Paper/patches/unapplied/server/0703-Optimise-random-block-ticking.patch

From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: Spottedleaf <Spottedleaf@users.noreply.github.com>
Date: Sun, 20 Jun 2021 16:19:26 -0700
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/io/papermc/paper/util/math/ThreadUnsafeRandom.java b/src/main/java/io/papermc/paper/util/math/ThreadUnsafeRandom.java
new file mode 100644
index 0000000000000000000000000000000000000000..7d93652c1abbb6aee6eb7c26cf35d4d032ef7b69
--- /dev/null
+++ b/src/main/java/io/papermc/paper/util/math/ThreadUnsafeRandom.java
@@ -0,0 +1,65 @@
+package io.papermc.paper.util.math;
+
+import net.minecraft.util.RandomSource;
+import net.minecraft.world.level.levelgen.LegacyRandomSource;
+import net.minecraft.world.level.levelgen.PositionalRandomFactory;
+import org.checkerframework.checker.nullness.qual.NonNull;
+import org.checkerframework.framework.qual.DefaultQualifier;
+
+@DefaultQualifier(NonNull.class)
+public final class ThreadUnsafeRandom extends LegacyRandomSource {
+
+    // 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;
+
+    public ThreadUnsafeRandom(long seed) {
+        super(seed);
+    }
+
+    @Override
+    public RandomSource fork() {
+        return new ThreadUnsafeRandom(this.nextLong());
+    }
+
+    @Override
+    public PositionalRandomFactory forkPositional() {
+        throw new UnsupportedOperationException();
+    }
+
+    @Override
+    public void setSeed(long seed) {
+        // note: called by Random constructor
+        this.seed = initialScramble(seed);
+    }
+
+    @Override
+    public 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/level/ServerLevel.java b/src/main/java/net/minecraft/server/level/ServerLevel.java
index d6429d721116aac2a4df8d0b217e9efcb698094e..fb9cf86250939fbc9cf1bfb90f6a1a7f4a489460 100644
--- a/src/main/java/net/minecraft/server/level/ServerLevel.java
+++ b/src/main/java/net/minecraft/server/level/ServerLevel.java
@@ -845,6 +845,10 @@ public class ServerLevel extends Level implements WorldGenLevel {
             entityplayer.stopSleepInBed(false, false);
         });
     }
+    // Paper start - optimise random block ticking
+    private final BlockPos.MutableBlockPos chunkTickMutablePosition = new BlockPos.MutableBlockPos();
+    private final io.papermc.paper.util.math.ThreadUnsafeRandom randomTickRandom = new io.papermc.paper.util.math.ThreadUnsafeRandom(this.random.nextLong());
+    // Paper end
 
     public void tickChunk(LevelChunk chunk, int randomTickSpeed) {
         ChunkPos chunkcoordintpair = chunk.getPos();
@@ -854,10 +858,10 @@ public class ServerLevel extends Level implements WorldGenLevel {
         ProfilerFiller gameprofilerfiller = this.getProfiler();
 
         gameprofilerfiller.push("thunder");
-        BlockPos blockposition;
+        final BlockPos.MutableBlockPos blockposition = this.chunkTickMutablePosition; // Paper - use mutable to reduce allocation rate, final to force compile fail on change
 
         if (!this.paperConfig().environment.disableThunder && flag && this.isThundering() && this.spigotConfig.thunderChance > 0 && this.random.nextInt(this.spigotConfig.thunderChance) == 0) { // Spigot // Paper - disable thunder
-            blockposition = this.findLightningTargetAround(this.getBlockRandomPos(j, 0, k, 15));
+            blockposition.set(this.findLightningTargetAround(this.getBlockRandomPos(j, 0, k, 15))); // Paper
             if (this.isRainingAt(blockposition)) {
                 DifficultyInstance difficultydamagescaler = this.getCurrentDifficultyAt(blockposition);
                 boolean flag1 = this.getGameRules().getBoolean(GameRules.RULE_DOMOBSPAWNING) && this.random.nextDouble() < (double) difficultydamagescaler.getEffectiveDifficulty() * this.paperConfig().entities.spawning.skeletonHorseThunderSpawnChance.or(0.01D) && !this.getBlockState(blockposition.below()).is(Blocks.LIGHTNING_ROD); // Paper
@@ -888,16 +892,25 @@ public class ServerLevel extends Level implements WorldGenLevel {
         int i1;
 
