Paper/patches/server/0791-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..e8b4053babe46999980b92643125405064af1c04
--- /dev/null
+++ b/src/main/java/io/papermc/paper/util/math/ThreadUnsafeRandom.java
@@ -0,0 +1,46 @@
+package io.papermc.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/level/ServerLevel.java b/src/main/java/net/minecraft/server/level/ServerLevel.java
index b5a2445bbd691cbfed0d0bf7c688b1f10c267039..3b26b6a24516bb2e2331edb7dc41a28b57835aa1 100644
--- a/src/main/java/net/minecraft/server/level/ServerLevel.java
+++ b/src/main/java/net/minecraft/server/level/ServerLevel.java
@@ -743,6 +743,10 @@ 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();
+    // Paper end
 
     public void tickChunk(LevelChunk chunk, int randomTickSpeed) {
         ChunkPos chunkcoordintpair = chunk.getPos();
@@ -752,10 +756,10 @@ 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.disableThunder && flag && this.isThundering() && this.random.nextInt(100000) == 0) { // 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() * paperConfig.skeleHorseSpawnChance && !this.getBlockState(blockposition.below()).is(Blocks.LIGHTNING_ROD); // Paper
@@ -778,65 +782,78 @@ public class ServerLevel extends Level implements WorldGenLevel {
         }
 
         gameprofilerfiller.popPush("iceandsnow");
-        if (!this.paperConfig.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();
+         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.getHeight(Heightmap.Types.MOTION_BLOCKING, blockposition.getX() & 15, blockposition.getZ() & 15) + 1;
+            int downY = normalY - 1;
+            blockposition.setY(normalY);
+            // Paper end
             Biome biomebase = this.getBiome(blockposition);
 
-            if (biomebase.shouldFreeze((LevelReader) 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) {
+                blockposition.setY(normalY); // Paper
                 if (biomebase.shouldSnow(this, blockposition)) {
                     org.bukkit.craftbukkit.event.CraftEventFactory.handleBlockFormEvent(this, blockposition, Blocks.SNOW.defaultBlockState(), null); // CraftBukkit
                 }
 
-                BlockState iblockdata = this.getBlockState(blockposition1);
+                blockposition.setY(downY); // Paper
+                BlockState iblockdata = this.getBlockState(blockposition); // Paper
+                blockposition.setY(normalY); // Paper
                 Biome.Precipitation biomebase_precipitation = this.getBiome(blockposition).getPrecipitation();
 
-                if (biomebase_precipitation == Biome.Precipitation.RAIN && biomebase.isColdEnoughToSnow(blockposition1)) {
+                blockposition.setY(downY); // Paper
+                if (biomebase_precipitation == Biome.Precipitation.RAIN && biomebase.isColdEnoughToSnow(blockposition)) { // Paper
                     biomebase_precipitation = Biome.Precipitation.SNOW;
                 }
 
-                iblockdata.getBlock().handlePrecipitation(iblockdata, (Level) this, blockposition1, biomebase_precipitation);
+                iblockdata.getBlock().handlePrecipitation(iblockdata, (Level) 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();
-            int l = achunksection.length;
-
-            for (int i1 = 0; i1 < l; ++i1) {
-                LevelChunkSection chunksection = achunksection[i1];
-
-                if (chunksection != LevelChunk.EMPTY_SECTION && chunksection.isRandomlyTicking()) {
-                    int j1 = chunksection.bottomBlockY();
-
-                    for (int k1 = 0; k1 < randomTickSpeed; ++k1) {
-                        BlockPos blockposition2 = this.getBlockRandomPos(j, j1, k, 15);
-
-                        gameprofilerfiller.push("randomTick");
-                        BlockState iblockdata1 = chunksection.getBlockState(blockposition2.getX() - j, blockposition2.getY() - j1, 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 (iblockdata1.isRandomlyTicking()) {
-                            iblockdata1.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 = iblockdata1.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
                 }
             }
         }
-
+        // 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 07e1374ac3430662edd9f585e59b785e329f0820..9f9c0b56f0891e9c423d79f8ae4c3643a2b91048 100644
--- a/src/main/java/net/minecraft/util/BitStorage.java
+++ b/src/main/java/net/minecraft/util/BitStorage.java
@@ -104,4 +104,32 @@ public class BitStorage {
         }
 
