0014-Optimize-random-calls-in-chunk-ticking.patch

From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: Paul Sauve <paul@technove.co>
Date: Thu, 7 Jan 2021 11:49:36 -0600
Subject: [PATCH] Optimize random calls in chunk ticking

Especially at over 30,000 chunks these random calls are fairly heavy. We
use a different method here for checking lightning, and for checking
ice.

Lightning: Each chunk now keeps an int of how many ticks until the
lightning should strike. This int is a random number from 0 to 100000 * 2,
the multiplication is required to keep the probability the same.

Ice and snow: We just generate a single random number 0-16 and increment
it, while checking if it's 0 for the current chunk.

Depending on configuration for things that tick in a chunk, this is a
5-10% improvement.

Airplane
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
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diff --git a/src/main/java/net/minecraft/server/level/ServerChunkCache.java b/src/main/java/net/minecraft/server/level/ServerChunkCache.java
index cdf68a2eafb2794250ac94b6203ae6ed0c585e5b..f51fcaba69c9ddc27130ab615526e05b1b4f0e07 100644
--- a/src/main/java/net/minecraft/server/level/ServerChunkCache.java
+++ b/src/main/java/net/minecraft/server/level/ServerChunkCache.java
@@ -978,6 +978,7 @@ public class ServerChunkCache extends ChunkSource {
             ProfilerFiller gameprofilerfiller = this.level.getProfiler();
 
             gameprofilerfiller.push("pollingChunks");
+            this.level.resetIceAndSnowTick(); // Pufferfish - reset ice & snow tick random
             int k = this.level.getGameRules().getInt(GameRules.RULE_RANDOMTICKING);
             boolean flag1 = level.ticksPerAnimalSpawns != 0L && worlddata.getGameTime() % level.ticksPerAnimalSpawns == 0L; // CraftBukkit
 
diff --git a/src/main/java/net/minecraft/server/level/ServerLevel.java b/src/main/java/net/minecraft/server/level/ServerLevel.java
index a2abb8aa1a257ccd2b5dbddc037fffc6eb600758..9445f4652b955cb3a84c8695a1e1d1e11d4ed69c 100644
--- a/src/main/java/net/minecraft/server/level/ServerLevel.java
+++ b/src/main/java/net/minecraft/server/level/ServerLevel.java
@@ -732,6 +732,8 @@ public class ServerLevel extends Level implements WorldGenLevel {
     private final io.papermc.paper.util.math.ThreadUnsafeRandom randomTickRandom = new io.papermc.paper.util.math.ThreadUnsafeRandom();
     // Paper end
 
+    private int currentIceAndSnowTick = 0; protected void resetIceAndSnowTick() { this.currentIceAndSnowTick = this.randomTickRandom.nextInt(16); } // Pufferfish
+
     public void tickChunk(LevelChunk chunk, int randomTickSpeed) {
         ChunkPos chunkcoordintpair = chunk.getPos();
         boolean flag = this.isRaining();
@@ -742,7 +744,7 @@ public class ServerLevel extends Level implements WorldGenLevel {
         gameprofilerfiller.push("thunder");
         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.spigotConfig.thunderChance > 0 && this.random.nextInt(this.spigotConfig.thunderChance) == 0) { // Spigot // Paper - disable thunder
+        if (!this.paperConfig.disableThunder && flag && this.isThundering() && this.spigotConfig.thunderChance > 0 && this.random.nextInt(this.spigotConfig.thunderChance) == 0 && chunk.shouldDoLightning(this.random)) { // Spigot // Paper - disable thunder // Pufferfish - replace random with shouldDoLightning
             blockposition.set(this.findLightningTargetAround(this.getBlockRandomPos(j, 0, k, 15))); // Paper
             if (this.isRainingAt(blockposition)) {
                 DifficultyInstance difficultydamagescaler = this.getCurrentDifficultyAt(blockposition);
@@ -766,7 +768,7 @@ public class ServerLevel extends Level implements WorldGenLevel {
         }
 
         gameprofilerfiller.popPush("iceandsnow");
-         if (!this.paperConfig.disableIceAndSnow && this.randomTickRandom.nextInt(16) == 0) { // Paper - Disable ice and snow // Paper - optimise random ticking
+         if (!this.paperConfig.disableIceAndSnow && (this.currentIceAndSnowTick++ & 15) == 0) { // Paper - Disable ice and snow // Paper - optimise random ticking  // Pufferfish - optimize further 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;
diff --git a/src/main/java/net/minecraft/world/level/chunk/LevelChunk.java b/src/main/java/net/minecraft/world/level/chunk/LevelChunk.java
index 7567a8bf848c82b27383f084056cb43c41df6d0c..2b697f0d0b59b5af5aa59850d5e501cde9acf577 100644
--- a/src/main/java/net/minecraft/world/level/chunk/LevelChunk.java
+++ b/src/main/java/net/minecraft/world/level/chunk/LevelChunk.java
@@ -94,6 +94,18 @@ public class LevelChunk extends ChunkAccess {
     }
     // Paper end
 
+    // Pufferfish start - instead of using a random every time the chunk is ticked, define when lightning strikes preemptively
+    private int lightningTick;
+    // shouldDoLightning compiles down to 29 bytes, which with the default of 35 byte inlining should guarantee an inline
+    public final boolean shouldDoLightning(java.util.Random random) {
+        if (this.lightningTick-- <= 0) {
+            this.lightningTick = random.nextInt(100000) << 1;
+            return true;
+        }
+        return false;
+    }
+    // Pufferfish end
+
     public LevelChunk(Level world, ChunkPos pos) {
         this(world, pos, UpgradeData.EMPTY, new LevelChunkTicks<>(), new LevelChunkTicks<>(), 0L, (LevelChunkSection[]) null, (LevelChunk.PostLoadProcessor) null, (BlendingData) null);
     }
@@ -124,6 +136,7 @@ public class LevelChunk extends ChunkAccess {
         this.fluidTicks = fluidTickScheduler;
         // CraftBukkit start
         this.bukkitChunk = new org.bukkit.craftbukkit.CraftChunk(this);
+        this.lightningTick = this.level.random.nextInt(100000) << 1; // Pufferfish - initialize lightning tick
     }
 
     public org.bukkit.Chunk bukkitChunk;