param parallelismThreshold the (estimated) number of elements + * needed for this operation to be executed in parallel + * @param transformer a function returning the transformation + * for an element + * @param basis the identity (initial default value) for the reduction + * @param reducer a commutative associative combining function + * @return the result of accumulating the given transformation + * of all keys + * @since 1.8 + */ + public int reduceKeysToInt(long parallelismThreshold, + ObjectToInt transformer, + int basis, + IntByIntToInt reducer) { + if (transformer == null || reducer == null) + throw new NullPointerException(); + return new MapReduceKeysToIntTask + (null, batchFor(parallelismThreshold), 0, 0, table, + null, transformer, basis, reducer).invoke(); + } + + /** + * Performs the given action for each value. + * + * @param parallelismThreshold the (estimated) number of elements + * needed for this operation to be executed in parallel + * @param action the action + * @since 1.8 + */ + public void forEachValue(long parallelismThreshold, + Action action) { + if (action == null) + throw new NullPointerException(); + new ForEachValueTask + (null, batchFor(parallelismThreshold), 0, 0, table, + action).invoke(); + } + + /** + * Performs the given action for each non-null transformation + * of each value. + * + * @param parallelismThreshold the (estimated) number of elements + * needed for this operation to be executed in parallel + * @param transformer a function returning the transformation + * for an element, or null if there is no transformation (in + * which case the action is not applied) + * @param action the action + * @since 1.8 + */ + public void forEachValue(long parallelismThreshold, + Fun transformer, + Action action) { + if (transformer == null || action == null) + throw new NullPointerException(); + new ForEachTransformedValueTask + (null, batchFor(parallelismThreshold), 0, 0, table, + transformer, action).invoke(); + } + + /** + * Returns a non-null result from applying the given search + * function on each value, or null if none. Upon success, + * further element processing is suppressed and the results of + * any other parallel invocations of the search function are + * ignored. + * + * @param parallelismThreshold the (estimated) number of elements + * needed for this operation to be executed in parallel + * @param searchFunction a function returning a non-null + * result on success, else null + * @return a non-null result from applying the given search + * function on each value, or null if none + * @since 1.8 + */ + public U searchValues(long parallelismThreshold, + Fun searchFunction) { + if (searchFunction == null) throw new NullPointerException(); + return new SearchValuesTask + (null, batchFor(parallelismThreshold), 0, 0, table, + searchFunction, new AtomicReference()).invoke(); + } + + /** + * Returns the result of accumulating all values using the + * given reducer to combine values, or null if none. + * + * @param parallelismThreshold the (estimated) number of elements + * needed for this operation to be executed in parallel + * @param reducer a commutative associative combining function + * @return the result of accumulating all values + * @since 1.8 + */ + public V reduceValues(long parallelismThreshold, + BiFun reducer) { + if (reducer == null) throw new NullPointerException(); + return new ReduceValuesTask + (null, batchFor(parallelismThreshold), 0, 0, table, + null, reducer).invoke(); + } + + /** + * Returns the result of accumulating the given transformation + * of all values using the given reducer to combine values, or + * null if none. + * + * @param parallelismThreshold the (estimated) number of elements + * needed for this operation to be executed in parallel + * @param transformer a function returning the transformation + * for an element, or null if there is no transformation (in + * which case it is not combined) + * @param reducer a commutative associative combining function + * @return the result of accumulating the given transformation + * of all values + * @since 1.8 + */ + public U reduceValues(long parallelismThreshold, + Fun transformer, + BiFun reducer) { + if (transformer == null || reducer == null) + throw new NullPointerException(); + return new MapReduceValuesTask + (null, batchFor(parallelismThreshold), 0, 0, table, + null, transformer, reducer).invoke(); + } + + /** + * Returns the result of accumulating the given transformation + * of all values using the given reducer to combine values, + * and the given basis as an identity value. + * + * @param parallelismThreshold the (estimated) number of elements + * needed for this operation to be executed in parallel + * @param transformer a function returning the transformation + * for an element + * @param basis the identity (initial default value) for the reduction + * @param reducer a commutative associative combining function + * @return the result of accumulating the given transformation + * of all values + * @since 1.8 + */ + public double reduceValuesToDouble(long parallelismThreshold, + ObjectToDouble transformer, + double basis, + DoubleByDoubleToDouble reducer) { + if (transformer == null || reducer == null) + throw new NullPointerException(); + return new MapReduceValuesToDoubleTask + (null, batchFor(parallelismThreshold), 0, 0, table, + null, transformer, basis, reducer).invoke(); + } + + /** + * Returns the result of accumulating the given transformation + * of all values using the given reducer to combine values, + * and the given basis as an identity value. + * + * @param parallelismThreshold the (estimated) number of elements + * needed for this operation to be executed in parallel + * @param transformer a function returning the transformation + * for an element + * @param basis the identity (initial default value) for the reduction + * @param reducer a commutative associative combining function + * @return the result of accumulating the given transformation + * of all values + * @since 1.8 + */ + public long reduceValuesToLong(long parallelismThreshold, + ObjectToLong transformer, + long basis, + LongByLongToLong reducer) { + if (transformer == null || reducer == null) + throw new NullPointerException(); + return new MapReduceValuesToLongTask + (null, batchFor(parallelismThreshold), 0, 0, table, + null, transformer, basis, reducer).invoke(); + } + + /** + * Returns the result of accumulating the given transformation + * of all values using the given reducer to combine values, + * and the given basis as an identity value. + * + * @param parallelismThreshold the (estimated) number of elements + * needed for this operation to be executed in parallel + * @param transformer a function returning the transformation + * for an element + * @param basis the identity (initial default value) for the reduction + * @param reducer a commutative associative combining function + * @return the result of accumulating the given transformation + * of all values + * @since 1.8 + */ + public int reduceValuesToInt(long parallelismThreshold, + ObjectToInt transformer, + int basis, + IntByIntToInt reducer) { + if (transformer == null || reducer == null) + throw new NullPointerException(); + return new MapReduceValuesToIntTask + (null, batchFor(parallelismThreshold), 0, 0, table, + null, transformer, basis, reducer).invoke(); + } + + /** + * Performs the given action for each entry. + * + * @param parallelismThreshold the (estimated) number of elements + * needed for this operation to be executed in parallel + * @param action the action + * @since 1.8 + */ + public void forEachEntry(long parallelismThreshold, + Action> action) { + if (action == null) throw new NullPointerException(); + new ForEachEntryTask(null, batchFor(parallelismThreshold), 0, 0, table, + action).invoke(); + } + + /** + * Performs the given action for each non-null transformation + * of each entry. + * + * @param parallelismThreshold the (estimated) number of elements + * needed for this operation to be executed in parallel + * @param transformer a function returning the transformation + * for an element, or null if there is no transformation (in + * which case the action is not applied) + * @param action the action + * @since 1.8 + */ + public void forEachEntry(long parallelismThreshold, + Fun, ? extends U> transformer, + Action action) { + if (transformer == null || action == null) + throw new NullPointerException(); + new ForEachTransformedEntryTask + (null, batchFor(parallelismThreshold), 0, 0, table, + transformer, action).invoke(); + } + + /** + * Returns a non-null result from applying the given search + * function on each entry, or null if none. Upon success, + * further element processing is suppressed and the results of + * any other parallel invocations of the search function are + * ignored. + * + * @param parallelismThreshold the (estimated) number of elements + * needed for this operation to be executed in parallel + * @param searchFunction a function returning a non-null + * result on success, else null + * @return a non-null result from applying the given search + * function on each entry, or null if none + * @since 1.8 + */ + public U searchEntries(long parallelismThreshold, + Fun, ? extends U> searchFunction) { + if (searchFunction == null) throw new NullPointerException(); + return new SearchEntriesTask + (null, batchFor(parallelismThreshold), 0, 0, table, + searchFunction, new AtomicReference()).invoke(); + } + + /** + * Returns the result of accumulating all entries using the + * given reducer to combine values, or null if none. + * + * @param parallelismThreshold the (estimated) number of elements + * needed for this operation to be executed in parallel + * @param reducer a commutative associative combining function + * @return the result of accumulating all entries + * @since 1.8 + */ + public Map.Entry reduceEntries(long parallelismThreshold, + BiFun, Map.Entry, ? extends Map.Entry> reducer) { + if (reducer == null) throw new NullPointerException(); + return new ReduceEntriesTask + (null, batchFor(parallelismThreshold), 0, 0, table, + null, reducer).invoke(); + } + + /** + * Returns the result of accumulating the given transformation + * of all entries using the given reducer to combine values, + * or null if none. + * + * @param parallelismThreshold the (estimated) number of elements + * needed for this operation to be executed in parallel + * @param transformer a function returning the transformation + * for an element, or null if there is no transformation (in + * which case it is not combined) + * @param reducer a commutative associative combining function + * @return the result of accumulating the given transformation + * of all entries + * @since 1.8 + */ + public U reduceEntries(long parallelismThreshold, + Fun, ? extends U> transformer, + BiFun reducer) { + if (transformer == null || reducer == null) + throw new NullPointerException(); + return new MapReduceEntriesTask + (null, batchFor(parallelismThreshold), 0, 0, table, + null, transformer, reducer).invoke(); + } + + /** + * Returns the result of accumulating the given transformation + * of all entries using the given reducer to combine values, + * and the given basis as an identity value. + * + * @param parallelismThreshold the (estimated) number of elements + * needed for this operation to be executed in parallel + * @param transformer a function returning the transformation + * for an element + * @param basis the identity (initial default value) for the reduction + * @param reducer a commutative associative combining function + * @return the result of accumulating the given transformation + * of all entries + * @since 1.8 + */ + public double reduceEntriesToDouble(long parallelismThreshold, + ObjectToDouble> transformer, + double basis, + DoubleByDoubleToDouble reducer) { + if (transformer == null || reducer == null) + throw new NullPointerException(); + return new MapReduceEntriesToDoubleTask + (null, batchFor(parallelismThreshold), 0, 0, table, + null, transformer, basis, reducer).invoke(); + } + + /** + * Returns the result of accumulating the given transformation + * of all entries using the given reducer to combine values, + * and the given basis as an identity value. + * + * @param parallelismThreshold the (estimated) number of elements + * needed for this operation to be executed in parallel + * @param transformer a function returning the transformation + * for an element + * @param basis the identity (initial default value) for the reduction + * @param reducer a commutative associative combining function + * @return the result of accumulating the given transformation + * of all entries + * @since 1.8 + */ + public long reduceEntriesToLong(long parallelismThreshold, + ObjectToLong> transformer, + long basis, + LongByLongToLong reducer) { + if (transformer == null || reducer == null) + throw new NullPointerException(); + return new MapReduceEntriesToLongTask + (null, batchFor(parallelismThreshold), 0, 0, table, + null, transformer, basis, reducer).invoke(); + } + + /** + * Returns the result of accumulating the given transformation + * of all entries using the given reducer to combine values, + * and the given basis as an identity value. + * + * @param parallelismThreshold the (estimated) number of elements + * needed for this operation to be executed in parallel + * @param transformer a function returning the transformation + * for an element + * @param basis the identity (initial default value) for the reduction + * @param reducer a commutative associative combining function + * @return the result of accumulating the given transformation + * of all entries + * @since 1.8 + */ + public int reduceEntriesToInt(long parallelismThreshold, + ObjectToInt> transformer, + int basis, + IntByIntToInt reducer) { + if (transformer == null || reducer == null) + throw new NullPointerException(); + return new MapReduceEntriesToIntTask + (null, batchFor(parallelismThreshold), 0, 0, table, + null, transformer, basis, reducer).invoke(); + } + + + /* ----------------Views -------------- */ + + /** + * Base class for views. + */ + abstract static class CollectionView + implements Collection, java.io.Serializable { + private static final long serialVersionUID = 7249069246763182397L; + final ConcurrentHashMapV8 map; + CollectionView(ConcurrentHashMapV8 map) { this.map = map; } + + /** + * Returns the map backing this view. + * + * @return the map backing this view + */ + public ConcurrentHashMapV8 getMap() { return map; } + + /** + * Removes all of the elements from this view, by removing all + * the mappings from the map backing this view. + */ + public final void clear() { map.clear(); } + public final int size() { return map.size(); } + public final boolean isEmpty() { return map.isEmpty(); } + + // implementations below rely on concrete classes supplying these + // abstract methods + /** + * Returns a "weakly consistent" iterator that will never + * throw {@link ConcurrentModificationException}, and + * guarantees to traverse elements as they existed upon + * construction of the iterator, and may (but is not + * guaranteed to) reflect any modifications subsequent to + * construction. + */ + public abstract Iterator iterator(); + public abstract boolean contains(Object o); + public abstract boolean remove(Object o); + + private static final String oomeMsg = "Required array size too large"; + + public final Object[] toArray() { + long sz = map.mappingCount(); + if (sz > MAX_ARRAY_SIZE) + throw new OutOfMemoryError(oomeMsg); + int n = (int)sz; + Object[] r = new Object[n]; + int i = 0; + for (E e : this) { + if (i == n) { + if (n >= MAX_ARRAY_SIZE) + throw new OutOfMemoryError(oomeMsg); + if (n >= MAX_ARRAY_SIZE - (MAX_ARRAY_SIZE >>> 1) - 1) + n = MAX_ARRAY_SIZE; + else + n += (n >>> 1) + 1; + r = Arrays.copyOf(r, n); + } + r[i++] = e; + } + return (i == n) ? r : Arrays.copyOf(r, i); + } + + @SuppressWarnings("unchecked") + public final T[] toArray(T[] a) { + long sz = map.mappingCount(); + if (sz > MAX_ARRAY_SIZE) + throw new OutOfMemoryError(oomeMsg); + int m = (int)sz; + T[] r = (a.length >= m) ? a : + (T[])java.lang.reflect.Array + .newInstance(a.getClass().getComponentType(), m); + int n = r.length; + int i = 0; + for (E e : this) { + if (i == n) { + if (n >= MAX_ARRAY_SIZE) + throw new OutOfMemoryError(oomeMsg); + if (n >= MAX_ARRAY_SIZE - (MAX_ARRAY_SIZE >>> 1) - 1) + n = MAX_ARRAY_SIZE; + else + n += (n >>> 1) + 1; + r = Arrays.copyOf(r, n); + } + r[i++] = (T)e; + } + if (a == r && i < n) { + r[i] = null; // null-terminate + return r; + } + return (i == n) ? r : Arrays.copyOf(r, i); + } + + /** + * Returns a string representation of this collection. + * The string representation consists of the string representations + * of the collection's elements in the order they are returned by + * its iterator, enclosed in square brackets ({@code "[]"}). + * Adjacent elements are separated by the characters {@code ", "} + * (comma and space). Elements are converted to strings as by + * {@link String#valueOf(Object)}. + * + * @return a string representation of this collection + */ + public final String toString() { + StringBuilder sb = new StringBuilder(); + sb.append('['); + Iterator it = iterator(); + if (it.hasNext()) { + for (;;) { + Object e = it.next(); + sb.append(e == this ? "(this Collection)" : e); + if (!it.hasNext()) + break; + sb.append(',').append(' '); + } + } + return sb.append(']').toString(); + } + + public final boolean containsAll(Collection c) { + if (c != this) { + for (Object e : c) { + if (e == null || !contains(e)) + return false; + } + } + return true; + } + + public final boolean removeAll(Collection c) { + boolean modified = false; + for (Iterator it = iterator(); it.hasNext();) { + if (c.contains(it.next())) { + it.remove(); + modified = true; + } + } + return modified; + } + + public final boolean retainAll(Collection c) { + boolean modified = false; + for (Iterator it = iterator(); it.hasNext();) { + if (!c.contains(it.next())) { + it.remove(); + modified = true; + } + } + return modified; + } + + } + + /** + * A view of a ConcurrentHashMapV8 as a {@link Set} of keys, in + * which additions may optionally be enabled by mapping to a + * common value. This class cannot be directly instantiated. + * See {@link #keySet() keySet()}, + * {@link #keySet(Object) keySet(V)}, + * {@link #newKeySet() newKeySet()}, + * {@link #newKeySet(int) newKeySet(int)}. + * + * @since 1.8 + */ + public static class KeySetView extends CollectionView + implements Set, java.io.Serializable { + private static final long serialVersionUID = 7249069246763182397L; + private final V value; + KeySetView(ConcurrentHashMapV8 map, V value) { // non-public + super(map); + this.value = value; + } + + /** + * Returns the default mapped value for additions, + * or {@code null} if additions are not supported. + * + * @return the default mapped value for additions, or {@code null} + * if not supported + */ + public V getMappedValue() { return value; } + + /** + * {@inheritDoc} + * @throws NullPointerException if the specified key is null + */ + public boolean contains(Object o) { return map.containsKey(o); } + + /** + * Removes the key from this map view, by removing the key (and its + * corresponding value) from the backing map. This method does + * nothing if the key is not in the map. + * + * @param o the key to be removed from the backing map + * @return {@code true} if the backing map contained the specified key + * @throws NullPointerException if the specified key is null + */ + public boolean remove(Object o) { return map.remove(o) != null; } + + /** + * @return an iterator over the keys of the backing map + */ + public Iterator iterator() { + Node[] t; + ConcurrentHashMapV8 m = map; + int f = (t = m.table) == null ? 0 : t.length; + return new KeyIterator(t, f, 0, f, m); + } + + /** + * Adds the specified key to this set view by mapping the key to + * the default mapped value in the backing map, if defined. + * + * @param e key to be added + * @return {@code true} if this set changed as a result of the call + * @throws NullPointerException if the specified key is null + * @throws UnsupportedOperationException if no default mapped value + * for additions was provided + */ + public boolean add(K e) { + V v; + if ((v = value) == null) + throw new UnsupportedOperationException(); + return map.putVal(e, v, true) == null; + } + + /** + * Adds all of the elements in the specified collection to this set, + * as if by calling {@link #add} on each one. + * + * @param c the elements to be inserted into this set + * @return {@code true} if this set changed as a result of the call + * @throws NullPointerException if the collection or any of its + * elements are {@code null} + * @throws UnsupportedOperationException if no default mapped value + * for additions was provided + */ + public boolean addAll(Collection c) { + boolean added = false; + V v; + if ((v = value) == null) + throw new UnsupportedOperationException(); + for (K e : c) { + if (map.putVal(e, v, true) == null) + added = true; + } + return added; + } + + public int hashCode() { + int h = 0; + for (K e : this) + h += e.hashCode(); + return h; + } + + public boolean equals(Object o) { + Set c; + return ((o instanceof Set) && + ((c = (Set)o) == this || + (containsAll(c) && c.containsAll(this)))); + } + + public ConcurrentHashMapSpliterator spliterator() { + Node[] t; + ConcurrentHashMapV8 m = map; + long n = m.sumCount(); + int f = (t = m.table) == null ? 0 : t.length; + return new KeySpliterator(t, f, 0, f, n < 0L ? 0L : n); + } + + public void forEach(Action action) { + if (action == null) throw new NullPointerException(); + Node[] t; + if ((t = map.table) != null) { + Traverser it = new Traverser(t, t.length, 0, t.length); + for (Node p; (p = it.advance()) != null; ) + action.apply(p.key); + } + } + } + + /** + * A view of a ConcurrentHashMapV8 as a {@link Collection} of + * values, in which additions are disabled. This class cannot be + * directly instantiated. See {@link #values()}. + */ + static final class ValuesView extends CollectionView + implements Collection, java.io.Serializable { + private static final long serialVersionUID = 2249069246763182397L; + ValuesView(ConcurrentHashMapV8 map) { super(map); } + public final boolean contains(Object o) { + return map.containsValue(o); + } + + public final boolean remove(Object o) { + if (o != null) { + for (Iterator it = iterator(); it.hasNext();) { + if (o.equals(it.next())) { + it.remove(); + return true; + } + } + } + return false; + } + + public final Iterator iterator() { + ConcurrentHashMapV8 m = map; + Node[] t; + int f = (t = m.table) == null ? 0 : t.length; + return new ValueIterator(t, f, 0, f, m); + } + + public final boolean add(V e) { + throw new UnsupportedOperationException(); + } + public final boolean addAll(Collection c) { + throw new UnsupportedOperationException(); + } + + public ConcurrentHashMapSpliterator spliterator() { + Node[] t; + ConcurrentHashMapV8 m = map; + long n = m.sumCount(); + int f = (t = m.table) == null ? 0 : t.length; + return new ValueSpliterator(t, f, 0, f, n < 0L ? 0L : n); + } + + public void forEach(Action action) { + if (action == null) throw new NullPointerException(); + Node[] t; + if ((t = map.table) != null) { + Traverser it = new Traverser(t, t.length, 0, t.length); + for (Node p; (p = it.advance()) != null; ) + action.apply(p.val); + } + } + } + + /** + * A view of a ConcurrentHashMapV8 as a {@link Set} of (key, value) + * entries. This class cannot be directly instantiated. See + * {@link #entrySet()}. + */ + static final class EntrySetView extends CollectionView> + implements Set>, java.io.Serializable { + private static final long serialVersionUID = 2249069246763182397L; + EntrySetView(ConcurrentHashMapV8 map) { super(map); } + + public boolean contains(Object o) { + Object k, v, r; Map.Entry e; + return ((o instanceof Map.Entry) && + (k = (e = (Map.Entry)o).getKey()) != null && + (r = map.get(k)) != null && + (v = e.getValue()) != null && + (v == r || v.equals(r))); + } + + public boolean remove(Object o) { + Object k, v; Map.Entry e; + return ((o instanceof Map.Entry) && + (k = (e = (Map.Entry)o).getKey()) != null && + (v = e.getValue()) != null && + map.remove(k, v)); + } + + /** + * @return an iterator over the entries of the backing map + */ + public Iterator> iterator() { + ConcurrentHashMapV8 m = map; + Node[] t; + int f = (t = m.table) == null ? 0 : t.length; + return new EntryIterator(t, f, 0, f, m); + } + + public boolean add(Entry e) { + return map.putVal(e.getKey(), e.getValue(), false) == null; + } + + public boolean addAll(Collection> c) { + boolean added = false; + for (Entry e : c) { + if (add(e)) + added = true; + } + return added; + } + + public final int hashCode() { + int h = 0; + Node[] t; + if ((t = map.table) != null) { + Traverser it = new Traverser(t, t.length, 0, t.length); + for (Node p; (p = it.advance()) != null; ) { + h += p.hashCode(); + } + } + return h; + } + + public final boolean equals(Object o) { + Set c; + return ((o instanceof Set) && + ((c = (Set)o) == this || + (containsAll(c) && c.containsAll(this)))); + } + + public ConcurrentHashMapSpliterator> spliterator() { + Node[] t; + ConcurrentHashMapV8 m = map; + long n = m.sumCount(); + int f = (t = m.table) == null ? 0 : t.length; + return new EntrySpliterator(t, f, 0, f, n < 0L ? 0L : n, m); + } + + public void forEach(Action> action) { + if (action == null) throw new NullPointerException(); + Node[] t; + if ((t = map.table) != null) { + Traverser it = new Traverser(t, t.length, 0, t.length); + for (Node p; (p = it.advance()) != null; ) + action.apply(new MapEntry(p.key, p.val, map)); + } + } + + } + + // ------------------------------------------------------- + + /** + * Base class for bulk tasks. Repeats some fields and code from + * class Traverser, because we need to subclass CountedCompleter. + */ + abstract static class BulkTask extends CountedCompleter { + Node[] tab; // same as Traverser + Node next; + int index; + int baseIndex; + int baseLimit; + final int baseSize; + int batch; // split control + + BulkTask(BulkTask par, int b, int i, int f, Node[] t) { + super(par); + this.batch = b; + this.index = this.baseIndex = i; + if ((this.tab = t) == null) + this.baseSize = this.baseLimit = 0; + else if (par == null) + this.baseSize = this.baseLimit = t.length; + else { + this.baseLimit = f; + this.baseSize = par.baseSize; + } + } + + /** + * Same as Traverser version + */ + final Node advance() { + Node e; + if ((e = next) != null) + e = e.next; + for (;;) { + Node[] t; int i, n; K ek; // must use locals in checks + if (e != null) + return next = e; + if (baseIndex >= baseLimit || (t = tab) == null || + (n = t.length) <= (i = index) || i < 0) + return next = null; + if ((e = tabAt(t, index)) != null && e.hash < 0) { + if (e instanceof ForwardingNode) { + tab = ((ForwardingNode)e).nextTable; + e = null; + continue; + } + else if (e instanceof TreeBin) + e = ((TreeBin)e).first; + else + e = null; + } + if ((index += baseSize) >= n) + index = ++baseIndex; // visit upper slots if present + } + } + } + + /* + * Task classes. Coded in a regular but ugly format/style to + * simplify checks that each variant differs in the right way from + * others. The null screenings exist because compilers cannot tell + * that we've already null-checked task arguments, so we force + * simplest hoisted bypass to help avoid convoluted traps. + */ + @SuppressWarnings("serial") + static final class ForEachKeyTask + extends BulkTask { + final Action action; + ForEachKeyTask + (BulkTask p, int b, int i, int f, Node[] t, + Action action) { + super(p, b, i, f, t); + this.action = action; + } + public final void compute() { + final Action action; + if ((action = this.action) != null) { + for (int i = baseIndex, f, h; batch > 0 && + (h = ((f = baseLimit) + i) >>> 1) > i;) { + addToPendingCount(1); + new ForEachKeyTask + (this, batch >>>= 1, baseLimit = h, f, tab, + action).fork(); + } + for (Node p; (p = advance()) != null;) + action.apply(p.key); + propagateCompletion(); + } + } + } + + @SuppressWarnings("serial") + static final class ForEachValueTask + extends BulkTask { + final Action action; + ForEachValueTask + (BulkTask p, int b, int i, int f, Node[] t, + Action action) { + super(p, b, i, f, t); + this.action = action; + } + public final void compute() { + final Action action; + if ((action = this.action) != null) { + for (int i = baseIndex, f, h; batch > 0 && + (h = ((f = baseLimit) + i) >>> 1) > i;) { + addToPendingCount(1); + new ForEachValueTask + (this, batch >>>= 1, baseLimit = h, f, tab, + action).fork(); + } + for (Node p; (p = advance()) != null;) + action.apply(p.val); + propagateCompletion(); + } + } + } + + @SuppressWarnings("serial") + static final class ForEachEntryTask + extends BulkTask { + final Action> action; + ForEachEntryTask + (BulkTask p, int b, int i, int f, Node[] t, + Action> action) { + super(p, b, i, f, t); + this.action = action; + } + public final void compute() { + final Action> action; + if ((action = this.action) != null) { + for (int i = baseIndex, f, h; batch > 0 && + (h = ((f = baseLimit) + i) >>> 1) > i;) { + addToPendingCount(1); + new ForEachEntryTask + (this, batch >>>= 1, baseLimit = h, f, tab, + action).fork(); + } + for (Node p; (p = advance()) != null; ) + action.apply(p); + propagateCompletion(); + } + } + } + + @SuppressWarnings("serial") + static final class ForEachMappingTask + extends BulkTask { + final BiAction action; + ForEachMappingTask + (BulkTask p, int b, int i, int f, Node[] t, + BiAction action) { + super(p, b, i, f, t); + this.action = action; + } + public final void compute() { + final BiAction action; + if ((action = this.action) != null) { + for (int i = baseIndex, f, h; batch > 0 && + (h = ((f = baseLimit) + i) >>> 1) > i;) { + addToPendingCount(1); + new ForEachMappingTask + (this, batch >>>= 1, baseLimit = h, f, tab, + action).fork(); + } + for (Node p; (p = advance()) != null; ) + action.apply(p.key, p.val); + propagateCompletion(); + } + } + } + + @SuppressWarnings("serial") + static final class ForEachTransformedKeyTask + extends BulkTask { + final Fun transformer; + final Action action; + ForEachTransformedKeyTask + (BulkTask p, int b, int i, int f, Node[] t, + Fun transformer, Action action) { + super(p, b, i, f, t); + this.transformer = transformer; this.action = action; + } + public final void compute() { + final Fun transformer; + final Action action; + if ((transformer = this.transformer) != null && + (action = this.action) != null) { + for (int i = baseIndex, f, h; batch > 0 && + (h = ((f = baseLimit) + i) >>> 1) > i;) { + addToPendingCount(1); + new ForEachTransformedKeyTask + (this, batch >>>= 1, baseLimit = h, f, tab, + transformer, action).fork(); + } + for (Node p; (p = advance()) != null; ) { + U u; + if ((u = transformer.apply(p.key)) != null) + action.apply(u); + } + propagateCompletion(); + } + } + } + + @SuppressWarnings("serial") + static final class ForEachTransformedValueTask + extends BulkTask { + final Fun transformer; + final Action action; + ForEachTransformedValueTask + (BulkTask p, int b, int i, int f, Node[] t, + Fun transformer, Action action) { + super(p, b, i, f, t); + this.transformer = transformer; this.action = action; + } + public final void compute() { + final Fun transformer; + final Action action; + if ((transformer = this.transformer) != null && + (action = this.action) != null) { + for (int i = baseIndex, f, h; batch > 0 && + (h = ((f = baseLimit) + i) >>> 1) > i;) { + addToPendingCount(1); + new ForEachTransformedValueTask + (this, batch >>>= 1, baseLimit = h, f, tab, + transformer, action).fork(); + } + for (Node p; (p = advance()) != null; ) { + U u; + if ((u = transformer.apply(p.val)) != null) + action.apply(u); + } + propagateCompletion(); + } + } + } + + @SuppressWarnings("serial") + static final class ForEachTransformedEntryTask + extends BulkTask { + final Fun, ? extends U> transformer; + final Action action; + ForEachTransformedEntryTask + (BulkTask p, int b, int i, int f, Node[] t, + Fun, ? extends U> transformer, Action action) { + super(p, b, i, f, t); + this.transformer = transformer; this.action = action; + } + public final void compute() { + final Fun, ? extends U> transformer; + final Action action; + if ((transformer = this.transformer) != null && + (action = this.action) != null) { + for (int i = baseIndex, f, h; batch > 0 && + (h = ((f = baseLimit) + i) >>> 1) > i;) { + addToPendingCount(1); + new ForEachTransformedEntryTask + (this, batch >>>= 1, baseLimit = h, f, tab, + transformer, action).fork(); + } + for (Node p; (p = advance()) != null; ) { + U u; + if ((u = transformer.apply(p)) != null) + action.apply(u); + } + propagateCompletion(); + } + } + } + + @SuppressWarnings("serial") + static final class ForEachTransformedMappingTask + extends BulkTask { + final BiFun transformer; + final Action action; + ForEachTransformedMappingTask + (BulkTask p, int b, int i, int f, Node[] t, + BiFun transformer, + Action action) { + super(p, b, i, f, t); + this.transformer = transformer; this.action = action; + } + public final void compute() { + final BiFun transformer; + final Action action; + if ((transformer = this.transformer) != null && + (action = this.action) != null) { + for (int i = baseIndex, f, h; batch > 0 && + (h = ((f = baseLimit) + i) >>> 1) > i;) { + addToPendingCount(1); + new ForEachTransformedMappingTask + (this, batch >>>= 1, baseLimit = h, f, tab, + transformer, action).fork(); + } + for (Node p; (p = advance()) != null; ) { + U u; + if ((u = transformer.apply(p.key, p.val)) != null) + action.apply(u); + } + propagateCompletion(); + } + } + } + + @SuppressWarnings("serial") + static final class SearchKeysTask + extends BulkTask { + final Fun searchFunction; + final AtomicReference result; + SearchKeysTask + (BulkTask p, int b, int i, int f, Node[] t, + Fun searchFunction, + AtomicReference result) { + super(p, b, i, f, t); + this.searchFunction = searchFunction; this.result = result; + } + public final U getRawResult() { return result.get(); } + public final void compute() { + final Fun searchFunction; + final AtomicReference result; + if ((searchFunction = this.searchFunction) != null && + (result = this.result) != null) { + for (int i = baseIndex, f, h; batch > 0 && + (h = ((f = baseLimit) + i) >>> 1) > i;) { + if (result.get() != null) + return; + addToPendingCount(1); + new SearchKeysTask + (this, batch >>>= 1, baseLimit = h, f, tab, + searchFunction, result).fork(); + } + while (result.get() == null) { + U u; + Node p; + if ((p = advance()) == null) { + propagateCompletion(); + break; + } + if ((u = searchFunction.apply(p.key)) != null) { + if (result.compareAndSet(null, u)) + quietlyCompleteRoot(); + break; + } + } + } + } + } + + @SuppressWarnings("serial") + static final class SearchValuesTask + extends BulkTask { + final Fun searchFunction; + final AtomicReference result; + SearchValuesTask + (BulkTask p, int b, int i, int f, Node[] t, + Fun searchFunction, + AtomicReference result) { + super(p, b, i, f, t); + this.searchFunction = searchFunction; this.result = result; + } + public final U getRawResult() { return result.get(); } + public final void compute() { + final Fun searchFunction; + final AtomicReference result; + if ((searchFunction = this.searchFunction) != null && + (result = this.result) != null) { + for (int i = baseIndex, f, h; batch > 0 && + (h = ((f = baseLimit) + i) >>> 1) > i;) { + if (result.get() != null) + return; + addToPendingCount(1); + new SearchValuesTask + (this, batch >>>= 1, baseLimit = h, f, tab, + searchFunction, result).fork(); + } + while (result.get() == null) { + U u; + Node p; + if ((p = advance()) == null) { + propagateCompletion(); + break; + } + if ((u = searchFunction.apply(p.val)) != null) { + if (result.compareAndSet(null, u)) + quietlyCompleteRoot(); + break; + } + } + } + } + } + + @SuppressWarnings("serial") + static final class SearchEntriesTask + extends BulkTask { + final Fun, ? extends U> searchFunction; + final AtomicReference result; + SearchEntriesTask + (BulkTask p, int b, int i, int f, Node[] t, + Fun, ? extends U> searchFunction, + AtomicReference result) { + super(p, b, i, f, t); + this.searchFunction = searchFunction; this.result = result; + } + public final U getRawResult() { return result.get(); } + public final void compute() { + final Fun, ? extends U> searchFunction; + final AtomicReference result; + if ((searchFunction = this.searchFunction) != null && + (result = this.result) != null) { + for (int i = baseIndex, f, h; batch > 0 && + (h = ((f = baseLimit) + i) >>> 1) > i;) { + if (result.get() != null) + return; + addToPendingCount(1); + new SearchEntriesTask + (this, batch >>>= 1, baseLimit = h, f, tab, + searchFunction, result).fork(); + } + while (result.get() == null) { + U u; + Node p; + if ((p = advance()) == null) { + propagateCompletion(); + break; + } + if ((u = searchFunction.apply(p)) != null) { + if (result.compareAndSet(null, u)) + quietlyCompleteRoot(); + return; + } + } + } + } + } + + @SuppressWarnings("serial") + static final class SearchMappingsTask + extends