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Adding transitionStore optimization back to ByteState #90

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May 1, 2023
Merged

Adding transitionStore optimization back to ByteState #90

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178 changes: 167 additions & 11 deletions src/main/software/amazon/event/ruler/ByteState.java
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Original file line number Diff line number Diff line change
@@ -1,10 +1,13 @@
package software.amazon.event.ruler;

import javax.annotation.Nonnull;
import javax.annotation.Nullable;
import javax.annotation.concurrent.ThreadSafe;

import java.util.Collections;
import java.util.Set;
import java.util.stream.Collectors;
import java.util.stream.Stream;

/**
* Represents a state in a state machine and maps utf-8 bytes to transitions. One byte can have many transitions,
Expand All @@ -13,7 +16,12 @@
@ThreadSafe
class ByteState extends SingleByteTransition {

private final ByteMap map = new ByteMap();
/**
* The field is a {@link ByteMap}, however, to optimize on memory, this field may be {@code null} when this state
* contains no transitions, and may be a {@link SingleByteTransitionEntry} when this state contains one transition.
*/
@Nullable
private volatile Object transitionStore;

/* True if this state's placement in the machine means there is more than one possible value that can be matched on
* a traversal from the start state to this state. This will happen, for example, when a wildcard or regex
Expand Down Expand Up @@ -51,7 +59,7 @@ public Set<ShortcutTransition> getShortcuts() {
* @return {@code true} if this state contains no transitions
*/
boolean hasNoTransitions() {
return map.isEmpty();
return transitionStore == null;
}

/**
Expand All @@ -64,16 +72,40 @@ boolean hasNoTransitions() {
*/
@Override
ByteTransition getTransition(byte utf8byte) {
// Saving the value to avoid reading an updated value
Object transitionStore = this.transitionStore;
if (transitionStore == null) {
return null;
} else if (transitionStore instanceof SingleByteTransitionEntry) {
SingleByteTransitionEntry entry = (SingleByteTransitionEntry) transitionStore;
return utf8byte == entry.utf8byte ? entry.transition : null;
}
ByteMap map = (ByteMap) transitionStore;
return map.getTransition(utf8byte);
}

@Override
ByteTransition getTransitionForAllBytes() {
// Saving the value to avoid reading an updated value
Object transitionStore = this.transitionStore;
if (transitionStore == null || transitionStore instanceof SingleByteTransitionEntry) {
return ByteMachine.EmptyByteTransition.INSTANCE;
}
ByteMap map = (ByteMap) transitionStore;
return map.getTransitionForAllBytes();
}

@Override
Set<ByteTransition> getTransitions() {
// Saving the value to avoid reading an updated value
Object transitionStore = this.transitionStore;
if (transitionStore == null) {
return Collections.emptySet();
} else if (transitionStore instanceof SingleByteTransitionEntry) {
SingleByteTransitionEntry entry = (SingleByteTransitionEntry) transitionStore;
return Stream.of(entry.transition).collect(Collectors.toSet());
}
ByteMap map = (ByteMap) transitionStore;
return map.getTransitions();
}

Expand All @@ -85,7 +117,24 @@ Set<ByteTransition> getTransitions() {
* @param transition the transition to be associated with the given byte value
*/
void putTransition(byte utf8byte, @Nonnull SingleByteTransition transition) {
map.putTransition(utf8byte, transition);
// Saving the value to avoid reading an updated value
Object transitionStore = this.transitionStore;
if (transitionStore == null) {
this.transitionStore = new SingleByteTransitionEntry(utf8byte, transition);
} else if (transitionStore instanceof SingleByteTransitionEntry) {
SingleByteTransitionEntry entry = (SingleByteTransitionEntry) transitionStore;
if (utf8byte == entry.utf8byte) {
entry.transition = transition;
} else {
ByteMap map = new ByteMap();
map.putTransition(entry.utf8byte, entry.transition);
map.putTransition(utf8byte, transition);
this.transitionStore = map;
}
} else {
ByteMap map = (ByteMap) transitionStore;
map.putTransition(utf8byte, transition);
}
}

/**
Expand All @@ -95,7 +144,9 @@ void putTransition(byte utf8byte, @Nonnull SingleByteTransition transition) {
* @param transition the transition to be associated with the given byte value
*/
void putTransitionForAllBytes(@Nonnull SingleByteTransition transition) {
ByteMap map = new ByteMap();
map.putTransitionForAllBytes(transition);
this.transitionStore = map;
}

/**
Expand All @@ -106,7 +157,20 @@ void putTransitionForAllBytes(@Nonnull SingleByteTransition transition) {
* @param transition the transition to be associated with the given byte value
*/
void addTransition(byte utf8byte, @Nonnull SingleByteTransition transition) {
map.addTransition(utf8byte, transition);
// Saving the value to avoid reading an updated value
Object transitionStore = this.transitionStore;
if (transitionStore == null) {
this.transitionStore = new SingleByteTransitionEntry(utf8byte, transition);
} else if (transitionStore instanceof SingleByteTransitionEntry) {
SingleByteTransitionEntry entry = (SingleByteTransitionEntry) transitionStore;
ByteMap map = new ByteMap();
map.addTransition(entry.utf8byte, entry.transition);
map.addTransition(utf8byte, transition);
this.transitionStore = map;
} else {
ByteMap map = (ByteMap) transitionStore;
map.addTransition(utf8byte, transition);
}
}