         if (!this.paperConfig().environment.disableIceAndSnow && this.random.nextInt(16) == 0) { // Paper - Disable ice and snow
-            blockposition = this.getHeightmapPos(Heightmap.Types.MOTION_BLOCKING, this.getBlockRandomPos(j, 0, k, 15));
-            BlockPos blockposition1 = blockposition.below();
+            // Paper start - optimise chunk ticking
+            this.getRandomBlockPosition(j, 0, k, 15, blockposition);
+            int normalY = chunk.getHeight(Heightmap.Types.MOTION_BLOCKING, blockposition.getX() & 15, blockposition.getZ() & 15) + 1;
+            int downY = normalY - 1;
+            blockposition.setY(normalY);
+            // Paper end
             Biome biomebase = (Biome) this.getBiome(blockposition).value();
 
-            if (biomebase.shouldFreeze(this, blockposition1)) {
-                org.bukkit.craftbukkit.event.CraftEventFactory.handleBlockFormEvent(this, blockposition1, Blocks.ICE.defaultBlockState(), null); // CraftBukkit
+            // Paper start - optimise chunk ticking
+            blockposition.setY(downY);
+            if (biomebase.shouldFreeze(this, blockposition)) {
+                org.bukkit.craftbukkit.event.CraftEventFactory.handleBlockFormEvent(this, blockposition, Blocks.ICE.defaultBlockState(), null); // CraftBukkit
+                // Paper end
             }
 
             if (flag) {
                 l = this.getGameRules().getInt(GameRules.RULE_SNOW_ACCUMULATION_HEIGHT);
+
+                blockposition.setY(normalY); // Paper
                 if (l > 0 && biomebase.shouldSnow(this, blockposition)) {
                     BlockState iblockdata = this.getBlockState(blockposition);
 
@@ -913,51 +926,54 @@ public class ServerLevel extends Level implements WorldGenLevel {
                         org.bukkit.craftbukkit.event.CraftEventFactory.handleBlockFormEvent(this, blockposition, Blocks.SNOW.defaultBlockState(), null); // CraftBukkit
                     }
                 }
+                blockposition.setY(downY); // Paper
 
-                Biome.Precipitation biomebase_precipitation = biomebase.getPrecipitationAt(blockposition1);
+                Biome.Precipitation biomebase_precipitation = biomebase.getPrecipitationAt(blockposition); // Paper
 
                 if (biomebase_precipitation != Biome.Precipitation.NONE) {
-                    BlockState iblockdata2 = this.getBlockState(blockposition1);
+                    BlockState iblockdata2 = this.getBlockState(blockposition); // Paper
 
-                    iblockdata2.getBlock().handlePrecipitation(iblockdata2, this, blockposition1, biomebase_precipitation);
+                    iblockdata2.getBlock().handlePrecipitation(iblockdata2, this, blockposition, biomebase_precipitation); // Paper
                 }
             }
         }
 
-        gameprofilerfiller.popPush("tickBlocks");
+        // Paper start - optimise random block ticking
+        gameprofilerfiller.popPush("randomTick");
         timings.chunkTicksBlocks.startTiming(); // Paper
         if (randomTickSpeed > 0) {
-            LevelChunkSection[] achunksection = chunk.getSections();
-
-            for (int j1 = 0; j1 < achunksection.length; ++j1) {
-                LevelChunkSection chunksection = achunksection[j1];
-
-                if (chunksection.isRandomlyTicking()) {
-                    l = chunk.getSectionYFromSectionIndex(j1);
-                    int k1 = SectionPos.sectionToBlockCoord(l);
-
-                    for (i1 = 0; i1 < randomTickSpeed; ++i1) {
-                        BlockPos blockposition2 = this.getBlockRandomPos(j, k1, k, 15);
-
-                        gameprofilerfiller.push("randomTick");
-                        BlockState iblockdata3 = chunksection.getBlockState(blockposition2.getX() - j, blockposition2.getY() - k1, blockposition2.getZ() - k);
+            LevelChunkSection[] sections = chunk.getSections();
+            int minSection = io.papermc.paper.util.WorldUtil.getMinSection(this);
+            for (int sectionIndex = 0; sectionIndex < sections.length; ++sectionIndex) {
+                LevelChunkSection section = sections[sectionIndex];
+                if (section == null || section.tickingList.size() == 0) {
+                    continue;
+                }
 