BulkTask { + final BiFun searchFunction; + final AtomicReference result; + SearchMappingsTask + (BulkTask p, int b, int i, int f, Node[] t, + BiFun searchFunction, + AtomicReference result) { + super(p, b, i, f, t); + this.searchFunction = searchFunction; this.result = result; + } + public final U getRawResult() { return result.get(); } + public final void compute() { + final BiFun searchFunction; + final AtomicReference result; + if ((searchFunction = this.searchFunction) != null && + (result = this.result) != null) { + for (int i = baseIndex, f, h; batch > 0 && + (h = ((f = baseLimit) + i) >>> 1) > i;) { + if (result.get() != null) + return; + addToPendingCount(1); + new SearchMappingsTask + (this, batch >>>= 1, baseLimit = h, f, tab, + searchFunction, result).fork(); + } + while (result.get() == null) { + U u; + Node p; + if ((p = advance()) == null) { + propagateCompletion(); + break; + } + if ((u = searchFunction.apply(p.key, p.val)) != null) { + if (result.compareAndSet(null, u)) + quietlyCompleteRoot(); + break; + } + } + } + } + } + + @SuppressWarnings("serial") + static final class ReduceKeysTask + extends BulkTask { + final BiFun reducer; + K result; + ReduceKeysTask rights, nextRight; + ReduceKeysTask + (BulkTask p, int b, int i, int f, Node[] t, + ReduceKeysTask nextRight, + BiFun reducer) { + super(p, b, i, f, t); this.nextRight = nextRight; + this.reducer = reducer; + } + public final K getRawResult() { return result; } + public final void compute() { + final BiFun reducer; + if ((reducer = this.reducer) != null) { + for (int i = baseIndex, f, h; batch > 0 && + (h = ((f = baseLimit) + i) >>> 1) > i;) { + addToPendingCount(1); + (rights = new ReduceKeysTask + (this, batch >>>= 1, baseLimit = h, f, tab, + rights, reducer)).fork(); + } + K r = null; + for (Node p; (p = advance()) != null; ) { + K u = p.key; + r = (r == null) ? u : u == null ? r : reducer.apply(r, u); + } + result = r; + CountedCompleter c; + for (c = firstComplete(); c != null; c = c.nextComplete()) { + @SuppressWarnings("unchecked") ReduceKeysTask + t = (ReduceKeysTask)c, + s = t.rights; + while (s != null) { + K tr, sr; + if ((sr = s.result) != null) + t.result = (((tr = t.result) == null) ? sr : + reducer.apply(tr, sr)); + s = t.rights = s.nextRight; + } + } + } + } + } + + @SuppressWarnings("serial") + static final class ReduceValuesTask + extends BulkTask { + final BiFun reducer; + V result; + ReduceValuesTask rights, nextRight; + ReduceValuesTask + (BulkTask p, int b, int i, int f, Node[] t, + ReduceValuesTask nextRight, + BiFun reducer) { + super(p, b, i, f, t); this.nextRight = nextRight; + this.reducer = reducer; + } + public final V getRawResult() { return result; } + public final void compute() { + final BiFun reducer; + if ((reducer = this.reducer) != null) { + for (int i = baseIndex, f, h; batch > 0 && + (h = ((f = baseLimit) + i) >>> 1) > i;) { + addToPendingCount(1); + (rights = new ReduceValuesTask + (this, batch >>>= 1, baseLimit = h, f, tab, + rights, reducer)).fork(); + } + V r = null; + for (Node p; (p = advance()) != null; ) { + V v = p.val; + r = (r == null) ? v : reducer.apply(r, v); + } + result = r; + CountedCompleter c; + for (c = firstComplete(); c != null; c = c.nextComplete()) { + @SuppressWarnings("unchecked") ReduceValuesTask + t = (ReduceValuesTask)c, + s = t.rights; + while (s != null) { + V tr, sr; + if ((sr = s.result) != null) + t.result = (((tr = t.result) == null) ? sr : + reducer.apply(tr, sr)); + s = t.rights = s.nextRight; + } + } + } + } + } + + @SuppressWarnings("serial") + static final class ReduceEntriesTask + extends BulkTask> { + final BiFun, Map.Entry, ? extends Map.Entry> reducer; + Map.Entry result; + ReduceEntriesTask rights, nextRight; + ReduceEntriesTask + (BulkTask p, int b, int i, int f, Node[] t, + ReduceEntriesTask nextRight, + BiFun, Map.Entry, ? extends Map.Entry> reducer) { + super(p, b, i, f, t); this.nextRight = nextRight; + this.reducer = reducer; + } + public final Map.Entry getRawResult() { return result; } + public final void compute() { + final BiFun, Map.Entry, ? extends Map.Entry> reducer; + if ((reducer = this.reducer) != null) { + for (int i = baseIndex, f, h; batch > 0 && + (h = ((f = baseLimit) + i) >>> 1) > i;) { + addToPendingCount(1); + (rights = new ReduceEntriesTask + (this, batch >>>= 1, baseLimit = h, f, tab, + rights, reducer)).fork(); + } + Map.Entry r = null; + for (Node p; (p = advance()) != null; ) + r = (r == null) ? p : reducer.apply(r, p); + result = r; + CountedCompleter c; + for (c = firstComplete(); c != null; c = c.nextComplete()) { + @SuppressWarnings("unchecked") ReduceEntriesTask + t = (ReduceEntriesTask)c, + s = t.rights; + while (s != null) { + Map.Entry tr, sr; + if ((sr = s.result) != null) + t.result = (((tr = t.result) == null) ? sr : + reducer.apply(tr, sr)); + s = t.rights = s.nextRight; + } + } + } + } + } + + @SuppressWarnings("serial") + static final class MapReduceKeysTask + extends BulkTask { + final Fun transformer; + final BiFun reducer; + U result; + MapReduceKeysTask rights, nextRight; + MapReduceKeysTask + (BulkTask p, int b, int i, int f, Node[] t, + MapReduceKeysTask nextRight, + Fun transformer, + BiFun reducer) { + super(p, b, i, f, t); this.nextRight = nextRight; + this.transformer = transformer; + this.reducer = reducer; + } + public final U getRawResult() { return result; } + public final void compute() { + final Fun transformer; + final BiFun reducer; + if ((transformer = this.transformer) != null && + (reducer = this.reducer) != null) { + for (int i = baseIndex, f, h; batch > 0 && + (h = ((f = baseLimit) + i) >>> 1) > i;) { + addToPendingCount(1); + (rights = new MapReduceKeysTask + (this, batch >>>= 1, baseLimit = h, f, tab, + rights, transformer, reducer)).fork(); + } + U r = null; + for (Node p; (p = advance()) != null; ) { + U u; + if ((u = transformer.apply(p.key)) != null) + r = (r == null) ? u : reducer.apply(r, u); + } + result = r; + CountedCompleter c; + for (c = firstComplete(); c != null; c = c.nextComplete()) { + @SuppressWarnings("unchecked") MapReduceKeysTask + t = (MapReduceKeysTask)c, + s = t.rights; + while (s != null) { + U tr, sr; + if ((sr = s.result) != null) + t.result = (((tr = t.result) == null) ? sr : + reducer.apply(tr, sr)); + s = t.rights = s.nextRight; + } + } + } + } + } + + @SuppressWarnings("serial") + static final class MapReduceValuesTask + extends BulkTask { + final Fun transformer; + final BiFun reducer; + U result; + MapReduceValuesTask rights, nextRight; + MapReduceValuesTask + (BulkTask p, int b, int i, int f, Node[] t, + MapReduceValuesTask nextRight, + Fun transformer, + BiFun reducer) { + super(p, b, i, f, t); this.nextRight = nextRight; + this.transformer = transformer; + this.reducer = reducer; + } + public final U getRawResult() { return result; } + public final void compute() { + final Fun transformer; + final BiFun reducer; + if ((transformer = this.transformer) != null && + (reducer = this.reducer) != null) { + for (int i = baseIndex, f, h; batch > 0 && + (h = ((f = baseLimit) + i) >>> 1) > i;) { + addToPendingCount(1); + (rights = new MapReduceValuesTask + (this, batch >>>= 1, baseLimit = h, f, tab, + rights, transformer, reducer)).fork(); + } + U r = null; + for (Node p; (p = advance()) != null; ) { + U u; + if ((u = transformer.apply(p.val)) != null) + r = (r == null) ? u : reducer.apply(r, u); + } + result = r; + CountedCompleter c; + for (c = firstComplete(); c != null; c = c.nextComplete()) { + @SuppressWarnings("unchecked") MapReduceValuesTask + t = (MapReduceValuesTask)c, + s = t.rights; + while (s != null) { + U tr, sr; + if ((sr = s.result) != null) + t.result = (((tr = t.result) == null) ? sr : + reducer.apply(tr, sr)); + s = t.rights = s.nextRight; + } + } + } + } + } + + @SuppressWarnings("serial") + static final class MapReduceEntriesTask + extends BulkTask { + final Fun, ? extends U> transformer; + final BiFun reducer; + U result; + MapReduceEntriesTask rights, nextRight; + MapReduceEntriesTask + (BulkTask p, int b, int i, int f, Node[] t, + MapReduceEntriesTask nextRight, + Fun, ? extends U> transformer, + BiFun reducer) { + super(p, b, i, f, t); this.nextRight = nextRight; + this.transformer = transformer; + this.reducer = reducer; + } + public final U getRawResult() { return result; } + public final void compute() { + final Fun, ? extends U> transformer; + final BiFun reducer; + if ((transformer = this.transformer) != null && + (reducer = this.reducer) != null) { + for (int i = baseIndex, f, h; batch > 0 && + (h = ((f = baseLimit) + i) >>> 1) > i;) { + addToPendingCount(1); + (rights = new MapReduceEntriesTask + (this, batch >>>= 1, baseLimit = h, f, tab, + rights, transformer, reducer)).fork(); + } + U r = null; + for (Node p; (p = advance()) != null; ) { + U u; + if ((u = transformer.apply(p)) != null) + r = (r == null) ? u : reducer.apply(r, u); + } + result = r; + CountedCompleter c; + for (c = firstComplete(); c != null; c = c.nextComplete()) { + @SuppressWarnings("unchecked") MapReduceEntriesTask + t = (MapReduceEntriesTask)c, + s = t.rights; + while (s != null) { + U tr, sr; + if ((sr = s.result) != null) + t.result = (((tr = t.result) == null) ? sr : + reducer.apply(tr, sr)); + s = t.rights = s.nextRight; + } + } + } + } + } + + @SuppressWarnings("serial") + static final class MapReduceMappingsTask + extends BulkTask { + final BiFun transformer; + final BiFun reducer; + U result; + MapReduceMappingsTask rights, nextRight; + MapReduceMappingsTask + (BulkTask p, int b, int i, int f, Node[] t, + MapReduceMappingsTask nextRight, + BiFun transformer, + BiFun reducer) { + super(p, b, i, f, t); this.nextRight = nextRight; + this.transformer = transformer; + this.reducer = reducer; + } + public final U getRawResult() { return result; } + public final void compute() { + final BiFun transformer; + final BiFun reducer; + if ((transformer = this.transformer) != null && + (reducer = this.reducer) != null) { + for (int i = baseIndex, f, h; batch > 0 && + (h = ((f = baseLimit) + i) >>> 1) > i;) { + addToPendingCount(1); + (rights = new MapReduceMappingsTask + (this, batch >>>= 1, baseLimit = h, f, tab, + rights, transformer, reducer)).fork(); + } + U r = null; + for (Node p; (p = advance()) != null; ) { + U u; + if ((u = transformer.apply(p.key, p.val)) != null) + r = (r == null) ? u : reducer.apply(r, u); + } + result = r; + CountedCompleter c; + for (c = firstComplete(); c != null; c = c.nextComplete()) { + @SuppressWarnings("unchecked") MapReduceMappingsTask + t = (MapReduceMappingsTask)c, + s = t.rights; + while (s != null) { + U tr, sr; + if ((sr = s.result) != null) + t.result = (((tr = t.result) == null) ? sr : + reducer.apply(tr, sr)); + s = t.rights = s.nextRight; + } + } + } + } + } + + @SuppressWarnings("serial") + static final class MapReduceKeysToDoubleTask + extends BulkTask { + final ObjectToDouble transformer; + final DoubleByDoubleToDouble reducer; + final double basis; + double result; + MapReduceKeysToDoubleTask rights, nextRight; + MapReduceKeysToDoubleTask + (BulkTask p, int b, int i, int f, Node[] t, + MapReduceKeysToDoubleTask nextRight, + ObjectToDouble transformer, + double basis, + DoubleByDoubleToDouble reducer) { + super(p, b, i, f, t); this.nextRight = nextRight; + this.transformer = transformer; + this.basis = basis; this.reducer = reducer; + } + public final Double getRawResult() { return result; } + public final void compute() { + final ObjectToDouble transformer; + final DoubleByDoubleToDouble reducer; + if ((transformer = this.transformer) != null && + (reducer = this.reducer) != null) { + double r = this.basis; + for (int i = baseIndex, f, h; batch > 0 && + (h = ((f = baseLimit) + i) >>> 1) > i;) { + addToPendingCount(1); + (rights = new MapReduceKeysToDoubleTask + (this, batch >>>= 1, baseLimit = h, f, tab, + rights, transformer, r, reducer)).fork(); + } + for (Node p; (p = advance()) != null; ) + r = reducer.apply(r, transformer.apply(p.key)); + result = r; + CountedCompleter c; + for (c = firstComplete(); c != null; c = c.nextComplete()) { + @SuppressWarnings("unchecked") MapReduceKeysToDoubleTask + t = (MapReduceKeysToDoubleTask)c, + s = t.rights; + while (s != null) { + t.result = reducer.apply(t.result, s.result); + s = t.rights = s.nextRight; + } + } + } + } + } + + @SuppressWarnings("serial") + static final class MapReduceValuesToDoubleTask + extends BulkTask { + final ObjectToDouble transformer; + final DoubleByDoubleToDouble reducer; + final double basis; + double result; + MapReduceValuesToDoubleTask rights, nextRight; + MapReduceValuesToDoubleTask + (BulkTask p, int b, int i, int f, Node[] t, + MapReduceValuesToDoubleTask nextRight, + ObjectToDouble transformer, + double basis, + DoubleByDoubleToDouble reducer) { + super(p, b, i, f, t); this.nextRight = nextRight; + this.transformer = transformer; + this.basis = basis; this.reducer = reducer; + } + public final Double getRawResult() { return result; } + public final void compute() { + final ObjectToDouble transformer; + final DoubleByDoubleToDouble reducer; + if ((transformer = this.transformer) != null && + (reducer = this.reducer) != null) { + double r = this.basis; + for (int i = baseIndex, f, h; batch > 0 && + (h = ((f = baseLimit) + i) >>> 1) > i;) { + addToPendingCount(1); + (rights = new MapReduceValuesToDoubleTask + (this, batch >>>= 1, baseLimit = h, f, tab, + rights, transformer, r, reducer)).fork(); + } + for (Node p; (p = advance()) != null; ) + r = reducer.apply(r, transformer.apply(p.val)); + result = r; + CountedCompleter c; + for (c = firstComplete(); c != null; c = c.nextComplete()) { + @SuppressWarnings("unchecked") MapReduceValuesToDoubleTask + t = (MapReduceValuesToDoubleTask)c, + s = t.rights; + while (s != null) { + t.result = reducer.apply(t.result, s.result); + s = t.rights = s.nextRight; + } + } + } + } + } + + @SuppressWarnings("serial") + static final class MapReduceEntriesToDoubleTask + extends BulkTask { + final ObjectToDouble> transformer; + final DoubleByDoubleToDouble reducer; + final double basis; + double result; + MapReduceEntriesToDoubleTask rights, nextRight; + MapReduceEntriesToDoubleTask + (BulkTask p, int b, int i, int f, Node[] t, + MapReduceEntriesToDoubleTask nextRight, + ObjectToDouble> transformer, + double basis, + DoubleByDoubleToDouble reducer) { + super(p, b, i, f, t); this.nextRight = nextRight; + this.transformer = transformer; + this.basis = basis; this.reducer = reducer; + } + public final Double getRawResult() { return result; } + public final void compute() { + final ObjectToDouble> transformer; + final DoubleByDoubleToDouble reducer; + if ((transformer = this.transformer) != null && + (reducer = this.reducer) != null) { + double r = this.basis; + for (int i = baseIndex, f, h; batch > 0 && + (h = ((f = baseLimit) + i) >>> 1) > i;) { + addToPendingCount(1); + (rights = new MapReduceEntriesToDoubleTask + (this, batch >>>= 1, baseLimit = h, f, tab, + rights, transformer, r, reducer)).fork(); + } + for (Node p; (p = advance()) != null; ) + r = reducer.apply(r, transformer.apply(p)); + result = r; + CountedCompleter c; + for (c = firstComplete(); c != null; c = c.nextComplete()) { + @SuppressWarnings("unchecked") MapReduceEntriesToDoubleTask + t = (MapReduceEntriesToDoubleTask)c, + s = t.rights; + while (s != null) { + t.result = reducer.apply(t.result, s.result); + s = t.rights = s.nextRight; + } + } + } + } + } + + @SuppressWarnings("serial") + static final class MapReduceMappingsToDoubleTask + extends BulkTask { + final ObjectByObjectToDouble transformer; + final DoubleByDoubleToDouble reducer; + final double basis; + double result; + MapReduceMappingsToDoubleTask rights, nextRight; + MapReduceMappingsToDoubleTask + (BulkTask p, int b, int i, int f, Node[] t, + MapReduceMappingsToDoubleTask nextRight, + ObjectByObjectToDouble transformer, + double basis, + DoubleByDoubleToDouble reducer) { + super(p, b, i, f, t); this.nextRight = nextRight; + this.transformer = transformer; + this.basis = basis; this.reducer = reducer; + } + public final Double getRawResult() { return result; } + public final void compute() { + final ObjectByObjectToDouble transformer; + final DoubleByDoubleToDouble reducer; + if ((transformer = this.transformer) != null && + (reducer = this.reducer) != null) { + double r = this.basis; + for (int i = baseIndex, f, h; batch > 0 && + (h = ((f = baseLimit) + i) >>> 1) > i;) { + addToPendingCount(1); + (rights = new MapReduceMappingsToDoubleTask + (this, batch >>>= 1, baseLimit = h, f, tab, + rights, transformer, r, reducer)).fork(); + } + for (Node p; (p = advance()) != null; ) + r = reducer.apply(r, transformer.apply(p.key, p.val)); + result = r; + CountedCompleter c; + for (c = firstComplete(); c != null; c = c.nextComplete()) { + @SuppressWarnings("unchecked") MapReduceMappingsToDoubleTask + t = (MapReduceMappingsToDoubleTask)c, + s = t.rights; + while (s != null) { + t.result = reducer.apply(t.result, s.result); + s = t.rights = s.nextRight; + } + } + } + } + } + + @SuppressWarnings("serial") + static final class MapReduceKeysToLongTask + extends BulkTask { + final ObjectToLong transformer; + final LongByLongToLong reducer; + final long basis; + long result; + MapReduceKeysToLongTask rights, nextRight; + MapReduceKeysToLongTask + (BulkTask p, int b, int i, int f, Node[] t, + MapReduceKeysToLongTask nextRight, + ObjectToLong transformer, + long basis, + LongByLongToLong reducer) { + super(p, b, i, f, t); this.nextRight = nextRight; + this.transformer = transformer; + this.basis = basis; this.reducer = reducer; + } + public final Long getRawResult() { return result; } + public final void compute() { + final ObjectToLong transformer; + final LongByLongToLong reducer; + if ((transformer = this.transformer) != null && + (reducer = this.reducer) != null) { + long r = this.basis; + for (int i = baseIndex, f, h; batch > 0 && + (h = ((f = baseLimit) + i) >>> 1) > i;) { + addToPendingCount(1); + (rights = new MapReduceKeysToLongTask + (this, batch >>>= 1, baseLimit = h, f, tab, + rights, transformer, r, reducer)).fork(); + } + for (Node p; (p = advance()) != null; ) + r = reducer.apply(r, transformer.apply(p.key)); + result = r; + CountedCompleter c; + for (c = firstComplete(); c != null; c = c.nextComplete()) { + @SuppressWarnings("unchecked") MapReduceKeysToLongTask + t = (MapReduceKeysToLongTask)c, + s = t.rights; + while (s != null) { + t.result = reducer.apply(t.result, s.result); + s = t.rights = s.nextRight; + } + } + } + } + } + + @SuppressWarnings("serial") + static final class MapReduceValuesToLongTask + extends BulkTask { + final ObjectToLong transformer; + final LongByLongToLong reducer; + final long basis; + long result; + MapReduceValuesToLongTask rights, nextRight; + MapReduceValuesToLongTask + (BulkTask p, int b, int i, int f, Node[] t, + MapReduceValuesToLongTask nextRight, + ObjectToLong transformer, + long basis, + LongByLongToLong reducer) { + super(p, b, i, f, t); this.nextRight = nextRight; + this.transformer = transformer; + this.basis = basis; this.reducer = reducer; + } + public final Long getRawResult() { return result; } + public final void compute() { + final ObjectToLong transformer; + final LongByLongToLong reducer; + if ((transformer = this.transformer) != null && + (reducer = this.reducer) != null) { + long r = this.basis; + for (int i = baseIndex, f, h; batch > 0 && + (h = ((f = baseLimit) + i) >>> 1) > i;) { + addToPendingCount(1); + (rights = new MapReduceValuesToLongTask + (this, batch >>>= 1, baseLimit = h, f, tab, + rights, transformer, r, reducer)).fork(); + } + for (Node p; (p = advance()) != null; ) + r = reducer.apply(r, transformer.apply(p.val)); + result = r; + CountedCompleter c; + for (c = firstComplete(); c != null; c = c.nextComplete()) { + @SuppressWarnings("unchecked") MapReduceValuesToLongTask + t = (MapReduceValuesToLongTask)c, + s = t.rights; + while (s != null) { + t.result = reducer.apply(t.result, s.result); + s = t.rights = s.nextRight; + } + } + } + } + } + + @SuppressWarnings("serial") + static final class MapReduceEntriesToLongTask + extends BulkTask { + final ObjectToLong> transformer; + final LongByLongToLong reducer; + final long basis; + long result; + MapReduceEntriesToLongTask rights, nextRight; + MapReduceEntriesToLongTask + (BulkTask p, int b, int i, int f, Node[] t, + MapReduceEntriesToLongTask nextRight, + ObjectToLong> transformer, + long basis, + LongByLongToLong reducer) { + super(p, b, i, f, t); this.nextRight = nextRight; + this.transformer = transformer; + this.basis = basis; this.reducer = reducer; + } + public final Long getRawResult() { return result; } + public final void compute() { + final ObjectToLong> transformer; + final LongByLongToLong reducer; + if ((transformer = this.transformer) != null && + (reducer = this.reducer) != null) { + long r = this.basis; + for (int i = baseIndex, f, h; batch > 0 && + (h = ((f = baseLimit) + i) >>> 1) > i;) { + addToPendingCount(1); + (rights = new MapReduceEntriesToLongTask + (this, batch >>>= 1, baseLimit = h, f, tab, + rights, transformer, r, reducer)).fork(); + } + for (Node p; (p = advance()) != null; ) + r = reducer.apply(r, transformer.apply(p)); + result = r; + CountedCompleter c; + for (c = firstComplete(); c != null; c = c.nextComplete()) { + @SuppressWarnings("unchecked") MapReduceEntriesToLongTask + t = (MapReduceEntriesToLongTask)c, + s = t.rights; + while (s != null) { + t.result = reducer.apply(t.result, s.result); + s = t.rights = s.nextRight; + } + } + } + } + } + + @SuppressWarnings("serial") + static final class MapReduceMappingsToLongTask + extends BulkTask { + final ObjectByObjectToLong transformer; + final LongByLongToLong reducer; + final long basis; + long result; + MapReduceMappingsToLongTask rights, nextRight; + MapReduceMappingsToLongTask + (BulkTask p, int b, int i, int f, Node[] t, + MapReduceMappingsToLongTask nextRight, + ObjectByObjectToLong transformer, + long basis, + LongByLongToLong reducer) { + super(p, b, i, f, t); this.nextRight = nextRight; + this.transformer = transformer; + this.basis = basis; this.reducer = reducer; + } + public final Long getRawResult() { return result; } + public final void compute() { + final ObjectByObjectToLong transformer; + final LongByLongToLong reducer; + if ((transformer = this.transformer) != null && + (reducer = this.reducer) != null) { + long r = this.basis; + for (int i = baseIndex, f, h; batch > 0 && + (h = ((f = baseLimit) + i) >>> 1) > i;) { + addToPendingCount(1); + (rights = new MapReduceMappingsToLongTask + (this, batch >>>= 1, baseLimit = h, f, tab, + rights, transformer, r, reducer)).fork(); + } + for (Node p; (p = advance()) != null; ) + r = reducer.apply(r, transformer.apply(p.key, p.val)); + result = r; + CountedCompleter c; + for (c = firstComplete(); c != null; c = c.nextComplete()) { + @SuppressWarnings("unchecked") MapReduceMappingsToLongTask + t = (MapReduceMappingsToLongTask)c, + s = t.rights; + while (s != null) { + t.result = reducer.apply(t.result, s.result); + s = t.rights = s.nextRight; + } + } + } + } + } + + @SuppressWarnings("serial") + static final class MapReduceKeysToIntTask + extends BulkTask { + final ObjectToInt transformer; + final IntByIntToInt reducer; + final int basis; + int result; + MapReduceKeysToIntTask rights, nextRight; + MapReduceKeysToIntTask + (BulkTask p, int b, int i, int f, Node[] t, + MapReduceKeysToIntTask nextRight, + ObjectToInt transformer, + int basis, + IntByIntToInt reducer) { + super(p, b, i, f, t); this.nextRight = nextRight; + this.transformer = transformer; + this.basis = basis; this.reducer = reducer; + } + public final Integer getRawResult() { return result; } + public final void compute() { + final ObjectToInt transformer; + final IntByIntToInt reducer; + if ((transformer = this.transformer) != null && + (reducer = this.reducer) != null) { + int r = this.basis; + for (int i = baseIndex, f, h; batch > 0 && + (h = ((f = baseLimit) + i) >>> 1) > i;) { + addToPendingCount(1); + (rights = new MapReduceKeysToIntTask + (this, batch >>>= 1, baseLimit = h, f, tab, + rights, transformer, r, reducer)).fork(); + } + for (Node p; (p = advance()) != null; ) + r = reducer.apply(r, transformer.apply(p.key)); + result = r; + CountedCompleter c; + for (c = firstComplete(); c != null; c = c.nextComplete()) { + @SuppressWarnings("unchecked") MapReduceKeysToIntTask + t = (MapReduceKeysToIntTask)c, + s = t.rights; + while (s != null) { + t.result = reducer.apply(t.result, s.result); + s = t.rights = s.nextRight; + } + } + } + } + } + + @SuppressWarnings("serial") + static final class MapReduceValuesToIntTask + extends BulkTask { + final ObjectToInt transformer; + final IntByIntToInt reducer; + final int basis; + int result; + MapReduceValuesToIntTask rights, nextRight; + MapReduceValuesToIntTask + (BulkTask p, int b, int i, int f, Node[] t, + MapReduceValuesToIntTask nextRight, + ObjectToInt transformer, + int basis, + IntByIntToInt reducer) { + super(p, b, i, f, t); this.nextRight = nextRight; + this.transformer = transformer; + this.basis = basis; this.reducer = reducer; + } + public final Integer getRawResult() { return result; } + public final void compute() { + final ObjectToInt transformer; + final IntByIntToInt reducer; + if ((transformer = this.transformer) != null && + (reducer = this.reducer) != null) { + int r = this.basis; + for (int i = baseIndex, f, h; batch > 0 && + (h = ((f = baseLimit) + i) >>> 1) > i;) { + addToPendingCount(1); + (rights = new MapReduceValuesToIntTask + (this, batch >>>= 1, baseLimit = h, f, tab, + rights, transformer, r, reducer)).fork(); + } + for (Node p; (p = advance()) != null; ) + r = reducer.apply(r, transformer.apply(p.val)); + result = r; + CountedCompleter c; + for (c = firstComplete(); c != null; c = c.nextComplete()) { + @SuppressWarnings("unchecked") MapReduceValuesToIntTask + t = (MapReduceValuesToIntTask)c, + s = t.rights; + while (s != null) { + t.result = reducer.apply(t.result, s.result); + s = t.rights = s.nextRight; + } + } + } + } + } + + @SuppressWarnings("serial") + static final class MapReduceEntriesToIntTask + extends BulkTask { + final ObjectToInt> transformer; + final IntByIntToInt reducer; + final int basis; + int result; + MapReduceEntriesToIntTask rights, nextRight; + MapReduceEntriesToIntTask + (BulkTask p, int b, int i, int f, Node[] t, + MapReduceEntriesToIntTask nextRight, + ObjectToInt> transformer, + int basis, + IntByIntToInt reducer) { + super(p, b, i, f, t); this.nextRight = nextRight; + this.transformer = transformer; + this.basis = basis; this.reducer = reducer; + } + public final Integer getRawResult() { return result; } + public final void compute() { + final ObjectToInt> transformer; + final IntByIntToInt reducer; + if ((transformer = this.transformer) != null && + (reducer = this.reducer) != null) { + int r = this.basis; + for (int i = baseIndex, f, h; batch > 0 && + (h = ((f = baseLimit) + i) >>> 1) > i;) { + addToPendingCount(1); + (rights = new MapReduceEntriesToIntTask + (this, batch >>>= 1, baseLimit = h, f, tab, + rights, transformer, r, reducer)).fork(); + } + for (Node p; (p = advance()) != null; ) + r = reducer.apply(r, transformer.apply(p)); + result = r; + CountedCompleter c; + for (c = firstComplete(); c != null; c = c.nextComplete()) { + @SuppressWarnings("unchecked") MapReduceEntriesToIntTask + t = (MapReduceEntriesToIntTask)c, + s = t.rights; + while (s != null) { + t.result = reducer.apply(t.result, s.result); + s = t.rights = s.nextRight; + } + } + } + } + } + + @SuppressWarnings("serial") + static final class MapReduceMappingsToIntTask + extends BulkTask { + final ObjectByObjectToInt transformer; + final IntByIntToInt reducer; + final int basis; + int result; + MapReduceMappingsToIntTask rights, nextRight; + MapReduceMappingsToIntTask + (BulkTask p, int b, int i, int f, Node[] t, + MapReduceMappingsToIntTask nextRight, + ObjectByObjectToInt transformer, + int basis, + IntByIntToInt reducer) { + super(p, b, i, f, t); this.nextRight = nextRight; + this.transformer = transformer; + this.basis = basis; this.reducer = reducer; + } + public final Integer getRawResult() { return result; } + public final void compute() { + final ObjectByObjectToInt transformer; + final IntByIntToInt reducer; + if ((transformer = this.transformer) != null && + (reducer = this.reducer) != null) { + int r = this.basis; + for (int i = baseIndex, f, h; batch > 0 && + (h = ((f = baseLimit) + i) >>> 1) > i;) { + addToPendingCount(1); + (rights = new MapReduceMappingsToIntTask + (this, batch >>>= 1, baseLimit = h, f, tab, + rights, transformer, r, reducer)).fork(); + } + for (Node p; (p = advance()) != null; ) + r = reducer.apply(r, transformer.apply(p.key, p.val)); + result = r; + CountedCompleter c; + for (c = firstComplete(); c != null; c = c.nextComplete()) { + @SuppressWarnings("unchecked") MapReduceMappingsToIntTask + t = (MapReduceMappingsToIntTask)c, + s = t.rights; + while (s != null) { + t.result = reducer.apply(t.result, s.result); + s = t.rights = s.nextRight; + } + } + } + } + } + + /* ---------------- Counters -------------- */ + + // Adapted from LongAdder and Striped64. + // See their internal docs for explanation. + + // A padded cell for distributing counts + static final class CounterCell { + volatile long p0, p1, p2, p3, p4, p5, p6; + volatile long value; + volatile long q0, q1, q2, q3, q4, q5, q6; + CounterCell(long x) { value = x; } + } + + /** + * Holder for the thread-local hash code determining which + * CounterCell to use. The code is initialized via the + * counterHashCodeGenerator, but may be moved upon collisions. + */ + static final class CounterHashCode { + int code; + } + + /** + * Generates initial value for per-thread CounterHashCodes. + */ + static final AtomicInteger counterHashCodeGenerator = new AtomicInteger(); + + /** + * Increment for counterHashCodeGenerator. See class ThreadLocal + * for explanation. + */ + static final int SEED_INCREMENT = 0x61c88647; + + /** + * Per-thread counter hash codes. Shared across all instances. + */ + static final ThreadLocal threadCounterHashCode = + new ThreadLocal(); + + + final long sumCount() { + CounterCell[] as = counterCells; CounterCell a; + long sum = baseCount; + if (as != null) { + for (int i = 0; i < as.length; ++i) { + if ((a = as[i]) != null) + sum += a.value; + } + } + return sum; + } + + // See LongAdder version for explanation + private final void fullAddCount(long x, CounterHashCode hc, + boolean wasUncontended) { + int h; + if (hc == null) { + hc = new CounterHashCode(); + int s = counterHashCodeGenerator.addAndGet(SEED_INCREMENT); + h = hc.code = (s == 0) ? 1 : s; // Avoid zero + threadCounterHashCode.set(hc); + } + else + h = hc.code; + boolean collide = false; // True if last slot nonempty + for (;;) { + CounterCell[] as; CounterCell a; int n; long v; + if ((as = counterCells) != null && (n = as.length) > 0) { + if ((a = as[(n - 1) & h]) == null) { + if (cellsBusy == 0) { // Try to attach new Cell + CounterCell r = new CounterCell(x); // Optimistic create + if (cellsBusy == 0 && + U.compareAndSwapInt(this, CELLSBUSY, 0, 1)) { + boolean created = false; + try { // Recheck under lock + CounterCell[] rs; int m, j; + if ((rs = counterCells) != null && + (m = rs.length) > 0 && + rs[j = (m - 1) & h] == null) { + rs[j] = r; + created = true; + } + } finally { + cellsBusy = 0; + } + if (created) + break; + continue; // Slot is now non-empty + } + } + collide = false; + } + else if (!wasUncontended) // CAS already known to fail + wasUncontended = true; // Continue after rehash + else if (U.compareAndSwapLong(a, CELLVALUE, v = a.value, v + x)) + break; + else if (counterCells != as || n >= NCPU) + collide = false; // At max size or stale + else if (!collide) + collide = true; + else if (cellsBusy == 0 && + U.compareAndSwapInt(this, CELLSBUSY, 0, 1)) { + try { + if (counterCells == as) {// Expand table unless stale + CounterCell[] rs = new CounterCell[n << 1]; + for (int i = 0; i < n; ++i) + rs[i] = as[i]; + counterCells = rs; + } + } finally { + cellsBusy = 0; + } + collide = false; + continue; // Retry with expanded table + } + h ^= h << 13; // Rehash + h ^= h >>> 17; + h ^= h << 5; + } + else if (cellsBusy == 0 && counterCells == as && + U.compareAndSwapInt(this, CELLSBUSY, 0, 1)) { + boolean init = false; + try { // Initialize table + if (counterCells == as) { + CounterCell[] rs = new CounterCell[2]; + rs[h & 1] = new CounterCell(x); + counterCells = rs; + init = true; + } + } finally { + cellsBusy = 0; + } + if (init) + break; + } + else if (U.compareAndSwapLong(this, BASECOUNT, v = baseCount, v + x)) + break; // Fall back on using base + } + hc.code = h; // Record index for next time + } + + // Unsafe mechanics + private static final sun.misc.Unsafe U; + private static final long SIZECTL; + private static final long TRANSFERINDEX; + private static final long BASECOUNT; + private static final long CELLSBUSY; + private static final long CELLVALUE; + private static final long ABASE; + private static final int ASHIFT; + + static { + try { + U = getUnsafe(); + Class k = ConcurrentHashMapV8.class; + SIZECTL = U.objectFieldOffset + (k.getDeclaredField("sizeCtl")); + TRANSFERINDEX = U.objectFieldOffset + (k.getDeclaredField("transferIndex")); + BASECOUNT = U.objectFieldOffset + (k.getDeclaredField("baseCount")); + CELLSBUSY = U.objectFieldOffset + (k.getDeclaredField("cellsBusy")); + Class ck = CounterCell.class; + CELLVALUE = U.objectFieldOffset + (ck.getDeclaredField("value")); + Class ak = Node[].class; + ABASE = U.arrayBaseOffset(ak); + int scale = U.arrayIndexScale(ak); + if ((scale & (scale - 1)) != 0) + throw new Error("data type scale not a power of two"); + ASHIFT = 31 - Integer.numberOfLeadingZeros(scale); + } catch (Exception e) { + throw new Error(e); + } + } + + /** + * Returns a sun.misc.Unsafe. Suitable for use in a 3rd party package. + * Replace with a simple call to Unsafe.getUnsafe when integrating + * into a jdk. + * + * @return a sun.misc.Unsafe + */ + private static sun.misc.Unsafe getUnsafe() { + try { + return sun.misc.Unsafe.getUnsafe(); + } catch (SecurityException tryReflectionInstead) {} + try { + return java.security.AccessController.doPrivileged + (new java.security.PrivilegedExceptionAction() { + public sun.misc.Unsafe run() throws Exception { + Class k = sun.misc.Unsafe.class; + for (java.lang.reflect.Field f : k.getDeclaredFields()) { + f.setAccessible(true); + Object x = f.get(null); + if (k.isInstance(x)) + return k.cast(x); + } + throw new NoSuchFieldError("the Unsafe"); + }}); + } catch (java.security.PrivilegedActionException e) { + throw new RuntimeException("Could not initialize intrinsics", + e.getCause()); + } + } +} + diff --git a/src/main/java/jsr166e/CountedCompleter.java b/src/main/java/jsr166e/CountedCompleter.java new file mode 100644 index 0000000000000..817710519a4f1 --- /dev/null +++ b/src/main/java/jsr166e/CountedCompleter.java @@ -0,0 +1,753 @@ +// Rev 1.31 from http://gee.cs.oswego.edu/cgi-bin/viewcvs.cgi/jsr166/src/jsr166e/CountedCompleter.java?view=log + +/* + * Written by Doug Lea with assistance from members of JCP JSR-166 + * Expert Group and released to the public domain, as explained at + * http://creativecommons.org/publicdomain/zero/1.0/ + */ + +package jsr166e; + +/** + * A {@link ForkJoinTask} with a completion action performed when + * triggered and there are no remaining pending actions. + * CountedCompleters are in general more robust in the + * presence of subtask stalls and blockage than are other forms of + * ForkJoinTasks, but are less intuitive to program. Uses of + * CountedCompleter are similar to those of other completion based + * components (such as {@link java.nio.channels.CompletionHandler}) + * except that multiple pending completions may be necessary + * to trigger the completion action {@link #onCompletion(CountedCompleter)}, + * not just one. + * Unless initialized otherwise, the {@linkplain #getPendingCount pending + * count} starts at zero, but may be (atomically) changed using + * methods {@link #setPendingCount}, {@link #addToPendingCount}, and + * {@link #compareAndSetPendingCount}. Upon invocation of {@link + * #tryComplete}, if the pending action count is nonzero, it is + * decremented; otherwise, the completion action is performed, and if + * this completer itself has a completer, the process is continued + * with its completer. As is the case with related synchronization + * components such as {@link java.util.concurrent.Phaser Phaser} and + * {@link java.util.concurrent.Semaphore Semaphore}, these methods + * affect only internal counts; they do not establish any further + * internal bookkeeping. In particular, the identities of pending + * tasks are not maintained. As illustrated below, you can create + * subclasses that do record some or all pending tasks or their + * results when needed. As illustrated below, utility methods + * supporting customization of completion traversals are also + * provided. However, because CountedCompleters provide only basic + * synchronization mechanisms, it may be useful to create further + * abstract subclasses that maintain linkages, fields, and additional + * support methods appropriate for a set of related usages. + * + *

