From 3ca522e3f2ce88a0be43c1d933a921e310346642 Mon Sep 17 00:00:00 2001
From: Aikar <aikar@aikar.co>
Date: Thu, 27 Aug 2015 01:15:02 -0400
Subject: [PATCH] Optimize Chunk Access

getting a loaded chunk is one of the most hottest pieces of code in the game.
getChunkAt is called for the same chunk multiple times in a row, often from getType();

Optimize this look up by using a Last Access cache.

diff --git a/src/main/java/net/minecraft/server/Chunk.java b/src/main/java/net/minecraft/server/Chunk.java
index bc6e190..770d7ed 100644
--- a/src/main/java/net/minecraft/server/Chunk.java
+++ b/src/main/java/net/minecraft/server/Chunk.java
@@ -30,6 +30,7 @@ public class Chunk {
     private boolean j;
     public final World world;
     public final int[] heightMap;
+    public final long chunkKey; // Paper
     public final int locX;
     public final int locZ;
     private boolean m;
@@ -96,6 +97,7 @@ public class Chunk {
         this.world = world;
         this.locX = i;
         this.locZ = j;
+        this.chunkKey = org.bukkit.craftbukkit.util.LongHash.toLong(this.locX, this.locZ); // Paper
         this.heightMap = new int[256];
 
         for (int k = 0; k < this.entitySlices.length; ++k) {
diff --git a/src/main/java/net/minecraft/server/ChunkProviderServer.java b/src/main/java/net/minecraft/server/ChunkProviderServer.java
index 990e3f0..1fd844b 100644
--- a/src/main/java/net/minecraft/server/ChunkProviderServer.java
+++ b/src/main/java/net/minecraft/server/ChunkProviderServer.java
@@ -27,7 +27,27 @@ public class ChunkProviderServer implements IChunkProvider {
     public final Set<Long> unloadQueue = Sets.newHashSet();
     public final ChunkGenerator chunkGenerator;
     private final IChunkLoader chunkLoader;
-    public final Long2ObjectMap<Chunk> chunks = new Long2ObjectOpenHashMap(8192);
+    // Paper start
+    protected Chunk lastChunkByPos = null;
+    public Long2ObjectOpenHashMap<Chunk> chunks = new Long2ObjectOpenHashMap<Chunk>(8192) {
+
+        @Override
+        public Chunk get(long key) {
+            if (lastChunkByPos != null && key == lastChunkByPos.chunkKey) {
+                return lastChunkByPos;
+            }
+            return lastChunkByPos = super.get(key);
+        }
+
+        @Override
+        public Chunk remove(long key) {
+            if (lastChunkByPos != null && key == lastChunkByPos.chunkKey) {
+                lastChunkByPos = null;
+            }
+            return super.remove(key);
+        }
+    }; // CraftBukkit
+    // Paper end
     public final WorldServer world;
 
     public ChunkProviderServer(WorldServer worldserver, IChunkLoader ichunkloader, ChunkGenerator chunkgenerator) {
-- 
2.8.3