papermc/Spigot-Server-Patches/0417-Optimise-random-block-ticking.patch

From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: Spottedleaf <Spottedleaf@users.noreply.github.com>
Date: Mon, 27 Jan 2020 21:28:00 -0800
Subject: [PATCH] Optimise random block ticking

Massive performance improvement for random block ticking.
The performance increase comes from the fact that the vast
majority of attempted block ticks (~95% in my testing) fail
because the randomly selected block is not tickable.

Now only tickable blocks are targeted, however this means that
the maximum number of block ticks occurs per chunk. However,
not all chunks are going to be targeted. The percent chance
of a chunk being targeted is based on how many tickable blocks
are in the chunk.
This means that while block ticks are spread out less, the
total number of blocks ticked per world tick remains the same.
Therefore, the chance of a random tickable block being ticked
remains the same.

diff --git a/src/main/java/com/destroystokyo/paper/util/math/ThreadUnsafeRandom.java b/src/main/java/com/destroystokyo/paper/util/math/ThreadUnsafeRandom.java
new file mode 100644
index 0000000000000000000000000000000000000000..3edc8e52e06a62ce9f8cc734fd7458b37cfaad91
--- /dev/null
+++ b/src/main/java/com/destroystokyo/paper/util/math/ThreadUnsafeRandom.java
@@ -0,0 +1,46 @@
+package com.destroystokyo.paper.util.math;
+
+import java.util.Random;
+
+public final class ThreadUnsafeRandom extends Random {
+
+    // See javadoc and internal comments for java.util.Random where these values come from, how they are used, and the author for them.
+    private static final long multiplier = 0x5DEECE66DL;
+    private static final long addend = 0xBL;
+    private static final long mask = (1L << 48) - 1;
+
+    private static long initialScramble(long seed) {
+        return (seed ^ multiplier) & mask;
+    }
+
+    private long seed;
+
+    @Override
+    public void setSeed(long seed) {
+        // note: called by Random constructor
+        this.seed = initialScramble(seed);
+    }
+
+    @Override
+    protected int next(int bits) {
+        // avoid the expensive CAS logic used by superclass
+        return (int) (((this.seed = this.seed * multiplier + addend) & mask) >>> (48 - bits));
+    }
+
+    // Taken from
+    // https://lemire.me/blog/2016/06/27/a-fast-alternative-to-the-modulo-reduction/
+    // https://github.com/lemire/Code-used-on-Daniel-Lemire-s-blog/blob/master/2016/06/25/fastrange.c
+    // Original license is public domain
+    public static int fastRandomBounded(final long randomInteger, final long limit) {
+        // randomInteger must be [0, pow(2, 32))
+        // limit must be [0, pow(2, 32))
+        return (int)((randomInteger * limit) >>> 32);
+    }
+
+    @Override
+    public int nextInt(int bound) {
+        // yes this breaks random's spec
+        // however there's nothing that uses this class that relies on it
+        return fastRandomBounded(this.next(32) & 0xFFFFFFFFL, bound);
+    }
+}
diff --git a/src/main/java/net/minecraft/server/BlockPosition.java b/src/main/java/net/minecraft/server/BlockPosition.java
index b50d86b39d2296e1dfb9aaaeb8f8f6f62a4e7430..2d3e73ef92c7b88d49f8eb27233cb823b425ea4a 100644
--- a/src/main/java/net/minecraft/server/BlockPosition.java
+++ b/src/main/java/net/minecraft/server/BlockPosition.java
@@ -402,6 +402,7 @@ public class BlockPosition extends BaseBlockPosition {
             return this.d(MathHelper.floor(d0), MathHelper.floor(d1), MathHelper.floor(d2));
         }
 
+        public final BlockPosition.MutableBlockPosition setValues(final BaseBlockPosition baseblockposition) { return this.g(baseblockposition); } // Paper - OBFHELPER
         public BlockPosition.MutableBlockPosition g(BaseBlockPosition baseblockposition) {
             return this.d(baseblockposition.getX(), baseblockposition.getY(), baseblockposition.getZ());
         }
diff --git a/src/main/java/net/minecraft/server/Chunk.java b/src/main/java/net/minecraft/server/Chunk.java
index b2713942d8cf5bedd91ac63df18a336743c72da5..a76b1d2fd81aaedb37190bcb8510020d5df2513e 100644
--- a/src/main/java/net/minecraft/server/Chunk.java
+++ b/src/main/java/net/minecraft/server/Chunk.java
@@ -593,8 +593,8 @@ public class Chunk implements IChunkAccess {
         this.entities.remove(entity); // Paper
     }
 