A concrete CountedCompleter class must define method {@link + * #compute}, that should in most cases (as illustrated below), invoke + * {@code tryComplete()} once before returning. The class may also + * optionally override method {@link #onCompletion(CountedCompleter)} + * to perform an action upon normal completion, and method + * {@link #onExceptionalCompletion(Throwable, CountedCompleter)} to + * perform an action upon any exception. + * + *

CountedCompleters most often do not bear results, in which case + * they are normally declared as {@code CountedCompleter}, and + * will always return {@code null} as a result value. In other cases, + * you should override method {@link #getRawResult} to provide a + * result from {@code join(), invoke()}, and related methods. In + * general, this method should return the value of a field (or a + * function of one or more fields) of the CountedCompleter object that + * holds the result upon completion. Method {@link #setRawResult} by + * default plays no role in CountedCompleters. It is possible, but + * rarely applicable, to override this method to maintain other + * objects or fields holding result data. + * + *

A CountedCompleter that does not itself have a completer (i.e., + * one for which {@link #getCompleter} returns {@code null}) can be + * used as a regular ForkJoinTask with this added functionality. + * However, any completer that in turn has another completer serves + * only as an internal helper for other computations, so its own task + * status (as reported in methods such as {@link ForkJoinTask#isDone}) + * is arbitrary; this status changes only upon explicit invocations of + * {@link #complete}, {@link ForkJoinTask#cancel}, + * {@link ForkJoinTask#completeExceptionally(Throwable)} or upon + * exceptional completion of method {@code compute}. Upon any + * exceptional completion, the exception may be relayed to a task's + * completer (and its completer, and so on), if one exists and it has + * not otherwise already completed. Similarly, cancelling an internal + * CountedCompleter has only a local effect on that completer, so is + * not often useful. + * + *

Sample Usages. + * + *

Parallel recursive decomposition. CountedCompleters may + * be arranged in trees similar to those often used with {@link + * RecursiveAction}s, although the constructions involved in setting + * them up typically vary. Here, the completer of each task is its + * parent in the computation tree. Even though they entail a bit more + * bookkeeping, CountedCompleters may be better choices when applying + * a possibly time-consuming operation (that cannot be further + * subdivided) to each element of an array or collection; especially + * when the operation takes a significantly different amount of time + * to complete for some elements than others, either because of + * intrinsic variation (for example I/O) or auxiliary effects such as + * garbage collection. Because CountedCompleters provide their own + * continuations, other threads need not block waiting to perform + * them. + * + *

For example, here is an initial version of a class that uses + * divide-by-two recursive decomposition to divide work into single + * pieces (leaf tasks). Even when work is split into individual calls, + * tree-based techniques are usually preferable to directly forking + * leaf tasks, because they reduce inter-thread communication and + * improve load balancing. In the recursive case, the second of each + * pair of subtasks to finish triggers completion of its parent + * (because no result combination is performed, the default no-op + * implementation of method {@code onCompletion} is not overridden). + * A static utility method sets up the base task and invokes it + * (here, implicitly using the {@link ForkJoinPool#commonPool()}). + * + * 

 {@code
+ * class MyOperation { void apply(E e) { ... }  }
+ *
+ * class ForEach extends CountedCompleter {
+ *
+ *   public static  void forEach(E[] array, MyOperation op) {
+ *     new ForEach(null, array, op, 0, array.length).invoke();
+ *   }
+ *
+ *   final E[] array; final MyOperation op; final int lo, hi;
+ *   ForEach(CountedCompleter p, E[] array, MyOperation op, int lo, int hi) {
+ *     super(p);
+ *     this.array = array; this.op = op; this.lo = lo; this.hi = hi;
+ *   }
+ *
+ *   public void compute() { // version 1
+ *     if (hi - lo >= 2) {
+ *       int mid = (lo + hi) >>> 1;
+ *       setPendingCount(2); // must set pending count before fork
+ *       new ForEach(this, array, op, mid, hi).fork(); // right child
+ *       new ForEach(this, array, op, lo, mid).fork(); // left child
+ *     }
+ *     else if (hi > lo)
+ *       op.apply(array[lo]);
+ *     tryComplete();
+ *   }
+ * }}
+ * + * This design can be improved by noticing that in the recursive case, + * the task has nothing to do after forking its right task, so can + * directly invoke its left task before returning. (This is an analog + * of tail recursion removal.) Also, because the task returns upon + * executing its left task (rather than falling through to invoke + * {@code tryComplete}) the pending count is set to one: + * + * 
 {@code
+ * class ForEach ...
+ *   public void compute() { // version 2
+ *     if (hi - lo >= 2) {
+ *       int mid = (lo + hi) >>> 1;
+ *       setPendingCount(1); // only one pending
+ *       new ForEach(this, array, op, mid, hi).fork(); // right child
+ *       new ForEach(this, array, op, lo, mid).compute(); // direct invoke
+ *     }
+ *     else {
+ *       if (hi > lo)
+ *         op.apply(array[lo]);
+ *       tryComplete();
+ *     }
+ *   }
+ * }
+ * + * As a further improvement, notice that the left task need not even exist. + * Instead of creating a new one, we can iterate using the original task, + * and add a pending count for each fork. Additionally, because no task + * in this tree implements an {@link #onCompletion(CountedCompleter)} method, + * {@code tryComplete()} can be replaced with {@link #propagateCompletion}. + * + * 
 {@code
+ * class ForEach ...
+ *   public void compute() { // version 3
+ *     int l = lo,  h = hi;
+ *     while (h - l >= 2) {
+ *       int mid = (l + h) >>> 1;
+ *       addToPendingCount(1);
+ *       new ForEach(this, array, op, mid, h).fork(); // right child
+ *       h = mid;
+ *     }
+ *     if (h > l)
+ *       op.apply(array[l]);
+ *     propagateCompletion();
+ *   }
+ * }
+ * + * Additional improvements of such classes might entail precomputing + * pending counts so that they can be established in constructors, + * specializing classes for leaf steps, subdividing by say, four, + * instead of two per iteration, and using an adaptive threshold + * instead of always subdividing down to single elements. + * + *

Searching. A tree of CountedCompleters can search for a + * value or property in different parts of a data structure, and + * report a result in an {@link + * java.util.concurrent.atomic.AtomicReference AtomicReference} as + * soon as one is found. The others can poll the result to avoid + * unnecessary work. (You could additionally {@linkplain #cancel + * cancel} other tasks, but it is usually simpler and more efficient + * to just let them notice that the result is set and if so skip + * further processing.) Illustrating again with an array using full + * partitioning (again, in practice, leaf tasks will almost always + * process more than one element): + * + * 

 {@code
+ * class Searcher extends CountedCompleter {
+ *   final E[] array; final AtomicReference result; final int lo, hi;
+ *   Searcher(CountedCompleter p, E[] array, AtomicReference result, int lo, int hi) {
+ *     super(p);
+ *     this.array = array; this.result = result; this.lo = lo; this.hi = hi;
+ *   }
+ *   public E getRawResult() { return result.get(); }
+ *   public void compute() { // similar to ForEach version 3
+ *     int l = lo,  h = hi;
+ *     while (result.get() == null && h >= l) {
+ *       if (h - l >= 2) {
+ *         int mid = (l + h) >>> 1;
+ *         addToPendingCount(1);
+ *         new Searcher(this, array, result, mid, h).fork();
+ *         h = mid;
+ *       }
+ *       else {
+ *         E x = array[l];
+ *         if (matches(x) && result.compareAndSet(null, x))
+ *           quietlyCompleteRoot(); // root task is now joinable
+ *         break;
+ *       }
+ *     }
+ *     tryComplete(); // normally complete whether or not found
+ *   }
+ *   boolean matches(E e) { ... } // return true if found
+ *
+ *   public static  E search(E[] array) {
+ *       return new Searcher(null, array, new AtomicReference(), 0, array.length).invoke();
+ *   }
+ * }}
+ * + * In this example, as well as others in which tasks have no other + * effects except to compareAndSet a common result, the trailing + * unconditional invocation of {@code tryComplete} could be made + * conditional ({@code if (result.get() == null) tryComplete();}) + * because no further bookkeeping is required to manage completions + * once the root task completes. + * + *

Recording subtasks. CountedCompleter tasks that combine + * results of multiple subtasks usually need to access these results + * in method {@link #onCompletion(CountedCompleter)}. As illustrated in the following + * class (that performs a simplified form of map-reduce where mappings + * and reductions are all of type {@code E}), one way to do this in + * divide and conquer designs is to have each subtask record its + * sibling, so that it can be accessed in method {@code onCompletion}. + * This technique applies to reductions in which the order of + * combining left and right results does not matter; ordered + * reductions require explicit left/right designations. Variants of + * other streamlinings seen in the above examples may also apply. + * + * 

 {@code
+ * class MyMapper { E apply(E v) {  ...  } }
+ * class MyReducer { E apply(E x, E y) {  ...  } }
+ * class MapReducer extends CountedCompleter {
+ *   final E[] array; final MyMapper mapper;
+ *   final MyReducer reducer; final int lo, hi;
+ *   MapReducer sibling;
+ *   E result;
+ *   MapReducer(CountedCompleter p, E[] array, MyMapper mapper,
+ *              MyReducer reducer, int lo, int hi) {
+ *     super(p);
+ *     this.array = array; this.mapper = mapper;
+ *     this.reducer = reducer; this.lo = lo; this.hi = hi;
+ *   }
+ *   public void compute() {
+ *     if (hi - lo >= 2) {
+ *       int mid = (lo + hi) >>> 1;
+ *       MapReducer left = new MapReducer(this, array, mapper, reducer, lo, mid);
+ *       MapReducer right = new MapReducer(this, array, mapper, reducer, mid, hi);
+ *       left.sibling = right;
+ *       right.sibling = left;
+ *       setPendingCount(1); // only right is pending
+ *       right.fork();
+ *       left.compute();     // directly execute left
+ *     }
+ *     else {
+ *       if (hi > lo)
+ *           result = mapper.apply(array[lo]);
+ *       tryComplete();
+ *     }
+ *   }
+ *   public void onCompletion(CountedCompleter caller) {
+ *     if (caller != this) {
+ *       MapReducer child = (MapReducer)caller;
+ *       MapReducer sib = child.sibling;
+ *       if (sib == null || sib.result == null)
+ *         result = child.result;
+ *       else
+ *         result = reducer.apply(child.result, sib.result);
+ *     }
+ *   }
+ *   public E getRawResult() { return result; }
+ *
+ *   public static  E mapReduce(E[] array, MyMapper mapper, MyReducer reducer) {
+ *     return new MapReducer(null, array, mapper, reducer,
+ *                              0, array.length).invoke();
+ *   }
+ * }}
+ * + * Here, method {@code onCompletion} takes a form common to many + * completion designs that combine results. This callback-style method + * is triggered once per task, in either of the two different contexts + * in which the pending count is, or becomes, zero: (1) by a task + * itself, if its pending count is zero upon invocation of {@code + * tryComplete}, or (2) by any of its subtasks when they complete and + * decrement the pending count to zero. The {@code caller} argument + * distinguishes cases. Most often, when the caller is {@code this}, + * no action is necessary. Otherwise the caller argument can be used + * (usually via a cast) to supply a value (and/or links to other + * values) to be combined. Assuming proper use of pending counts, the + * actions inside {@code onCompletion} occur (once) upon completion of + * a task and its subtasks. No additional synchronization is required + * within this method to ensure thread safety of accesses to fields of + * this task or other completed tasks. + * + *

Completion Traversals. If using {@code onCompletion} to + * process completions is inapplicable or inconvenient, you can use + * methods {@link #firstComplete} and {@link #nextComplete} to create + * custom traversals. For example, to define a MapReducer that only + * splits out right-hand tasks in the form of the third ForEach + * example, the completions must cooperatively reduce along + * unexhausted subtask links, which can be done as follows: + * + * 

 {@code
+ * class MapReducer extends CountedCompleter { // version 2
+ *   final E[] array; final MyMapper mapper;
+ *   final MyReducer reducer; final int lo, hi;
+ *   MapReducer forks, next; // record subtask forks in list
+ *   E result;
+ *   MapReducer(CountedCompleter p, E[] array, MyMapper mapper,
+ *              MyReducer reducer, int lo, int hi, MapReducer next) {
+ *     super(p);
+ *     this.array = array; this.mapper = mapper;
+ *     this.reducer = reducer; this.lo = lo; this.hi = hi;
+ *     this.next = next;
+ *   }
+ *   public void compute() {
+ *     int l = lo,  h = hi;
+ *     while (h - l >= 2) {
+ *       int mid = (l + h) >>> 1;
+ *       addToPendingCount(1);
+ *       (forks = new MapReducer(this, array, mapper, reducer, mid, h, forks)).fork();
+ *       h = mid;
+ *     }
+ *     if (h > l)
+ *       result = mapper.apply(array[l]);
+ *     // process completions by reducing along and advancing subtask links
+ *     for (CountedCompleter c = firstComplete(); c != null; c = c.nextComplete()) {
+ *       for (MapReducer t = (MapReducer)c, s = t.forks;  s != null; s = t.forks = s.next)
+ *         t.result = reducer.apply(t.result, s.result);
+ *     }
+ *   }
+ *   public E getRawResult() { return result; }
+ *
+ *   public static  E mapReduce(E[] array, MyMapper mapper, MyReducer reducer) {
+ *     return new MapReducer(null, array, mapper, reducer,
+ *                              0, array.length, null).invoke();
+ *   }
+ * }}
+ * + *

Triggers. Some CountedCompleters are themselves never + * forked, but instead serve as bits of plumbing in other designs; + * including those in which the completion of one or more async tasks + * triggers another async task. For example: + * + * 

 {@code
+ * class HeaderBuilder extends CountedCompleter<...> { ... }
+ * class BodyBuilder extends CountedCompleter<...> { ... }
+ * class PacketSender extends CountedCompleter<...> {
+ *   PacketSender(...) { super(null, 1); ... } // trigger on second completion
+ *   public void compute() { } // never called
+ *   public void onCompletion(CountedCompleter caller) { sendPacket(); }
+ * }
+ * // sample use:
+ * PacketSender p = new PacketSender();
+ * new HeaderBuilder(p, ...).fork();
+ * new BodyBuilder(p, ...).fork();
+ * }
+ * + * @since 1.8 + * @author Doug Lea + */ +public abstract class CountedCompleter extends ForkJoinTask { + private static final long serialVersionUID = 5232453752276485070L; + + /** This task's completer, or null if none */ + final CountedCompleter completer; + /** The number of pending tasks until completion */ + volatile int pending; + + /** + * Creates a new CountedCompleter with the given completer + * and initial pending count. + * + * @param completer this task's completer, or {@code null} if none + * @param initialPendingCount the initial pending count + */ + protected CountedCompleter(CountedCompleter completer, + int initialPendingCount) { + this.completer = completer; + this.pending = initialPendingCount; + } + + /** + * Creates a new CountedCompleter with the given completer + * and an initial pending count of zero. + * + * @param completer this task's completer, or {@code null} if none + */ + protected CountedCompleter(CountedCompleter completer) { + this.completer = completer; + } + + /** + * Creates a new CountedCompleter with no completer + * and an initial pending count of zero. + */ + protected CountedCompleter() { + this.completer = null; + } + + /** + * The main computation performed by this task. + */ + public abstract void compute(); + + /** + * Performs an action when method {@link #tryComplete} is invoked + * and the pending count is zero, or when the unconditional + * method {@link #complete} is invoked. By default, this method + * does nothing. You can distinguish cases by checking the + * identity of the given caller argument. If not equal to {@code + * this}, then it is typically a subtask that may contain results + * (and/or links to other results) to combine. + * + * @param caller the task invoking this method (which may + * be this task itself) + */ + public void onCompletion(CountedCompleter caller) { + } + + /** + * Performs an action when method {@link + * #completeExceptionally(Throwable)} is invoked or method {@link + * #compute} throws an exception, and this task has not already + * otherwise completed normally. On entry to this method, this task + * {@link ForkJoinTask#isCompletedAbnormally}. The return value + * of this method controls further propagation: If {@code true} + * and this task has a completer that has not completed, then that + * completer is also completed exceptionally, with the same + * exception as this completer. The default implementation of + * this method does nothing except return {@code true}. + * + * @param ex the exception + * @param caller the task invoking this method (which may + * be this task itself) + * @return {@code true} if this exception should be propagated to this + * task's completer, if one exists + */ + public boolean onExceptionalCompletion(Throwable ex, CountedCompleter caller) { + return true; + } + + /** + * Returns the completer established in this task's constructor, + * or {@code null} if none. + * + * @return the completer + */ + public final CountedCompleter getCompleter() { + return completer; + } + + /** + * Returns the current pending count. + * + * @return the current pending count + */ + public final int getPendingCount() { + return pending; + } + + /** + * Sets the pending count to the given value. + * + * @param count the count + */ + public final void setPendingCount(int count) { + pending = count; + } + + /** + * Adds (atomically) the given value to the pending count. + * + * @param delta the value to add + */ + public final void addToPendingCount(int delta) { + int c; + do {} while (!U.compareAndSwapInt(this, PENDING, c = pending, c+delta)); + } + + /** + * Sets (atomically) the pending count to the given count only if + * it currently holds the given expected value. + * + * @param expected the expected value + * @param count the new value + * @return {@code true} if successful + */ + public final boolean compareAndSetPendingCount(int expected, int count) { + return U.compareAndSwapInt(this, PENDING, expected, count); + } + + /** + * If the pending count is nonzero, (atomically) decrements it. + * + * @return the initial (undecremented) pending count holding on entry + * to this method + */ + public final int decrementPendingCountUnlessZero() { + int c; + do {} while ((c = pending) != 0 && + !U.compareAndSwapInt(this, PENDING, c, c - 1)); + return c; + } + + /** + * Returns the root of the current computation; i.e., this + * task if it has no completer, else its completer's root. + * + * @return the root of the current computation + */ + public final CountedCompleter getRoot() { + CountedCompleter a = this, p; + while ((p = a.completer) != null) + a = p; + return a; + } + + /** + * If the pending count is nonzero, decrements the count; + * otherwise invokes {@link #onCompletion(CountedCompleter)} + * and then similarly tries to complete this task's completer, + * if one exists, else marks this task as complete. + */ + public final void tryComplete() { + CountedCompleter a = this, s = a; + for (int c;;) { + if ((c = a.pending) == 0) { + a.onCompletion(s); + if ((a = (s = a).completer) == null) { + s.quietlyComplete(); + return; + } + } + else if (U.compareAndSwapInt(a, PENDING, c, c - 1)) + return; + } + } + + /** + * Equivalent to {@link #tryComplete} but does not invoke {@link + * #onCompletion(CountedCompleter)} along the completion path: + * If the pending count is nonzero, decrements the count; + * otherwise, similarly tries to complete this task's completer, if + * one exists, else marks this task as complete. This method may be + * useful in cases where {@code onCompletion} should not, or need + * not, be invoked for each completer in a computation. + */ + public final void propagateCompletion() { + CountedCompleter a = this, s = a; + for (int c;;) { + if ((c = a.pending) == 0) { + if ((a = (s = a).completer) == null) { + s.quietlyComplete(); + return; + } + } + else if (U.compareAndSwapInt(a, PENDING, c, c - 1)) + return; + } + } + + /** + * Regardless of pending count, invokes + * {@link #onCompletion(CountedCompleter)}, marks this task as + * complete and further triggers {@link #tryComplete} on this + * task's completer, if one exists. The given rawResult is + * used as an argument to {@link #setRawResult} before invoking + * {@link #onCompletion(CountedCompleter)} or marking this task + * as complete; its value is meaningful only for classes + * overriding {@code setRawResult}. This method does not modify + * the pending count. + * + *

This method may be useful when forcing completion as soon as + * any one (versus all) of several subtask results are obtained. + * However, in the common (and recommended) case in which {@code + * setRawResult} is not overridden, this effect can be obtained + * more simply using {@code quietlyCompleteRoot();}. + * + * @param rawResult the raw result + */ + public void complete(T rawResult) { + CountedCompleter p; + setRawResult(rawResult); + onCompletion(this); + quietlyComplete(); + if ((p = completer) != null) + p.tryComplete(); + } + + + /** + * If this task's pending count is zero, returns this task; + * otherwise decrements its pending count and returns {@code + * null}. This method is designed to be used with {@link + * #nextComplete} in completion traversal loops. + * + * @return this task, if pending count was zero, else {@code null} + */ + public final CountedCompleter firstComplete() { + for (int c;;) { + if ((c = pending) == 0) + return this; + else if (U.compareAndSwapInt(this, PENDING, c, c - 1)) + return null; + } + } + + /** + * If this task does not have a completer, invokes {@link + * ForkJoinTask#quietlyComplete} and returns {@code null}. Or, if + * the completer's pending count is non-zero, decrements that + * pending count and returns {@code null}. Otherwise, returns the + * completer. This method can be used as part of a completion + * traversal loop for homogeneous task hierarchies: + * + * 

 {@code
+     * for (CountedCompleter c = firstComplete();
+     *      c != null;
+     *      c = c.nextComplete()) {
+     *   // ... process c ...
+     * }}
+ * + * @return the completer, or {@code null} if none + */ + public final CountedCompleter nextComplete() { + CountedCompleter p; + if ((p = completer) != null) + return p.firstComplete(); + else { + quietlyComplete(); + return null; + } + } + + /** + * Equivalent to {@code getRoot().quietlyComplete()}. + */ + public final void quietlyCompleteRoot() { + for (CountedCompleter a = this, p;;) { + if ((p = a.completer) == null) { + a.quietlyComplete(); + return; + } + a = p; + } + } + + /** + * Supports ForkJoinTask exception propagation. + */ + void internalPropagateException(Throwable ex) { + CountedCompleter a = this, s = a; + while (a.onExceptionalCompletion(ex, s) && + (a = (s = a).completer) != null && a.status >= 0 && + a.recordExceptionalCompletion(ex) == EXCEPTIONAL) + ; + } + + /** + * Implements execution conventions for CountedCompleters. + */ + protected final boolean exec() { + compute(); + return false; + } + + /** + * Returns the result of the computation. By default, + * returns {@code null}, which is appropriate for {@code Void} + * actions, but in other cases should be overridden, almost + * always to return a field or function of a field that + * holds the result upon completion. + * + * @return the result of the computation + */ + public T getRawResult() { return null; } + + /** + * A method that result-bearing CountedCompleters may optionally + * use to help maintain result data. By default, does nothing. + * Overrides are not recommended. However, if this method is + * overridden to update existing objects or fields, then it must + * in general be defined to be thread-safe. + */ + protected void setRawResult(T t) { } + + // Unsafe mechanics + private static final sun.misc.Unsafe U; + private static final long PENDING; + static { + try { + U = getUnsafe(); + PENDING = U.objectFieldOffset + (CountedCompleter.class.getDeclaredField("pending")); + } catch (Exception e) { + throw new Error(e); + } + } + + /** + * Returns a sun.misc.Unsafe. Suitable for use in a 3rd party package. + * Replace with a simple call to Unsafe.getUnsafe when integrating + * into a jdk. + * + * @return a sun.misc.Unsafe + */ + private static sun.misc.Unsafe getUnsafe() { + try { + return sun.misc.Unsafe.getUnsafe(); + } catch (SecurityException tryReflectionInstead) {} + try { + return java.security.AccessController.doPrivileged + (new java.security.PrivilegedExceptionAction() { + public sun.misc.Unsafe run() throws Exception { + Class k = sun.misc.Unsafe.class; + for (java.lang.reflect.Field f : k.getDeclaredFields()) { + f.setAccessible(true); + Object x = f.get(null); + if (k.isInstance(x)) + return k.cast(x); + } + throw new NoSuchFieldError("the Unsafe"); + }}); + } catch (java.security.PrivilegedActionException e) { + throw new RuntimeException("Could not initialize intrinsics", + e.getCause()); + } + } +} + diff --git a/src/main/java/jsr166e/ForkJoinPool.java b/src/main/java/jsr166e/ForkJoinPool.java new file mode 100644 index 0000000000000..be1c18cbce6d0 --- /dev/null +++ b/src/main/java/jsr166e/ForkJoinPool.java @@ -0,0 +1,3345 @@ +// Rev 1.64 from http://gee.cs.oswego.edu/cgi-bin/viewcvs.cgi/jsr166/src/jsr166e/ForkJoinPool.java?view=co + +/* + * Written by Doug Lea with assistance from members of JCP JSR-166 + * Expert Group and released to the public domain, as explained at + * http://creativecommons.org/publicdomain/zero/1.0/ + */ + +package jsr166e; + +import java.lang.Thread.UncaughtExceptionHandler; +import java.util.ArrayList; +import java.util.Arrays; +import java.util.Collection; +import java.util.Collections; +import java.util.List; +import java.util.concurrent.AbstractExecutorService; +import java.util.concurrent.Callable; +import java.util.concurrent.ExecutorService; +import java.util.concurrent.Future; +import java.util.concurrent.RejectedExecutionException; +import java.util.concurrent.RunnableFuture; +import java.util.concurrent.TimeUnit; + +/** + * An {@link ExecutorService} for running {@link ForkJoinTask}s. + * A {@code ForkJoinPool} provides the entry point for submissions + * from non-{@code ForkJoinTask} clients, as well as management and + * monitoring operations. + * + *

A {@code ForkJoinPool} differs from other kinds of {@link + * ExecutorService} mainly by virtue of employing + * work-stealing: all threads in the pool attempt to find and + * execute tasks submitted to the pool and/or created by other active + * tasks (eventually blocking waiting for work if none exist). This + * enables efficient processing when most tasks spawn other subtasks + * (as do most {@code ForkJoinTask}s), as well as when many small + * tasks are submitted to the pool from external clients. Especially + * when setting asyncMode to true in constructors, {@code + * ForkJoinPool}s may also be appropriate for use with event-style + * tasks that are never joined. + * + *

A static {@link #commonPool()} is available and appropriate for + * most applications. The common pool is used by any ForkJoinTask that + * is not explicitly submitted to a specified pool. Using the common + * pool normally reduces resource usage (its threads are slowly + * reclaimed during periods of non-use, and reinstated upon subsequent + * use). + * + *

For applications that require separate or custom pools, a {@code + * ForkJoinPool} may be constructed with a given target parallelism + * level; by default, equal to the number of available processors. The + * pool attempts to maintain enough active (or available) threads by + * dynamically adding, suspending, or resuming internal worker + * threads, even if some tasks are stalled waiting to join others. + * However, no such adjustments are guaranteed in the face of blocked + * I/O or other unmanaged synchronization. The nested {@link + * ManagedBlocker} interface enables extension of the kinds of + * synchronization accommodated. + * + *

In addition to execution and lifecycle control methods, this + * class provides status check methods (for example + * {@link #getStealCount}) that are intended to aid in developing, + * tuning, and monitoring fork/join applications. Also, method + * {@link #toString} returns indications of pool state in a + * convenient form for informal monitoring. + * + *

As is the case with other ExecutorServices, there are three + * main task execution methods summarized in the following table. + * These are designed to be used primarily by clients not already + * engaged in fork/join computations in the current pool. The main + * forms of these methods accept instances of {@code ForkJoinTask}, + * but overloaded forms also allow mixed execution of plain {@code + * Runnable}- or {@code Callable}- based activities as well. However, + * tasks that are already executing in a pool should normally instead + * use the within-computation forms listed in the table unless using + * async event-style tasks that are not usually joined, in which case + * there is little difference among choice of methods. + * + * + * + * + * + * + * + * + * + * + * + * + * + * + * + * + * + * + * + * + * + * + * + *
Summary of task execution methods
Call from non-fork/join clients Call from within fork/join computations
Arrange async execution {@link #execute(ForkJoinTask)} {@link ForkJoinTask#fork}
Await and obtain result {@link #invoke(ForkJoinTask)} {@link ForkJoinTask#invoke}
Arrange exec and obtain Future {@link #submit(ForkJoinTask)} {@link ForkJoinTask#fork} (ForkJoinTasks are Futures)
+ * + *

The common pool is by default constructed with default + * parameters, but these may be controlled by setting three + * {@linkplain System#getProperty system properties}: + *

    + *
  • {@code java.util.concurrent.ForkJoinPool.common.parallelism} + * - the parallelism level, a non-negative integer + *
  • {@code java.util.concurrent.ForkJoinPool.common.threadFactory} + * - the class name of a {@link ForkJoinWorkerThreadFactory} + *
  • {@code java.util.concurrent.ForkJoinPool.common.exceptionHandler} + * - the class name of a {@link UncaughtExceptionHandler} + *
+ * The system class loader is used to load these classes. + * Upon any error in establishing these settings, default parameters + * are used. It is possible to disable or limit the use of threads in + * the common pool by setting the parallelism property to zero, and/or + * using a factory that may return {@code null}. + * + *