-                        if (iblockdata3.isRandomlyTicking()) {
-                            iblockdata3.randomTick(this, blockposition2, this.random);
-                        }
+                int yPos = (sectionIndex + minSection) << 4;
+                for (int a = 0; a < randomTickSpeed; ++a) {
+                    int tickingBlocks = section.tickingList.size();
+                    int index = this.randomTickRandom.nextInt(16 * 16 * 16);
+                    if (index >= tickingBlocks) {
+                        continue;
+                    }
 
-                        FluidState fluid = iblockdata3.getFluidState();
+                    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;
 
-                        if (fluid.isRandomlyTicking()) {
-                            fluid.randomTick(this, blockposition2, this.random);
-                        }
+                    BlockPos blockposition2 = blockposition.set(j + randomX, randomY, k + randomZ);
+                    BlockState iblockdata = com.destroystokyo.paper.util.maplist.IBlockDataList.getBlockDataFromRaw(raw);
 
-                        gameprofilerfiller.pop();
-                    }
+                    iblockdata.randomTick(this, blockposition2, this.randomTickRandom);
+                    // We drop the fluid tick since LAVA is ALREADY TICKED by the above method (See LiquidBlock).
+                    // TODO CHECK ON UPDATE (ping the Canadian)
                 }
             }
         }
-
+        // Paper end - optimise random block ticking
         timings.chunkTicksBlocks.stopTiming(); // Paper
         gameprofilerfiller.pop();
     }
diff --git a/src/main/java/net/minecraft/util/BitStorage.java b/src/main/java/net/minecraft/util/BitStorage.java
index 68648c5a5e3ff079f832092af0f2f801c42d1ede..8bafd5fd7499ba4a04bf706cfd1e156073716e21 100644
--- a/src/main/java/net/minecraft/util/BitStorage.java
+++ b/src/main/java/net/minecraft/util/BitStorage.java
@@ -20,4 +20,15 @@ public interface BitStorage {
     void unpack(int[] out);
 
     BitStorage copy();
+
+    // Paper start
+    void forEach(DataBitConsumer consumer);
+
+    @FunctionalInterface
+    interface DataBitConsumer {
+
+        void accept(int location, int data);
+
+    }
+    // Paper end
 }
diff --git a/src/main/java/net/minecraft/util/SimpleBitStorage.java b/src/main/java/net/minecraft/util/SimpleBitStorage.java
index 2b3fd62dca2d1475075b5dcde56cea85b749cb44..e4d0d7e8fc58b8f9f614d74a141e452166e0364c 100644
--- a/src/main/java/net/minecraft/util/SimpleBitStorage.java
+++ b/src/main/java/net/minecraft/util/SimpleBitStorage.java
@@ -124,6 +124,28 @@ public class SimpleBitStorage implements BitStorage {
         return this.bits;
     }
 
+    // Paper start
+    @Override
+    public final void forEach(DataBitConsumer consumer) {
+        int i = 0;
+        long[] along = this.data;
+        int j = along.length;
+
+        for (int k = 0; k < j; ++k) {
+            long l = along[k];
+
+            for (int i1 = 0; i1 < this.valuesPerLong; ++i1) {
+                consumer.accept(i, (int) (l & this.mask));
+                l >>= this.bits;
+                ++i;
+                if (i >= this.size) {
+                    return;
+                }
+            }
+        }
+    }
+    // Paper end
+
     @Override
     public void getAll(IntConsumer action) {
         int i = 0;
diff --git a/src/main/java/net/minecraft/util/ZeroBitStorage.java b/src/main/java/net/minecraft/util/ZeroBitStorage.java
index f0f764f36fb92c64ab2dc8a0a50c3f48321c3c9a..311625277a26c9c187025a1036978229241b965f 100644
--- a/src/main/java/net/minecraft/util/ZeroBitStorage.java
+++ b/src/main/java/net/minecraft/util/ZeroBitStorage.java
@@ -46,6 +46,15 @@ public class ZeroBitStorage implements BitStorage {
         return 0;
     }
 