     }
+
+    // Paper start
+    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;
+                }
+            }
+        }
+    }
+
+    @FunctionalInterface
+    public static interface DataBitConsumer {
+
+        void accept(int location, int data);
+
+    }
+    // Paper end
 }
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 925f16d5eb092518ef774f69a8d99689feb0f5d7..01d8af06f19427354cac95d691e65d31253fef94 100644
--- a/src/main/java/net/minecraft/world/entity/animal/Turtle.java
+++ b/src/main/java/net/minecraft/world/entity/animal/Turtle.java
@@ -91,7 +91,7 @@ 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() { // Paper - public
diff --git a/src/main/java/net/minecraft/world/level/Level.java b/src/main/java/net/minecraft/world/level/Level.java
index 921aba3463b9f86a9e3c7d59aaa48b9760693eab..5efafcadda2bfc5cab8ce5d3ede83a0467fe696f 100644
--- a/src/main/java/net/minecraft/world/level/Level.java
+++ b/src/main/java/net/minecraft/world/level/Level.java
@@ -1363,10 +1363,18 @@ public abstract class Level implements LevelAccessor, AutoCloseable {
     public abstract TagContainer getTagManager();
 
     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 c1c95ac9deb134a0cf5c7763090ac5f3cddf24cc..72e3264dc74822f746fb84fec0be400047d2d9f5 100644
--- a/src/main/java/net/minecraft/world/level/chunk/LevelChunkSection.java
+++ b/src/main/java/net/minecraft/world/level/chunk/LevelChunkSection.java
@@ -19,6 +19,7 @@ public class LevelChunkSection {
     private short tickingBlockCount;
     private short tickingFluidCount;
     public final PalettedContainer<BlockState> states; // Paper - package-private // Paper - public
+    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 LevelChunkSection(int yOffset) { this(yOffset, null, null, true); } // Notice for updates: Please make sure this constructor isn't used anywhere
@@ -79,6 +80,9 @@ public class LevelChunkSection {
             --this.nonEmptyBlockCount;
             if (blockState.isRandomlyTicking()) {
                 --this.tickingBlockCount;
+                // Paper start
+                this.tickingList.remove(x, y, z);
+                // Paper end
             }
         }
 
@@ -90,6 +94,9 @@ public class LevelChunkSection {
             ++this.nonEmptyBlockCount;
             if (state.isRandomlyTicking()) {
                 ++this.tickingBlockCount;
+                // Paper start
+                this.tickingList.add(x, y, z, state);
+                // Paper end
             }
         }
 
@@ -125,22 +132,28 @@ public class LevelChunkSection {
     }
 
     public void recalcBlockCounts() {
+        // Paper start
+        this.tickingList.clear();
+        // Paper end
         this.nonEmptyBlockCount = 0;
         this.tickingBlockCount = 0;
         this.tickingFluidCount = 0;
-        this.states.count((state, count) -> {
+        this.states.forEachLocation((state, location) -> { // Paper
             FluidState fluidState = state.getFluidState();
             if (!state.isAir()) {
-                this.nonEmptyBlockCount = (short)(this.nonEmptyBlockCount + count);
+                this.nonEmptyBlockCount = (short)(this.nonEmptyBlockCount + 1); // Paper
                 if (state.isRandomlyTicking()) {
-                    this.tickingBlockCount = (short)(this.tickingBlockCount + count);
+                    // Paper start
+                    this.tickingBlockCount = (short)(this.tickingBlockCount + 1);
+                    this.tickingList.add(location, state);
+                    // Paper end
                 }
             }
 
             if (!fluidState.isEmpty()) {
-                this.nonEmptyBlockCount = (short)(this.nonEmptyBlockCount + count);
+                this.nonEmptyBlockCount = (short)(this.nonEmptyBlockCount + 1); // Paper
                 if (fluidState.isRandomlyTicking()) {
-                    this.tickingFluidCount = (short)(this.tickingFluidCount + count);
+                    this.tickingFluidCount = (short)(this.tickingFluidCount + 1); // Paper
                 }
             }
 
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 79fd7a6e8a6eb1f699d03801910d97066677311c..c9e942669458668a184aaec3bc0a5509dd6ab5f0 100644
--- a/src/main/java/net/minecraft/world/level/chunk/PalettedContainer.java
+++ b/src/main/java/net/minecraft/world/level/chunk/PalettedContainer.java
@@ -320,4 +320,12 @@ public class PalettedContainer<T> implements PaletteResize<T> {
     public interface CountConsumer<T> {
         void accept(T object, int count);
     }
+
+    // Paper start
+   public void forEachLocation(PalettedContainer.CountConsumer<T> datapaletteblock_a) {
+       this.storage.forEach((int location, int data) -> {
+           datapaletteblock_a.accept(this.palette.valueFor(data), location);
+       });
+   }
+    // Paper end
 }