Implementation notes: This implementation restricts the + * maximum number of running threads to 32767. Attempts to create + * pools with greater than the maximum number result in + * {@code IllegalArgumentException}. + * + *

This implementation rejects submitted tasks (that is, by throwing + * {@link RejectedExecutionException}) only when the pool is shut down + * or internal resources have been exhausted. + * + * @since 1.7 + * @author Doug Lea + */ +public class ForkJoinPool extends AbstractExecutorService { + + /* + * Implementation Overview + * + * This class and its nested classes provide the main + * functionality and control for a set of worker threads: + * Submissions from non-FJ threads enter into submission queues. + * Workers take these tasks and typically split them into subtasks + * that may be stolen by other workers. Preference rules give + * first priority to processing tasks from their own queues (LIFO + * or FIFO, depending on mode), then to randomized FIFO steals of + * tasks in other queues. + * + * WorkQueues + * ========== + * + * Most operations occur within work-stealing queues (in nested + * class WorkQueue). These are special forms of Deques that + * support only three of the four possible end-operations -- push, + * pop, and poll (aka steal), under the further constraints that + * push and pop are called only from the owning thread (or, as + * extended here, under a lock), while poll may be called from + * other threads. (If you are unfamiliar with them, you probably + * want to read Herlihy and Shavit's book "The Art of + * Multiprocessor programming", chapter 16 describing these in + * more detail before proceeding.) The main work-stealing queue + * design is roughly similar to those in the papers "Dynamic + * Circular Work-Stealing Deque" by Chase and Lev, SPAA 2005 + * (http://research.sun.com/scalable/pubs/index.html) and + * "Idempotent work stealing" by Michael, Saraswat, and Vechev, + * PPoPP 2009 (http://portal.acm.org/citation.cfm?id=1504186). + * See also "Correct and Efficient Work-Stealing for Weak Memory + * Models" by Le, Pop, Cohen, and Nardelli, PPoPP 2013 + * (http://www.di.ens.fr/~zappa/readings/ppopp13.pdf) for an + * analysis of memory ordering (atomic, volatile etc) issues. The + * main differences ultimately stem from GC requirements that we + * null out taken slots as soon as we can, to maintain as small a + * footprint as possible even in programs generating huge numbers + * of tasks. To accomplish this, we shift the CAS arbitrating pop + * vs poll (steal) from being on the indices ("base" and "top") to + * the slots themselves. So, both a successful pop and poll + * mainly entail a CAS of a slot from non-null to null. Because + * we rely on CASes of references, we do not need tag bits on base + * or top. They are simple ints as used in any circular + * array-based queue (see for example ArrayDeque). Updates to the + * indices must still be ordered in a way that guarantees that top + * == base means the queue is empty, but otherwise may err on the + * side of possibly making the queue appear nonempty when a push, + * pop, or poll have not fully committed. Note that this means + * that the poll operation, considered individually, is not + * wait-free. One thief cannot successfully continue until another + * in-progress one (or, if previously empty, a push) completes. + * However, in the aggregate, we ensure at least probabilistic + * non-blockingness. If an attempted steal fails, a thief always + * chooses a different random victim target to try next. So, in + * order for one thief to progress, it suffices for any + * in-progress poll or new push on any empty queue to + * complete. (This is why we normally use method pollAt and its + * variants that try once at the apparent base index, else + * consider alternative actions, rather than method poll.) + * + * This approach also enables support of a user mode in which local + * task processing is in FIFO, not LIFO order, simply by using + * poll rather than pop. This can be useful in message-passing + * frameworks in which tasks are never joined. However neither + * mode considers affinities, loads, cache localities, etc, so + * rarely provide the best possible performance on a given + * machine, but portably provide good throughput by averaging over + * these factors. (Further, even if we did try to use such + * information, we do not usually have a basis for exploiting it. + * For example, some sets of tasks profit from cache affinities, + * but others are harmed by cache pollution effects.) + * + * WorkQueues are also used in a similar way for tasks submitted + * to the pool. We cannot mix these tasks in the same queues used + * for work-stealing (this would contaminate lifo/fifo + * processing). Instead, we randomly associate submission queues + * with submitting threads, using a form of hashing. The + * Submitter probe value serves as a hash code for + * choosing existing queues, and may be randomly repositioned upon + * contention with other submitters. In essence, submitters act + * like workers except that they are restricted to executing local + * tasks that they submitted (or in the case of CountedCompleters, + * others with the same root task). However, because most + * shared/external queue operations are more expensive than + * internal, and because, at steady state, external submitters + * will compete for CPU with workers, ForkJoinTask.join and + * related methods disable them from repeatedly helping to process + * tasks if all workers are active. Insertion of tasks in shared + * mode requires a lock (mainly to protect in the case of + * resizing) but we use only a simple spinlock (using bits in + * field qlock), because submitters encountering a busy queue move + * on to try or create other queues -- they block only when + * creating and registering new queues. + * + * Management + * ========== + * + * The main throughput advantages of work-stealing stem from + * decentralized control -- workers mostly take tasks from + * themselves or each other. We cannot negate this in the + * implementation of other management responsibilities. The main + * tactic for avoiding bottlenecks is packing nearly all + * essentially atomic control state into two volatile variables + * that are by far most often read (not written) as status and + * consistency checks. + * + * Field "ctl" contains 64 bits holding all the information needed + * to atomically decide to add, inactivate, enqueue (on an event + * queue), dequeue, and/or re-activate workers. To enable this + * packing, we restrict maximum parallelism to (1<<15)-1 (which is + * far in excess of normal operating range) to allow ids, counts, + * and their negations (used for thresholding) to fit into 16bit + * fields. + * + * Field "plock" is a form of sequence lock with a saturating + * shutdown bit (similarly for per-queue "qlocks"), mainly + * protecting updates to the workQueues array, as well as to + * enable shutdown. When used as a lock, it is normally only very + * briefly held, so is nearly always available after at most a + * brief spin, but we use a monitor-based backup strategy to + * block when needed. + * + * Recording WorkQueues. WorkQueues are recorded in the + * "workQueues" array that is created upon first use and expanded + * if necessary. Updates to the array while recording new workers + * and unrecording terminated ones are protected from each other + * by a lock but the array is otherwise concurrently readable, and + * accessed directly. To simplify index-based operations, the + * array size is always a power of two, and all readers must + * tolerate null slots. Worker queues are at odd indices. Shared + * (submission) queues are at even indices, up to a maximum of 64 + * slots, to limit growth even if array needs to expand to add + * more workers. Grouping them together in this way simplifies and + * speeds up task scanning. + * + * All worker thread creation is on-demand, triggered by task + * submissions, replacement of terminated workers, and/or + * compensation for blocked workers. However, all other support + * code is set up to work with other policies. To ensure that we + * do not hold on to worker references that would prevent GC, ALL + * accesses to workQueues are via indices into the workQueues + * array (which is one source of some of the messy code + * constructions here). In essence, the workQueues array serves as + * a weak reference mechanism. Thus for example the wait queue + * field of ctl stores indices, not references. Access to the + * workQueues in associated methods (for example signalWork) must + * both index-check and null-check the IDs. All such accesses + * ignore bad IDs by returning out early from what they are doing, + * since this can only be associated with termination, in which + * case it is OK to give up. All uses of the workQueues array + * also check that it is non-null (even if previously + * non-null). This allows nulling during termination, which is + * currently not necessary, but remains an option for + * resource-revocation-based shutdown schemes. It also helps + * reduce JIT issuance of uncommon-trap code, which tends to + * unnecessarily complicate control flow in some methods. + * + * Event Queuing. Unlike HPC work-stealing frameworks, we cannot + * let workers spin indefinitely scanning for tasks when none can + * be found immediately, and we cannot start/resume workers unless + * there appear to be tasks available. On the other hand, we must + * quickly prod them into action when new tasks are submitted or + * generated. In many usages, ramp-up time to activate workers is + * the main limiting factor in overall performance (this is + * compounded at program start-up by JIT compilation and + * allocation). So we try to streamline this as much as possible. + * We park/unpark workers after placing in an event wait queue + * when they cannot find work. This "queue" is actually a simple + * Treiber stack, headed by the "id" field of ctl, plus a 15bit + * counter value (that reflects the number of times a worker has + * been inactivated) to avoid ABA effects (we need only as many + * version numbers as worker threads). Successors are held in + * field WorkQueue.nextWait. Queuing deals with several intrinsic + * races, mainly that a task-producing thread can miss seeing (and + * signalling) another thread that gave up looking for work but + * has not yet entered the wait queue. We solve this by requiring + * a full sweep of all workers (via repeated calls to method + * scan()) both before and after a newly waiting worker is added + * to the wait queue. Because enqueued workers may actually be + * rescanning rather than waiting, we set and clear the "parker" + * field of WorkQueues to reduce unnecessary calls to unpark. + * (This requires a secondary recheck to avoid missed signals.) + * Note the unusual conventions about Thread.interrupts + * surrounding parking and other blocking: Because interrupts are + * used solely to alert threads to check termination, which is + * checked anyway upon blocking, we clear status (using + * Thread.interrupted) before any call to park, so that park does + * not immediately return due to status being set via some other + * unrelated call to interrupt in user code. + * + * Signalling. We create or wake up workers only when there + * appears to be at least one task they might be able to find and + * execute. When a submission is added or another worker adds a + * task to a queue that has fewer than two tasks, they signal + * waiting workers (or trigger creation of new ones if fewer than + * the given parallelism level -- signalWork). These primary + * signals are buttressed by others whenever other threads remove + * a task from a queue and notice that there are other tasks there + * as well. So in general, pools will be over-signalled. On most + * platforms, signalling (unpark) overhead time is noticeably + * long, and the time between signalling a thread and it actually + * making progress can be very noticeably long, so it is worth + * offloading these delays from critical paths as much as + * possible. Additionally, workers spin-down gradually, by staying + * alive so long as they see the ctl state changing. Similar + * stability-sensing techniques are also used before blocking in + * awaitJoin and helpComplete. + * + * Trimming workers. To release resources after periods of lack of + * use, a worker starting to wait when the pool is quiescent will + * time out and terminate if the pool has remained quiescent for a + * given period -- a short period if there are more threads than + * parallelism, longer as the number of threads decreases. This + * will slowly propagate, eventually terminating all workers after + * periods of non-use. + * + * Shutdown and Termination. A call to shutdownNow atomically sets + * a plock bit and then (non-atomically) sets each worker's + * qlock status, cancels all unprocessed tasks, and wakes up + * all waiting workers. Detecting whether termination should + * commence after a non-abrupt shutdown() call requires more work + * and bookkeeping. We need consensus about quiescence (i.e., that + * there is no more work). The active count provides a primary + * indication but non-abrupt shutdown still requires a rechecking + * scan for any workers that are inactive but not queued. + * + * Joining Tasks + * ============= + * + * Any of several actions may be taken when one worker is waiting + * to join a task stolen (or always held) by another. Because we + * are multiplexing many tasks on to a pool of workers, we can't + * just let them block (as in Thread.join). We also cannot just + * reassign the joiner's run-time stack with another and replace + * it later, which would be a form of "continuation", that even if + * possible is not necessarily a good idea since we sometimes need + * both an unblocked task and its continuation to progress. + * Instead we combine two tactics: + * + * Helping: Arranging for the joiner to execute some task that it + * would be running if the steal had not occurred. + * + * Compensating: Unless there are already enough live threads, + * method tryCompensate() may create or re-activate a spare + * thread to compensate for blocked joiners until they unblock. + * + * A third form (implemented in tryRemoveAndExec) amounts to + * helping a hypothetical compensator: If we can readily tell that + * a possible action of a compensator is to steal and execute the + * task being joined, the joining thread can do so directly, + * without the need for a compensation thread (although at the + * expense of larger run-time stacks, but the tradeoff is + * typically worthwhile). + * + * The ManagedBlocker extension API can't use helping so relies + * only on compensation in method awaitBlocker. + * + * The algorithm in tryHelpStealer entails a form of "linear" + * helping: Each worker records (in field currentSteal) the most + * recent task it stole from some other worker. Plus, it records + * (in field currentJoin) the task it is currently actively + * joining. Method tryHelpStealer uses these markers to try to + * find a worker to help (i.e., steal back a task from and execute + * it) that could hasten completion of the actively joined task. + * In essence, the joiner executes a task that would be on its own + * local deque had the to-be-joined task not been stolen. This may + * be seen as a conservative variant of the approach in Wagner & + * Calder "Leapfrogging: a portable technique for implementing + * efficient futures" SIGPLAN Notices, 1993 + * (http://portal.acm.org/citation.cfm?id=155354). It differs in + * that: (1) We only maintain dependency links across workers upon + * steals, rather than use per-task bookkeeping. This sometimes + * requires a linear scan of workQueues array to locate stealers, + * but often doesn't because stealers leave hints (that may become + * stale/wrong) of where to locate them. It is only a hint + * because a worker might have had multiple steals and the hint + * records only one of them (usually the most current). Hinting + * isolates cost to when it is needed, rather than adding to + * per-task overhead. (2) It is "shallow", ignoring nesting and + * potentially cyclic mutual steals. (3) It is intentionally + * racy: field currentJoin is updated only while actively joining, + * which means that we miss links in the chain during long-lived + * tasks, GC stalls etc (which is OK since blocking in such cases + * is usually a good idea). (4) We bound the number of attempts + * to find work (see MAX_HELP) and fall back to suspending the + * worker and if necessary replacing it with another. + * + * Helping actions for CountedCompleters are much simpler: Method + * helpComplete can take and execute any task with the same root + * as the task being waited on. However, this still entails some + * traversal of completer chains, so is less efficient than using + * CountedCompleters without explicit joins. + * + * It is impossible to keep exactly the target parallelism number + * of threads running at any given time. Determining the + * existence of conservatively safe helping targets, the + * availability of already-created spares, and the apparent need + * to create new spares are all racy, so we rely on multiple + * retries of each. Compensation in the apparent absence of + * helping opportunities is challenging to control on JVMs, where + * GC and other activities can stall progress of tasks that in + * turn stall out many other dependent tasks, without us being + * able to determine whether they will ever require compensation. + * Even though work-stealing otherwise encounters little + * degradation in the presence of more threads than cores, + * aggressively adding new threads in such cases entails risk of + * unwanted positive feedback control loops in which more threads + * cause more dependent stalls (as well as delayed progress of + * unblocked threads to the point that we know they are available) + * leading to more situations requiring more threads, and so + * on. This aspect of control can be seen as an (analytically + * intractable) game with an opponent that may choose the worst + * (for us) active thread to stall at any time. We take several + * precautions to bound losses (and thus bound gains), mainly in + * methods tryCompensate and awaitJoin. + * + * Common Pool + * =========== + * + * The static common pool always exists after static + * initialization. Since it (or any other created pool) need + * never be used, we minimize initial construction overhead and + * footprint to the setup of about a dozen fields, with no nested + * allocation. Most bootstrapping occurs within method + * fullExternalPush during the first submission to the pool. + * + * When external threads submit to the common pool, they can + * perform subtask processing (see externalHelpJoin and related + * methods). This caller-helps policy makes it sensible to set + * common pool parallelism level to one (or more) less than the + * total number of available cores, or even zero for pure + * caller-runs. We do not need to record whether external + * submissions are to the common pool -- if not, externalHelpJoin + * returns quickly (at the most helping to signal some common pool + * workers). These submitters would otherwise be blocked waiting + * for completion, so the extra effort (with liberally sprinkled + * task status checks) in inapplicable cases amounts to an odd + * form of limited spin-wait before blocking in ForkJoinTask.join. + * + * Style notes + * =========== + * + * There is a lot of representation-level coupling among classes + * ForkJoinPool, ForkJoinWorkerThread, and ForkJoinTask. The + * fields of WorkQueue maintain data structures managed by + * ForkJoinPool, so are directly accessed. There is little point + * trying to reduce this, since any associated future changes in + * representations will need to be accompanied by algorithmic + * changes anyway. Several methods intrinsically sprawl because + * they must accumulate sets of consistent reads of volatiles held + * in local variables. Methods signalWork() and scan() are the + * main bottlenecks, so are especially heavily + * micro-optimized/mangled. There are lots of inline assignments + * (of form "while ((local = field) != 0)") which are usually the + * simplest way to ensure the required read orderings (which are + * sometimes critical). This leads to a "C"-like style of listing + * declarations of these locals at the heads of methods or blocks. + * There are several occurrences of the unusual "do {} while + * (!cas...)" which is the simplest way to force an update of a + * CAS'ed variable. There are also other coding oddities (including + * several unnecessary-looking hoisted null checks) that help + * some methods perform reasonably even when interpreted (not + * compiled). + * + * The order of declarations in this file is: + * (1) Static utility functions + * (2) Nested (static) classes + * (3) Static fields + * (4) Fields, along with constants used when unpacking some of them + * (5) Internal control methods + * (6) Callbacks and other support for ForkJoinTask methods + * (7) Exported methods + * (8) Static block initializing statics in minimally dependent order + */ + + // Static utilities + + /** + * If there is a security manager, makes sure caller has + * permission to modify threads. + */ + private static void checkPermission() { + SecurityManager security = System.getSecurityManager(); + if (security != null) + security.checkPermission(modifyThreadPermission); + } + + // Nested classes + + /** + * Factory for creating new {@link ForkJoinWorkerThread}s. + * A {@code ForkJoinWorkerThreadFactory} must be defined and used + * for {@code ForkJoinWorkerThread} subclasses that extend base + * functionality or initialize threads with different contexts. + */ + public static interface ForkJoinWorkerThreadFactory { + /** + * Returns a new worker thread operating in the given pool. + * + * @param pool the pool this thread works in + * @return the new worker thread + * @throws NullPointerException if the pool is null + */ + public ForkJoinWorkerThread newThread(ForkJoinPool pool); + } + + /** + * Default ForkJoinWorkerThreadFactory implementation; creates a + * new ForkJoinWorkerThread. + */ + static final class DefaultForkJoinWorkerThreadFactory + implements ForkJoinWorkerThreadFactory { + public final ForkJoinWorkerThread newThread(ForkJoinPool pool) { + return new ForkJoinWorkerThread(pool); + } + } + + /** + * Class for artificial tasks that are used to replace the target + * of local joins if they are removed from an interior queue slot + * in WorkQueue.tryRemoveAndExec. We don't need the proxy to + * actually do anything beyond having a unique identity. + */ + static final class EmptyTask extends ForkJoinTask { + private static final long serialVersionUID = -7721805057305804111L; + EmptyTask() { status = ForkJoinTask.NORMAL; } // force done + public final Void getRawResult() { return null; } + public final void setRawResult(Void x) {} + public final boolean exec() { return true; } + } + + /** + * Queues supporting work-stealing as well as external task + * submission. See above for main rationale and algorithms. + * Implementation relies heavily on "Unsafe" intrinsics + * and selective use of "volatile": + * + * Field "base" is the index (mod array.length) of the least valid + * queue slot, which is always the next position to steal (poll) + * from if nonempty. Reads and writes require volatile orderings + * but not CAS, because updates are only performed after slot + * CASes. + * + * Field "top" is the index (mod array.length) of the next queue + * slot to push to or pop from. It is written only by owner thread + * for push, or under lock for external/shared push, and accessed + * by other threads only after reading (volatile) base. Both top + * and base are allowed to wrap around on overflow, but (top - + * base) (or more commonly -(base - top) to force volatile read of + * base before top) still estimates size. The lock ("qlock") is + * forced to -1 on termination, causing all further lock attempts + * to fail. (Note: we don't need CAS for termination state because + * upon pool shutdown, all shared-queues will stop being used + * anyway.) Nearly all lock bodies are set up so that exceptions + * within lock bodies are "impossible" (modulo JVM errors that + * would cause failure anyway.) + * + * The array slots are read and written using the emulation of + * volatiles/atomics provided by Unsafe. Insertions must in + * general use putOrderedObject as a form of releasing store to + * ensure that all writes to the task object are ordered before + * its publication in the queue. All removals entail a CAS to + * null. The array is always a power of two. To ensure safety of + * Unsafe array operations, all accesses perform explicit null + * checks and implicit bounds checks via power-of-two masking. + * + * In addition to basic queuing support, this class contains + * fields described elsewhere to control execution. It turns out + * to work better memory-layout-wise to include them in this class + * rather than a separate class. + * + * Performance on most platforms is very sensitive to placement of + * instances of both WorkQueues and their arrays -- we absolutely + * do not want multiple WorkQueue instances or multiple queue + * arrays sharing cache lines. (It would be best for queue objects + * and their arrays to share, but there is nothing available to + * help arrange that). The @Contended annotation alerts JVMs to + * try to keep instances apart. + */ + static final class WorkQueue { + /** + * Capacity of work-stealing queue array upon initialization. + * Must be a power of two; at least 4, but should be larger to + * reduce or eliminate cacheline sharing among queues. + * Currently, it is much larger, as a partial workaround for + * the fact that JVMs often place arrays in locations that + * share GC bookkeeping (especially cardmarks) such that + * per-write accesses encounter serious memory contention. + */ + static final int INITIAL_QUEUE_CAPACITY = 1 << 13; + + /** + * Maximum size for queue arrays. Must be a power of two less + * than or equal to 1 << (31 - width of array entry) to ensure + * lack of wraparound of index calculations, but defined to a + * value a bit less than this to help users trap runaway + * programs before saturating systems. + */ + static final int MAXIMUM_QUEUE_CAPACITY = 1 << 26; // 64M + + // Heuristic padding to ameliorate unfortunate memory placements + volatile long pad00, pad01, pad02, pad03, pad04, pad05, pad06; + + volatile int eventCount; // encoded inactivation count; < 0 if inactive + int nextWait; // encoded record of next event waiter + int nsteals; // number of steals + int hint; // steal index hint + short poolIndex; // index of this queue in pool + final short mode; // 0: lifo, > 0: fifo, < 0: shared + volatile int qlock; // 1: locked, -1: terminate; else 0 + volatile int base; // index of next slot for poll + int top; // index of next slot for push + ForkJoinTask[] array; // the elements (initially unallocated) + final ForkJoinPool pool; // the containing pool (may be null) + final ForkJoinWorkerThread owner; // owning thread or null if shared + volatile Thread parker; // == owner during call to park; else null + volatile ForkJoinTask currentJoin; // task being joined in awaitJoin + ForkJoinTask currentSteal; // current non-local task being executed + + volatile Object pad10, pad11, pad12, pad13, pad14, pad15, pad16, pad17; + volatile Object pad18, pad19, pad1a, pad1b, pad1c, pad1d; + + WorkQueue(ForkJoinPool pool, ForkJoinWorkerThread owner, int mode, + int seed) { + this.pool = pool; + this.owner = owner; + this.mode = (short)mode; + this.hint = seed; // store initial seed for runWorker + // Place indices in the center of array (that is not yet allocated) + base = top = INITIAL_QUEUE_CAPACITY >>> 1; + } + + /** + * Returns the approximate number of tasks in the queue. + */ + final int queueSize() { + int n = base - top; // non-owner callers must read base first + return (n >= 0) ? 0 : -n; // ignore transient negative + } + + /** + * Provides a more accurate estimate of whether this queue has + * any tasks than does queueSize, by checking whether a + * near-empty queue has at least one unclaimed task. + */ + final boolean isEmpty() { + ForkJoinTask[] a; int m, s; + int n = base - (s = top); + return (n >= 0 || + (n == -1 && + ((a = array) == null || + (m = a.length - 1) < 0 || + U.getObject + (a, (long)((m & (s - 1)) << ASHIFT) + ABASE) == null))); + } + + /** + * Pushes a task. Call only by owner in unshared queues. (The + * shared-queue version is embedded in method externalPush.) + * + * @param task the task. Caller must ensure non-null. + * @throws RejectedExecutionException if array cannot be resized + */ + final void push(ForkJoinTask task) { + ForkJoinTask[] a; ForkJoinPool p; + int s = top, n; + if ((a = array) != null) { // ignore if queue removed + int m = a.length - 1; + U.putOrderedObject(a, ((m & s) << ASHIFT) + ABASE, task); + if ((n = (top = s + 1) - base) <= 2) + (p = pool).signalWork(p.workQueues, this); + else if (n >= m) + growArray(); + } + } + + /** + * Initializes or doubles the capacity of array. Call either + * by owner or with lock held -- it is OK for base, but not + * top, to move while resizings are in progress. + */ + final ForkJoinTask[] growArray() { + ForkJoinTask[] oldA = array; + int size = oldA != null ? oldA.length << 1 : INITIAL_QUEUE_CAPACITY; + if (size > MAXIMUM_QUEUE_CAPACITY) + throw new RejectedExecutionException("Queue capacity exceeded"); + int oldMask, t, b; + ForkJoinTask[] a = array = new ForkJoinTask[size]; + if (oldA != null && (oldMask = oldA.length - 1) >= 0 && + (t = top) - (b = base) > 0) { + int mask = size - 1; + do { + ForkJoinTask x; + int oldj = ((b & oldMask) << ASHIFT) + ABASE; + int j = ((b & mask) << ASHIFT) + ABASE; + x = (ForkJoinTask)U.getObjectVolatile(oldA, oldj); + if (x != null && + U.compareAndSwapObject(oldA, oldj, x, null)) + U.putObjectVolatile(a, j, x); + } while (++b != t); + } + return a; + } + + /** + * Takes next task, if one exists, in LIFO order. Call only + * by owner in unshared queues. + */ + final ForkJoinTask pop() { + ForkJoinTask[] a; ForkJoinTask t; int m; + if ((a = array) != null && (m = a.length - 1) >= 0) { + for (int s; (s = top - 1) - base >= 0;) { + long j = ((m & s) << ASHIFT) + ABASE; + if ((t = (ForkJoinTask)U.getObject(a, j)) == null) + break; + if (U.compareAndSwapObject(a, j, t, null)) { + top = s; + return t; + } + } + } + return null; + } + + /** + * Takes a task in FIFO order if b is base of queue and a task + * can be claimed without contention. Specialized versions + * appear in ForkJoinPool methods scan and tryHelpStealer. + */ + final ForkJoinTask pollAt(int b) { + ForkJoinTask t; ForkJoinTask[] a; + if ((a = array) != null) { + int j = (((a.length - 1) & b) << ASHIFT) + ABASE; + if ((t = (ForkJoinTask)U.getObjectVolatile(a, j)) != null && + base == b && U.compareAndSwapObject(a, j, t, null)) { + U.putOrderedInt(this, QBASE, b + 1); + return t; + } + } + return null; + } + + /** + * Takes next task, if one exists, in FIFO order. + */ + final ForkJoinTask poll() { + ForkJoinTask[] a; int b; ForkJoinTask t; + while ((b = base) - top < 0 && (a = array) != null) { + int j = (((a.length - 1) & b) << ASHIFT) + ABASE; + t = (ForkJoinTask)U.getObjectVolatile(a, j); + if (t != null) { + if (U.compareAndSwapObject(a, j, t, null)) { + U.putOrderedInt(this, QBASE, b + 1); + return t; + } + } + else if (base == b) { + if (b + 1 == top) + break; + Thread.yield(); // wait for lagging update (very rare) + } + } + return null; + } + + /** + * Takes next task, if one exists, in order specified by mode. + */ + final ForkJoinTask nextLocalTask() { + return mode == 0 ? pop() : poll(); + } + + /** + * Returns next task, if one exists, in order specified by mode. + */ + final ForkJoinTask peek() { + ForkJoinTask[] a = array; int m; + if (a == null || (m = a.length - 1) < 0) + return null; + int i = mode == 0 ? top - 1 : base; + int j = ((i & m) << ASHIFT) + ABASE; + return (ForkJoinTask)U.getObjectVolatile(a, j); + } + + /** + * Pops the given task only if it is at the current top. + * (A shared version is available only via FJP.tryExternalUnpush) + */ + final boolean tryUnpush(ForkJoinTask t) { + ForkJoinTask[] a; int s; + if ((a = array) != null && (s = top) != base && + U.compareAndSwapObject + (a, (((a.length - 1) & --s) << ASHIFT) + ABASE, t, null)) { + top = s; + return true; + } + return false; + } + + /** + * Removes and cancels all known tasks, ignoring any exceptions. + */ + final void cancelAll() { + ForkJoinTask.cancelIgnoringExceptions(currentJoin); + ForkJoinTask.cancelIgnoringExceptions(currentSteal); + for (ForkJoinTask t; (t = poll()) != null; ) + ForkJoinTask.cancelIgnoringExceptions(t); + } + + // Specialized execution methods + + /** + * Polls and runs tasks until empty. + */ + final void pollAndExecAll() { + for (ForkJoinTask t; (t = poll()) != null;) + t.doExec(); + } + + /** + * Executes a top-level task and any local tasks remaining + * after execution. + */ + final void runTask(ForkJoinTask task) { + if ((currentSteal = task) != null) { + task.doExec(); + ForkJoinTask[] a = array; + int md = mode; + ++nsteals; + currentSteal = null; + if (md != 0) + pollAndExecAll(); + else if (a != null) { + int s, m = a.length - 1; + while ((s = top - 1) - base >= 0) { + long i = ((m & s) << ASHIFT) + ABASE; + ForkJoinTask t = (ForkJoinTask)U.getObject(a, i); + if (t == null) + break; + if (U.compareAndSwapObject(a, i, t, null)) { + top = s; + t.doExec(); + } + } + } + } + } + + /** + * If present, removes from queue and executes the given task, + * or any other cancelled task. Returns (true) on any CAS + * or consistency check failure so caller can retry. + * + * @return false if no progress can be made, else true + */ + final boolean tryRemoveAndExec(ForkJoinTask task) { + boolean stat; + ForkJoinTask[] a; int m, s, b, n; + if (task != null && (a = array) != null && (m = a.length - 1) >= 0 && + (n = (s = top) - (b = base)) > 0) { + boolean removed = false, empty = true; + stat = true; + for (ForkJoinTask t;;) { // traverse from s to b + long j = ((--s & m) << ASHIFT) + ABASE; + t = (ForkJoinTask)U.getObject(a, j); + if (t == null) // inconsistent length + break; + else if (t == task) { + if (s + 1 == top) { // pop + if (!U.compareAndSwapObject(a, j, task, null)) + break; + top = s; + removed = true; + } + else if (base == b) // replace with proxy + removed = U.compareAndSwapObject(a, j, task, + new EmptyTask()); + break; + } + else if (t.status >= 0) + empty = false; + else if (s + 1 == top) { // pop and throw away + if (U.compareAndSwapObject(a, j, t, null)) + top = s; + break; + } + if (--n == 0) { + if (!empty && base == b) + stat = false; + break; + } + } + if (removed) + task.doExec(); + } + else + stat = false; + return stat; + } + + /** + * Tries to poll for and execute the given task or any other + * task in its CountedCompleter computation. + */ + final boolean pollAndExecCC(CountedCompleter root) { + ForkJoinTask[] a; int b; Object o; CountedCompleter t, r; + if ((b = base) - top < 0 && (a = array) != null) { + long j = (((a.length - 1) & b) << ASHIFT) + ABASE; + if ((o = U.getObjectVolatile(a, j)) == null) + return true; // retry + if (o instanceof CountedCompleter) { + for (t = (CountedCompleter)o, r = t;;) { + if (r == root) { + if (base == b && + U.compareAndSwapObject(a, j, t, null)) { + U.putOrderedInt(this, QBASE, b + 1); + t.doExec(); + } + return true; + } + else if ((r = r.completer) == null) + break; // not part of root computation + } + } + } + return false; + } + + /** + * Tries to pop and execute the given task or any other task + * in its CountedCompleter computation. + */ + final boolean externalPopAndExecCC(CountedCompleter root) { + ForkJoinTask[] a; int s; Object o; CountedCompleter t, r; + if (base - (s = top) < 0 && (a = array) != null) { + long j = (((a.length - 1) & (s - 1)) << ASHIFT) + ABASE; + if ((o = U.getObject(a, j)) instanceof CountedCompleter) { + for (t = (CountedCompleter)o, r = t;;) { + if (r == root) { + if (U.compareAndSwapInt(this, QLOCK, 0, 1)) { + if (top == s && array == a && + U.compareAndSwapObject(a, j, t, null)) { + top = s - 1; + qlock = 0; + t.doExec(); + } + else + qlock = 0; + } + return true; + } + else if ((r = r.completer) == null) + break; + } + } + } + return false; + } + + /** + * Internal version + */ + final boolean internalPopAndExecCC(CountedCompleter root) { + ForkJoinTask[] a; int s; Object o; CountedCompleter t, r; + if (base - (s = top) < 0 && (a = array) != null) { + long j = (((a.length - 1) & (s - 1)) << ASHIFT) + ABASE; + if ((o = U.getObject(a, j)) instanceof CountedCompleter) { + for (t = (CountedCompleter)o, r = t;;) { + if (r == root) { + if (U.compareAndSwapObject(a, j, t, null)) { + top = s - 1; + t.doExec(); + } + return true; + } + else if ((r = r.completer) == null) + break; + } + } + } + return false; + } + + /** + * Returns true if owned and not known to be blocked. + */ + final boolean isApparentlyUnblocked() { + Thread wt; Thread.State s; + return (eventCount >= 0 && + (wt = owner) != null && + (s = wt.getState()) != Thread.State.BLOCKED && + s != Thread.State.WAITING && + s != Thread.State.TIMED_WAITING); + } + + // Unsafe mechanics + private static final sun.misc.Unsafe U; + private static final long QBASE; + private static final long QLOCK; + private static final int ABASE; + private static final int ASHIFT; + static { + try { + U = getUnsafe(); + Class k = WorkQueue.class; + Class ak = ForkJoinTask[].class; + QBASE = U.objectFieldOffset + (k.getDeclaredField("base")); + QLOCK = U.objectFieldOffset + (k.getDeclaredField("qlock")); + ABASE = U.arrayBaseOffset(ak); + int scale = U.arrayIndexScale(ak); + if ((scale & (scale - 1)) != 0) + throw new Error("data type scale not a power of two"); + ASHIFT = 31 - Integer.numberOfLeadingZeros(scale); + } catch (Exception e) { + throw new Error(e); + } + } + } + + // static fields (initialized in static initializer below) + + /** + * Per-thread submission bookkeeping. Shared across all pools + * to reduce ThreadLocal pollution and because random motion + * to avoid contention in one pool is likely to hold for others. + * Lazily initialized on first submission (but null-checked + * in other contexts to avoid unnecessary initialization). + */ + static final ThreadLocal submitters; + + /** + * Creates a new ForkJoinWorkerThread. This factory is used unless + * overridden in ForkJoinPool constructors. + */ + public static final ForkJoinWorkerThreadFactory + defaultForkJoinWorkerThreadFactory; + + /** + * Permission required for callers of methods that may start or + * kill threads. + */ + private static final RuntimePermission modifyThreadPermission; + + /** + * Common (static) pool. Non-null for public use unless a static + * construction exception, but internal usages null-check on use + * to paranoically avoid potential initialization circularities + * as well as to simplify generated code. + */ + static final ForkJoinPool common; + + /** + * Common pool parallelism. To allow simpler use and management + * when common pool threads are disabled, we allow the underlying + * common.parallelism field to be zero, but in that case still report + * parallelism as 1 to reflect resulting caller-runs mechanics. + */ + static final int commonParallelism; + + /** + * Sequence number for creating workerNamePrefix. + */ + private static int poolNumberSequence; + + /** + * Returns the next sequence number. We don't expect this to + * ever contend, so use simple builtin sync. + */ + private static final synchronized int nextPoolId() { + return ++poolNumberSequence; + } + + // static constants + + /** + * Initial timeout value (in nanoseconds) for the thread + * triggering quiescence to park waiting for new work. On timeout, + * the thread will instead try to shrink the number of + * workers. The value should be large enough to avoid overly + * aggressive shrinkage during most transient stalls (long GCs + * etc). + */ + private static final long IDLE_TIMEOUT = 2000L * 1000L * 1000L; // 2sec + + /** + * Timeout value when there are more threads than parallelism level + */ + private static final long FAST_IDLE_TIMEOUT = 200L * 1000L * 1000L; + + /** + * Tolerance for idle timeouts, to cope with timer undershoots + */ + private static final long TIMEOUT_SLOP = 2000000L; + + /** + * The maximum stolen->joining link depth allowed in method + * tryHelpStealer. Must be a power of two. Depths for legitimate + * chains are unbounded, but we use a fixed constant to avoid + * (otherwise unchecked) cycles and to bound staleness of + * traversal parameters at the expense of sometimes blocking when + * we could be helping. + */ + private static final int MAX_HELP = 64; + + /** + * Increment for seed generators. See class ThreadLocal for + * explanation. + */ + private static final int SEED_INCREMENT = 0x61c88647; + + /* + * Bits and masks for control variables + * + * Field ctl is a long packed with: + * AC: Number of active running workers minus target parallelism (16 bits) + * TC: Number of total workers minus target parallelism (16 bits) + * ST: true if pool is terminating (1 bit) + * EC: the wait count of top waiting thread (15 bits) + * ID: poolIndex of top of Treiber stack of waiters (16 bits) + * + * When convenient, we can extract the upper 32 bits of counts and + * the lower 32 bits of queue state, u = (int)(ctl >>> 32) and e = + * (int)ctl. The ec field is never accessed alone, but always + * together with id and st. The offsets of counts by the target + * parallelism and the positionings of fields makes it possible to + * perform the most common checks via sign tests of fields: When + * ac is negative, there are not enough active workers, when tc is + * negative, there are not enough total workers, and when e is + * negative, the pool is terminating. To deal with these possibly + * negative fields, we use casts in and out of "short" and/or + * signed shifts to maintain signedness. + * + * When a thread is queued (inactivated), its eventCount field is + * set negative, which is the only way to tell if a worker is + * prevented from executing tasks, even though it must continue to + * scan for them to avoid queuing races. Note however that + * eventCount updates lag releases so usage requires care. + * + * Field plock is an int packed with: + * SHUTDOWN: true if shutdown is enabled (1 bit) + * SEQ: a sequence lock, with PL_LOCK bit set if locked (30 bits) + * SIGNAL: set when threads may be waiting on the lock (1 bit) + * + * The sequence number enables simple consistency checks: + * Staleness of read-only operations on the workQueues array can + * be checked by comparing plock before vs after the reads. + */ + + // bit positions/shifts for fields + private static final int AC_SHIFT = 48; + private static final int TC_SHIFT = 32; + private static final int ST_SHIFT = 31; + private static final int EC_SHIFT = 16; + + // bounds + private static final int SMASK = 0xffff; // short bits + private static final int MAX_CAP = 0x7fff; // max #workers - 1 + private static final int EVENMASK = 0xfffe; // even short bits + private static final int SQMASK = 0x007e; // max 64 (even) slots + private static final int SHORT_SIGN = 1 << 15; + private static final int INT_SIGN = 1 << 31; + + // masks + private static final long STOP_BIT = 0x0001L << ST_SHIFT; + private static final long AC_MASK = ((long)SMASK) << AC_SHIFT; + private static final long TC_MASK = ((long)SMASK) << TC_SHIFT; + + // units for incrementing and decrementing + private static final long TC_UNIT = 1L << TC_SHIFT; + private static final long AC_UNIT = 1L << AC_SHIFT; + + // masks and units for dealing with u = (int)(ctl >>> 32) + private static final int UAC_SHIFT = AC_SHIFT - 32; + private static final int UTC_SHIFT = TC_SHIFT - 32; + private static final int UAC_MASK = SMASK << UAC_SHIFT; + private static final int UTC_MASK = SMASK << UTC_SHIFT; + private static final int UAC_UNIT = 1 << UAC_SHIFT; + private static final int UTC_UNIT = 1 << UTC_SHIFT; + + // masks and units for dealing with e = (int)ctl + private static final int E_MASK = 0x7fffffff; // no STOP_BIT + private static final int E_SEQ = 1 << EC_SHIFT; + + // plock bits + private static final int SHUTDOWN = 1 << 31; + private static final int PL_LOCK = 2; + private static final int PL_SIGNAL = 1; + private static final int PL_SPINS = 1 << 8; + + // access mode for WorkQueue + static final int LIFO_QUEUE = 0; + static final int FIFO_QUEUE = 1; + static final int SHARED_QUEUE = -1; + + // Heuristic padding to ameliorate unfortunate memory placements + volatile long pad00, pad01, pad02, pad03, pad04, pad05, pad06; + + // Instance fields + volatile long stealCount; // collects worker counts + volatile long ctl; // main pool control + volatile int plock; // shutdown status and seqLock + volatile int indexSeed; // worker/submitter index seed + final short parallelism; // parallelism level + final short mode; // LIFO/FIFO + WorkQueue[] workQueues; // main registry + final ForkJoinWorkerThreadFactory factory; + final UncaughtExceptionHandler ueh; // per-worker UEH + final String workerNamePrefix; // to create worker name string + + volatile Object pad10, pad11, pad12, pad13, pad14, pad15, pad16, pad17; + volatile Object pad18, pad19, pad1a, pad1b; + + /** + * Acquires the plock lock to protect worker array and related + * updates. This method is called only if an initial CAS on plock + * fails. This acts as a spinlock for normal cases, but falls back + * to builtin monitor to block when (rarely) needed. This would be + * a terrible idea for a highly contended lock, but works fine as + * a more conservative alternative to a pure spinlock. + */ + private int acquirePlock() { + int spins = PL_SPINS, ps, nps; + for (;;) { + if (((ps = plock) & PL_LOCK) == 0 && + U.compareAndSwapInt(this, PLOCK, ps, nps = ps + PL_LOCK)) + return nps; + else if (spins >= 0) { + if (ThreadLocalRandom.current().nextInt() >= 0) + --spins; + } + else if (U.compareAndSwapInt(this, PLOCK, ps, ps | PL_SIGNAL)) { + synchronized (this) { + if ((plock & PL_SIGNAL) != 0) { + try { + wait(); + } catch (InterruptedException ie) { + try { + Thread.currentThread().interrupt(); + } catch (SecurityException ignore) { + } + } + } + else + notifyAll(); + } + } + } + } + + /** + * Unlocks and signals any thread waiting for plock. Called only + * when CAS of seq value for unlock fails. + */ + private void releasePlock(int ps) { + plock = ps; + synchronized (this) { notifyAll(); } + } + + /** + * Tries to create and start one worker if fewer than target + * parallelism level exist. Adjusts counts etc on failure. + */ + private void tryAddWorker() { + long c; int u, e; + while ((u = (int)((c = ctl) >>> 32)) < 0 && + (u & SHORT_SIGN) != 0 && (e = (int)c) >= 0) { + long nc = ((long)(((u + UTC_UNIT) & UTC_MASK) | + ((u + UAC_UNIT) & UAC_MASK)) << 32) | (long)e; + if (U.compareAndSwapLong(this, CTL, c, nc)) { + ForkJoinWorkerThreadFactory fac; + Throwable ex = null; + ForkJoinWorkerThread wt = null; + try { + if ((fac = factory) != null && + (wt = fac.newThread(this)) != null) { + wt.start(); + break; + } + } catch (Throwable rex) { + ex = rex; + } + deregisterWorker(wt, ex); + break; + } + } + } + + // Registering and deregistering workers + + /** + * Callback from ForkJoinWorkerThread to establish and record its + * WorkQueue. To avoid scanning bias due to packing entries in + * front of the workQueues array, we treat the array as a simple + * power-of-two hash table using per-thread seed as hash, + * expanding as needed. + * + * @param wt the worker thread + * @return the worker's queue + */ + final WorkQueue registerWorker(ForkJoinWorkerThread wt) { + UncaughtExceptionHandler handler; WorkQueue[] ws; int s, ps; + wt.setDaemon(true); + if ((handler = ueh) != null) + wt.setUncaughtExceptionHandler(handler); + do {} while (!U.compareAndSwapInt(this, INDEXSEED, s = indexSeed, + s += SEED_INCREMENT) || + s == 0); // skip 0 + WorkQueue w = new WorkQueue(this, wt, mode, s); + if (((ps = plock) & PL_LOCK) != 0 || + !U.compareAndSwapInt(this, PLOCK, ps, ps += PL_LOCK)) + ps = acquirePlock(); + int nps = (ps & SHUTDOWN) | ((ps + PL_LOCK) & ~SHUTDOWN); + try { + if ((ws = workQueues) != null) { // skip if shutting down + int n = ws.length, m = n - 1; + int r = (s << 1) | 1; // use odd-numbered indices + if (ws[r &= m] != null) { // collision + int probes = 0; // step by approx half size + int step = (n <= 4) ? 