0078-lithium-cache-iterate-outwards.patch

From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: 2No2Name <2No2Name@web.de>
Date: Thu, 13 Jan 2022 15:38:29 -0500
Subject: [PATCH] lithium: cache iterate outwards

Original code by the PR below, licensed under GNU Lesser General Public License v3.0
You can find the original code on https://github.com/CaffeineMC/lithium-fabric/pull/123 (Yarn mappings)

diff --git a/src/main/java/me/jellysquid/mods/lithium/common/cached_blockpos_iteration/IterateOutwardsCache.java b/src/main/java/me/jellysquid/mods/lithium/common/cached_blockpos_iteration/IterateOutwardsCache.java
new file mode 100644
index 0000000000000000000000000000000000000000..a5d3aa309d3fdaab9e0fea2dfb91a080a3ac1193
--- /dev/null
+++ b/src/main/java/me/jellysquid/mods/lithium/common/cached_blockpos_iteration/IterateOutwardsCache.java
@@ -0,0 +1,71 @@
+package me.jellysquid.mods.lithium.common.cached_blockpos_iteration;
+
+import it.unimi.dsi.fastutil.longs.LongArrayList;
+import it.unimi.dsi.fastutil.longs.LongList;
+import java.util.Iterator;
+import java.util.Random;
+import java.util.concurrent.ConcurrentHashMap;
+import net.minecraft.core.BlockPos;
+
+/**
+ * @author 2No2Name, original implemenation by SuperCoder7979 and Gegy1000
+ */
+public class IterateOutwardsCache {
+    //POS_ZERO must not be replaced with BlockPos.ORIGIN, otherwise iterateOutwards at BlockPos.ORIGIN will not use the cache
+    public static final BlockPos POS_ZERO = new BlockPos(0,0,0);
+
+
+    private final ConcurrentHashMap<Long, LongArrayList> table;
+    private final int capacity;
+    private final Random random;
+
+    public IterateOutwardsCache(int capacity) {
+        this.capacity = capacity;
+        this.table = new ConcurrentHashMap<>(31);
+        this.random = new Random();
+    }
+
+    private void fillPositionsWithIterateOutwards(LongList entry, int xRange, int yRange, int zRange) {
+        // Add all positions to the cached list
+        for (BlockPos pos : BlockPos.withinManhattan(POS_ZERO, xRange, yRange, zRange)) {
+            entry.add(pos.asLong());
+        }
+    }
+
+    public LongList getOrCompute(int xRange, int yRange, int zRange) {
+        long key = BlockPos.asLong(xRange, yRange, zRange);
+
+        LongArrayList entry = this.table.get(key);
+        if (entry != null) {
+            return entry;
+        }
+
+        // Cache miss: compute and store
+        entry = new LongArrayList(128);
+
+        this.fillPositionsWithIterateOutwards(entry, xRange, yRange, zRange);
+
+        //decrease the array size, as of now it won't be modified anymore anyways
+        entry.trim();
+
+        //this might overwrite an entry as the same entry could have been computed and added during this thread's computation
+        //we do not use computeIfAbsent, as it can delay other threads for too long
+        Object previousEntry = this.table.put(key, entry);
+
+
+        if (previousEntry == null && this.table.size() > this.capacity) {
+            //prevent a memory leak by randomly removing about 1/8th of the elements when the exceed the desired capacity is exceeded
+            final Iterator<Long> iterator = this.table.keySet().iterator();
+            //prevent an unlikely infinite loop caused by another thread filling the table concurrently using counting
+            for (int i = -this.capacity; iterator.hasNext() && i < 5; i++) {
+                Long key2 = iterator.next();
+                //random is not threadsafe, but it doesn't matter here, because we don't need quality random numbers
+                if (this.random.nextInt(8) == 0 && key2 != key) {
+                    iterator.remove();
+                }
+            }
+        }
+
+        return entry;
+    }
+}
\ No newline at end of file
diff --git a/src/main/java/me/jellysquid/mods/lithium/common/cached_blockpos_iteration/LongList2BlockPosMutableIterable.java b/src/main/java/me/jellysquid/mods/lithium/common/cached_blockpos_iteration/LongList2BlockPosMutableIterable.java
