From d7fcb32baec0d55a136e857ddde9a07201a7cb7f Mon Sep 17 00:00:00 2001
From: DGun Otto <102713261+HaHaWTH@users.noreply.github.com>
Date: Fri, 14 Jun 2024 23:53:47 +0800
Subject: [PATCH] Reduce worldgen allocations by reusing supplier objects (#68)

* Reduce worldgen allocations by reusing supplier objects

This change optimizes the way SurfaceRules update their biome supplier,avoiding unnecessary object creations and thus reducing memory allocations
during world generation. The update method now reuses the existingPositionalBiomeGetter object if it's already present, otherwise it
initializes a new one.

Additionally, the tryApply method in SurfaceRules now avoids iterator
allocation by directly accessing the rules list, which further contributes
to reducing garbage collection pressure during world generation.
---
 .../0084-Reduce-worldgen-allocations.patch    | 90 +++++++++++++++++++
 1 file changed, 90 insertions(+)
 create mode 100644 patches/server/0084-Reduce-worldgen-allocations.patch

diff --git a/patches/server/0084-Reduce-worldgen-allocations.patch b/patches/server/0084-Reduce-worldgen-allocations.patch
new file mode 100644
index 00000000..2421b944
--- /dev/null
+++ b/patches/server/0084-Reduce-worldgen-allocations.patch
@@ -0,0 +1,90 @@
+From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
+From: HaHaWTH <102713261+HaHaWTH@users.noreply.github.com>
+Date: Fri, 14 Jun 2024 23:19:55 +0800
+Subject: [PATCH] Reduce-worldgen-allocations
+
+This change optimizes the way SurfaceRules update their biome supplier,avoiding unnecessary object creations and thus reducing memory allocations
+during world generation. The update method now reuses the existing PositionalBiomeGetter object if it's already present, otherwise it
+initializes a new one.
+Additionally, the tryApply method in SurfaceRules now avoids iterator
+allocation by directly accessing the rules list, which further contributes
+to reducing garbage collection pressure during world generation.
+
+diff --git a/src/main/java/net/minecraft/world/level/levelgen/SurfaceRules.java b/src/main/java/net/minecraft/world/level/levelgen/SurfaceRules.java
+index a506f3ef40ec34a89abb73a60cedf3b556585bee..c79aceb58549235a6064fa6951509d0ee77ddf1a 100644
+--- a/src/main/java/net/minecraft/world/level/levelgen/SurfaceRules.java
++++ b/src/main/java/net/minecraft/world/level/levelgen/SurfaceRules.java
+@@ -314,8 +314,14 @@ public class SurfaceRules {
+         }
+ 
+         protected void updateY(int stoneDepthAbove, int stoneDepthBelow, int fluidHeight, int blockX, int blockY, int blockZ) {
+-            this.lastUpdateY++;
+-            this.biome = Suppliers.memoize(() -> this.biomeGetter.apply(this.pos.set(blockX, blockY, blockZ)));
++            // Leaf start - Reuse supplier object instead of creating new ones every time
++            ++this.lastUpdateY;
++            var getter = this.biome;
++            if (getter == null) {
++                this.biome = getter = new org.dreeam.leaf.util.biome.PositionalBiomeGetter(this.biomeGetter, this.pos);
++            }
++            ((org.dreeam.leaf.util.biome.PositionalBiomeGetter)getter).update(blockX, blockY, blockZ);
++            // Leaf end
+             this.blockY = blockY;
+             this.waterHeight = fluidHeight;
+             this.stoneDepthBelow = stoneDepthBelow;
+@@ -577,8 +583,12 @@ public class SurfaceRules {
+         @Nullable
+         @Override
+         public BlockState tryApply(int x, int y, int z) {
+-            for (SurfaceRules.SurfaceRule surfaceRule : this.rules) {
+-                BlockState blockState = surfaceRule.tryApply(x, y, z);
++            // Leaf start - Avoid iterator allocation
++            int size = this.rules.size();
++            //noinspection ForLoopReplaceableByForEach
++            for (int i = 0; i < size; i++) {
++                BlockState blockState = this.rules.get(i).tryApply(x, y, z);
++                // Leaf end
+                 if (blockState != null) {
+                     return blockState;
+                 }
+diff --git a/src/main/java/org/dreeam/leaf/util/biome/PositionalBiomeGetter.java b/src/main/java/org/dreeam/leaf/util/biome/PositionalBiomeGetter.java
+new file mode 100644
+index 0000000000000000000000000000000000000000..2385f09404274aa650d082e2928deab847b570a0
+--- /dev/null
++++ b/src/main/java/org/dreeam/leaf/util/biome/PositionalBiomeGetter.java
+@@ -0,0 +1,36 @@
++package org.dreeam.leaf.util.biome;
++
++import net.minecraft.core.BlockPos;
++import net.minecraft.core.Holder;
++import net.minecraft.world.level.biome.Biome;
++
++import java.util.function.Function;
++import java.util.function.Supplier;
++
++public class PositionalBiomeGetter implements Supplier<Holder<Biome>> {
++    private final Function<BlockPos, Holder<Biome>> biomeGetter;
++    private final BlockPos.MutableBlockPos pos;
++    private int nextX, nextY, nextZ;
++    private volatile Holder<Biome> curBiome;
++
++    public PositionalBiomeGetter(Function<BlockPos, Holder<Biome>> biomeGetter, BlockPos.MutableBlockPos pos) {
++        this.biomeGetter = biomeGetter;
++        this.pos = pos;
++    }
++
++    public void update(int nextX, int nextY, int nextZ) {
++        this.nextX = nextX;
++        this.nextY = nextY;
++        this.nextZ = nextZ;
++        this.curBiome = null;
++    }
++
++    @Override
++    public Holder<Biome> get() {
++        var biome = curBiome;
++        if(biome == null) {
++            curBiome = biome = biomeGetter.apply(pos.set(nextX, nextY, nextZ));
++        }
++        return biome;
++    }
++}