2 : ((n >>> 1) & EVENMASK) + 2; + while (ws[r = (r + step) & m] != null) { + if (++probes >= n) { + workQueues = ws = Arrays.copyOf(ws, n <<= 1); + m = n - 1; + probes = 0; + } + } + } + w.poolIndex = (short)r; + w.eventCount = r; // volatile write orders + ws[r] = w; + } + } finally { + if (!U.compareAndSwapInt(this, PLOCK, ps, nps)) + releasePlock(nps); + } + wt.setName(workerNamePrefix.concat(Integer.toString(w.poolIndex >>> 1))); + return w; + } + + /** + * Final callback from terminating worker, as well as upon failure + * to construct or start a worker. Removes record of worker from + * array, and adjusts counts. If pool is shutting down, tries to + * complete termination. + * + * @param wt the worker thread, or null if construction failed + * @param ex the exception causing failure, or null if none + */ + final void deregisterWorker(ForkJoinWorkerThread wt, Throwable ex) { + WorkQueue w = null; + if (wt != null && (w = wt.workQueue) != null) { + int ps; long sc; + w.qlock = -1; // ensure set + do {} while (!U.compareAndSwapLong(this, STEALCOUNT, + sc = stealCount, + sc + w.nsteals)); + if (((ps = plock) & PL_LOCK) != 0 || + !U.compareAndSwapInt(this, PLOCK, ps, ps += PL_LOCK)) + ps = acquirePlock(); + int nps = (ps & SHUTDOWN) | ((ps + PL_LOCK) & ~SHUTDOWN); + try { + int idx = w.poolIndex; + WorkQueue[] ws = workQueues; + if (ws != null && idx >= 0 && idx < ws.length && ws[idx] == w) + ws[idx] = null; + } finally { + if (!U.compareAndSwapInt(this, PLOCK, ps, nps)) + releasePlock(nps); + } + } + + long c; // adjust ctl counts + do {} while (!U.compareAndSwapLong + (this, CTL, c = ctl, (((c - AC_UNIT) & AC_MASK) | + ((c - TC_UNIT) & TC_MASK) | + (c & ~(AC_MASK|TC_MASK))))); + + if (!tryTerminate(false, false) && w != null && w.array != null) { + w.cancelAll(); // cancel remaining tasks + WorkQueue[] ws; WorkQueue v; Thread p; int u, i, e; + while ((u = (int)((c = ctl) >>> 32)) < 0 && (e = (int)c) >= 0) { + if (e > 0) { // activate or create replacement + if ((ws = workQueues) == null || + (i = e & SMASK) >= ws.length || + (v = ws[i]) == null) + break; + long nc = (((long)(v.nextWait & E_MASK)) | + ((long)(u + UAC_UNIT) << 32)); + if (v.eventCount != (e | INT_SIGN)) + break; + if (U.compareAndSwapLong(this, CTL, c, nc)) { + v.eventCount = (e + E_SEQ) & E_MASK; + if ((p = v.parker) != null) + U.unpark(p); + break; + } + } + else { + if ((short)u < 0) + tryAddWorker(); + break; + } + } + } + if (ex == null) // help clean refs on way out + ForkJoinTask.helpExpungeStaleExceptions(); + else // rethrow + ForkJoinTask.rethrow(ex); + } + + // Submissions + + /** + * Per-thread records for threads that submit to pools. Currently + * holds only pseudo-random seed / index that is used to choose + * submission queues in method externalPush. In the future, this may + * also incorporate a means to implement different task rejection + * and resubmission policies. + * + * Seeds for submitters and workers/workQueues work in basically + * the same way but are initialized and updated using slightly + * different mechanics. Both are initialized using the same + * approach as in class ThreadLocal, where successive values are + * unlikely to collide with previous values. Seeds are then + * randomly modified upon collisions using xorshifts, which + * requires a non-zero seed. + */ + static final class Submitter { + int seed; + Submitter(int s) { seed = s; } + } + + /** + * Unless shutting down, adds the given task to a submission queue + * at submitter's current queue index (modulo submission + * range). Only the most common path is directly handled in this + * method. All others are relayed to fullExternalPush. + * + * @param task the task. Caller must ensure non-null. + */ + final void externalPush(ForkJoinTask task) { + Submitter z = submitters.get(); + WorkQueue q; int r, m, s, n, am; ForkJoinTask[] a; + int ps = plock; + WorkQueue[] ws = workQueues; + if (z != null && ps > 0 && ws != null && (m = (ws.length - 1)) >= 0 && + (q = ws[m & (r = z.seed) & SQMASK]) != null && r != 0 && + U.compareAndSwapInt(q, QLOCK, 0, 1)) { // lock + if ((a = q.array) != null && + (am = a.length - 1) > (n = (s = q.top) - q.base)) { + int j = ((am & s) << ASHIFT) + ABASE; + U.putOrderedObject(a, j, task); + q.top = s + 1; // push on to deque + q.qlock = 0; + if (n <= 1) + signalWork(ws, q); + return; + } + q.qlock = 0; + } + fullExternalPush(task); + } + + /** + * Full version of externalPush. This method is called, among + * other times, upon the first submission of the first task to the + * pool, so must perform secondary initialization. It also + * detects first submission by an external thread by looking up + * its ThreadLocal, and creates a new shared queue if the one at + * index if empty or contended. The plock lock body must be + * exception-free (so no try/finally) so we optimistically + * allocate new queues outside the lock and throw them away if + * (very rarely) not needed. + * + * Secondary initialization occurs when plock is zero, to create + * workQueue array and set plock to a valid value. This lock body + * must also be exception-free. Because the plock seq value can + * eventually wrap around zero, this method harmlessly fails to + * reinitialize if workQueues exists, while still advancing plock. + */ + private void fullExternalPush(ForkJoinTask task) { + int r = 0; // random index seed + for (Submitter z = submitters.get();;) { + WorkQueue[] ws; WorkQueue q; int ps, m, k; + if (z == null) { + if (U.compareAndSwapInt(this, INDEXSEED, r = indexSeed, + r += SEED_INCREMENT) && r != 0) + submitters.set(z = new Submitter(r)); + } + else if (r == 0) { // move to a different index + r = z.seed; + r ^= r << 13; // same xorshift as WorkQueues + r ^= r >>> 17; + z.seed = r ^= (r << 5); + } + if ((ps = plock) < 0) + throw new RejectedExecutionException(); + else if (ps == 0 || (ws = workQueues) == null || + (m = ws.length - 1) < 0) { // initialize workQueues + int p = parallelism; // find power of two table size + int n = (p > 1) ? p - 1 : 1; // ensure at least 2 slots + n |= n >>> 1; n |= n >>> 2; n |= n >>> 4; + n |= n >>> 8; n |= n >>> 16; n = (n + 1) << 1; + WorkQueue[] nws = ((ws = workQueues) == null || ws.length == 0 ? + new WorkQueue[n] : null); + if (((ps = plock) & PL_LOCK) != 0 || + !U.compareAndSwapInt(this, PLOCK, ps, ps += PL_LOCK)) + ps = acquirePlock(); + if (((ws = workQueues) == null || ws.length == 0) && nws != null) + workQueues = nws; + int nps = (ps & SHUTDOWN) | ((ps + PL_LOCK) & ~SHUTDOWN); + if (!U.compareAndSwapInt(this, PLOCK, ps, nps)) + releasePlock(nps); + } + else if ((q = ws[k = r & m & SQMASK]) != null) { + if (q.qlock == 0 && U.compareAndSwapInt(q, QLOCK, 0, 1)) { + ForkJoinTask[] a = q.array; + int s = q.top; + boolean submitted = false; + try { // locked version of push + if ((a != null && a.length > s + 1 - q.base) || + (a = q.growArray()) != null) { // must presize + int j = (((a.length - 1) & s) << ASHIFT) + ABASE; + U.putOrderedObject(a, j, task); + q.top = s + 1; + submitted = true; + } + } finally { + q.qlock = 0; // unlock + } + if (submitted) { + signalWork(ws, q); + return; + } + } + r = 0; // move on failure + } + else if (((ps = plock) & PL_LOCK) == 0) { // create new queue + q = new WorkQueue(this, null, SHARED_QUEUE, r); + q.poolIndex = (short)k; + if (((ps = plock) & PL_LOCK) != 0 || + !U.compareAndSwapInt(this, PLOCK, ps, ps += PL_LOCK)) + ps = acquirePlock(); + if ((ws = workQueues) != null && k < ws.length && ws[k] == null) + ws[k] = q; + int nps = (ps & SHUTDOWN) | ((ps + PL_LOCK) & ~SHUTDOWN); + if (!U.compareAndSwapInt(this, PLOCK, ps, nps)) + releasePlock(nps); + } + else + r = 0; + } + } + + // Maintaining ctl counts + + /** + * Increments active count; mainly called upon return from blocking. + */ + final void incrementActiveCount() { + long c; + do {} while (!U.compareAndSwapLong + (this, CTL, c = ctl, ((c & ~AC_MASK) | + ((c & AC_MASK) + AC_UNIT)))); + } + + /** + * Tries to create or activate a worker if too few are active. + * + * @param ws the worker array to use to find signallees + * @param q if non-null, the queue holding tasks to be processed + */ + final void signalWork(WorkQueue[] ws, WorkQueue q) { + for (;;) { + long c; int e, u, i; WorkQueue w; Thread p; + if ((u = (int)((c = ctl) >>> 32)) >= 0) + break; + if ((e = (int)c) <= 0) { + if ((short)u < 0) + tryAddWorker(); + break; + } + if (ws == null || ws.length <= (i = e & SMASK) || + (w = ws[i]) == null) + break; + long nc = (((long)(w.nextWait & E_MASK)) | + ((long)(u + UAC_UNIT)) << 32); + int ne = (e + E_SEQ) & E_MASK; + if (w.eventCount == (e | INT_SIGN) && + U.compareAndSwapLong(this, CTL, c, nc)) { + w.eventCount = ne; + if ((p = w.parker) != null) + U.unpark(p); + break; + } + if (q != null && q.base >= q.top) + break; + } + } + + // Scanning for tasks + + /** + * Top-level runloop for workers, called by ForkJoinWorkerThread.run. + */ + final void runWorker(WorkQueue w) { + w.growArray(); // allocate queue + for (int r = w.hint; scan(w, r) == 0; ) { + r ^= r << 13; r ^= r >>> 17; r ^= r << 5; // xorshift + } + } + + /** + * Scans for and, if found, runs one task, else possibly + * inactivates the worker. This method operates on single reads of + * volatile state and is designed to be re-invoked continuously, + * in part because it returns upon detecting inconsistencies, + * contention, or state changes that indicate possible success on + * re-invocation. + * + * The scan searches for tasks across queues starting at a random + * index, checking each at least twice. The scan terminates upon + * either finding a non-empty queue, or completing the sweep. If + * the worker is not inactivated, it takes and runs a task from + * this queue. Otherwise, if not activated, it tries to activate + * itself or some other worker by signalling. On failure to find a + * task, returns (for retry) if pool state may have changed during + * an empty scan, or tries to inactivate if active, else possibly + * blocks or terminates via method awaitWork. + * + * @param w the worker (via its WorkQueue) + * @param r a random seed + * @return worker qlock status if would have waited, else 0 + */ + private final int scan(WorkQueue w, int r) { + WorkQueue[] ws; int m; + long c = ctl; // for consistency check + if ((ws = workQueues) != null && (m = ws.length - 1) >= 0 && w != null) { + for (int j = m + m + 1, ec = w.eventCount;;) { + WorkQueue q; int b, e; ForkJoinTask[] a; ForkJoinTask t; + if ((q = ws[(r - j) & m]) != null && + (b = q.base) - q.top < 0 && (a = q.array) != null) { + long i = (((a.length - 1) & b) << ASHIFT) + ABASE; + if ((t = ((ForkJoinTask) + U.getObjectVolatile(a, i))) != null) { + if (ec < 0) + helpRelease(c, ws, w, q, b); + else if (q.base == b && + U.compareAndSwapObject(a, i, t, null)) { + U.putOrderedInt(q, QBASE, b + 1); + if ((b + 1) - q.top < 0) + signalWork(ws, q); + w.runTask(t); + } + } + break; + } + else if (--j < 0) { + if ((ec | (e = (int)c)) < 0) // inactive or terminating + return awaitWork(w, c, ec); + else if (ctl == c) { // try to inactivate and enqueue + long nc = (long)ec | ((c - AC_UNIT) & (AC_MASK|TC_MASK)); + w.nextWait = e; + w.eventCount = ec | INT_SIGN; + if (!U.compareAndSwapLong(this, CTL, c, nc)) + w.eventCount = ec; // back out + } + break; + } + } + } + return 0; + } + + /** + * A continuation of scan(), possibly blocking or terminating + * worker w. Returns without blocking if pool state has apparently + * changed since last invocation. Also, if inactivating w has + * caused the pool to become quiescent, checks for pool + * termination, and, so long as this is not the only worker, waits + * for event for up to a given duration. On timeout, if ctl has + * not changed, terminates the worker, which will in turn wake up + * another worker to possibly repeat this process. + * + * @param w the calling worker + * @param c the ctl value on entry to scan + * @param ec the worker's eventCount on entry to scan + */ + private final int awaitWork(WorkQueue w, long c, int ec) { + int stat, ns; long parkTime, deadline; + if ((stat = w.qlock) >= 0 && w.eventCount == ec && ctl == c && + !Thread.interrupted()) { + int e = (int)c; + int u = (int)(c >>> 32); + int d = (u >> UAC_SHIFT) + parallelism; // active count + + if (e < 0 || (d <= 0 && tryTerminate(false, false))) + stat = w.qlock = -1; // pool is terminating + else if ((ns = w.nsteals) != 0) { // collect steals and retry + long sc; + w.nsteals = 0; + do {} while (!U.compareAndSwapLong(this, STEALCOUNT, + sc = stealCount, sc + ns)); + } + else { + long pc = ((d > 0 || ec != (e | INT_SIGN)) ? 0L : + ((long)(w.nextWait & E_MASK)) | // ctl to restore + ((long)(u + UAC_UNIT)) << 32); + if (pc != 0L) { // timed wait if last waiter + int dc = -(short)(c >>> TC_SHIFT); + parkTime = (dc < 0 ? FAST_IDLE_TIMEOUT: + (dc + 1) * IDLE_TIMEOUT); + deadline = System.nanoTime() + parkTime - TIMEOUT_SLOP; + } + else + parkTime = deadline = 0L; + if (w.eventCount == ec && ctl == c) { + Thread wt = Thread.currentThread(); + U.putObject(wt, PARKBLOCKER, this); + w.parker = wt; // emulate LockSupport.park + if (w.eventCount == ec && ctl == c) + U.park(false, parkTime); // must recheck before park + w.parker = null; + U.putObject(wt, PARKBLOCKER, null); + if (parkTime != 0L && ctl == c && + deadline - System.nanoTime() <= 0L && + U.compareAndSwapLong(this, CTL, c, pc)) + stat = w.qlock = -1; // shrink pool + } + } + } + return stat; + } + + /** + * Possibly releases (signals) a worker. Called only from scan() + * when a worker with apparently inactive status finds a non-empty + * queue. This requires revalidating all of the associated state + * from caller. + */ + private final void helpRelease(long c, WorkQueue[] ws, WorkQueue w, + WorkQueue q, int b) { + WorkQueue v; int e, i; Thread p; + if (w != null && w.eventCount < 0 && (e = (int)c) > 0 && + ws != null && ws.length > (i = e & SMASK) && + (v = ws[i]) != null && ctl == c) { + long nc = (((long)(v.nextWait & E_MASK)) | + ((long)((int)(c >>> 32) + UAC_UNIT)) << 32); + int ne = (e + E_SEQ) & E_MASK; + if (q != null && q.base == b && w.eventCount < 0 && + v.eventCount == (e | INT_SIGN) && + U.compareAndSwapLong(this, CTL, c, nc)) { + v.eventCount = ne; + if ((p = v.parker) != null) + U.unpark(p); + } + } + } + + /** + * Tries to locate and execute tasks for a stealer of the given + * task, or in turn one of its stealers, Traces currentSteal -> + * currentJoin links looking for a thread working on a descendant + * of the given task and with a non-empty queue to steal back and + * execute tasks from. The first call to this method upon a + * waiting join will often entail scanning/search, (which is OK + * because the joiner has nothing better to do), but this method + * leaves hints in workers to speed up subsequent calls. The + * implementation is very branchy to cope with potential + * inconsistencies or loops encountering chains that are stale, + * unknown, or so long that they are likely cyclic. + * + * @param joiner the joining worker + * @param task the task to join + * @return 0 if no progress can be made, negative if task + * known complete, else positive + */ + private int tryHelpStealer(WorkQueue joiner, ForkJoinTask task) { + int stat = 0, steps = 0; // bound to avoid cycles + if (task != null && joiner != null && + joiner.base - joiner.top >= 0) { // hoist checks + restart: for (;;) { + ForkJoinTask subtask = task; // current target + for (WorkQueue j = joiner, v;;) { // v is stealer of subtask + WorkQueue[] ws; int m, s, h; + if ((s = task.status) < 0) { + stat = s; + break restart; + } + if ((ws = workQueues) == null || (m = ws.length - 1) <= 0) + break restart; // shutting down + if ((v = ws[h = (j.hint | 1) & m]) == null || + v.currentSteal != subtask) { + for (int origin = h;;) { // find stealer + if (((h = (h + 2) & m) & 15) == 1 && + (subtask.status < 0 || j.currentJoin != subtask)) + continue restart; // occasional staleness check + if ((v = ws[h]) != null && + v.currentSteal == subtask) { + j.hint = h; // save hint + break; + } + if (h == origin) + break restart; // cannot find stealer + } + } + for (;;) { // help stealer or descend to its stealer + ForkJoinTask[] a; int b; + if (subtask.status < 0) // surround probes with + continue restart; // consistency checks + if ((b = v.base) - v.top < 0 && (a = v.array) != null) { + int i = (((a.length - 1) & b) << ASHIFT) + ABASE; + ForkJoinTask t = + (ForkJoinTask)U.getObjectVolatile(a, i); + if (subtask.status < 0 || j.currentJoin != subtask || + v.currentSteal != subtask) + continue restart; // stale + stat = 1; // apparent progress + if (v.base == b) { + if (t == null) + break restart; + if (U.compareAndSwapObject(a, i, t, null)) { + U.putOrderedInt(v, QBASE, b + 1); + ForkJoinTask ps = joiner.currentSteal; + int jt = joiner.top; + do { + joiner.currentSteal = t; + t.doExec(); // clear local tasks too + } while (task.status >= 0 && + joiner.top != jt && + (t = joiner.pop()) != null); + joiner.currentSteal = ps; + break restart; + } + } + } + else { // empty -- try to descend + ForkJoinTask next = v.currentJoin; + if (subtask.status < 0 || j.currentJoin != subtask || + v.currentSteal != subtask) + continue restart; // stale + else if (next == null || ++steps == MAX_HELP) + break restart; // dead-end or maybe cyclic + else { + subtask = next; + j = v; + break; + } + } + } + } + } + } + return stat; + } + + /** + * Analog of tryHelpStealer for CountedCompleters. Tries to steal + * and run tasks within the target's computation. + * + * @param task the task to join + */ + private int helpComplete(WorkQueue joiner, CountedCompleter task) { + WorkQueue[] ws; int m; + int s = 0; + if ((ws = workQueues) != null && (m = ws.length - 1) >= 0 && + joiner != null && task != null) { + int j = joiner.poolIndex; + int scans = m + m + 1; + long c = 0L; // for stability check + for (int k = scans; ; j += 2) { + WorkQueue q; + if ((s = task.status) < 0) + break; + else if (joiner.internalPopAndExecCC(task)) + k = scans; + else if ((s = task.status) < 0) + break; + else if ((q = ws[j & m]) != null && q.pollAndExecCC(task)) + k = scans; + else if (--k < 0) { + if (c == (c = ctl)) + break; + k = scans; + } + } + } + return s; + } + + /** + * Tries to decrement active count (sometimes implicitly) and + * possibly release or create a compensating worker in preparation + * for blocking. Fails on contention or termination. Otherwise, + * adds a new thread if no idle workers are available and pool + * may become starved. + * + * @param c the assumed ctl value + */ + final boolean tryCompensate(long c) { + WorkQueue[] ws = workQueues; + int pc = parallelism, e = (int)c, m, tc; + if (ws != null && (m = ws.length - 1) >= 0 && e >= 0 && ctl == c) { + WorkQueue w = ws[e & m]; + if (e != 0 && w != null) { + Thread p; + long nc = ((long)(w.nextWait & E_MASK) | + (c & (AC_MASK|TC_MASK))); + int ne = (e + E_SEQ) & E_MASK; + if (w.eventCount == (e | INT_SIGN) && + U.compareAndSwapLong(this, CTL, c, nc)) { + w.eventCount = ne; + if ((p = w.parker) != null) + U.unpark(p); + return true; // replace with idle worker + } + } + else if ((tc = (short)(c >>> TC_SHIFT)) >= 0 && + (int)(c >> AC_SHIFT) + pc > 1) { + long nc = ((c - AC_UNIT) & AC_MASK) | (c & ~AC_MASK); + if (U.compareAndSwapLong(this, CTL, c, nc)) + return true; // no compensation + } + else if (tc + pc < MAX_CAP) { + long nc = ((c + TC_UNIT) & TC_MASK) | (c & ~TC_MASK); + if (U.compareAndSwapLong(this, CTL, c, nc)) { + ForkJoinWorkerThreadFactory fac; + Throwable ex = null; + ForkJoinWorkerThread wt = null; + try { + if ((fac = factory) != null && + (wt = fac.newThread(this)) != null) { + wt.start(); + return true; + } + } catch (Throwable rex) { + ex = rex; + } + deregisterWorker(wt, ex); // clean up and return false + } + } + } + return false; + } + + /** + * Helps and/or blocks until the given task is done. + * + * @param joiner the joining worker + * @param task the task + * @return task status on exit + */ + final int awaitJoin(WorkQueue joiner, ForkJoinTask task) { + int s = 0; + if (task != null && (s = task.status) >= 0 && joiner != null) { + ForkJoinTask prevJoin = joiner.currentJoin; + joiner.currentJoin = task; + do {} while (joiner.tryRemoveAndExec(task) && // process local tasks + (s = task.status) >= 0); + if (s >= 0 && (task instanceof CountedCompleter)) + s = helpComplete(joiner, (CountedCompleter)task); + long cc = 0; // for stability checks + while (s >= 0 && (s = task.status) >= 0) { + if ((s = tryHelpStealer(joiner, task)) == 0 && + (s = task.status) >= 0) { + if (!tryCompensate(cc)) + cc = ctl; + else { + if (task.trySetSignal() && (s = task.status) >= 0) { + synchronized (task) { + if (task.status >= 0) { + try { // see ForkJoinTask + task.wait(); // for explanation + } catch (InterruptedException ie) { + } + } + else + task.notifyAll(); + } + } + long c; // reactivate + do {} while (!U.compareAndSwapLong + (this, CTL, c = ctl, + ((c & ~AC_MASK) | + ((c & AC_MASK) + AC_UNIT)))); + } + } + } + joiner.currentJoin = prevJoin; + } + return s; + } + + /** + * Stripped-down variant of awaitJoin used by timed joins. Tries + * to help join only while there is continuous progress. (Caller + * will then enter a timed wait.) + * + * @param joiner the joining worker + * @param task the task + */ + final void helpJoinOnce(WorkQueue joiner, ForkJoinTask task) { + int s; + if (joiner != null && task != null && (s = task.status) >= 0) { + ForkJoinTask prevJoin = joiner.currentJoin; + joiner.currentJoin = task; + do {} while (joiner.tryRemoveAndExec(task) && // process local tasks + (s = task.status) >= 0); + if (s >= 0) { + if (task instanceof CountedCompleter) + helpComplete(joiner, (CountedCompleter)task); + do {} while (task.status >= 0 && + tryHelpStealer(joiner, task) > 0); + } + joiner.currentJoin = prevJoin; + } + } + + /** + * Returns a (probably) non-empty steal queue, if one is found + * during a scan, else null. This method must be retried by + * caller if, by the time it tries to use the queue, it is empty. + */ + private WorkQueue findNonEmptyStealQueue() { + int r = ThreadLocalRandom.current().nextInt(); + for (;;) { + int ps = plock, m; WorkQueue[] ws; WorkQueue q; + if ((ws = workQueues) != null && (m = ws.length - 1) >= 0) { + for (int j = (m + 1) << 2; j >= 0; --j) { + if ((q = ws[(((r - j) << 1) | 1) & m]) != null && + q.base - q.top < 0) + return q; + } + } + if (plock == ps) + return null; + } + } + + /** + * Runs tasks until {@code isQuiescent()}. We piggyback on + * active count ctl maintenance, but rather than blocking + * when tasks cannot be found, we rescan until all others cannot + * find tasks either. + */ + final void helpQuiescePool(WorkQueue w) { + ForkJoinTask ps = w.currentSteal; + for (boolean active = true;;) { + long c; WorkQueue q; ForkJoinTask t; int b; + while ((t = w.nextLocalTask()) != null) + t.doExec(); + if ((q = findNonEmptyStealQueue()) != null) { + if (!active) { // re-establish active count + active = true; + do {} while (!U.compareAndSwapLong + (this, CTL, c = ctl, + ((c & ~AC_MASK) | + ((c & AC_MASK) + AC_UNIT)))); + } + if ((b = q.base) - q.top < 0 && (t = q.pollAt(b)) != null) { + (w.currentSteal = t).doExec(); + w.currentSteal = ps; + } + } + else if (active) { // decrement active count without queuing + long nc = ((c = ctl) & ~AC_MASK) | ((c & AC_MASK) - AC_UNIT); + if ((int)(nc >> AC_SHIFT) + parallelism == 0) + break; // bypass decrement-then-increment + if (U.compareAndSwapLong(this, CTL, c, nc)) + active = false; + } + else if ((int)((c = ctl) >> AC_SHIFT) + parallelism <= 0 && + U.compareAndSwapLong + (this, CTL, c, ((c & ~AC_MASK) | + ((c & AC_MASK) + AC_UNIT)))) + break; + } + } + + /** + * Gets and removes a local or stolen task for the given worker. + * + * @return a task, if available + */ + final ForkJoinTask nextTaskFor(WorkQueue w) { + for (ForkJoinTask t;;) { + WorkQueue q; int b; + if ((t = w.nextLocalTask()) != null) + return t; + if ((q = findNonEmptyStealQueue()) == null) + return null; + if ((b = q.base) - q.top < 0 && (t = q.pollAt(b)) != null) + return t; + } + } + + /** + * Returns a cheap heuristic guide for task partitioning when + * programmers, frameworks, tools, or languages have little or no + * idea about task granularity. In essence by offering this + * method, we ask users only about tradeoffs in overhead vs + * expected throughput and its variance, rather than how finely to + * partition tasks. + * + * In a steady state strict (tree-structured) computation, each + * thread makes available for stealing enough tasks for other + * threads to remain active. Inductively, if all threads play by + * the same rules, each thread should make available only a + * constant number of tasks. + * + * The minimum useful constant is just 1. But using a value of 1 + * would require immediate replenishment upon each steal to + * maintain enough tasks, which is infeasible. Further, + * partitionings/granularities of offered tasks should minimize + * steal rates, which in general means that threads nearer the top + * of computation tree should generate more than those nearer the + * bottom. In perfect steady state, each thread is at + * approximately the same level of computation tree. However, + * producing extra tasks amortizes the uncertainty of progress and + * diffusion assumptions. + * + * So, users will want to use values larger (but not much larger) + * than 1 to both smooth over transient shortages and hedge + * against uneven progress; as traded off against the cost of + * extra task overhead. We leave the user to pick a threshold + * value to compare with the results of this call to guide + * decisions, but recommend values such as 3. + * + * When all threads are active, it is on average OK to estimate + * surplus strictly locally. In steady-state, if one thread is + * maintaining say 2 surplus tasks, then so are others. So we can + * just use estimated queue length. However, this strategy alone + * leads to serious mis-estimates in some non-steady-state + * conditions (ramp-up, ramp-down, other stalls). We can detect + * many of these by further considering the number of "idle" + * threads, that are known to have zero queued tasks, so + * compensate by a factor of (#idle/#active) threads. + * + * Note: The approximation of #busy workers as #active workers is + * not very good under current signalling scheme, and should be + * improved. + */ + static int getSurplusQueuedTaskCount() { + Thread t; ForkJoinWorkerThread wt; ForkJoinPool pool; WorkQueue q; + if (((t = Thread.currentThread()) instanceof ForkJoinWorkerThread)) { + int p = (pool = (wt = (ForkJoinWorkerThread)t).pool).parallelism; + int n = (q = wt.workQueue).top - q.base; + int a = (int)(pool.ctl >> AC_SHIFT) + p; + return n - (a > (p >>>= 1) ? 0 : + a > (p >>>= 1) ? 1 : + a > (p >>>= 1) ? 2 : + a > (p >>>= 1) ? 4 : + 8); + } + return 0; + } + + // Termination + + /** + * Possibly initiates and/or completes termination. The caller + * triggering termination runs three passes through workQueues: + * (0) Setting termination status, followed by wakeups of queued + * workers; (1) cancelling all tasks; (2) interrupting lagging + * threads (likely in external tasks, but possibly also blocked in + * joins). Each pass repeats previous steps because of potential + * lagging thread creation. + * + * @param now if true, unconditionally terminate, else only + * if no work and no active workers + * @param enable if true, enable shutdown when next possible + * @return true if now terminating or terminated + */ + private boolean tryTerminate(boolean now, boolean enable) { + int ps; + if (this == common) // cannot shut down + return false; + if ((ps = plock) >= 0) { // enable by setting plock + if (!enable) + return false; + if ((ps & PL_LOCK) != 0 || + !U.compareAndSwapInt(this, PLOCK, ps, ps += PL_LOCK)) + ps = acquirePlock(); + int nps = ((ps + PL_LOCK) & ~SHUTDOWN) | SHUTDOWN; + if (!U.compareAndSwapInt(this, PLOCK, ps, nps)) + releasePlock(nps); + } + for (long c;;) { + if (((c = ctl) & STOP_BIT) != 0) { // already terminating + if ((short)(c >>> TC_SHIFT) + parallelism <= 0) { + synchronized (this) { + notifyAll(); // signal when 0 workers + } + } + return true; + } + if (!now) { // check if idle & no tasks + WorkQueue[] ws; WorkQueue w; + if ((int)(c >> AC_SHIFT) + parallelism > 0) + return false; + if ((ws = workQueues) != null) { + for (int i = 0; i < ws.length; ++i) { + if ((w = ws[i]) != null && + (!w.isEmpty() || + ((i & 1) != 0 && w.eventCount >= 0))) { + signalWork(ws, w); + return false; + } + } + } + } + if (U.compareAndSwapLong(this, CTL, c, c | STOP_BIT)) { + for (int pass = 0; pass < 3; ++pass) { + WorkQueue[] ws; WorkQueue w; Thread wt; + if ((ws = workQueues) != null) { + int n = ws.length; + for (int i = 0; i < n; ++i) { + if ((w = ws[i]) != null) { + w.qlock = -1; + if (pass > 0) { + w.cancelAll(); + if (pass > 1 && (wt = w.owner) != null) { + if (!wt.isInterrupted()) { + try { + wt.interrupt(); + } catch (Throwable ignore) { + } + } + U.unpark(wt); + } + } + } + } + // Wake up workers parked on event queue + int i, e; long cc; Thread p; + while ((e = (int)(cc = ctl) & E_MASK) != 0 && + (i = e & SMASK) < n && i >= 0 && + (w = ws[i]) != null) { + long nc = ((long)(w.nextWait & E_MASK) | + ((cc + AC_UNIT) & AC_MASK) | + (cc & (TC_MASK|STOP_BIT))); + if (w.eventCount == (e | INT_SIGN) && + U.compareAndSwapLong(this, CTL, cc, nc)) { + w.eventCount = (e + E_SEQ) & E_MASK; + w.qlock = -1; + if ((p = w.parker) != null) + U.unpark(p); + } + } + } + } + } + } + } + + // external operations on common pool + + /** + * Returns common pool queue for a thread that has submitted at + * least one task. + */ + static WorkQueue commonSubmitterQueue() { + Submitter z; ForkJoinPool p; WorkQueue[] ws; int m, r; + return ((z = submitters.get()) != null && + (p = common) != null && + (ws = p.workQueues) != null && + (m = ws.length - 1) >= 0) ? + ws[m & z.seed & SQMASK] : null; + } + + /** + * Tries to pop the given task from submitter's queue in common pool. + */ + final boolean tryExternalUnpush(ForkJoinTask task) { + WorkQueue joiner; ForkJoinTask[] a; int m, s; + Submitter z = submitters.get(); + WorkQueue[] ws = workQueues; + boolean popped = false; + if (z != null && ws != null && (m = ws.length - 1) >= 0 && + (joiner = ws[z.seed & m & SQMASK]) != null && + joiner.base != (s = joiner.top) && + (a = joiner.array) != null) { + long j = (((a.length - 1) & (s - 1)) << ASHIFT) + ABASE; + if (U.getObject(a, j) == task && + U.compareAndSwapInt(joiner, QLOCK, 0, 1)) { + if (joiner.top == s && joiner.array == a && + U.compareAndSwapObject(a, j, task, null)) { + joiner.top = s - 1; + popped = true; + } + joiner.qlock = 0; + } + } + return popped; + } + + final int externalHelpComplete(CountedCompleter task) { + WorkQueue joiner; int m, j; + Submitter z = submitters.get(); + WorkQueue[] ws = workQueues; + int s = 0; + if (z != null && ws != null && (m = ws.length - 1) >= 0 && + (joiner = ws[(j = z.seed) & m & SQMASK]) != null && task != null) { + int scans = m + m + 1; + long c = 0L; // for stability check + j |= 1; // poll odd queues + for (int k = scans; ; j += 2) { + WorkQueue q; + if ((s = task.status) < 0) + break; + else if (joiner.externalPopAndExecCC(task)) + k = scans; + else if ((s = task.status) < 0) + break; + else if ((q = ws[j & m]) != null && q.pollAndExecCC(task)) + k = scans; + else if (--k < 0) { + if (c == (c = ctl)) + break; + k = scans; + } + } + } + return s; + } + + // Exported methods + + // Constructors + + /** + * Creates a {@code ForkJoinPool} with parallelism equal to {@link + * java.lang.Runtime#availableProcessors}, using the {@linkplain + * #defaultForkJoinWorkerThreadFactory default thread factory}, + * no UncaughtExceptionHandler, and non-async LIFO processing mode. + * + * @throws SecurityException if a security manager exists and + * the caller is not permitted to modify threads + * because it does not hold {@link + * java.lang.RuntimePermission}{@code ("modifyThread")} + */ + public ForkJoinPool() { + this(Math.min(MAX_CAP, Runtime.getRuntime().availableProcessors()), + defaultForkJoinWorkerThreadFactory, null, false); + } + + /** + * Creates a {@code ForkJoinPool} with the indicated parallelism + * level, the {@linkplain + * #defaultForkJoinWorkerThreadFactory default thread factory}, + * no UncaughtExceptionHandler, and non-async LIFO processing mode. + * + * @param parallelism the parallelism level + * @throws IllegalArgumentException if parallelism less than or + * equal to zero, or greater than implementation limit + * @throws SecurityException if a security manager exists and + * the caller is not permitted to modify threads + * because it does not hold {@link + * java.lang.RuntimePermission}{@code ("modifyThread")} + */ + public ForkJoinPool(int parallelism) { + this(parallelism, defaultForkJoinWorkerThreadFactory, null, false); + } + + /** + * Creates a {@code ForkJoinPool} with the given parameters. + * + * @param parallelism the parallelism level. For default value, + * use {@link java.lang.Runtime#availableProcessors}. + * @param factory the factory for creating new threads. For default value, + * use {@link #defaultForkJoinWorkerThreadFactory}. + * @param handler the handler for internal worker threads that + * terminate due to unrecoverable errors encountered while executing + * tasks. For default value, use {@code null}. + * @param asyncMode if true, + * establishes local first-in-first-out scheduling mode for forked + * tasks that are never joined. This mode may be more appropriate + * than default locally stack-based mode in applications in which + * worker threads only process event-style asynchronous tasks. + * For default value, use {@code false}. + * @throws IllegalArgumentException if parallelism less than or + * equal to zero, or greater than implementation limit + * @throws NullPointerException if the factory is null + * @throws SecurityException if a security manager exists and + * the caller is not permitted to modify threads + * because it does not hold {@link + * java.lang.RuntimePermission}{@code ("modifyThread")} + */ + public ForkJoinPool(int parallelism, + ForkJoinWorkerThreadFactory factory, + UncaughtExceptionHandler handler, + boolean asyncMode) { + this(checkParallelism(parallelism), + checkFactory(factory), + handler, + (asyncMode ? FIFO_QUEUE : LIFO_QUEUE), + "ForkJoinPool-" + nextPoolId() + "-worker-"); + checkPermission(); + } + + private static int checkParallelism(int parallelism) { + if (parallelism <= 0 || parallelism > MAX_CAP) + throw new IllegalArgumentException(); + return parallelism; + } + + private static ForkJoinWorkerThreadFactory checkFactory + (ForkJoinWorkerThreadFactory factory) { + if (factory == null) + throw new NullPointerException(); + return factory; + } + + /** + * Creates a {@code ForkJoinPool} with the given parameters, without + * any security checks or parameter validation. Invoked directly by + * makeCommonPool. + */ + private ForkJoinPool(int parallelism, + ForkJoinWorkerThreadFactory factory, + UncaughtExceptionHandler handler, + int mode, + String workerNamePrefix) { + this.workerNamePrefix = workerNamePrefix; + this.factory = factory; + this.ueh = handler; + this.mode = (short)mode; + this.parallelism = (short)parallelism; + long np = (long)(-parallelism); // offset ctl counts + this.ctl = ((np << AC_SHIFT) & AC_MASK) | ((np << TC_SHIFT) & TC_MASK); + } + + /** + * Returns the common pool instance. This pool is statically + * constructed; its run state is unaffected by attempts to {@link + * #shutdown} or {@link #shutdownNow}. However this pool and any + * ongoing processing are automatically terminated upon program + * {@link System#exit}. Any program that relies on asynchronous + * task processing to complete before program termination should + * invoke {@code commonPool().}{@link #awaitQuiescence awaitQuiescence}, + * before exit. + * + * @return the common pool instance + * @since 1.8 + */ + public static ForkJoinPool commonPool() { + // assert common != null : "static init error"; + return common; + } + + // Execution methods + + /** + * Performs the given task, returning its result upon completion. + * If the computation encounters an unchecked Exception or Error, + * it is rethrown as the outcome of this invocation. Rethrown + * exceptions behave in the same way as regular exceptions, but, + * when possible, contain stack traces (as displayed for example + * using {@code ex.printStackTrace()}) of both the current thread + * as well as the thread actually encountering the exception; + * minimally only the latter. + * + * @param task the task + * @param the type of the task's result + * @return the task's result + * @throws NullPointerException if the task is null + * @throws RejectedExecutionException if the task cannot be + * scheduled for execution + */ + public T invoke(ForkJoinTask task) { + if (task == null) + throw new NullPointerException(); + externalPush(task); + return task.join(); + } + + /** + * Arranges for (asynchronous) execution of the given task. + * + * @param task the task + * @throws NullPointerException if the task is null + * @throws RejectedExecutionException if the task cannot be + * scheduled for execution + */ + public void execute(ForkJoinTask task) { + if (task == null) + throw new NullPointerException(); + externalPush(task); + } + + // AbstractExecutorService methods + + /** + * @throws NullPointerException if the task is null + * @throws RejectedExecutionException if the task cannot be + * scheduled for execution + */ + public void execute(Runnable task) { + if (task == null) + throw new NullPointerException(); + ForkJoinTask job; + if (task instanceof ForkJoinTask) // avoid re-wrap + job = (ForkJoinTask) task; + else + job = new ForkJoinTask.RunnableExecuteAction(task); + externalPush(job); + } + + /** + * Submits a ForkJoinTask for execution. + * + * @param task the task to submit + * @param the type of the task's result + * @return the task + * @throws NullPointerException if the task is null + * @throws RejectedExecutionException if the task cannot be + * scheduled for execution + */ + public ForkJoinTask submit(ForkJoinTask task) { + if (task == null) + throw new NullPointerException(); + externalPush(task); + return task; + } + + /** + * @throws NullPointerException if the task is null + * @throws RejectedExecutionException if the task cannot be + * scheduled for execution + */ + public ForkJoinTask submit(Callable task) { + ForkJoinTask job = new ForkJoinTask.AdaptedCallable(task); + externalPush(job); + return job; + } + + /** + * @throws NullPointerException if the task is null + * @throws RejectedExecutionException if the task cannot be + * scheduled for execution + */ + public ForkJoinTask submit(Runnable task, T result) { + ForkJoinTask job = new ForkJoinTask.AdaptedRunnable(task, result); + externalPush(job); + return job; + } + + /** + * @throws NullPointerException if the task is null + * @throws RejectedExecutionException if the task cannot be + * scheduled for execution + */ + public ForkJoinTask submit(Runnable task) { + if (task == null) + throw new NullPointerException(); + ForkJoinTask job; + if (task instanceof ForkJoinTask) // avoid re-wrap + job = (ForkJoinTask) task; + else + job = new ForkJoinTask.AdaptedRunnableAction(task); + externalPush(job); + return job; + } + + /** + * @throws NullPointerException {@inheritDoc} + * @throws RejectedExecutionException {@inheritDoc} + */ + public List> invokeAll(Collection> tasks) { + // In previous versions of this class, this method constructed + // a task to run ForkJoinTask.invokeAll, but now external + // invocation of multiple tasks is at least as efficient. + ArrayList> futures = new ArrayList>(tasks.size()); + + boolean done = false; + try { + for (Callable t : tasks) { + ForkJoinTask f = new ForkJoinTask.AdaptedCallable(t); + futures.add(f); + externalPush(f); + } + for (int i = 0, size = futures.size(); i < size; i++) + ((ForkJoinTask)futures.get(i)).quietlyJoin(); + done = true; + return futures; + } finally { + if (!done) + for (int i = 0, size = futures.size(); i < size; i++) + futures.get(i).cancel(false); + } + } + + /** + * Returns the factory used for constructing new workers. + * + * @return the factory used for constructing new workers + */ + public ForkJoinWorkerThreadFactory getFactory() { + return factory; + } + + /** + * Returns the handler for internal worker threads that terminate + * due to unrecoverable errors encountered while executing tasks. + * + * @return the handler, or {@code null} if none + */ + public UncaughtExceptionHandler getUncaughtExceptionHandler() { + return ueh; + } + + /** + * Returns the targeted parallelism level of this pool. + * + * @return the targeted parallelism level of this pool + */ + public int getParallelism() { + int par; + return ((par = parallelism) > 0) ? par : 1; + } + + /** + * Returns the targeted parallelism level of the common pool. + * + * @return the targeted parallelism level of the common pool + * @since 1.8 + */ + public static int getCommonPoolParallelism() { + return commonParallelism; + } + + /** + * Returns the number of worker threads that have started but not + * yet terminated. The result returned by this method may differ + * from {@link #getParallelism} when threads are created to + * maintain parallelism when others are cooperatively blocked. + * + * @return the number of worker threads + */ + public int getPoolSize() { + return parallelism + (short)(ctl >>> TC_SHIFT); + } + + /** + * Returns {@code true} if this pool uses local first-in-first-out + * scheduling mode for forked tasks that are never joined. + * + * @return {@code true} if this pool uses async mode + */ + public boolean getAsyncMode() { + return mode == FIFO_QUEUE; + } + + /** + * Returns an estimate of the number of worker threads that are + * not blocked waiting to join tasks or for other managed + * synchronization. This method may overestimate the + * number of running threads. + * + * @return the number of worker threads + */ + public int getRunningThreadCount() { + int rc = 0; + WorkQueue[] ws; WorkQueue w; + if ((ws = workQueues) != null) { + for (int i = 1; i < ws.length; i += 2) { + if ((w = ws[i]) != null && w.isApparentlyUnblocked()) + ++rc; + } + } + return rc; + } + + /** + * Returns an estimate of the number of threads that are currently + * stealing or executing tasks. This method may overestimate the + * number of active threads. + * + * @return the number of active threads + */ + public int getActiveThreadCount() { + int r = parallelism + (int)(ctl >> AC_SHIFT); + return (r <= 0) ? 0 : r; // suppress momentarily negative values + } + + /** + * Returns {@code true} if all worker threads are currently idle. + * An idle worker is one that cannot obtain a task to execute + * because none are available to steal from other threads, and + * there are no pending submissions to the pool. This method is + * conservative; it might not return {@code true} immediately upon + * idleness of all threads, but will eventually become true if + * threads remain inactive. + * + * @return {@code true} if all threads are currently idle + */ + public boolean isQuiescent() { + return parallelism + (int)(ctl >> AC_SHIFT) <= 0; + } + + /** + * Returns an estimate of the total number of tasks stolen from + * one thread's work queue by another. The reported value + * underestimates the actual total number of steals when the pool + * is not quiescent. This value may be useful for monitoring and + * tuning fork/join programs: in general, steal counts should be + * high enough to keep threads busy, but low enough to avoid + * overhead and contention across threads. + * + * @return the number of steals + */ + public long getStealCount() { + long count = stealCount; + WorkQueue[] ws; WorkQueue w; + if ((ws = workQueues) != null) { + for (int i = 1; i < ws.length; i += 2) { + if ((w = ws[i]) != null) + count += w.nsteals; + } + } + return count; + } + + /** + * Returns an estimate of the total number of tasks currently held + * in queues by worker threads (but not including tasks submitted + * to the pool that have not begun executing). This value is only + * an approximation, obtained by iterating across all threads in + * the pool. This method may be useful for tuning task + * granularities. + * + * @return the number of queued tasks + */ + public long getQueuedTaskCount() { + long count = 0; + WorkQueue[] ws; WorkQueue w; + if ((ws = workQueues) != null) { + for (int i = 1; i < ws.length; i += 2) { + if ((w = ws[i]) != null) + count += w.queueSize(); + } + } + return count; + } + + /** + * Returns an estimate of the number of tasks submitted to this + * pool that have not yet begun executing. This method may take + * time proportional to the number of submissions. + * + * @return the number of queued submissions + */ + public int getQueuedSubmissionCount() { + int count = 0; + WorkQueue[] ws; WorkQueue w; + if ((ws = workQueues) != null) { + for (int i = 0; i < ws.length; i += 2) { + if ((w = ws[i]) != null) + count += w.queueSize(); + } + } + return count; + } + + /** + * Returns {@code true} if there are any tasks submitted to this + * pool that have not yet begun executing. + * + * @return {@code true} if there are any queued submissions + */ + public boolean hasQueuedSubmissions() { + WorkQueue[] ws; WorkQueue w; + if ((ws = workQueues) != null) { + for (int i = 0; i < ws.length; i += 2) { + if ((w = ws[i]) != null && !w.isEmpty()) + return true; + } + } + return false; + } + + /** + * Removes and returns the next unexecuted submission if one is + * available. This method may be useful in extensions to this + * class that re-assign work in systems with multiple pools. + * + * @return the next submission, or {@code null} if none + */ + protected ForkJoinTask pollSubmission() { + WorkQueue[] ws; WorkQueue w; ForkJoinTask t; + if ((ws = workQueues) != null) { + for (int i = 0; i < ws.length; i += 2) { + if ((w = ws[i]) != null && (t = w.poll()) != null) + return t; + } + } + return null; + } + + /** + * Removes all available unexecuted submitted and forked tasks + * from scheduling queues and adds them to the given collection, + * without altering their execution status. These may include + * artificially generated or wrapped tasks. This method is + * designed to be invoked only when the pool is known to be + * quiescent. Invocations at other times may not remove all + * tasks. A failure encountered while attempting to add elements + * to collection {@code c} may result in elements being in + * neither, either or both collections when the associated + * exception is thrown. The behavior of this operation is + * undefined if the specified collection is modified while the + * operation is in progress. + * + * @param c the collection to transfer elements into + * @return the number of elements transferred + */ + protected int drainTasksTo(Collection> c) { + int count = 0; + WorkQueue[] ws; WorkQueue w; ForkJoinTask t; + if ((ws = workQueues) != null) { + for (int i = 0; i < ws.length; ++i) { + if ((w = ws[i]) != null) { + while ((t = w.poll()) != null) { + c.add(t); + ++count; + } + } + } + } + return count; + } + + /** + * Returns a string identifying this pool, as well as its state, + * including indications of run state, parallelism level, and + * worker and task counts. + * + * @return a string identifying this pool, as well as its state + */ + public String toString() { + // Use a single pass through workQueues to collect counts + long qt = 0L, qs = 0L; int rc = 0; + long st = stealCount; + long c = ctl; + WorkQueue[] ws; WorkQueue w; + if ((ws = workQueues) != null) { + for (int i = 0; i < ws.length; ++i) { + if ((w = ws[i]) != null) { + int size = w.queueSize(); + if ((i & 1) == 0) + qs += size; + else { + qt += size; + st += w.nsteals; + if (w.isApparentlyUnblocked()) + ++rc; + } + } + } + } + int pc = parallelism; + int tc = pc + (short)(c >>> TC_SHIFT); + int ac = pc + (int)(c >> AC_SHIFT); + if (ac < 0) // ignore transient negative + ac = 0; + String level; + if ((c & STOP_BIT) != 0) + level = (tc == 0) ? "Terminated" : "Terminating"; + else + level = plock < 0 ? "Shutting down" : "Running"; + return super.toString() + + "[" + level + + ", parallelism = " + pc + + ", size = " + tc + + ", active = " + ac + + ", running = " + rc + + ", steals = " + st + + ", tasks = " + qt + + ", submissions = " + qs + + "]"; + } + + /** + * Possibly initiates an orderly shutdown in which previously + * submitted tasks are executed, but no new tasks will be + * accepted. Invocation has no effect on execution state if this + * is the {@link #commonPool()}, and no additional effect if + * already shut down. Tasks that are in the process of being + * submitted concurrently during the course of this method may or + * may not be rejected. + * + * @throws SecurityException if a security manager exists and + * the caller is not permitted to modify threads + * because it does not hold {@link + * java.lang.RuntimePermission}{@code ("modifyThread")} + */ + public void shutdown() { + checkPermission(); + tryTerminate(false, true); + } + + /** + * Possibly attempts to cancel and/or stop all tasks, and reject + * all subsequently submitted tasks. Invocation has no effect on + * execution state if this is the {@link #commonPool()}, and no + * additional effect if already shut down. Otherwise, tasks that + * are in the process of being submitted or executed concurrently + * during the course of this method may or may not be + * rejected. This method cancels both existing and unexecuted + * tasks, in order to permit termination in the presence of task + * dependencies. So the method always returns an empty list + * (unlike the case for some other Executors). + * + * @return an empty list + * @throws SecurityException if a security manager exists and + * the caller is not permitted to modify threads + * because it does not hold {@link + * java.lang.RuntimePermission}{@code ("modifyThread")} + */ + public List shutdownNow() { + checkPermission(); + tryTerminate(true, true); + return Collections.emptyList(); + } + + /** + * Returns {@code true} if all tasks have completed following shut down. + * + * @return {@code true} if all tasks have completed following shut down + */ + public boolean isTerminated() { + long c = ctl; + return ((c & STOP_BIT) != 0L && + (short)(c >>> TC_SHIFT) + parallelism <= 0); + } + + /** + * Returns {@code true} if the process of termination has + * commenced but not yet completed. This method may be useful for + * debugging. A return of {@code true} reported a sufficient + * period after shutdown may indicate that submitted tasks have + * ignored or suppressed interruption, or are waiting for I/O, + * causing this executor not to properly terminate. (See the + * advisory notes for class {@link ForkJoinTask} stating that + * tasks should not normally entail blocking operations. But if + * they do, they must abort them on interrupt.) + * + * @return {@code true} if terminating but not yet terminated + */ + public boolean isTerminating() { + long c = ctl; + return ((c & STOP_BIT) != 0L && + (short)(c >>> TC_SHIFT) + parallelism > 0); + } + + /** + * Returns {@code true} if this pool has been shut down. + * + * @return {@code true} if this pool has been shut down + */ + public boolean isShutdown() { + return plock < 0; + } + + /** + * Blocks until all tasks have completed execution after a + * shutdown request, or the timeout occurs, or the current thread + * is interrupted, whichever happens first. Because the {@link + * #commonPool()} never terminates until program shutdown, when + * applied to the common pool, this method is equivalent to {@link + * #awaitQuiescence(long, TimeUnit)} but always returns {@code false}. + * + * @param timeout the maximum time to wait + * @param unit the time unit of the timeout argument + * @return {@code true} if this executor terminated and + * {@code false} if the timeout elapsed before termination + * @throws InterruptedException if interrupted while waiting + */ + public boolean awaitTermination(long timeout, TimeUnit unit) + throws InterruptedException { + if (Thread.interrupted()) + throw new InterruptedException(); + if (this == common) { + awaitQuiescence(timeout, unit); + return false; + } + long nanos = unit.toNanos(timeout); + if (isTerminated()) + return true; + if (nanos <= 0L) + return false; + long deadline = System.nanoTime() + nanos; + synchronized (this) { + for (;;) { + if (isTerminated()) + return true; + if (nanos <= 0L) + return false; + long millis = TimeUnit.NANOSECONDS.toMillis(nanos); + wait(millis > 0L ? millis : 1L); + nanos = deadline - System.nanoTime(); + } + } + } + + /** + * If called by a ForkJoinTask operating in this pool, equivalent + * in effect to {@link ForkJoinTask#helpQuiesce}. Otherwise, + * waits and/or attempts to assist performing tasks until this + * pool {@link #isQuiescent} or the indicated timeout elapses. + * + * @param timeout the maximum time to wait + * @param unit the time unit of the timeout argument + * @return {@code true} if quiescent; {@code false} if the + * timeout elapsed. + */ + public boolean awaitQuiescence(long timeout, TimeUnit unit) { + long nanos = unit.toNanos(timeout); + ForkJoinWorkerThread wt; + Thread thread = Thread.currentThread(); + if ((thread instanceof ForkJoinWorkerThread) && + (wt = (ForkJoinWorkerThread)thread).pool == this) { + helpQuiescePool(wt.workQueue); + return true; + } + long startTime = System.nanoTime(); + WorkQueue[] ws; + int r = 0, m; + boolean found = true; + while (!isQuiescent() && (ws = workQueues) != null && + (m = ws.length - 1) >= 0) { + if (!found) { + if ((System.nanoTime() - startTime) > nanos) + return false; + Thread.yield(); // cannot block + } + found = false; + for (int j = (m + 1) << 2; j >= 0; --j) { + ForkJoinTask t; WorkQueue q; int b; + if ((q = ws[r++ & m]) != null && (b = q.base) - q.top < 0) { + found = true; + if ((t = q.pollAt(b)) != null) + t.doExec(); + break; + } + } + } + return true; + } + + /** + * Waits and/or attempts to assist performing tasks indefinitely + * until the {@link #commonPool()} {@link #isQuiescent}. + */ + static void quiesceCommonPool() { + common.awaitQuiescence(Long.MAX_VALUE, TimeUnit.NANOSECONDS); + } + + /** + * Interface for extending managed parallelism for tasks running + * in {@link ForkJoinPool}s. + * + *

