PaperMC/Spigot-Server-Patches/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 00000000000..3edc8e52e06
--- /dev/null
+++ b/src/main/java/com/destroystokyo/paper/util/math/ThreadUnsafeRandom.java
@@ -0,0 +0,0 @@
+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/Block.java b/src/main/java/net/minecraft/server/Block.java
index e29ec958b35..e40375b67a4 100644
--- a/src/main/java/net/minecraft/server/Block.java
+++ b/src/main/java/net/minecraft/server/Block.java
@@ -0,0 +0,0 @@ public class Block implements IMaterial {
         return iblockdata.d(iblockaccess, blockposition, EnumDirection.UP) && this.n < 14;
     }
 
-    @Deprecated
-    public boolean d(IBlockData iblockdata) {
+    public final boolean isAir(IBlockData iblockdata) { return this.d(iblockdata); } // Paper - OBFHELPER
+    @Deprecated public boolean d(IBlockData iblockdata) { // Paper - OBFHELPER
         return false;
     }
 
diff --git a/src/main/java/net/minecraft/server/BlockFluids.java b/src/main/java/net/minecraft/server/BlockFluids.java
index 6d351f0979e..a44f65f40d2 100644
--- a/src/main/java/net/minecraft/server/BlockFluids.java
+++ b/src/main/java/net/minecraft/server/BlockFluids.java
@@ -0,0 +0,0 @@ public class BlockFluids extends Block implements IFluidSource {
 
     @Override
     public void b(IBlockData iblockdata, WorldServer worldserver, BlockPosition blockposition, Random random) {
-        worldserver.getFluid(blockposition).b(worldserver, blockposition, random);
+        iblockdata.getFluid().b(worldserver, blockposition, random); // Paper - avoid getType call
     }
 
     @Override
diff --git a/src/main/java/net/minecraft/server/BlockPosition.java b/src/main/java/net/minecraft/server/BlockPosition.java
index db7ba12fd4f..9010359fbdc 100644
--- a/src/main/java/net/minecraft/server/BlockPosition.java
+++ b/src/main/java/net/minecraft/server/BlockPosition.java
@@ -0,0 +0,0 @@ public class BlockPosition extends BaseBlockPosition implements MinecraftSeriali
             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 a2a0ca3394c..bb95fe20e8a 100644
--- a/src/main/java/net/minecraft/server/Chunk.java
+++ b/src/main/java/net/minecraft/server/Chunk.java
@@ -0,0 +0,0 @@ public class Chunk implements IChunkAccess {
         this.entities.remove(entity); // Paper
     }
 
-    @Override
-    public int a(HeightMap.Type heightmap_type, int i, int j) {
+    public int getHighestBlockY(HeightMap.Type heightmap_type, int i, int j) { return this.a(heightmap_type, i, j) + 1; } // Paper - sort of an obfhelper, but without -1
+    @Override public int a(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 eeb7eee925d..64b625e988f 100644
--- a/src/main/java/net/minecraft/server/ChunkSection.java
+++ b/src/main/java/net/minecraft/server/ChunkSection.java
@@ -0,0 +0,0 @@ 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
     private short nonEmptyBlockCount;
-    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) {
@@ -0,0 +0,0 @@ public class ChunkSection {
             --this.nonEmptyBlockCount;
             if (iblockdata1.q()) {
                 --this.tickingBlockCount;
+                // Paper start
+                this.tickingList.remove(i, j, k);
+                // Paper end
             }
         }
 
@@ -0,0 +0,0 @@ public class ChunkSection {
             ++this.nonEmptyBlockCount;
             if (iblockdata.q()) {
                 ++this.tickingBlockCount;
+                // Paper start
+                this.tickingList.add(i, j, k, iblockdata);
+                // Paper end
             }
         }
 
@@ -0,0 +0,0 @@ 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); // Paper
                 if (iblockdata.q()) {
-                    this.tickingBlockCount = (short) (this.tickingBlockCount + i);
+                    this.tickingBlockCount = (short) (this.tickingBlockCount + 1); // Paper
+                    // Paper start
+                    this.tickingList.add(location, iblockdata);
+                    // Paper end
                 }
             }
 
             if (!fluid.isEmpty()) {
-                this.nonEmptyBlockCount = (short) (this.nonEmptyBlockCount + i);
+                this.nonEmptyBlockCount = (short) (this.nonEmptyBlockCount + 1); // Paper
                 if (fluid.h()) {
-                    this.e = (short) (this.e + i);
+                    this.e = (short) (this.e + 1); // Paper
                 }
             }
 
diff --git a/src/main/java/net/minecraft/server/DataBits.java b/src/main/java/net/minecraft/server/DataBits.java
index f9680b6830c..a61cffa3f49 100644
--- a/src/main/java/net/minecraft/server/DataBits.java
+++ b/src/main/java/net/minecraft/server/DataBits.java
@@ -0,0 +0,0 @@ public class DataBits {
 
