Paper/Spigot-Server-Patches/0406-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/core/BlockPosition.java b/src/main/java/net/minecraft/core/BlockPosition.java
index 4c9ec211470f95d538d1d95c74796190edf99b87..8c0aeb51f5e230fd6109e750732eb54559bc9637 100644
--- a/src/main/java/net/minecraft/core/BlockPosition.java
+++ b/src/main/java/net/minecraft/core/BlockPosition.java
@@ -468,6 +468,7 @@ 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/level/WorldServer.java b/src/main/java/net/minecraft/server/level/WorldServer.java
index fda19e1639cfbae00c8ba946b41c16faa09acbd5..cf6e9a949a864df12ca1670dbc456494d2b5e473 100644
--- a/src/main/java/net/minecraft/server/level/WorldServer.java
+++ b/src/main/java/net/minecraft/server/level/WorldServer.java
@@ -675,7 +675,12 @@ 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();
@@ -683,10 +688,10 @@ 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.W() && 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
@@ -709,59 +714,77 @@ 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(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(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).c() == BiomeBase.Precipitation.RAIN) {
-                this.getType(blockposition1).getBlock().c((World) this, blockposition1);
+            // Paper start - optimise chunk ticking
+            blockposition.setY(downY);
+            if (flag && this.getBiome(blockposition).c() == 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) {
diff --git a/src/main/java/net/minecraft/util/DataBits.java b/src/main/java/net/minecraft/util/DataBits.java
index c4f3b680512fb15cea01ad12d0a00c6e60bf34b7..cfa444cf384920d446c6dc14b23e5158fc28df3b 100644
--- a/src/main/java/net/minecraft/util/DataBits.java
+++ b/src/main/java/net/minecraft/util/DataBits.java
@@ -112,4 +112,32 @@ 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
+    public static interface DataBitConsumer {
+
+        void accept(int location, int data);
+
+    }
+    // Paper end
 }
diff --git a/src/main/java/net/minecraft/world/entity/animal/EntityTurtle.java b/src/main/java/net/minecraft/world/entity/animal/EntityTurtle.java
index 09a6310af6712d36c20167256b60dc3235e76021..ecec8a3c4d4b5d491f79ad60d7ce5a118f30b3db 100644
--- a/src/main/java/net/minecraft/world/entity/animal/EntityTurtle.java
+++ b/src/main/java/net/minecraft/world/entity/animal/EntityTurtle.java
@@ -91,7 +91,7 @@ public class EntityTurtle extends EntityAnimal {
     }
 
     public void setHomePos(BlockPosition blockposition) {
-        this.datawatcher.set(EntityTurtle.bp, blockposition);
+        this.datawatcher.set(EntityTurtle.bp, blockposition.immutableCopy()); // Paper - called with mutablepos...
     }
 
     public BlockPosition getHomePos() { // Paper - public
diff --git a/src/main/java/net/minecraft/world/level/World.java b/src/main/java/net/minecraft/world/level/World.java
index c4680142bf23d30169555abe7db78d85811e042b..cc41dcd85760b57bb8076b37e9a907d1cb4e12c7 100644
--- a/src/main/java/net/minecraft/world/level/World.java
+++ b/src/main/java/net/minecraft/world/level/World.java
@@ -1472,10 +1472,18 @@ public abstract class World implements GeneratorAccess, AutoCloseable {
     public abstract ITagRegistry 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/world/level/chunk/Chunk.java b/src/main/java/net/minecraft/world/level/chunk/Chunk.java
index e7bb33125a25b9e5a68013b15d7b5b6b6769ab9b..fc55e89260fdec2c5045e8f00e091191980ff1f2 100644
--- a/src/main/java/net/minecraft/world/level/chunk/Chunk.java
+++ b/src/main/java/net/minecraft/world/level/chunk/Chunk.java
@@ -640,8 +640,8 @@ 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/world/level/chunk/ChunkSection.java b/src/main/java/net/minecraft/world/level/chunk/ChunkSection.java
index 0b4e346daaea91565fde2f789fafa8b431a7b042..4bc26a7a4ae91aac90c256758ec8868d83027c0c 100644
--- a/src/main/java/net/minecraft/world/level/chunk/ChunkSection.java
+++ b/src/main/java/net/minecraft/world/level/chunk/ChunkSection.java
@@ -14,12 +14,14 @@ import net.minecraft.world.level.material.Fluid;
 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; // Paper - package-private
 
+    public 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) {
@@ -74,6 +76,9 @@ public class ChunkSection {
             --this.nonEmptyBlockCount;
             if (iblockdata1.isTicking()) {
                 --this.tickingBlockCount;
+                // Paper start
+                this.tickingList.remove(i, j, k);
+                // Paper end
             }
         }
 
@@ -85,6 +90,9 @@ public class ChunkSection {
             ++this.nonEmptyBlockCount;
             if (iblockdata.isTicking()) {
                 ++this.tickingBlockCount;
+                // Paper start
+                this.tickingList.add(i, j, k, iblockdata);
+                // Paper end
             }
         }
 
@@ -120,23 +128,29 @@ 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/world/level/chunk/DataPaletteBlock.java b/src/main/java/net/minecraft/world/level/chunk/DataPaletteBlock.java
index 68d53a51acc9790b9cda20ec4d2ec6edd1baac1a..86dfab740883c138a0df8a3da9dfb4eb9acefaa3 100644
--- a/src/main/java/net/minecraft/world/level/chunk/DataPaletteBlock.java
+++ b/src/main/java/net/minecraft/world/level/chunk/DataPaletteBlock.java
@@ -286,6 +286,14 @@ 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> {