A {@code ManagedBlocker} provides two methods. Method + * {@code isReleasable} must return {@code true} if blocking is + * not necessary. Method {@code block} blocks the current thread + * if necessary (perhaps internally invoking {@code isReleasable} + * before actually blocking). These actions are performed by any + * thread invoking {@link ForkJoinPool#managedBlock(ManagedBlocker)}. + * The unusual methods in this API accommodate synchronizers that + * may, but don't usually, block for long periods. Similarly, they + * allow more efficient internal handling of cases in which + * additional workers may be, but usually are not, needed to + * ensure sufficient parallelism. Toward this end, + * implementations of method {@code isReleasable} must be amenable + * to repeated invocation. + * + *

For example, here is a ManagedBlocker based on a + * ReentrantLock: + * 

 {@code
+     * class ManagedLocker implements ManagedBlocker {
+     *   final ReentrantLock lock;
+     *   boolean hasLock = false;
+     *   ManagedLocker(ReentrantLock lock) { this.lock = lock; }
+     *   public boolean block() {
+     *     if (!hasLock)
+     *       lock.lock();
+     *     return true;
+     *   }
+     *   public boolean isReleasable() {
+     *     return hasLock || (hasLock = lock.tryLock());
+     *   }
+     * }}
+ * + *

Here is a class that possibly blocks waiting for an + * item on a given queue: + * 

 {@code
+     * class QueueTaker implements ManagedBlocker {
+     *   final BlockingQueue queue;
+     *   volatile E item = null;
+     *   QueueTaker(BlockingQueue q) { this.queue = q; }
+     *   public boolean block() throws InterruptedException {
+     *     if (item == null)
+     *       item = queue.take();
+     *     return true;
+     *   }
+     *   public boolean isReleasable() {
+     *     return item != null || (item = queue.poll()) != null;
+     *   }
+     *   public E getItem() { // call after pool.managedBlock completes
+     *     return item;
+     *   }
+     * }}
+ */ + public static interface ManagedBlocker { + /** + * Possibly blocks the current thread, for example waiting for + * a lock or condition. + * + * @return {@code true} if no additional blocking is necessary + * (i.e., if isReleasable would return true) + * @throws InterruptedException if interrupted while waiting + * (the method is not required to do so, but is allowed to) + */ + boolean block() throws InterruptedException; + + /** + * Returns {@code true} if blocking is unnecessary. + * @return {@code true} if blocking is unnecessary + */ + boolean isReleasable(); + } + + /** + * Blocks in accord with the given blocker. If the current thread + * is a {@link ForkJoinWorkerThread}, this method possibly + * arranges for a spare thread to be activated if necessary to + * ensure sufficient parallelism while the current thread is blocked. + * + *

If the caller is not a {@link ForkJoinTask}, this method is + * behaviorally equivalent to + * 