/**
Expand All @@ -116,16 +180,47 @@ void addTransition(byte utf8byte, @Nonnull SingleByteTransition transition) {
* @param transition the transition to be associated with all possible byte values
*/
void addTransitionForAllBytes(final SingleByteTransition transition) {
// Saving the value to avoid reading an updated value
Object transitionStore = this.transitionStore;
ByteMap map;
if (transitionStore instanceof ByteMap) {
map = (ByteMap) transitionStore;
} else {
map = new ByteMap();
}
if (transitionStore instanceof SingleByteTransitionEntry) {
SingleByteTransitionEntry entry = (SingleByteTransitionEntry) transitionStore;
map.addTransition(entry.utf8byte, entry.transition);
}
map.addTransitionForAllBytes(transition);
this.transitionStore = map;
}

/**
* Removes all transitions for the given byte value from this state.
* Removes provided transition for the given byte value from this state.
*
* @param utf8byte the byte value whose transitions are to be removed from the state
* @param utf8byte the byte value for which to remove transition from the state
* @param transition remove this transition for provided byte value from the state
*/
void removeTransition(byte utf8byte, SingleByteTransition transition) {
map.removeTransition(utf8byte, transition);
// Saving the value to avoid reading an updated value
Object transitionStore = this.transitionStore;
if (transitionStore == null) {
return;
}

if (transitionStore instanceof SingleByteTransitionEntry) {
SingleByteTransitionEntry entry = (SingleByteTransitionEntry) transitionStore;
if (utf8byte == entry.utf8byte && transition.equals(entry.transition)) {
this.transitionStore = null;
}
} else {
ByteMap map = (ByteMap) transitionStore;
map.removeTransition(utf8byte, transition);
if (map.isEmpty()) {
this.transitionStore = null;
}
}
}

/**
Expand All @@ -134,7 +229,24 @@ void removeTransition(byte utf8byte, SingleByteTransition transition) {
* @param transition the transition to be removed for all possible byte values
*/
void removeTransitionForAllBytes(final SingleByteTransition transition) {
map.removeTransitionForAllBytes(transition);
// Saving the value to avoid reading an updated value
Object transitionStore = this.transitionStore;
if (transitionStore == null) {
return;
}

if (transitionStore instanceof SingleByteTransitionEntry) {
SingleByteTransitionEntry entry = (SingleByteTransitionEntry) transitionStore;
if (transition.equals(entry.transition)) {
this.transitionStore = null;
}
} else {
ByteMap map = (ByteMap) transitionStore;
map.removeTransitionForAllBytes(transition);
if (map.isEmpty()) {
this.transitionStore = null;
}
}
}

@Override
Expand All @@ -152,20 +264,64 @@ void setIndeterminatePrefix(boolean hasIndeterminatePrefix) {
* @return True if this state has a self-referential transition and no others, false otherwise.
*/
boolean hasOnlySelfReferentialTransition() {
// Saving the value to avoid reading an updated value
Object transitionStore = this.transitionStore;
if (transitionStore == null) {
return false;
} else if (transitionStore instanceof SingleByteTransitionEntry) {
SingleByteTransitionEntry entry = (SingleByteTransitionEntry) transitionStore;
return this.equals(entry.transition);
}
ByteMap map = (ByteMap) transitionStore;
return map.numberOfTransitions() == 1 && map.hasTransition(this);
}

/**
* Gets all the ceiling values contained in the ByteMap.
* Gets all the ceiling values contained in the ByteMap or SingleByteTransitionEntry.
*
* @return All the ceiling values contained in the ByteMap.
* @return All the ceiling values contained in the ByteMap or SingleByteTransitionEntry.
*/
Set<Integer> getCeilings() {
// Saving the value to avoid reading an updated value
Object transitionStore = this.transitionStore;
if (transitionStore == null) {
return Collections.emptySet();
} else if (transitionStore instanceof SingleByteTransitionEntry) {
SingleByteTransitionEntry entry = (SingleByteTransitionEntry) transitionStore;
int index = entry.utf8byte & 0xFF;
if (index == 0) {
return Stream.of(index + 1, 256).collect(Collectors.toSet());
} else if (index == 255) {
return Stream.of(index, index + 1).collect(Collectors.toSet());
} else {
return Stream.of(index, index + 1, 256).collect(Collectors.toSet());
}
}
ByteMap map = (ByteMap) transitionStore;
return map.getCeilings();
}

@Override
public String toString() {
return "BS: " + map;
return "BS: " + transitionStore;
}


private static final class SingleByteTransitionEntry {

final byte utf8byte;
volatile SingleByteTransition transition;

SingleByteTransitionEntry(byte utf8byte, SingleByteTransition transition) {
this.utf8byte = utf8byte;
this.transition = transition;
}

@Override
public String toString() {
ByteState next = transition.getNextByteState();
String nextLabel = (next == null) ? "null" : Integer.toString(next.hashCode());
return "SBTE: " + (char) utf8byte + "=>" + nextLabel;
}
}
}
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