-    @Override
-    public int getHighestBlock(HeightMap.Type heightmap_type, int i, int j) {
+    public final int getHighestBlockY(HeightMap.Type heightmap_type, int i, int j) { return this.getHighestBlock(heightmap_type, i, j) + 1; } // Paper - sort of an obfhelper, but without -1
+    @Override public int getHighestBlock(HeightMap.Type heightmap_type, int i, int j) { // Paper
         return ((HeightMap) this.heightMap.get(heightmap_type)).a(i & 15, j & 15) - 1;
     }
 
diff --git a/src/main/java/net/minecraft/server/ChunkSection.java b/src/main/java/net/minecraft/server/ChunkSection.java
index b168ad8021a5387e05023cd03ec1a69c8a86a233..cf444fa1cc96e881a1f9ed0c78d45935fe1c90ab 100644
--- a/src/main/java/net/minecraft/server/ChunkSection.java
+++ b/src/main/java/net/minecraft/server/ChunkSection.java
@@ -7,12 +7,14 @@ import javax.annotation.Nullable;
 public class ChunkSection {
 
     public static final DataPalette<IBlockData> GLOBAL_PALETTE = new DataPaletteGlobal<>(Block.REGISTRY_ID, Blocks.AIR.getBlockData());
-    private final int yPos;
+    final int yPos; // Paper - private -> package-private
     short nonEmptyBlockCount; // Paper - package-private
-    private short tickingBlockCount;
+    short tickingBlockCount; // Paper - private -> package-private
     private short e;
     final DataPaletteBlock<IBlockData> blockIds;
 
+    final com.destroystokyo.paper.util.maplist.IBlockDataList tickingList = new com.destroystokyo.paper.util.maplist.IBlockDataList(); // Paper
+
     // Paper start - Anti-Xray - Add parameters
     @Deprecated public ChunkSection(int i) { this(i, null, null, true); } // Notice for updates: Please make sure this constructor isn't used anywhere
     public ChunkSection(int i, IChunkAccess chunk, World world, boolean initializeBlocks) {
@@ -67,6 +69,9 @@ public class ChunkSection {
             --this.nonEmptyBlockCount;
             if (iblockdata1.isTicking()) {
                 --this.tickingBlockCount;
+                // Paper start
+                this.tickingList.remove(i, j, k);
+                // Paper end
             }
         }
 
@@ -78,6 +83,9 @@ public class ChunkSection {
             ++this.nonEmptyBlockCount;
             if (iblockdata.isTicking()) {
                 ++this.tickingBlockCount;
+                // Paper start
+                this.tickingList.add(i, j, k, iblockdata);
+                // Paper end
             }
         }
 
@@ -113,23 +121,29 @@ public class ChunkSection {
     }
 
     public void recalcBlockCounts() {
+        // Paper start
+        this.tickingList.clear();
+        // Paper end
         this.nonEmptyBlockCount = 0;
         this.tickingBlockCount = 0;
         this.e = 0;
-        this.blockIds.a((iblockdata, i) -> {
+        this.blockIds.forEachLocation((iblockdata, location) -> { // Paper
             Fluid fluid = iblockdata.getFluid();
 
             if (!iblockdata.isAir()) {
-                this.nonEmptyBlockCount = (short) (this.nonEmptyBlockCount + i);
+                this.nonEmptyBlockCount = (short) (this.nonEmptyBlockCount + 1);
                 if (iblockdata.isTicking()) {
-                    this.tickingBlockCount = (short) (this.tickingBlockCount + i);
+                    this.tickingBlockCount = (short) (this.tickingBlockCount + 1);
+                    // Paper start
+                    this.tickingList.add(location, iblockdata);
+                    // Paper end
                 }
             }
 
             if (!fluid.isEmpty()) {
-                this.nonEmptyBlockCount = (short) (this.nonEmptyBlockCount + i);
+                this.nonEmptyBlockCount = (short) (this.nonEmptyBlockCount + 1);
                 if (fluid.f()) {
-                    this.e = (short) (this.e + i);
+                    this.e = (short) (this.e + 1);
                 }
             }
 
diff --git a/src/main/java/net/minecraft/server/DataBits.java b/src/main/java/net/minecraft/server/DataBits.java
index 48cca2b9a1dbb071615625842123c0c47e281b29..235c9ec37c00ce8838b3e7c02284e402f9d30e38 100644
--- a/src/main/java/net/minecraft/server/DataBits.java
+++ b/src/main/java/net/minecraft/server/DataBits.java
@@ -111,4 +111,32 @@ public class DataBits {
         }
 