 {@code
+     * while (!blocker.isReleasable())
+     *   if (blocker.block())
+     *     return;
+     * }
+ * + * If the caller is a {@code ForkJoinTask}, then the pool may + * first be expanded to ensure parallelism, and later adjusted. + * + * @param blocker the blocker + * @throws InterruptedException if blocker.block did so + */ + public static void managedBlock(ManagedBlocker blocker) + throws InterruptedException { + Thread t = Thread.currentThread(); + if (t instanceof ForkJoinWorkerThread) { + ForkJoinPool p = ((ForkJoinWorkerThread)t).pool; + while (!blocker.isReleasable()) { + if (p.tryCompensate(p.ctl)) { + try { + do {} while (!blocker.isReleasable() && + !blocker.block()); + } finally { + p.incrementActiveCount(); + } + break; + } + } + } + else { + do {} while (!blocker.isReleasable() && + !blocker.block()); + } + } + + // AbstractExecutorService overrides. These rely on undocumented + // fact that ForkJoinTask.adapt returns ForkJoinTasks that also + // implement RunnableFuture. + + protected RunnableFuture newTaskFor(Runnable runnable, T value) { + return new ForkJoinTask.AdaptedRunnable(runnable, value); + } + + protected RunnableFuture newTaskFor(Callable callable) { + return new ForkJoinTask.AdaptedCallable(callable); + } + + // Unsafe mechanics + private static final sun.misc.Unsafe U; + private static final long CTL; + private static final long PARKBLOCKER; + private static final int ABASE; + private static final int ASHIFT; + private static final long STEALCOUNT; + private static final long PLOCK; + private static final long INDEXSEED; + private static final long QBASE; + private static final long QLOCK; + + static { + // initialize field offsets for CAS etc + try { + U = getUnsafe(); + Class k = ForkJoinPool.class; + CTL = U.objectFieldOffset + (k.getDeclaredField("ctl")); + STEALCOUNT = U.objectFieldOffset + (k.getDeclaredField("stealCount")); + PLOCK = U.objectFieldOffset + (k.getDeclaredField("plock")); + INDEXSEED = U.objectFieldOffset + (k.getDeclaredField("indexSeed")); + Class tk = Thread.class; + PARKBLOCKER = U.objectFieldOffset + (tk.getDeclaredField("parkBlocker")); + Class wk = WorkQueue.class; + QBASE = U.objectFieldOffset + (wk.getDeclaredField("base")); + QLOCK = U.objectFieldOffset + (wk.getDeclaredField("qlock")); + Class ak = ForkJoinTask[].class; + ABASE = U.arrayBaseOffset(ak); + int scale = U.arrayIndexScale(ak); + if ((scale & (scale - 1)) != 0) + throw new Error("data type scale not a power of two"); + ASHIFT = 31 - Integer.numberOfLeadingZeros(scale); + } catch (Exception e) { + throw new Error(e); + } + + submitters = new ThreadLocal(); + defaultForkJoinWorkerThreadFactory = + new DefaultForkJoinWorkerThreadFactory(); + modifyThreadPermission = new RuntimePermission("modifyThread"); + + common = java.security.AccessController.doPrivileged + (new java.security.PrivilegedAction() { + public ForkJoinPool run() { return makeCommonPool(); }}); + int par = common.parallelism; // report 1 even if threads disabled + commonParallelism = par > 0 ? par : 1; + } + + /** + * Creates and returns the common pool, respecting user settings + * specified via system properties. + */ + private static ForkJoinPool makeCommonPool() { + int parallelism = -1; + ForkJoinWorkerThreadFactory factory + = defaultForkJoinWorkerThreadFactory; + UncaughtExceptionHandler handler = null; + try { // ignore exceptions in accessing/parsing properties + String pp = System.getProperty + ("java.util.concurrent.ForkJoinPool.common.parallelism"); + String fp = System.getProperty + ("java.util.concurrent.ForkJoinPool.common.threadFactory"); + String hp = System.getProperty + ("java.util.concurrent.ForkJoinPool.common.exceptionHandler"); + if (pp != null) + parallelism = Integer.parseInt(pp); + if (fp != null) + factory = ((ForkJoinWorkerThreadFactory)ClassLoader. + getSystemClassLoader().loadClass(fp).newInstance()); + if (hp != null) + handler = ((UncaughtExceptionHandler)ClassLoader. + getSystemClassLoader().loadClass(hp).newInstance()); + } catch (Exception ignore) { + } + + if (parallelism < 0 && // default 1 less than #cores + (parallelism = Runtime.getRuntime().availableProcessors() - 1) < 0) + parallelism = 0; + if (parallelism > MAX_CAP) + parallelism = MAX_CAP; + return new ForkJoinPool(parallelism, factory, handler, LIFO_QUEUE, + "ForkJoinPool.commonPool-worker-"); + } + + /** + * Returns a sun.misc.Unsafe. Suitable for use in a 3rd party package. + * Replace with a simple call to Unsafe.getUnsafe when integrating + * into a jdk. + * + * @return a sun.misc.Unsafe + */ + private static sun.misc.Unsafe getUnsafe() { + try { + return sun.misc.Unsafe.getUnsafe(); + } catch (SecurityException tryReflectionInstead) {} + try { + return java.security.AccessController.doPrivileged + (new java.security.PrivilegedExceptionAction() { + public sun.misc.Unsafe run() throws Exception { + Class k = sun.misc.Unsafe.class; + for (java.lang.reflect.Field f : k.getDeclaredFields()) { + f.setAccessible(true); + Object x = f.get(null); + if (k.isInstance(x)) + return k.cast(x); + } + throw new NoSuchFieldError("the Unsafe"); + }}); + } catch (java.security.PrivilegedActionException e) { + throw new RuntimeException("Could not initialize intrinsics", + e.getCause()); + } + } +} + diff --git a/src/main/java/jsr166e/ForkJoinTask.java b/src/main/java/jsr166e/ForkJoinTask.java new file mode 100644 index 0000000000000..eb58114c2be7c --- /dev/null +++ b/src/main/java/jsr166e/ForkJoinTask.java @@ -0,0 +1,1557 @@ +// Rev 1.16 from http://gee.cs.oswego.edu/cgi-bin/viewcvs.cgi/jsr166/src/jsr166e/ForkJoinTask.java?view=co + +/* + * Written by Doug Lea with assistance from members of JCP JSR-166 + * Expert Group and released to the public domain, as explained at + * http://creativecommons.org/publicdomain/zero/1.0/ + */ + +package jsr166e; + +import java.io.Serializable; +import java.util.Collection; +import java.util.List; +import java.util.RandomAccess; +import java.lang.ref.WeakReference; +import java.lang.ref.ReferenceQueue; +import java.util.concurrent.Callable; +import java.util.concurrent.CancellationException; +import java.util.concurrent.ExecutionException; +import java.util.concurrent.Future; +import java.util.concurrent.RejectedExecutionException; +import java.util.concurrent.RunnableFuture; +import java.util.concurrent.TimeUnit; +import java.util.concurrent.TimeoutException; +import java.util.concurrent.locks.ReentrantLock; +import java.lang.reflect.Constructor; + +/** + * Abstract base class for tasks that run within a {@link ForkJoinPool}. + * A {@code ForkJoinTask} is a thread-like entity that is much + * lighter weight than a normal thread. Huge numbers of tasks and + * subtasks may be hosted by a small number of actual threads in a + * ForkJoinPool, at the price of some usage limitations. + * + *

A "main" {@code ForkJoinTask} begins execution when it is + * explicitly submitted to a {@link ForkJoinPool}, or, if not already + * engaged in a ForkJoin computation, commenced in the {@link + * ForkJoinPool#commonPool()} via {@link #fork}, {@link #invoke}, or + * related methods. Once started, it will usually in turn start other + * subtasks. As indicated by the name of this class, many programs + * using {@code ForkJoinTask} employ only methods {@link #fork} and + * {@link #join}, or derivatives such as {@link + * #invokeAll(ForkJoinTask...) invokeAll}. However, this class also + * provides a number of other methods that can come into play in + * advanced usages, as well as extension mechanics that allow support + * of new forms of fork/join processing. + * + *

A {@code ForkJoinTask} is a lightweight form of {@link Future}. + * The efficiency of {@code ForkJoinTask}s stems from a set of + * restrictions (that are only partially statically enforceable) + * reflecting their main use as computational tasks calculating pure + * functions or operating on purely isolated objects. The primary + * coordination mechanisms are {@link #fork}, that arranges + * asynchronous execution, and {@link #join}, that doesn't proceed + * until the task's result has been computed. Computations should + * ideally avoid {@code synchronized} methods or blocks, and should + * minimize other blocking synchronization apart from joining other + * tasks or using synchronizers such as Phasers that are advertised to + * cooperate with fork/join scheduling. Subdividable tasks should also + * not perform blocking I/O, and should ideally access variables that + * are completely independent of those accessed by other running + * tasks. These guidelines are loosely enforced by not permitting + * checked exceptions such as {@code IOExceptions} to be + * thrown. However, computations may still encounter unchecked + * exceptions, that are rethrown to callers attempting to join + * them. These exceptions may additionally include {@link + * RejectedExecutionException} stemming from internal resource + * exhaustion, such as failure to allocate internal task + * queues. Rethrown exceptions behave in the same way as regular + * exceptions, but, when possible, contain stack traces (as displayed + * for example using {@code ex.printStackTrace()}) of both the thread + * that initiated the computation as well as the thread actually + * encountering the exception; minimally only the latter. + * + *

It is possible to define and use ForkJoinTasks that may block, + * but doing do requires three further considerations: (1) Completion + * of few if any other tasks should be dependent on a task + * that blocks on external synchronization or I/O. Event-style async + * tasks that are never joined (for example, those subclassing {@link + * CountedCompleter}) often fall into this category. (2) To minimize + * resource impact, tasks should be small; ideally performing only the + * (possibly) blocking action. (3) Unless the {@link + * ForkJoinPool.ManagedBlocker} API is used, or the number of possibly + * blocked tasks is known to be less than the pool's {@link + * ForkJoinPool#getParallelism} level, the pool cannot guarantee that + * enough threads will be available to ensure progress or good + * performance. + * + *

The primary method for awaiting completion and extracting + * results of a task is {@link #join}, but there are several variants: + * The {@link Future#get} methods support interruptible and/or timed + * waits for completion and report results using {@code Future} + * conventions. Method {@link #invoke} is semantically + * equivalent to {@code fork(); join()} but always attempts to begin + * execution in the current thread. The "quiet" forms of + * these methods do not extract results or report exceptions. These + * may be useful when a set of tasks are being executed, and you need + * to delay processing of results or exceptions until all complete. + * Method {@code invokeAll} (available in multiple versions) + * performs the most common form of parallel invocation: forking a set + * of tasks and joining them all. + * + *

In the most typical usages, a fork-join pair act like a call + * (fork) and return (join) from a parallel recursive function. As is + * the case with other forms of recursive calls, returns (joins) + * should be performed innermost-first. For example, {@code a.fork(); + * b.fork(); b.join(); a.join();} is likely to be substantially more + * efficient than joining {@code a} before {@code b}. + * + *

The execution status of tasks may be queried at several levels + * of detail: {@link #isDone} is true if a task completed in any way + * (including the case where a task was cancelled without executing); + * {@link #isCompletedNormally} is true if a task completed without + * cancellation or encountering an exception; {@link #isCancelled} is + * true if the task was cancelled (in which case {@link #getException} + * returns a {@link java.util.concurrent.CancellationException}); and + * {@link #isCompletedAbnormally} is true if a task was either + * cancelled or encountered an exception, in which case {@link + * #getException} will return either the encountered exception or + * {@link java.util.concurrent.CancellationException}. + * + *

The ForkJoinTask class is not usually directly subclassed. + * Instead, you subclass one of the abstract classes that support a + * particular style of fork/join processing, typically {@link + * RecursiveAction} for most computations that do not return results, + * {@link RecursiveTask} for those that do, and {@link + * CountedCompleter} for those in which completed actions trigger + * other actions. Normally, a concrete ForkJoinTask subclass declares + * fields comprising its parameters, established in a constructor, and + * then defines a {@code compute} method that somehow uses the control + * methods supplied by this base class. + * + *

Method {@link #join} and its variants are appropriate for use + * only when completion dependencies are acyclic; that is, the + * parallel computation can be described as a directed acyclic graph + * (DAG). Otherwise, executions may encounter a form of deadlock as + * tasks cyclically wait for each other. However, this framework + * supports other methods and techniques (for example the use of + * {@link java.util.concurrent.Phaser Phaser}, {@link #helpQuiesce}, and {@link #complete}) that + * may be of use in constructing custom subclasses for problems that + * are not statically structured as DAGs. To support such usages, a + * ForkJoinTask may be atomically tagged with a {@code short} + * value using {@link #setForkJoinTaskTag} or {@link + * #compareAndSetForkJoinTaskTag} and checked using {@link + * #getForkJoinTaskTag}. The ForkJoinTask implementation does not use + * these {@code protected} methods or tags for any purpose, but they + * may be of use in the construction of specialized subclasses. For + * example, parallel graph traversals can use the supplied methods to + * avoid revisiting nodes/tasks that have already been processed. + * (Method names for tagging are bulky in part to encourage definition + * of methods that reflect their usage patterns.) + * + *

Most base support methods are {@code final}, to prevent + * overriding of implementations that are intrinsically tied to the + * underlying lightweight task scheduling framework. Developers + * creating new basic styles of fork/join processing should minimally + * implement {@code protected} methods {@link #exec}, {@link + * #setRawResult}, and {@link #getRawResult}, while also introducing + * an abstract computational method that can be implemented in its + * subclasses, possibly relying on other {@code protected} methods + * provided by this class. + * + *

ForkJoinTasks should perform relatively small amounts of + * computation. Large tasks should be split into smaller subtasks, + * usually via recursive decomposition. As a very rough rule of thumb, + * a task should perform more than 100 and less than 10000 basic + * computational steps, and should avoid indefinite looping. If tasks + * are too big, then parallelism cannot improve throughput. If too + * small, then memory and internal task maintenance overhead may + * overwhelm processing. + * + *

This class provides {@code adapt} methods for {@link Runnable} + * and {@link Callable}, that may be of use when mixing execution of + * {@code ForkJoinTasks} with other kinds of tasks. When all tasks are + * of this form, consider using a pool constructed in asyncMode. + * + *

ForkJoinTasks are {@code Serializable}, which enables them to be + * used in extensions such as remote execution frameworks. It is + * sensible to serialize tasks only before or after, but not during, + * execution. Serialization is not relied on during execution itself. + * + * @since 1.7 + * @author Doug Lea + */ +public abstract class ForkJoinTask implements Future, Serializable { + + /* + * See the internal documentation of class ForkJoinPool for a + * general implementation overview. ForkJoinTasks are mainly + * responsible for maintaining their "status" field amidst relays + * to methods in ForkJoinWorkerThread and ForkJoinPool. + * + * The methods of this class are more-or-less layered into + * (1) basic status maintenance + * (2) execution and awaiting completion + * (3) user-level methods that additionally report results. + * This is sometimes hard to see because this file orders exported + * methods in a way that flows well in javadocs. + */ + + /* + * The status field holds run control status bits packed into a + * single int to minimize footprint and to ensure atomicity (via + * CAS). Status is initially zero, and takes on nonnegative + * values until completed, upon which status (anded with + * DONE_MASK) holds value NORMAL, CANCELLED, or EXCEPTIONAL. Tasks + * undergoing blocking waits by other threads have the SIGNAL bit + * set. Completion of a stolen task with SIGNAL set awakens any + * waiters via notifyAll. Even though suboptimal for some + * purposes, we use basic builtin wait/notify to take advantage of + * "monitor inflation" in JVMs that we would otherwise need to + * emulate to avoid adding further per-task bookkeeping overhead. + * We want these monitors to be "fat", i.e., not use biasing or + * thin-lock techniques, so use some odd coding idioms that tend + * to avoid them, mainly by arranging that every synchronized + * block performs a wait, notifyAll or both. + * + * These control bits occupy only (some of) the upper half (16 + * bits) of status field. The lower bits are used for user-defined + * tags. + */ + + /** The run status of this task */ + volatile int status; // accessed directly by pool and workers + static final int DONE_MASK = 0xf0000000; // mask out non-completion bits + static final int NORMAL = 0xf0000000; // must be negative + static final int CANCELLED = 0xc0000000; // must be < NORMAL + static final int EXCEPTIONAL = 0x80000000; // must be < CANCELLED + static final int SIGNAL = 0x00010000; // must be >= 1 << 16 + static final int SMASK = 0x0000ffff; // short bits for tags + + /** + * Marks completion and wakes up threads waiting to join this + * task. + * + * @param completion one of NORMAL, CANCELLED, EXCEPTIONAL + * @return completion status on exit + */ + private int setCompletion(int completion) { + for (int s;;) { + if ((s = status) < 0) + return s; + if (U.compareAndSwapInt(this, STATUS, s, s | completion)) { + if ((s >>> 16) != 0) + synchronized (this) { notifyAll(); } + return completion; + } + } + } + + /** + * Primary execution method for stolen tasks. Unless done, calls + * exec and records status if completed, but doesn't wait for + * completion otherwise. + * + * @return status on exit from this method + */ + final int doExec() { + int s; boolean completed; + if ((s = status) >= 0) { + try { + completed = exec(); + } catch (Throwable rex) { + return setExceptionalCompletion(rex); + } + if (completed) + s = setCompletion(NORMAL); + } + return s; + } + + /** + * Tries to set SIGNAL status unless already completed. Used by + * ForkJoinPool. Other variants are directly incorporated into + * externalAwaitDone etc. + * + * @return true if successful + */ + final boolean trySetSignal() { + int s = status; + return s >= 0 && U.compareAndSwapInt(this, STATUS, s, s | SIGNAL); + } + + /** + * Blocks a non-worker-thread until completion. + * @return status upon completion + */ + private int externalAwaitDone() { + int s; + ForkJoinPool cp = ForkJoinPool.common; + if ((s = status) >= 0) { + if (cp != null) { + if (this instanceof CountedCompleter) + s = cp.externalHelpComplete((CountedCompleter)this); + else if (cp.tryExternalUnpush(this)) + s = doExec(); + } + if (s >= 0 && (s = status) >= 0) { + boolean interrupted = false; + do { + if (U.compareAndSwapInt(this, STATUS, s, s | SIGNAL)) { + synchronized (this) { + if (status >= 0) { + try { + wait(); + } catch (InterruptedException ie) { + interrupted = true; + } + } + else + notifyAll(); + } + } + } while ((s = status) >= 0); + if (interrupted) + Thread.currentThread().interrupt(); + } + } + return s; + } + + /** + * Blocks a non-worker-thread until completion or interruption. + */ + private int externalInterruptibleAwaitDone() throws InterruptedException { + int s; + ForkJoinPool cp = ForkJoinPool.common; + if (Thread.interrupted()) + throw new InterruptedException(); + if ((s = status) >= 0 && cp != null) { + if (this instanceof CountedCompleter) + cp.externalHelpComplete((CountedCompleter)this); + else if (cp.tryExternalUnpush(this)) + doExec(); + } + while ((s = status) >= 0) { + if (U.compareAndSwapInt(this, STATUS, s, s | SIGNAL)) { + synchronized (this) { + if (status >= 0) + wait(); + else + notifyAll(); + } + } + } + return s; + } + + + /** + * Implementation for join, get, quietlyJoin. Directly handles + * only cases of already-completed, external wait, and + * unfork+exec. Others are relayed to ForkJoinPool.awaitJoin. + * + * @return status upon completion + */ + private int doJoin() { + int s; Thread t; ForkJoinWorkerThread wt; ForkJoinPool.WorkQueue w; + return (s = status) < 0 ? s : + ((t = Thread.currentThread()) instanceof ForkJoinWorkerThread) ? + (w = (wt = (ForkJoinWorkerThread)t).workQueue). + tryUnpush(this) && (s = doExec()) < 0 ? s : + wt.pool.awaitJoin(w, this) : + externalAwaitDone(); + } + + /** + * Implementation for invoke, quietlyInvoke. + * + * @return status upon completion + */ + private int doInvoke() { + int s; Thread t; ForkJoinWorkerThread wt; + return (s = doExec()) < 0 ? s : + ((t = Thread.currentThread()) instanceof ForkJoinWorkerThread) ? + (wt = (ForkJoinWorkerThread)t).pool.awaitJoin(wt.workQueue, this) : + externalAwaitDone(); + } + + // Exception table support + + /** + * Table of exceptions thrown by tasks, to enable reporting by + * callers. Because exceptions are rare, we don't directly keep + * them with task objects, but instead use a weak ref table. Note + * that cancellation exceptions don't appear in the table, but are + * instead recorded as status values. + * + * Note: These statics are initialized below in static block. + */ + private static final ExceptionNode[] exceptionTable; + private static final ReentrantLock exceptionTableLock; + private static final ReferenceQueue exceptionTableRefQueue; + + /** + * Fixed capacity for exceptionTable. + */ + private static final int EXCEPTION_MAP_CAPACITY = 32; + + /** + * Key-value nodes for exception table. The chained hash table + * uses identity comparisons, full locking, and weak references + * for keys. The table has a fixed capacity because it only + * maintains task exceptions long enough for joiners to access + * them, so should never become very large for sustained + * periods. However, since we do not know when the last joiner + * completes, we must use weak references and expunge them. We do + * so on each operation (hence full locking). Also, some thread in + * any ForkJoinPool will call helpExpungeStaleExceptions when its + * pool becomes isQuiescent. + */ + static final class ExceptionNode extends WeakReference> { + final Throwable ex; + ExceptionNode next; + final long thrower; // use id not ref to avoid weak cycles + final int hashCode; // store task hashCode before weak ref disappears + ExceptionNode(ForkJoinTask task, Throwable ex, ExceptionNode next) { + super(task, exceptionTableRefQueue); + this.ex = ex; + this.next = next; + this.thrower = Thread.currentThread().getId(); + this.hashCode = System.identityHashCode(task); + } + } + + /** + * Records exception and sets status. + * + * @return status on exit + */ + final int recordExceptionalCompletion(Throwable ex) { + int s; + if ((s = status) >= 0) { + int h = System.identityHashCode(this); + final ReentrantLock lock = exceptionTableLock; + lock.lock(); + try { + expungeStaleExceptions(); + ExceptionNode[] t = exceptionTable; + int i = h & (t.length - 1); + for (ExceptionNode e = t[i]; ; e = e.next) { + if (e == null) { + t[i] = new ExceptionNode(this, ex, t[i]); + break; + } + if (e.get() == this) // already present + break; + } + } finally { + lock.unlock(); + } + s = setCompletion(EXCEPTIONAL); + } + return s; + } + + /** + * Records exception and possibly propagates. + * + * @return status on exit + */ + private int setExceptionalCompletion(Throwable ex) { + int s = recordExceptionalCompletion(ex); + if ((s & DONE_MASK) == EXCEPTIONAL) + internalPropagateException(ex); + return s; + } + + /** + * Hook for exception propagation support for tasks with completers. + */ + void internalPropagateException(Throwable ex) { + } + + /** + * Cancels, ignoring any exceptions thrown by cancel. Used during + * worker and pool shutdown. Cancel is spec'ed not to throw any + * exceptions, but if it does anyway, we have no recourse during + * shutdown, so guard against this case. + */ + static final void cancelIgnoringExceptions(ForkJoinTask t) { + if (t != null && t.status >= 0) { + try { + t.cancel(false); + } catch (Throwable ignore) { + } + } + } + + /** + * Removes exception node and clears status. + */ + private void clearExceptionalCompletion() { + int h = System.identityHashCode(this); + final ReentrantLock lock = exceptionTableLock; + lock.lock(); + try { + ExceptionNode[] t = exceptionTable; + int i = h & (t.length - 1); + ExceptionNode e = t[i]; + ExceptionNode pred = null; + while (e != null) { + ExceptionNode next = e.next; + if (e.get() == this) { + if (pred == null) + t[i] = next; + else + pred.next = next; + break; + } + pred = e; + e = next; + } + expungeStaleExceptions(); + status = 0; + } finally { + lock.unlock(); + } + } + + /** + * Returns a rethrowable exception for the given task, if + * available. To provide accurate stack traces, if the exception + * was not thrown by the current thread, we try to create a new + * exception of the same type as the one thrown, but with the + * recorded exception as its cause. If there is no such + * constructor, we instead try to use a no-arg constructor, + * followed by initCause, to the same effect. If none of these + * apply, or any fail due to other exceptions, we return the + * recorded exception, which is still correct, although it may + * contain a misleading stack trace. + * + * @return the exception, or null if none + */ + private Throwable getThrowableException() { + if ((status & DONE_MASK) != EXCEPTIONAL) + return null; + int h = System.identityHashCode(this); + ExceptionNode e; + final ReentrantLock lock = exceptionTableLock; + lock.lock(); + try { + expungeStaleExceptions(); + ExceptionNode[] t = exceptionTable; + e = t[h & (t.length - 1)]; + while (e != null && e.get() != this) + e = e.next; + } finally { + lock.unlock(); + } + Throwable ex; + if (e == null || (ex = e.ex) == null) + return null; + if (false && e.thrower != Thread.currentThread().getId()) { + Class ec = ex.getClass(); + try { + Constructor noArgCtor = null; + Constructor[] cs = ec.getConstructors();// public ctors only + for (int i = 0; i < cs.length; ++i) { + Constructor c = cs[i]; + Class[] ps = c.getParameterTypes(); + if (ps.length == 0) + noArgCtor = c; + else if (ps.length == 1 && ps[0] == Throwable.class) + return (Throwable)(c.newInstance(ex)); + } + if (noArgCtor != null) { + Throwable wx = (Throwable)(noArgCtor.newInstance()); + wx.initCause(ex); + return wx; + } + } catch (Exception ignore) { + } + } + return ex; + } + + /** + * Poll stale refs and remove them. Call only while holding lock. + */ + /** + * Poll stale refs and remove them. Call only while holding lock. + */ + private static void expungeStaleExceptions() { + for (Object x; (x = exceptionTableRefQueue.poll()) != null;) { + if (x instanceof ExceptionNode) { + int hashCode = ((ExceptionNode)x).hashCode; + ExceptionNode[] t = exceptionTable; + int i = hashCode & (t.length - 1); + ExceptionNode e = t[i]; + ExceptionNode pred = null; + while (e != null) { + ExceptionNode next = e.next; + if (e == x) { + if (pred == null) + t[i] = next; + else + pred.next = next; + break; + } + pred = e; + e = next; + } + } + } + } + + /** + * If lock is available, poll stale refs and remove them. + * Called from ForkJoinPool when pools become quiescent. + */ + static final void helpExpungeStaleExceptions() { + final ReentrantLock lock = exceptionTableLock; + if (lock.tryLock()) { + try { + expungeStaleExceptions(); + } finally { + lock.unlock(); + } + } + } + + /** + * A version of "sneaky throw" to relay exceptions + */ + static void rethrow(Throwable ex) { + if (ex != null) + ForkJoinTask.uncheckedThrow(ex); + } + + /** + * The sneaky part of sneaky throw, relying on generics + * limitations to evade compiler complaints about rethrowing + * unchecked exceptions + */ + @SuppressWarnings("unchecked") static + void uncheckedThrow(Throwable t) throws T { + throw (T)t; // rely on vacuous cast + } + + /** + * Throws exception, if any, associated with the given status. + */ + private void reportException(int s) { + if (s == CANCELLED) + throw new CancellationException(); + if (s == EXCEPTIONAL) + rethrow(getThrowableException()); + } + + // public methods + + /** + * Arranges to asynchronously execute this task in the pool the + * current task is running in, if applicable, or using the {@link + * ForkJoinPool#commonPool()} if not {@link #inForkJoinPool}. While + * it is not necessarily enforced, it is a usage error to fork a + * task more than once unless it has completed and been + * reinitialized. Subsequent modifications to the state of this + * task or any data it operates on are not necessarily + * consistently observable by any thread other than the one + * executing it unless preceded by a call to {@link #join} or + * related methods, or a call to {@link #isDone} returning {@code + * true}. + * + * @return {@code this}, to simplify usage + */ + public final ForkJoinTask fork() { + Thread t; + if ((t = Thread.currentThread()) instanceof ForkJoinWorkerThread) + ((ForkJoinWorkerThread)t).workQueue.push(this); + else + ForkJoinPool.common.externalPush(this); + return this; + } + + /** + * Returns the result of the computation when it {@link #isDone is + * done}. This method differs from {@link #get()} in that + * abnormal completion results in {@code RuntimeException} or + * {@code Error}, not {@code ExecutionException}, and that + * interrupts of the calling thread do not cause the + * method to abruptly return by throwing {@code + * InterruptedException}. + * + * @return the computed result + */ + public final V join() { + int s; + if ((s = doJoin() & DONE_MASK) != NORMAL) + reportException(s); + return getRawResult(); + } + + /** + * Commences performing this task, awaits its completion if + * necessary, and returns its result, or throws an (unchecked) + * {@code RuntimeException} or {@code Error} if the underlying + * computation did so. + * + * @return the computed result + */ + public final V invoke() { + int s; + if ((s = doInvoke() & DONE_MASK) != NORMAL) + reportException(s); + return getRawResult(); + } + + /** + * Forks the given tasks, returning when {@code isDone} holds for + * each task or an (unchecked) exception is encountered, in which + * case the exception is rethrown. If more than one task + * encounters an exception, then this method throws any one of + * these exceptions. If any task encounters an exception, the + * other may be cancelled. However, the execution status of + * individual tasks is not guaranteed upon exceptional return. The + * status of each task may be obtained using {@link + * #getException()} and related methods to check if they have been + * cancelled, completed normally or exceptionally, or left + * unprocessed. + * + * @param t1 the first task + * @param t2 the second task + * @throws NullPointerException if any task is null + */ + public static void invokeAll(ForkJoinTask t1, ForkJoinTask t2) { + int s1, s2; + t2.fork(); + if ((s1 = t1.doInvoke() & DONE_MASK) != NORMAL) + t1.reportException(s1); + if ((s2 = t2.doJoin() & DONE_MASK) != NORMAL) + t2.reportException(s2); + } + + /** + * Forks the given tasks, returning when {@code isDone} holds for + * each task or an (unchecked) exception is encountered, in which + * case the exception is rethrown. If more than one task + * encounters an exception, then this method throws any one of + * these exceptions. If any task encounters an exception, others + * may be cancelled. However, the execution status of individual + * tasks is not guaranteed upon exceptional return. The status of + * each task may be obtained using {@link #getException()} and + * related methods to check if they have been cancelled, completed + * normally or exceptionally, or left unprocessed. + * + * @param tasks the tasks + * @throws NullPointerException if any task is null + */ + public static void invokeAll(ForkJoinTask... tasks) { + Throwable ex = null; + int last = tasks.length - 1; + for (int i = last; i >= 0; --i) { + ForkJoinTask t = tasks[i]; + if (t == null) { + if (ex == null) + ex = new NullPointerException(); + } + else if (i != 0) + t.fork(); + else if (t.doInvoke() < NORMAL && ex == null) + ex = t.getException(); + } + for (int i = 1; i <= last; ++i) { + ForkJoinTask t = tasks[i]; + if (t != null) { + if (ex != null) + t.cancel(false); + else if (t.doJoin() < NORMAL) + ex = t.getException(); + } + } + if (ex != null) + rethrow(ex); + } + + /** + * Forks all tasks in the specified collection, returning when + * {@code isDone} holds for each task or an (unchecked) exception + * is encountered, in which case the exception is rethrown. If + * more than one task encounters an exception, then this method + * throws any one of these exceptions. If any task encounters an + * exception, others may be cancelled. However, the execution + * status of individual tasks is not guaranteed upon exceptional + * return. The status of each task may be obtained using {@link + * #getException()} and related methods to check if they have been + * cancelled, completed normally or exceptionally, or left + * unprocessed. + * + * @param tasks the collection of tasks + * @param the type of the values returned from the tasks + * @return the tasks argument, to simplify usage + * @throws NullPointerException if tasks or any element are null + */ + public static > Collection invokeAll(Collection tasks) { + if (!(tasks instanceof RandomAccess) || !(tasks instanceof List)) { + invokeAll(tasks.toArray(new ForkJoinTask[tasks.size()])); + return tasks; + } + @SuppressWarnings("unchecked") + List> ts = + (List>) tasks; + Throwable ex = null; + int last = ts.size() - 1; + for (int i = last; i >= 0; --i) { + ForkJoinTask t = ts.get(i); + if (t == null) { + if (ex == null) + ex = new NullPointerException(); + } + else if (i != 0) + t.fork(); + else if (t.doInvoke() < NORMAL && ex == null) + ex = t.getException(); + } + for (int i = 1; i <= last; ++i) { + ForkJoinTask t = ts.get(i); + if (t != null) { + if (ex != null) + t.cancel(false); + else if (t.doJoin() < NORMAL) + ex = t.getException(); + } + } + if (ex != null) + rethrow(ex); + return tasks; + } + + /** + * Attempts to cancel execution of this task. This attempt will + * fail if the task has already completed or could not be + * cancelled for some other reason. If successful, and this task + * has not started when {@code cancel} is called, execution of + * this task is suppressed. After this method returns + * successfully, unless there is an intervening call to {@link + * #reinitialize}, subsequent calls to {@link #isCancelled}, + * {@link #isDone}, and {@code cancel} will return {@code true} + * and calls to {@link #join} and related methods will result in + * {@code CancellationException}. + * + *

This method may be overridden in subclasses, but if so, must + * still ensure that these properties hold. In particular, the + * {@code cancel} method itself must not throw exceptions. + * + *