new file mode 100644
index 0000000000000000000000000000000000000000..493661ff3ac7247b68b7b02784b09b0eaf88fc52
--- /dev/null
+++ b/src/main/java/me/jellysquid/mods/lithium/common/cached_blockpos_iteration/LongList2BlockPosMutableIterable.java
@@ -0,0 +1,46 @@
+package me.jellysquid.mods.lithium.common.cached_blockpos_iteration;
+
+import it.unimi.dsi.fastutil.longs.LongIterator;
+import it.unimi.dsi.fastutil.longs.LongList;
+import java.util.Iterator;
+import net.minecraft.core.BlockPos;
+
+/**
+ * @author 2No2Name
+ */
+public class LongList2BlockPosMutableIterable implements Iterable<BlockPos> {
+
+    private final LongList positions;
+    private final int xOffset, yOffset, zOffset;
+
+    public LongList2BlockPosMutableIterable(BlockPos offset, LongList posList) {
+        this.xOffset = offset.getX();
+        this.yOffset = offset.getY();
+        this.zOffset = offset.getZ();
+        this.positions = posList;
+    }
+
+    @Override
+    public Iterator<BlockPos> iterator() {
+        return new Iterator<BlockPos>() {
+
+            private final LongIterator it = LongList2BlockPosMutableIterable.this.positions.iterator();
+            private final BlockPos.MutableBlockPos pos = new BlockPos.MutableBlockPos();
+
+            @Override
+            public boolean hasNext() {
+                return it.hasNext();
+            }
+
+            @Override
+            public net.minecraft.core.BlockPos next() {
+                long nextPos = this.it.nextLong();
+                return this.pos.set(
+                        LongList2BlockPosMutableIterable.this.xOffset + BlockPos.getX(nextPos),
+                        LongList2BlockPosMutableIterable.this.yOffset + BlockPos.getY(nextPos),
+                        LongList2BlockPosMutableIterable.this.zOffset + BlockPos.getZ(nextPos));
+            }
+        };
+    }
+
+}
\ No newline at end of file
diff --git a/src/main/java/net/minecraft/core/BlockPos.java b/src/main/java/net/minecraft/core/BlockPos.java
index 153451ecd5b3c8e8ecb2d5ec91ccd582d4300899..4487752469f9ab95e9d2aeb76a9627dc02095d76 100644
--- a/src/main/java/net/minecraft/core/BlockPos.java
+++ b/src/main/java/net/minecraft/core/BlockPos.java
@@ -18,6 +18,12 @@ import net.minecraft.world.phys.AABB;
 import net.minecraft.world.phys.Vec3;
 import org.apache.commons.lang3.Validate;
 import org.slf4j.Logger;
+// JettPack start
+import it.unimi.dsi.fastutil.longs.LongList;
+import me.jellysquid.mods.lithium.common.cached_blockpos_iteration.IterateOutwardsCache;
+import me.jellysquid.mods.lithium.common.cached_blockpos_iteration.LongList2BlockPosMutableIterable;
+import static me.jellysquid.mods.lithium.common.cached_blockpos_iteration.IterateOutwardsCache.POS_ZERO;
+// JettPack end
 
 @Immutable
 public class BlockPos extends Vec3i {
@@ -284,7 +290,18 @@ public class BlockPos extends Vec3i {
         };
     }
 
+    // JettPack start - lithium: cached iterate outwards
+    private static final IterateOutwardsCache ITERATE_OUTWARDS_CACHE = new IterateOutwardsCache(50);
+    private static final LongList HOGLIN_PIGLIN_CACHE = ITERATE_OUTWARDS_CACHE.getOrCompute(8, 4, 8);
+    // JettPack end
+
     public static Iterable<BlockPos> withinManhattan(BlockPos center, int rangeX, int rangeY, int rangeZ) {
+        // JettPack start - lithium: cached iterate outwards
+        if (center != POS_ZERO) {
+            final LongList positions = rangeX == 8 && rangeY == 4 && rangeZ == 8 ? HOGLIN_PIGLIN_CACHE : ITERATE_OUTWARDS_CACHE.getOrCompute(rangeX, rangeY, rangeZ);
+            return new LongList2BlockPosMutableIterable(center, positions);
+        }
+        // JettPack end
         int i = rangeX + rangeY + rangeZ;
         // Paper start - rename variables to fix conflict with anonymous class (remap fix)
         int centerX = center.getX();