     }
+
+    // Paper start
+    public final void forEach(DataBitConsumer consumer) {
+        int i = 0;
+        long[] along = this.b;
+        int j = along.length;
+
+        for (int k = 0; k < j; ++k) {
+            long l = along[k];
+
+            for (int i1 = 0; i1 < this.f; ++i1) {
+                consumer.accept(i, (int) (l & this.d));
+                l >>= this.c;
+                ++i;
+                if (i >= this.e) {
+                    return;
+                }
+            }
+        }
+    }
+
+    @FunctionalInterface
+    static interface DataBitConsumer {
+
+        void accept(int location, int data);
+
+    }
+    // Paper end
 }
diff --git a/src/main/java/net/minecraft/server/DataPaletteBlock.java b/src/main/java/net/minecraft/server/DataPaletteBlock.java
index 900b551f6f76862443b09c1e76ad596eda5655f4..1cb45f97b644347d16b66b46113b1e4455004fd3 100644
--- a/src/main/java/net/minecraft/server/DataPaletteBlock.java
+++ b/src/main/java/net/minecraft/server/DataPaletteBlock.java
@@ -277,6 +277,14 @@ public class DataPaletteBlock<T> implements DataPaletteExpandable<T> {
         });
     }
 
+    // Paper start
+    public void forEachLocation(DataPaletteBlock.a<T> datapaletteblock_a) {
+        this.getDataBits().forEach((int location, int data) -> {
+            datapaletteblock_a.accept(this.getDataPalette().getObject(data), location);
+        });
+    }
+    // Paper end
+
     @FunctionalInterface
     public interface a<T> {
 
diff --git a/src/main/java/net/minecraft/server/EntityTurtle.java b/src/main/java/net/minecraft/server/EntityTurtle.java
index 00827c335e9413e986d7f07d0adbcef0d106a553..c66a8011dde4932e03ea91194ea92a7263e48428 100644
--- a/src/main/java/net/minecraft/server/EntityTurtle.java
+++ b/src/main/java/net/minecraft/server/EntityTurtle.java
@@ -29,7 +29,7 @@ public class EntityTurtle extends EntityAnimal {
 
     public final void setHome(BlockPosition pos) { setHomePos(pos); } // Paper - OBFHELPER
     public void setHomePos(BlockPosition blockposition) {
-        this.datawatcher.set(EntityTurtle.bw, blockposition);
+        this.datawatcher.set(EntityTurtle.bw, blockposition.immutableCopy()); // Paper - called with mutablepos...
     }
     // TODO Paper: Obf helpers here can prolly be removed? check that no newer patches use them
     public final BlockPosition getHome() { return this.getHomePos(); } // Paper - OBFHELPER
diff --git a/src/main/java/net/minecraft/server/World.java b/src/main/java/net/minecraft/server/World.java
index 7c6b7955c454c585eed7457d6680ce67e6219162..a31d293a00d325e4ee1eba48126b112df117fcfc 100644
--- a/src/main/java/net/minecraft/server/World.java
+++ b/src/main/java/net/minecraft/server/World.java
@@ -1466,10 +1466,18 @@ public abstract class World implements GeneratorAccess, AutoCloseable {
     public abstract TagRegistry p();
 
     public BlockPosition a(int i, int j, int k, int l) {
+        // Paper start - allow use of mutable pos
+        BlockPosition.MutableBlockPosition ret = new BlockPosition.MutableBlockPosition();
+        this.getRandomBlockPosition(i, j, k, l, ret);
+        return ret.immutableCopy();
+    }
+    public final BlockPosition.MutableBlockPosition getRandomBlockPosition(int i, int j, int k, int l, BlockPosition.MutableBlockPosition out) {
+        // Paper end
         this.n = this.n * 3 + 1013904223;
         int i1 = this.n >> 2;
 