This method is designed to be invoked by other + * tasks. To terminate the current task, you can just return or + * throw an unchecked exception from its computation method, or + * invoke {@link #completeExceptionally(Throwable)}. + * + * @param mayInterruptIfRunning this value has no effect in the + * default implementation because interrupts are not used to + * control cancellation. + * + * @return {@code true} if this task is now cancelled + */ + public boolean cancel(boolean mayInterruptIfRunning) { + return (setCompletion(CANCELLED) & DONE_MASK) == CANCELLED; + } + + public final boolean isDone() { + return status < 0; + } + + public final boolean isCancelled() { + return (status & DONE_MASK) == CANCELLED; + } + + /** + * Returns {@code true} if this task threw an exception or was cancelled. + * + * @return {@code true} if this task threw an exception or was cancelled + */ + public final boolean isCompletedAbnormally() { + return status < NORMAL; + } + + /** + * Returns {@code true} if this task completed without throwing an + * exception and was not cancelled. + * + * @return {@code true} if this task completed without throwing an + * exception and was not cancelled + */ + public final boolean isCompletedNormally() { + return (status & DONE_MASK) == NORMAL; + } + + /** + * Returns the exception thrown by the base computation, or a + * {@code CancellationException} if cancelled, or {@code null} if + * none or if the method has not yet completed. + * + * @return the exception, or {@code null} if none + */ + public final Throwable getException() { + int s = status & DONE_MASK; + return ((s >= NORMAL) ? null : + (s == CANCELLED) ? new CancellationException() : + getThrowableException()); + } + + /** + * Completes this task abnormally, and if not already aborted or + * cancelled, causes it to throw the given exception upon + * {@code join} and related operations. This method may be used + * to induce exceptions in asynchronous tasks, or to force + * completion of tasks that would not otherwise complete. Its use + * in other situations is discouraged. This method is + * overridable, but overridden versions must invoke {@code super} + * implementation to maintain guarantees. + * + * @param ex the exception to throw. If this exception is not a + * {@code RuntimeException} or {@code Error}, the actual exception + * thrown will be a {@code RuntimeException} with cause {@code ex}. + */ + public void completeExceptionally(Throwable ex) { + setExceptionalCompletion((ex instanceof RuntimeException) || + (ex instanceof Error) ? ex : + new RuntimeException(ex)); + } + + /** + * Completes this task, and if not already aborted or cancelled, + * returning the given value as the result of subsequent + * invocations of {@code join} and related operations. This method + * may be used to provide results for asynchronous tasks, or to + * provide alternative handling for tasks that would not otherwise + * complete normally. Its use in other situations is + * discouraged. This method is overridable, but overridden + * versions must invoke {@code super} implementation to maintain + * guarantees. + * + * @param value the result value for this task + */ + public void complete(V value) { + try { + setRawResult(value); + } catch (Throwable rex) { + setExceptionalCompletion(rex); + return; + } + setCompletion(NORMAL); + } + + /** + * Completes this task normally without setting a value. The most + * recent value established by {@link #setRawResult} (or {@code + * null} by default) will be returned as the result of subsequent + * invocations of {@code join} and related operations. + * + * @since 1.8 + */ + public final void quietlyComplete() { + setCompletion(NORMAL); + } + + /** + * Waits if necessary for the computation to complete, and then + * retrieves its result. + * + * @return the computed result + * @throws CancellationException if the computation was cancelled + * @throws ExecutionException if the computation threw an + * exception + * @throws InterruptedException if the current thread is not a + * member of a ForkJoinPool and was interrupted while waiting + */ + public final V get() throws InterruptedException, ExecutionException { + int s = (Thread.currentThread() instanceof ForkJoinWorkerThread) ? + doJoin() : externalInterruptibleAwaitDone(); + Throwable ex; + if ((s &= DONE_MASK) == CANCELLED) + throw new CancellationException(); + if (s == EXCEPTIONAL && (ex = getThrowableException()) != null) + throw new ExecutionException(ex); + return getRawResult(); + } + + /** + * Waits if necessary for at most the given time for the computation + * to complete, and then retrieves its result, if available. + * + * @param timeout the maximum time to wait + * @param unit the time unit of the timeout argument + * @return the computed result + * @throws CancellationException if the computation was cancelled + * @throws ExecutionException if the computation threw an + * exception + * @throws InterruptedException if the current thread is not a + * member of a ForkJoinPool and was interrupted while waiting + * @throws TimeoutException if the wait timed out + */ + public final V get(long timeout, TimeUnit unit) + throws InterruptedException, ExecutionException, TimeoutException { + if (Thread.interrupted()) + throw new InterruptedException(); + // Messy in part because we measure in nanosecs, but wait in millisecs + int s; long ms; + long ns = unit.toNanos(timeout); + ForkJoinPool cp; + if ((s = status) >= 0 && ns > 0L) { + long deadline = System.nanoTime() + ns; + ForkJoinPool p = null; + ForkJoinPool.WorkQueue w = null; + Thread t = Thread.currentThread(); + if (t instanceof ForkJoinWorkerThread) { + ForkJoinWorkerThread wt = (ForkJoinWorkerThread)t; + p = wt.pool; + w = wt.workQueue; + p.helpJoinOnce(w, this); // no retries on failure + } + else if ((cp = ForkJoinPool.common) != null) { + if (this instanceof CountedCompleter) + cp.externalHelpComplete((CountedCompleter)this); + else if (cp.tryExternalUnpush(this)) + doExec(); + } + boolean canBlock = false; + boolean interrupted = false; + try { + while ((s = status) >= 0) { + if (w != null && w.qlock < 0) + cancelIgnoringExceptions(this); + else if (!canBlock) { + if (p == null || p.tryCompensate(p.ctl)) + canBlock = true; + } + else { + if ((ms = TimeUnit.NANOSECONDS.toMillis(ns)) > 0L && + U.compareAndSwapInt(this, STATUS, s, s | SIGNAL)) { + synchronized (this) { + if (status >= 0) { + try { + wait(ms); + } catch (InterruptedException ie) { + if (p == null) + interrupted = true; + } + } + else + notifyAll(); + } + } + if ((s = status) < 0 || interrupted || + (ns = deadline - System.nanoTime()) <= 0L) + break; + } + } + } finally { + if (p != null && canBlock) + p.incrementActiveCount(); + } + if (interrupted) + throw new InterruptedException(); + } + if ((s &= DONE_MASK) != NORMAL) { + Throwable ex; + if (s == CANCELLED) + throw new CancellationException(); + if (s != EXCEPTIONAL) + throw new TimeoutException(); + if ((ex = getThrowableException()) != null) + throw new ExecutionException(ex); + } + return getRawResult(); + } + + /** + * Joins this task, without returning its result or throwing its + * exception. This method may be useful when processing + * collections of tasks when some have been cancelled or otherwise + * known to have aborted. + */ + public final void quietlyJoin() { + doJoin(); + } + + /** + * Commences performing this task and awaits its completion if + * necessary, without returning its result or throwing its + * exception. + */ + public final void quietlyInvoke() { + doInvoke(); + } + + /** + * Possibly executes tasks until the pool hosting the current task + * {@link ForkJoinPool#isQuiescent is quiescent}. This method may + * be of use in designs in which many tasks are forked, but none + * are explicitly joined, instead executing them until all are + * processed. + */ + public static void helpQuiesce() { + Thread t; + if ((t = Thread.currentThread()) instanceof ForkJoinWorkerThread) { + ForkJoinWorkerThread wt = (ForkJoinWorkerThread)t; + wt.pool.helpQuiescePool(wt.workQueue); + } + else + ForkJoinPool.quiesceCommonPool(); + } + + /** + * Resets the internal bookkeeping state of this task, allowing a + * subsequent {@code fork}. This method allows repeated reuse of + * this task, but only if reuse occurs when this task has either + * never been forked, or has been forked, then completed and all + * outstanding joins of this task have also completed. Effects + * under any other usage conditions are not guaranteed. + * This method may be useful when executing + * pre-constructed trees of subtasks in loops. + * + *

Upon completion of this method, {@code isDone()} reports + * {@code false}, and {@code getException()} reports {@code + * null}. However, the value returned by {@code getRawResult} is + * unaffected. To clear this value, you can invoke {@code + * setRawResult(null)}. + */ + public void reinitialize() { + if ((status & DONE_MASK) == EXCEPTIONAL) + clearExceptionalCompletion(); + else + status = 0; + } + + /** + * Returns the pool hosting the current task execution, or null + * if this task is executing outside of any ForkJoinPool. + * + * @see #inForkJoinPool + * @return the pool, or {@code null} if none + */ + public static ForkJoinPool getPool() { + Thread t = Thread.currentThread(); + return (t instanceof ForkJoinWorkerThread) ? + ((ForkJoinWorkerThread) t).pool : null; + } + + /** + * Returns {@code true} if the current thread is a {@link + * ForkJoinWorkerThread} executing as a ForkJoinPool computation. + * + * @return {@code true} if the current thread is a {@link + * ForkJoinWorkerThread} executing as a ForkJoinPool computation, + * or {@code false} otherwise + */ + public static boolean inForkJoinPool() { + return Thread.currentThread() instanceof ForkJoinWorkerThread; + } + + /** + * Tries to unschedule this task for execution. This method will + * typically (but is not guaranteed to) succeed if this task is + * the most recently forked task by the current thread, and has + * not commenced executing in another thread. This method may be + * useful when arranging alternative local processing of tasks + * that could have been, but were not, stolen. + * + * @return {@code true} if unforked + */ + public boolean tryUnfork() { + Thread t; + return (((t = Thread.currentThread()) instanceof ForkJoinWorkerThread) ? + ((ForkJoinWorkerThread)t).workQueue.tryUnpush(this) : + ForkJoinPool.common.tryExternalUnpush(this)); + } + + /** + * Returns an estimate of the number of tasks that have been + * forked by the current worker thread but not yet executed. This + * value may be useful for heuristic decisions about whether to + * fork other tasks. + * + * @return the number of tasks + */ + public static int getQueuedTaskCount() { + Thread t; ForkJoinPool.WorkQueue q; + if ((t = Thread.currentThread()) instanceof ForkJoinWorkerThread) + q = ((ForkJoinWorkerThread)t).workQueue; + else + q = ForkJoinPool.commonSubmitterQueue(); + return (q == null) ? 0 : q.queueSize(); + } + + /** + * Returns an estimate of how many more locally queued tasks are + * held by the current worker thread than there are other worker + * threads that might steal them, or zero if this thread is not + * operating in a ForkJoinPool. This value may be useful for + * heuristic decisions about whether to fork other tasks. In many + * usages of ForkJoinTasks, at steady state, each worker should + * aim to maintain a small constant surplus (for example, 3) of + * tasks, and to process computations locally if this threshold is + * exceeded. + * + * @return the surplus number of tasks, which may be negative + */ + public static int getSurplusQueuedTaskCount() { + return ForkJoinPool.getSurplusQueuedTaskCount(); + } + + // Extension methods + + /** + * Returns the result that would be returned by {@link #join}, even + * if this task completed abnormally, or {@code null} if this task + * is not known to have been completed. This method is designed + * to aid debugging, as well as to support extensions. Its use in + * any other context is discouraged. + * + * @return the result, or {@code null} if not completed + */ + public abstract V getRawResult(); + + /** + * Forces the given value to be returned as a result. This method + * is designed to support extensions, and should not in general be + * called otherwise. + * + * @param value the value + */ + protected abstract void setRawResult(V value); + + /** + * Immediately performs the base action of this task and returns + * true if, upon return from this method, this task is guaranteed + * to have completed normally. This method may return false + * otherwise, to indicate that this task is not necessarily + * complete (or is not known to be complete), for example in + * asynchronous actions that require explicit invocations of + * completion methods. This method may also throw an (unchecked) + * exception to indicate abnormal exit. This method is designed to + * support extensions, and should not in general be called + * otherwise. + * + * @return {@code true} if this task is known to have completed normally + */ + protected abstract boolean exec(); + + /** + * Returns, but does not unschedule or execute, a task queued by + * the current thread but not yet executed, if one is immediately + * available. There is no guarantee that this task will actually + * be polled or executed next. Conversely, this method may return + * null even if a task exists but cannot be accessed without + * contention with other threads. This method is designed + * primarily to support extensions, and is unlikely to be useful + * otherwise. + * + * @return the next task, or {@code null} if none are available + */ + protected static ForkJoinTask peekNextLocalTask() { + Thread t; ForkJoinPool.WorkQueue q; + if ((t = Thread.currentThread()) instanceof ForkJoinWorkerThread) + q = ((ForkJoinWorkerThread)t).workQueue; + else + q = ForkJoinPool.commonSubmitterQueue(); + return (q == null) ? null : q.peek(); + } + + /** + * Unschedules and returns, without executing, the next task + * queued by the current thread but not yet executed, if the + * current thread is operating in a ForkJoinPool. This method is + * designed primarily to support extensions, and is unlikely to be + * useful otherwise. + * + * @return the next task, or {@code null} if none are available + */ + protected static ForkJoinTask pollNextLocalTask() { + Thread t; + return ((t = Thread.currentThread()) instanceof ForkJoinWorkerThread) ? + ((ForkJoinWorkerThread)t).workQueue.nextLocalTask() : + null; + } + + /** + * If the current thread is operating in a ForkJoinPool, + * unschedules and returns, without executing, the next task + * queued by the current thread but not yet executed, if one is + * available, or if not available, a task that was forked by some + * other thread, if available. Availability may be transient, so a + * {@code null} result does not necessarily imply quiescence of + * the pool this task is operating in. This method is designed + * primarily to support extensions, and is unlikely to be useful + * otherwise. + * + * @return a task, or {@code null} if none are available + */ + protected static ForkJoinTask pollTask() { + Thread t; ForkJoinWorkerThread wt; + return ((t = Thread.currentThread()) instanceof ForkJoinWorkerThread) ? + (wt = (ForkJoinWorkerThread)t).pool.nextTaskFor(wt.workQueue) : + null; + } + + // tag operations + + /** + * Returns the tag for this task. + * + * @return the tag for this task + * @since 1.8 + */ + public final short getForkJoinTaskTag() { + return (short)status; + } + + /** + * Atomically sets the tag value for this task. + * + * @param tag the tag value + * @return the previous value of the tag + * @since 1.8 + */ + public final short setForkJoinTaskTag(short tag) { + for (int s;;) { + if (U.compareAndSwapInt(this, STATUS, s = status, + (s & ~SMASK) | (tag & SMASK))) + return (short)s; + } + } + + /** + * Atomically conditionally sets the tag value for this task. + * Among other applications, tags can be used as visit markers + * in tasks operating on graphs, as in methods that check: {@code + * if (task.compareAndSetForkJoinTaskTag((short)0, (short)1))} + * before processing, otherwise exiting because the node has + * already been visited. + * + * @param e the expected tag value + * @param tag the new tag value + * @return {@code true} if successful; i.e., the current value was + * equal to e and is now tag. + * @since 1.8 + */ + public final boolean compareAndSetForkJoinTaskTag(short e, short tag) { + for (int s;;) { + if ((short)(s = status) != e) + return false; + if (U.compareAndSwapInt(this, STATUS, s, + (s & ~SMASK) | (tag & SMASK))) + return true; + } + } + + /** + * Adaptor for Runnables. This implements RunnableFuture + * to be compliant with AbstractExecutorService constraints + * when used in ForkJoinPool. + */ + static final class AdaptedRunnable extends ForkJoinTask + implements RunnableFuture { + final Runnable runnable; + T result; + AdaptedRunnable(Runnable runnable, T result) { + if (runnable == null) throw new NullPointerException(); + this.runnable = runnable; + this.result = result; // OK to set this even before completion + } + public final T getRawResult() { return result; } + public final void setRawResult(T v) { result = v; } + public final boolean exec() { runnable.run(); return true; } + public final void run() { invoke(); } + private static final long serialVersionUID = 5232453952276885070L; + } + + /** + * Adaptor for Runnables without results + */ + static final class AdaptedRunnableAction extends ForkJoinTask + implements RunnableFuture { + final Runnable runnable; + AdaptedRunnableAction(Runnable runnable) { + if (runnable == null) throw new NullPointerException(); + this.runnable = runnable; + } + public final Void getRawResult() { return null; } + public final void setRawResult(Void v) { } + public final boolean exec() { runnable.run(); return true; } + public final void run() { invoke(); } + private static final long serialVersionUID = 5232453952276885070L; + } + + /** + * Adaptor for Runnables in which failure forces worker exception + */ + static final class RunnableExecuteAction extends ForkJoinTask { + final Runnable runnable; + RunnableExecuteAction(Runnable runnable) { + if (runnable == null) throw new NullPointerException(); + this.runnable = runnable; + } + public final Void getRawResult() { return null; } + public final void setRawResult(Void v) { } + public final boolean exec() { runnable.run(); return true; } + void internalPropagateException(Throwable ex) { + rethrow(ex); // rethrow outside exec() catches. + } + private static final long serialVersionUID = 5232453952276885070L; + } + + /** + * Adaptor for Callables + */ + static final class AdaptedCallable extends ForkJoinTask + implements RunnableFuture { + final Callable callable; + T result; + AdaptedCallable(Callable callable) { + if (callable == null) throw new NullPointerException(); + this.callable = callable; + } + public final T getRawResult() { return result; } + public final void setRawResult(T v) { result = v; } + public final boolean exec() { + try { + result = callable.call(); + return true; + } catch (Error err) { + throw err; + } catch (RuntimeException rex) { + throw rex; + } catch (Exception ex) { + throw new RuntimeException(ex); + } + } + public final void run() { invoke(); } + private static final long serialVersionUID = 2838392045355241008L; + } + + /** + * Returns a new {@code ForkJoinTask} that performs the {@code run} + * method of the given {@code Runnable} as its action, and returns + * a null result upon {@link #join}. + * + * @param runnable the runnable action + * @return the task + */ + public static ForkJoinTask adapt(Runnable runnable) { + return new AdaptedRunnableAction(runnable); + } + + /** + * Returns a new {@code ForkJoinTask} that performs the {@code run} + * method of the given {@code Runnable} as its action, and returns + * the given result upon {@link #join}. + * + * @param runnable the runnable action + * @param result the result upon completion + * @param the type of the result + * @return the task + */ + public static ForkJoinTask adapt(Runnable runnable, T result) { + return new AdaptedRunnable(runnable, result); + } + + /** + * Returns a new {@code ForkJoinTask} that performs the {@code call} + * method of the given {@code Callable} as its action, and returns + * its result upon {@link #join}, translating any checked exceptions + * encountered into {@code RuntimeException}. + * + * @param callable the callable action + * @param the type of the callable's result + * @return the task + */ + public static ForkJoinTask adapt(Callable callable) { + return new AdaptedCallable(callable); + } + + // Serialization support + + private static final long serialVersionUID = -7721805057305804111L; + + /** + * Saves this task to a stream (that is, serializes it). + * + * @param s the stream + * @throws java.io.IOException if an I/O error occurs + * @serialData the current run status and the exception thrown + * during execution, or {@code null} if none + */ + private void writeObject(java.io.ObjectOutputStream s) + throws java.io.IOException { + s.defaultWriteObject(); + s.writeObject(getException()); + } + + /** + * Reconstitutes this task from a stream (that is, deserializes it). + * @param s the stream + * @throws ClassNotFoundException if the class of a serialized object + * could not be found + * @throws java.io.IOException if an I/O error occurs + */ + private void readObject(java.io.ObjectInputStream s) + throws java.io.IOException, ClassNotFoundException { + s.defaultReadObject(); + Object ex = s.readObject(); + if (ex != null) + setExceptionalCompletion((Throwable)ex); + } + + // Unsafe mechanics + private static final sun.misc.Unsafe U; + private static final long STATUS; + + static { + exceptionTableLock = new ReentrantLock(); + exceptionTableRefQueue = new ReferenceQueue(); + exceptionTable = new ExceptionNode[EXCEPTION_MAP_CAPACITY]; + try { + U = getUnsafe(); + Class k = ForkJoinTask.class; + STATUS = U.objectFieldOffset + (k.getDeclaredField("status")); + } catch (Exception e) { + throw new Error(e); + } + } + + /** + * Returns a sun.misc.Unsafe. Suitable for use in a 3rd party package. + * Replace with a simple call to Unsafe.getUnsafe when integrating + * into a jdk. + * + * @return a sun.misc.Unsafe + */ + private static sun.misc.Unsafe getUnsafe() { + try { + return sun.misc.Unsafe.getUnsafe(); + } catch (SecurityException tryReflectionInstead) {} + try { + return java.security.AccessController.doPrivileged + (new java.security.PrivilegedExceptionAction() { + public sun.misc.Unsafe run() throws Exception { + Class k = sun.misc.Unsafe.class; + for (java.lang.reflect.Field f : k.getDeclaredFields()) { + f.setAccessible(true); + Object x = f.get(null); + if (k.isInstance(x)) + return k.cast(x); + } + throw new NoSuchFieldError("the Unsafe"); + }}); + } catch (java.security.PrivilegedActionException e) { + throw new RuntimeException("Could not initialize intrinsics", + e.getCause()); + } + } +} + diff --git a/src/main/java/jsr166e/ForkJoinWorkerThread.java b/src/main/java/jsr166e/ForkJoinWorkerThread.java new file mode 100644 index 0000000000000..e247927a26317 --- /dev/null +++ b/src/main/java/jsr166e/ForkJoinWorkerThread.java @@ -0,0 +1,125 @@ +// Rev 1.5 from http://gee.cs.oswego.edu/cgi-bin/viewcvs.cgi/jsr166/src/jsr166e/ForkJoinWorkerThread.java?view=co + +/* + * Written by Doug Lea with assistance from members of JCP JSR-166 + * Expert Group and released to the public domain, as explained at + * http://creativecommons.org/publicdomain/zero/1.0/ + */ + +package jsr166e; + + +/** + * A thread managed by a {@link ForkJoinPool}, which executes + * {@link ForkJoinTask}s. + * This class is subclassable solely for the sake of adding + * functionality -- there are no overridable methods dealing with + * scheduling or execution. However, you can override initialization + * and termination methods surrounding the main task processing loop. + * If you do create such a subclass, you will also need to supply a + * custom {@link ForkJoinPool.ForkJoinWorkerThreadFactory} to + * {@linkplain ForkJoinPool#ForkJoinPool use it} in a {@code ForkJoinPool}. + * + * @since 1.7 + * @author Doug Lea + */ +public class ForkJoinWorkerThread extends Thread { + /* + * ForkJoinWorkerThreads are managed by ForkJoinPools and perform + * ForkJoinTasks. For explanation, see the internal documentation + * of class ForkJoinPool. + * + * This class just maintains links to its pool and WorkQueue. The + * pool field is set immediately upon construction, but the + * workQueue field is not set until a call to registerWorker + * completes. This leads to a visibility race, that is tolerated + * by requiring that the workQueue field is only accessed by the + * owning thread. + */ + + final ForkJoinPool pool; // the pool this thread works in + final ForkJoinPool.WorkQueue workQueue; // work-stealing mechanics + + /** + * Creates a ForkJoinWorkerThread operating in the given pool. + * + * @param pool the pool this thread works in + * @throws NullPointerException if pool is null + */ + protected ForkJoinWorkerThread(ForkJoinPool pool) { + // Use a placeholder until a useful name can be set in registerWorker + super("aForkJoinWorkerThread"); + this.pool = pool; + this.workQueue = pool.registerWorker(this); + } + + /** + * Returns the pool hosting this thread. + * + * @return the pool + */ + public ForkJoinPool getPool() { + return pool; + } + + /** + * Returns the unique index number of this thread in its pool. + * The returned value ranges from zero to the maximum number of + * threads (minus one) that may exist in the pool, and does not + * change during the lifetime of the thread. This method may be + * useful for applications that track status or collect results + * per-worker-thread rather than per-task. + * + * @return the index number + */ + public int getPoolIndex() { + return workQueue.poolIndex >>> 1; // ignore odd/even tag bit + } + + /** + * Initializes internal state after construction but before + * processing any tasks. If you override this method, you must + * invoke {@code super.onStart()} at the beginning of the method. + * Initialization requires care: Most fields must have legal + * default values, to ensure that attempted accesses from other + * threads work correctly even before this thread starts + * processing tasks. + */ + protected void onStart() { + } + + /** + * Performs cleanup associated with termination of this worker + * thread. If you override this method, you must invoke + * {@code super.onTermination} at the end of the overridden method. + * + * @param exception the exception causing this thread to abort due + * to an unrecoverable error, or {@code null} if completed normally + */ + protected void onTermination(Throwable exception) { + } + + /** + * This method is required to be public, but should never be + * called explicitly. It performs the main run loop to execute + * {@link ForkJoinTask}s. + */ + public void run() { + Throwable exception = null; + try { + onStart(); + pool.runWorker(workQueue); + } catch (Throwable ex) { + exception = ex; + } finally { + try { + onTermination(exception); + } catch (Throwable ex) { + if (exception == null) + exception = ex; + } finally { + pool.deregisterWorker(this, exception); + } + } + } +} diff --git a/src/main/java/jsr166e/ThreadLocalRandom.java b/src/main/java/jsr166e/ThreadLocalRandom.java new file mode 100644 index 0000000000000..42e6ff162231f --- /dev/null +++ b/src/main/java/jsr166e/ThreadLocalRandom.java @@ -0,0 +1,199 @@ +// Rev 1.2 from http://gee.cs.oswego.edu/cgi-bin/viewcvs.cgi/jsr166/src/jsr166e/ThreadLocalRandom.java?revision=1.2 + +/* + * Written by Doug Lea with assistance from members of JCP JSR-166 + * Expert Group and released to the public domain, as explained at + * http://creativecommons.org/publicdomain/zero/1.0/ + */ + +package jsr166e; + +import java.util.Random; + +/** + * A random number generator isolated to the current thread. Like the + * global {@link java.util.Random} generator used by the {@link + * java.lang.Math} class, a {@code ThreadLocalRandom} is initialized + * with an internally generated seed that may not otherwise be + * modified. When applicable, use of {@code ThreadLocalRandom} rather + * than shared {@code Random} objects in concurrent programs will + * typically encounter much less overhead and contention. Use of + * {@code ThreadLocalRandom} is particularly appropriate when multiple + * tasks (for example, each a {@link ForkJoinTask}) use random numbers + * in parallel in thread pools. + * + *

Usages of this class should typically be of the form: + * {@code ThreadLocalRandom.current().nextX(...)} (where + * {@code X} is {@code Int}, {@code Long}, etc). + * When all usages are of this form, it is never possible to + * accidently share a {@code ThreadLocalRandom} across multiple threads. + * + *

This class also provides additional commonly used bounded random + * generation methods. + * + * @since 1.7 + * @author Doug Lea + */ +public class ThreadLocalRandom extends Random { + // same constants as Random, but must be redeclared because private + private static final long multiplier = 0x5DEECE66DL; + private static final long addend = 0xBL; + private static final long mask = (1L << 48) - 1; + + /** + * The random seed. We can't use super.seed. + */ + private long rnd; + + /** + * Initialization flag to permit calls to setSeed to succeed only + * while executing the Random constructor. We can't allow others + * since it would cause setting seed in one part of a program to + * unintentionally impact other usages by the thread. + */ + boolean initialized; + + // Padding to help avoid memory contention among seed updates in + // different TLRs in the common case that they are located near + // each other. + private long pad0, pad1, pad2, pad3, pad4, pad5, pad6, pad7; + + /** + * The actual ThreadLocal + */ + private static final ThreadLocal localRandom = + new ThreadLocal() { + protected ThreadLocalRandom initialValue() { + return new ThreadLocalRandom(); + } + }; + + + /** + * Constructor called only by localRandom.initialValue. + */ + ThreadLocalRandom() { + super(); + initialized = true; + } + + /** + * Returns the current thread's {@code ThreadLocalRandom}. + * + * @return the current thread's {@code ThreadLocalRandom} + */ + public static ThreadLocalRandom current() { + return localRandom.get(); + } + + /** + * Throws {@code UnsupportedOperationException}. Setting seeds in + * this generator is not supported. + * + * @throws UnsupportedOperationException always + */ + public void setSeed(long seed) { + if (initialized) + throw new UnsupportedOperationException(); + rnd = (seed ^ multiplier) & mask; + } + + protected int next(int bits) { + rnd = (rnd * multiplier + addend) & mask; + return (int) (rnd >>> (48-bits)); + } + + /** + * Returns a pseudorandom, uniformly distributed value between the + * given least value (inclusive) and bound (exclusive). + * + * @param least the least value returned + * @param bound the upper bound (exclusive) + * @return the next value + * @throws IllegalArgumentException if least greater than or equal + * to bound + */ + public int nextInt(int least, int bound) { + if (least >= bound) + throw new IllegalArgumentException(); + return nextInt(bound - least) + least; + } + + /** + * Returns a pseudorandom, uniformly distributed value + * between 0 (inclusive) and the specified value (exclusive). + * + * @param n the bound on the random number to be returned. Must be + * positive. + * @return the next value + * @throws IllegalArgumentException if n is not positive + */ + public long nextLong(long n) { + if (n <= 0) + throw new IllegalArgumentException("n must be positive"); + // Divide n by two until small enough for nextInt. On each + // iteration (at most 31 of them but usually much less), + // randomly choose both whether to include high bit in result + // (offset) and whether to continue with the lower vs upper + // half (which makes a difference only if odd). + long offset = 0; + while (n >= Integer.MAX_VALUE) { + int bits = next(2); + long half = n >>> 1; + long nextn = ((bits & 2) == 0) ? half : n - half; + if ((bits & 1) == 0) + offset += n - nextn; + n = nextn; + } + return offset + nextInt((int) n); + } + + /** + * Returns a pseudorandom, uniformly distributed value between the + * given least value (inclusive) and bound (exclusive). + * + * @param least the least value returned + * @param bound the upper bound (exclusive) + * @return the next value + * @throws IllegalArgumentException if least greater than or equal + * to bound + */ + public long nextLong(long least, long bound) { + if (least >= bound) + throw new IllegalArgumentException(); + return nextLong(bound - least) + least; + } + + /** + * Returns a pseudorandom, uniformly distributed {@code double} value + * between 0 (inclusive) and the specified value (exclusive). + * + * @param n the bound on the random number to be returned. Must be + * positive. + * @return the next value + * @throws IllegalArgumentException if n is not positive + */ + public double nextDouble(double n) { + if (n <= 0) + throw new IllegalArgumentException("n must be positive"); + return nextDouble() * n; + } + + /** + * Returns a pseudorandom, uniformly distributed value between the + * given least value (inclusive) and bound (exclusive). + * + * @param least the least value returned + * @param bound the upper bound (exclusive) + * @return the next value + * @throws IllegalArgumentException if least greater than or equal + * to bound + */ + public double nextDouble(double least, double bound) { + if (least >= bound) + throw new IllegalArgumentException(); + return nextDouble() * (bound - least) + least; + } + + private static final long serialVersionUID = -5851777807851030925L; +} diff --git a/src/main/java/org/elasticsearch/common/lucene/uid/Versions.java b/src/main/java/org/elasticsearch/common/lucene/uid/Versions.java index 0cde1645cb66f..af5b4434f8a91 100644 --- a/src/main/java/org/elasticsearch/common/lucene/uid/Versions.java +++ b/src/main/java/org/elasticsearch/common/lucene/uid/Versions.java @@ -21,7 +21,7 @@ import java.io.IOException; import java.util.List; -import java.util.concurrent.ConcurrentHashMap; +import java.util.concurrent.ConcurrentMap; import org.apache.lucene.index.*; import org.apache.lucene.index.IndexReader.ReaderClosedListener; @@ -32,6 +32,7 @@ import org.elasticsearch.common.Numbers; import org.elasticsearch.common.io.stream.StreamInput; import org.elasticsearch.common.io.stream.StreamOutput; +import org.elasticsearch.common.util.concurrent.ConcurrentCollections; import org.elasticsearch.index.mapper.internal.UidFieldMapper; import org.elasticsearch.index.mapper.internal.VersionFieldMapper; @@ -46,7 +47,7 @@ public class Versions { public static final long NOT_SET = -2L; // TODO: is there somewhere else we can store these? - private static final ConcurrentHashMap> lookupStates = new ConcurrentHashMap<>(); + private static final ConcurrentMap> lookupStates = ConcurrentCollections.newConcurrentMapWithAggressiveConcurrency(); // Evict this reader from lookupStates once it's closed: private static final ReaderClosedListener removeLookupState = new ReaderClosedListener() { diff --git a/src/main/java/org/elasticsearch/common/util/concurrent/ConcurrentCollections.java b/src/main/java/org/elasticsearch/common/util/concurrent/ConcurrentCollections.java index 4314ff2f9b23e..fa708adb3bd87 100644 --- a/src/main/java/org/elasticsearch/common/util/concurrent/ConcurrentCollections.java +++ b/src/main/java/org/elasticsearch/common/util/concurrent/ConcurrentCollections.java @@ -21,11 +21,15 @@ import com.google.common.collect.Sets; +import org.apache.lucene.util.Constants; + import java.util.Deque; import java.util.Queue; import java.util.Set; import java.util.concurrent.*; +import jsr166e.ConcurrentHashMapV8; + /** * */ @@ -43,11 +47,21 @@ public abstract class ConcurrentCollections { * Creates a new CHM with an aggressive concurrency level, aimed at high concurrent update rate long living maps. */ public static ConcurrentMap newConcurrentMapWithAggressiveConcurrency() { - return new ConcurrentHashMap<>(16, 0.75f, aggressiveConcurrencyLevel); + if (Constants.JRE_IS_MINIMUM_JAVA8) { + // Just use JDK's impl when we are on Java8: + return new ConcurrentHashMap<>(16, 0.75f, aggressiveConcurrencyLevel); + } else { + return new ConcurrentHashMapV8<>(16, 0.75f, aggressiveConcurrencyLevel); + } } public static ConcurrentMap newConcurrentMap() { - return new ConcurrentHashMap<>(); + if (Constants.JRE_IS_MINIMUM_JAVA8) { + // Just use JDK's impl when we are on Java8: + return new ConcurrentHashMap<>(); + } else { + return new ConcurrentHashMapV8<>(); + } } /** diff --git a/src/main/java/org/elasticsearch/common/util/concurrent/KeyedLock.java b/src/main/java/org/elasticsearch/common/util/concurrent/KeyedLock.java index 60f1d569283c5..0d9a4689af1ee 100644 --- a/src/main/java/org/elasticsearch/common/util/concurrent/KeyedLock.java +++ b/src/main/java/org/elasticsearch/common/util/concurrent/KeyedLock.java @@ -20,12 +20,15 @@ package org.elasticsearch.common.util.concurrent; import org.elasticsearch.ElasticsearchIllegalStateException; +import org.elasticsearch.common.util.concurrent.ConcurrentCollections; import java.util.concurrent.ConcurrentHashMap; import java.util.concurrent.ConcurrentMap; import java.util.concurrent.atomic.AtomicInteger; import java.util.concurrent.locks.ReentrantLock; +import jsr166e.ConcurrentHashMapV8; + /** * This class manages locks. Locks can be accessed with an identifier and are * created the first time they are acquired and removed if no thread hold the @@ -38,7 +41,7 @@ public class KeyedLock { - private final ConcurrentMap map = new ConcurrentHashMap<>(); + private final ConcurrentMap map = ConcurrentCollections.newConcurrentMap(); private final ThreadLocal threadLocal = new ThreadLocal<>(); From 956995473f2a033fd28be4fed79913566ea2f373 Mon Sep 17 00:00:00 2001 From: mikemccand Date: Thu, 5 Jun 2014 09:21:17 -0400 Subject: [PATCH 2/2] remove unused import --- .../org/elasticsearch/common/util/concurrent/KeyedLock.java | 2 -- 1 file changed, 2 deletions(-) diff --git a/src/main/java/org/elasticsearch/common/util/concurrent/KeyedLock.java b/src/main/java/org/elasticsearch/common/util/concurrent/KeyedLock.java index 0d9a4689af1ee..98c8b4c32b622 100644 --- a/src/main/java/org/elasticsearch/common/util/concurrent/KeyedLock.java +++ b/src/main/java/org/elasticsearch/common/util/concurrent/KeyedLock.java @@ -27,8 +27,6 @@ import java.util.concurrent.atomic.AtomicInteger; import java.util.concurrent.locks.ReentrantLock; -import jsr166e.ConcurrentHashMapV8; - /** * This class manages locks. Locks can be accessed with an identifier and are * created the first time they are acquired and removed if no thread hold the