         }
     }
+
+    // Paper start
+    public final void forEach(DataBitConsumer consumer) {
+        // Note: copied from above
+        int i = this.a.length;
+
+        if (i != 0) {
+            int j = 0;
+            long k = this.a[0];
+            long l = i > 1 ? this.a[1] : 0L;
+
+            for (int i1 = 0; i1 < this.d; ++i1) {
+                int j1 = i1 * this.b;
+                int k1 = j1 >> 6;
+                int l1 = (i1 + 1) * this.b - 1 >> 6;
+                int i2 = j1 ^ k1 << 6;
+
+                if (k1 != j) {
+                    k = l;
+                    l = k1 + 1 < i ? this.a[k1 + 1] : 0L;
+                    j = k1;
+                }
+
+                if (k1 == l1) {
+                    consumer.accept(i1, (int) (k >>> i2 & this.c));
+                } else {
+                    int j2 = 64 - i2;
+
+                    consumer.accept(i1, (int) ((k >>> i2 | l << j2) & this.c));
+                }
+            }
+
+        }
+    }
+
+    @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 2c7872bd051..be5f98c3c36 100644
--- a/src/main/java/net/minecraft/server/DataPaletteBlock.java
+++ b/src/main/java/net/minecraft/server/DataPaletteBlock.java
@@ -0,0 +0,0 @@ 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 dd02cb34850..b24a5100b45 100644
--- a/src/main/java/net/minecraft/server/EntityTurtle.java
+++ b/src/main/java/net/minecraft/server/EntityTurtle.java
@@ -0,0 +0,0 @@ public class EntityTurtle extends EntityAnimal {
 
     public final void setHome(BlockPosition pos) { g(pos); } // Paper - OBFHELPER
     public void g(BlockPosition blockposition) {
-        this.datawatcher.set(EntityTurtle.bx, blockposition);
+        this.datawatcher.set(EntityTurtle.bx, blockposition.immutableCopy()); // Paper - make sure home position can't change
     }
 
     public final BlockPosition getHome() { return this.es(); } // Paper - OBFHELPER
diff --git a/src/main/java/net/minecraft/server/IBlockData.java b/src/main/java/net/minecraft/server/IBlockData.java
index de43881653f..e821c236b45 100644
--- a/src/main/java/net/minecraft/server/IBlockData.java
+++ b/src/main/java/net/minecraft/server/IBlockData.java
@@ -0,0 +0,0 @@ public class IBlockData extends BlockDataAbstract<Block, IBlockData> implements
     private IBlockData.a c;
     private final int d;
     private final boolean e;
+    private final boolean isAir; // Paper
+    private final boolean isTicking; // Paper
 
     public IBlockData(Block block, ImmutableMap<IBlockState<?>, Comparable<?>> immutablemap) {
         super(block, immutablemap);
         this.d = block.a(this);
         this.e = block.o(this);
+        this.isAir = this.getBlock().isAir(this); // Paper
+        this.isTicking = this.getBlock().isTicking(this); // Paper
     }
 
     public void c() {
@@ -0,0 +0,0 @@ public class IBlockData extends BlockDataAbstract<Block, IBlockData> implements
         return this.d;
     }
 
-    public boolean isAir() {
-        return this.getBlock().d(this);
+    public final boolean isAir() { // Paper - compile fail if the impl changes
+        return this.isAir; // Paper - improve inlining of isAir
     }
 
     public MaterialMapColor c(IBlockAccess iblockaccess, BlockPosition blockposition) {
@@ -0,0 +0,0 @@ public class IBlockData extends BlockDataAbstract<Block, IBlockData> implements
         return this.getBlock().a(tag);
     }
 
+    private Fluid fluidData; // Paper - cache result
     public Fluid getFluid() {
-        return this.getBlock().a_(this);
+        // Paper start
+        // This can't be done during the constructor, order issues
+        if (this.fluidData != null) {
+            return this.fluidData;
+        }
+        return this.fluidData = this.getBlock().a_(this);
+        // Paper end
     }
 
     public boolean q() {
-        return this.getBlock().isTicking(this);
+        return this.isTicking; // Paper
     }
 
     public final SoundEffectType getStepSound() { return this.r(); } // Paper - OBFHELPER
diff --git a/src/main/java/net/minecraft/server/World.java b/src/main/java/net/minecraft/server/World.java
index 0c23fc89d7a..de9f49b8848 100644
--- a/src/main/java/net/minecraft/server/World.java
+++ b/src/main/java/net/minecraft/server/World.java
@@ -0,0 +0,0 @@ public abstract class World implements GeneratorAccess, AutoCloseable {
     public abstract TagRegistry t();
 
     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.i = this.i * 3 + 1013904223;
         int i1 = this.i >> 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 c348e3e5008..fcbc9f29139 100644
--- a/src/main/java/net/minecraft/server/WorldServer.java
+++ b/src/main/java/net/minecraft/server/WorldServer.java
@@ -0,0 +0,0 @@ public class WorldServer extends World {
         });
     }
 
-    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();
@@ -0,0 +0,0 @@ public class WorldServer extends World {
         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.U() && this.random.nextInt(100000) == 0) { // Paper - Disable thunder
-            blockposition = this.a(this.a(j, 0, k, 15));
+        if (!this.paperConfig.disableThunder && flag && this.U() && this.randomTickRandom.nextInt(100000) == 0) { // Paper - Disable thunder // Paper - optimise random ticking
+            blockposition.setValues(this.a(this.getRandomBlockPosition(j, 0, k, 15, blockposition))); // 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
@@ -0,0 +0,0 @@ public class WorldServer extends World {
         }
 
         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.q()) {
-                            iblockdata.getBlock().randomTick = true; // Paper - fix MC-113809
-                            iblockdata.b(this, blockposition2, this.random);
-                            iblockdata.getBlock().randomTick = false; // Paper - fix MC-113809
-                        }
+                    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.h()) {
-                            fluid.b(this, blockposition2, this.random);
-                        }
+                    iblockdata.getBlock().randomTick = true; // Paper - fix MC-113809
+                    iblockdata.b(this, blockposition2, this.randomTickRandom);
+                    iblockdata.getBlock().randomTick = false; // Paper - fix MC-113809
 
-                        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) {
--