-        return new BlockPosition(i + (i1 & 15), j + (i1 >> 16 & l), k + (i1 >> 8 & 15));
+        out.setValues(i + (i1 & 15), j + (i1 >> 16 & l), k + (i1 >> 8 & 15)); // Paper - change to setValues call
+        return out; // Paper
     }
 
     public boolean isSavingDisabled() {
diff --git a/src/main/java/net/minecraft/server/WorldServer.java b/src/main/java/net/minecraft/server/WorldServer.java
index 4883b12a8033f62e7c777f6b6f21003d89f470e4..f4571b7892cb7962618c1fee3aad86311c92ca28 100644
--- a/src/main/java/net/minecraft/server/WorldServer.java
+++ b/src/main/java/net/minecraft/server/WorldServer.java
@@ -556,7 +556,12 @@ public class WorldServer extends World implements GeneratorAccessSeed {
         });
     }
 
-    public void a(Chunk chunk, int i) {
+    // Paper start - optimise random block ticking
+    private final BlockPosition.MutableBlockPosition chunkTickMutablePosition = new BlockPosition.MutableBlockPosition();
+    private final com.destroystokyo.paper.util.math.ThreadUnsafeRandom randomTickRandom = new com.destroystokyo.paper.util.math.ThreadUnsafeRandom();
+    // Paper end
+
+    public void a(Chunk chunk, int i) { final int randomTickSpeed = i; // Paper
         ChunkCoordIntPair chunkcoordintpair = chunk.getPos();
         boolean flag = this.isRaining();
         int j = chunkcoordintpair.d();
@@ -564,10 +569,10 @@ public class WorldServer extends World implements GeneratorAccessSeed {
         GameProfilerFiller gameprofilerfiller = this.getMethodProfiler();
 
         gameprofilerfiller.enter("thunder");
-        BlockPosition blockposition;
+        final BlockPosition.MutableBlockPosition blockposition = this.chunkTickMutablePosition; // Paper - use mutable to reduce allocation rate, final to force compile fail on change
 
         if (!this.paperConfig.disableThunder && flag && this.T() && this.random.nextInt(100000) == 0) { // Paper - Disable thunder
-            blockposition = this.a(this.a(j, 0, k, 15));
+            blockposition.setValues(this.a(this.a(j, 0, k, 15))); // Paper
             if (this.isRainingAt(blockposition)) {
                 DifficultyDamageScaler difficultydamagescaler = this.getDamageScaler(blockposition);
                 boolean flag1 = this.getGameRules().getBoolean(GameRules.DO_MOB_SPAWNING) && this.random.nextDouble() < (double) difficultydamagescaler.b() * paperConfig.skeleHorseSpawnChance; // Paper
@@ -590,59 +595,77 @@ public class WorldServer extends World implements GeneratorAccessSeed {
         }
 
         gameprofilerfiller.exitEnter("iceandsnow");
-        if (!this.paperConfig.disableIceAndSnow && this.random.nextInt(16) == 0) { // Paper - Disable ice and snow
-            blockposition = this.getHighestBlockYAt(HeightMap.Type.MOTION_BLOCKING, this.a(j, 0, k, 15));
-            BlockPosition blockposition1 = blockposition.down();
+        if (!this.paperConfig.disableIceAndSnow && this.randomTickRandom.nextInt(16) == 0) { // Paper - Disable ice and snow // Paper - optimise random ticking
+            // Paper start - optimise chunk ticking
+            this.getRandomBlockPosition(j, 0, k, 15, blockposition);
+            int normalY = chunk.getHighestBlockY(HeightMap.Type.MOTION_BLOCKING, blockposition.getX() & 15, blockposition.getZ() & 15);
+            int downY = normalY - 1;
+            blockposition.setY(normalY);
+            // Paper end
             BiomeBase biomebase = this.getBiome(blockposition);
 