+    // Paper start
+    @Override
+    public void forEach(DataBitConsumer consumer) {
+        for(int i = 0; i < this.size; ++i) {
+            consumer.accept(i, 0);
+        }
+    }
+    // Paper end
+
     @Override
     public void getAll(IntConsumer action) {
         for(int i = 0; i < this.size; ++i) {
diff --git a/src/main/java/net/minecraft/world/entity/animal/Turtle.java b/src/main/java/net/minecraft/world/entity/animal/Turtle.java
index fd6ce6e8a3a7c889276e06fb427e0d17ed093149..76ab82553488e129882fc9beb603636bb723ec42 100644
--- a/src/main/java/net/minecraft/world/entity/animal/Turtle.java
+++ b/src/main/java/net/minecraft/world/entity/animal/Turtle.java
@@ -84,7 +84,7 @@ public class Turtle extends Animal {
     }
 
     public void setHomePos(BlockPos pos) {
-        this.entityData.set(Turtle.HOME_POS, pos);
+        this.entityData.set(Turtle.HOME_POS, pos.immutable()); // Paper - called with mutablepos...
     }
 
     public BlockPos getHomePos() {
diff --git a/src/main/java/net/minecraft/world/level/Level.java b/src/main/java/net/minecraft/world/level/Level.java
index a21b2a100503b1fcceb700da11bef5866f3d178b..270ce3995229aa79074e981bb45e5480a5e924d4 100644
--- a/src/main/java/net/minecraft/world/level/Level.java
+++ b/src/main/java/net/minecraft/world/level/Level.java
@@ -1380,10 +1380,18 @@ public abstract class Level implements LevelAccessor, AutoCloseable {
     public abstract RecipeManager getRecipeManager();
 
     public BlockPos getBlockRandomPos(int x, int y, int z, int l) {
+        // Paper start - allow use of mutable pos
+        BlockPos.MutableBlockPos ret = new BlockPos.MutableBlockPos();
+        this.getRandomBlockPosition(x, y, z, l, ret);
+        return ret.immutable();
+    }
+    public final BlockPos.MutableBlockPos getRandomBlockPosition(int x, int y, int z, int l, BlockPos.MutableBlockPos out) {
+        // Paper end
         this.randValue = this.randValue * 3 + 1013904223;
         int i1 = this.randValue >> 2;
 
-        return new BlockPos(x + (i1 & 15), y + (i1 >> 16 & l), z + (i1 >> 8 & 15));
+        out.set(x + (i1 & 15), y + (i1 >> 16 & l), z + (i1 >> 8 & 15)); // Paper - change to setValues call
+        return out; // Paper
     }
 
     public boolean noSave() {
diff --git a/src/main/java/net/minecraft/world/level/chunk/LevelChunkSection.java b/src/main/java/net/minecraft/world/level/chunk/LevelChunkSection.java
index b8fee4f8a0cfe32b9ef7f3f3cf818cbaec0d3fca..12edaf88cca54540c617239ac31b2263dfa0ecd7 100644
--- a/src/main/java/net/minecraft/world/level/chunk/LevelChunkSection.java
+++ b/src/main/java/net/minecraft/world/level/chunk/LevelChunkSection.java
@@ -25,6 +25,7 @@ public class LevelChunkSection {
     public final PalettedContainer<BlockState> states;
     // CraftBukkit start - read/write
     private PalettedContainer<Holder<Biome>> biomes;
+    public final com.destroystokyo.paper.util.maplist.IBlockDataList tickingList = new com.destroystokyo.paper.util.maplist.IBlockDataList(); // Paper
 
     public LevelChunkSection(PalettedContainer<BlockState> datapaletteblock, PalettedContainer<Holder<Biome>> palettedcontainerro) {
         // CraftBukkit end
@@ -77,6 +78,9 @@ public class LevelChunkSection {
             --this.nonEmptyBlockCount;
             if (iblockdata1.isRandomlyTicking()) {
                 --this.tickingBlockCount;
+                // Paper start
+                this.tickingList.remove(x, y, z);
+                // Paper end
             }
         }
 