-            if (biomebase.a((IWorldReader) this, blockposition1)) {
-                org.bukkit.craftbukkit.event.CraftEventFactory.handleBlockFormEvent(this, blockposition1, Blocks.ICE.getBlockData(), null); // CraftBukkit
+            // Paper start - optimise chunk ticking
+            blockposition.setY(downY);
+            if (biomebase.a((IWorldReader) this, blockposition)) {
+                org.bukkit.craftbukkit.event.CraftEventFactory.handleBlockFormEvent(this, blockposition, Blocks.ICE.getBlockData(), null); // CraftBukkit
+                // Paper end
             }
 
+            blockposition.setY(normalY); // Paper
             if (flag && biomebase.b(this, blockposition)) {
                 org.bukkit.craftbukkit.event.CraftEventFactory.handleBlockFormEvent(this, blockposition, Blocks.SNOW.getBlockData(), null); // CraftBukkit
             }
 
-            if (flag && this.getBiome(blockposition1).d() == BiomeBase.Precipitation.RAIN) {
-                this.getType(blockposition1).getBlock().c((World) this, blockposition1);
+            // Paper start - optimise chunk ticking
+            blockposition.setY(downY);
+            if (flag && this.getBiome(blockposition).d() == BiomeBase.Precipitation.RAIN) {
+                chunk.getType(blockposition).getBlock().c((World) this, blockposition);
+                // Paper end
             }
         }
 
-        gameprofilerfiller.exitEnter("tickBlocks");
-        timings.chunkTicksBlocks.startTiming(); // Paper
+        // Paper start - optimise random block ticking
+        gameprofilerfiller.exit();
         if (i > 0) {
-            ChunkSection[] achunksection = chunk.getSections();
-            int l = achunksection.length;
+            gameprofilerfiller.enter("randomTick");
+            timings.chunkTicksBlocks.startTiming(); // Paper
 
-            for (int i1 = 0; i1 < l; ++i1) {
-                ChunkSection chunksection = achunksection[i1];
+            ChunkSection[] sections = chunk.getSections();
 
-                if (chunksection != Chunk.a && chunksection.d()) {
-                    int j1 = chunksection.getYPosition();
+            for (int sectionIndex = 0; sectionIndex < 16; ++sectionIndex) {
+                ChunkSection section = sections[sectionIndex];
+                if (section == null || section.tickingList.size() == 0) {
+                    continue;
+                }
 
-                    for (int k1 = 0; k1 < i; ++k1) {
-                        BlockPosition blockposition2 = this.a(j, j1, k, 15);
+                int yPos = sectionIndex << 4;
 
-                        gameprofilerfiller.enter("randomTick");
-                        IBlockData iblockdata = chunksection.getType(blockposition2.getX() - j, blockposition2.getY() - j1, blockposition2.getZ() - k);
+                for (int a = 0; a < randomTickSpeed; ++a) {
+                    int tickingBlocks = section.tickingList.size();
+                    int index = this.randomTickRandom.nextInt(16 * 16 * 16);
+                    if (index >= tickingBlocks) {
+                        continue;
+                    }
 
-                        if (iblockdata.isTicking()) {
-                            iblockdata.b(this, blockposition2, this.random);
-                        }
+                    long raw = section.tickingList.getRaw(index);
+                    int location = com.destroystokyo.paper.util.maplist.IBlockDataList.getLocationFromRaw(raw);
+                    int randomX = location & 15;
+                    int randomY = ((location >>> (4 + 4)) & 255) | yPos;
+                    int randomZ = (location >>> 4) & 15;
 
-                        Fluid fluid = iblockdata.getFluid();
+                    BlockPosition blockposition2 = blockposition.setValues(j + randomX, randomY, k + randomZ);
+                    IBlockData iblockdata = com.destroystokyo.paper.util.maplist.IBlockDataList.getBlockDataFromRaw(raw);
 
-                        if (fluid.f()) {
-                            fluid.b(this, blockposition2, this.random);
-                        }
+                    iblockdata.b(this, blockposition2, this.randomTickRandom);
 
-                        gameprofilerfiller.exit();
-                    }
+                    // We drop the fluid tick since LAVA is ALREADY TICKED by the above method.
+                    // TODO CHECK ON UPDATE
                 }
             }
+            gameprofilerfiller.exit();
+            timings.chunkTicksBlocks.stopTiming(); // Paper
+            // Paper end
         }
-        timings.chunkTicksBlocks.stopTiming(); // Paper
-        gameprofilerfiller.exit();
     }
 
     protected BlockPosition a(BlockPosition blockposition) {