@@ -88,6 +92,9 @@ public class LevelChunkSection {
             ++this.nonEmptyBlockCount;
             if (state.isRandomlyTicking()) {
                 ++this.tickingBlockCount;
+                // Paper start
+                this.tickingList.add(x, y, z, state);
+                // Paper end
             }
         }
 
@@ -115,40 +122,31 @@ public class LevelChunkSection {
     }
 
     public void recalcBlockCounts() {
-        class a implements PalettedContainer.CountConsumer<BlockState> {
-
-            public int nonEmptyBlockCount;
-            public int tickingBlockCount;
-            public int tickingFluidCount;
-
-            a() {}
-
-            public void accept(BlockState iblockdata, int i) {
-                FluidState fluid = iblockdata.getFluidState();
-
-                if (!iblockdata.isAir()) {
-                    this.nonEmptyBlockCount += i;
-                    if (iblockdata.isRandomlyTicking()) {
-                        this.tickingBlockCount += i;
-                    }
+        // Paper start - unfuck this
+        this.tickingList.clear();
+        this.nonEmptyBlockCount = 0;
+        this.tickingBlockCount = 0;
+        this.tickingFluidCount = 0;
+        this.states.forEachLocation((BlockState iblockdata, int i) -> {
+            FluidState fluid = iblockdata.getFluidState();
+
+            if (!iblockdata.isAir()) {
+                this.nonEmptyBlockCount = (short) (this.nonEmptyBlockCount + 1);
+                if (iblockdata.isRandomlyTicking()) {
+                    this.tickingBlockCount = (short)(this.tickingBlockCount + 1);
+                    this.tickingList.add(i, iblockdata);
                 }
+            }
 
-                if (!fluid.isEmpty()) {
-                    this.nonEmptyBlockCount += i;
-                    if (fluid.isRandomlyTicking()) {
-                        this.tickingFluidCount += i;
-                    }
+            if (!fluid.isEmpty()) {
+                this.nonEmptyBlockCount = (short) (this.nonEmptyBlockCount + 1);
+                if (fluid.isRandomlyTicking()) {
+                    this.tickingFluidCount = (short) (this.tickingFluidCount + 1);
                 }
-
             }
-        }
 
-        a a0 = new a();
-
-        this.states.count(a0);
-        this.nonEmptyBlockCount = (short) a0.nonEmptyBlockCount;
-        this.tickingBlockCount = (short) a0.tickingBlockCount;
-        this.tickingFluidCount = (short) a0.tickingFluidCount;
+        });
+        // Paper end
     }
 
     public PalettedContainer<BlockState> getStates() {
diff --git a/src/main/java/net/minecraft/world/level/chunk/PalettedContainer.java b/src/main/java/net/minecraft/world/level/chunk/PalettedContainer.java
index de91ed0d5f7f472cb2f24a8f6e4ebbdeaa4faf52..7f5547dc31aa53b2863f4c09f598fa88e7fe2afd 100644
--- a/src/main/java/net/minecraft/world/level/chunk/PalettedContainer.java
+++ b/src/main/java/net/minecraft/world/level/chunk/PalettedContainer.java
@@ -385,6 +385,14 @@ public class PalettedContainer<T> implements PaletteResize<T>, PalettedContainer
         }
     }
 
+    // Paper start
+    public void forEachLocation(PalettedContainer.CountConsumer<T> consumer) {
+        this.data.storage.forEach((int location, int data) -> {
+            consumer.accept(this.data.palette.valueFor(data), location);
+        });
+    }
+    // Paper end
+
     @FunctionalInterface
     public interface CountConsumer<T> {
         void accept(T object, int count);