From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: Spottedleaf <Spottedleaf@users.noreply.github.com>
Date: Fri, 19 Feb 2021 22:51:52 -0800
Subject: [PATCH] Oprimise map impl for tracked players

Reference2BooleanOpenHashMap is going to have
better lookups than HashMap.

diff --git a/src/main/java/net/minecraft/server/level/ChunkMap.java b/src/main/java/net/minecraft/server/level/ChunkMap.java
index 68a1cc5f4f7f5997dfb7d40647e3e027c23ffb14..77f064fb4437c1d98cf91dde98d4d88b28afa7c8 100644
--- a/src/main/java/net/minecraft/server/level/ChunkMap.java
+++ b/src/main/java/net/minecraft/server/level/ChunkMap.java
@@ -1529,7 +1529,7 @@ public class ChunkMap extends ChunkStorage implements ChunkHolder.PlayerProvider
         final Entity entity;
         private final int range;
         SectionPos lastSectionPos;
-        public final Set<ServerPlayerConnection> seenBy = Sets.newIdentityHashSet();
+        public final Set<ServerPlayerConnection> seenBy = new it.unimi.dsi.fastutil.objects.ReferenceOpenHashSet<>(); // Paper - Perf: optimise map impl
 
         public TrackedEntity(final Entity entity, final int i, final int j, final boolean flag) {
             this.serverEntity = new ServerEntity(ChunkMap.this.level, entity, j, flag, this::broadcast, this.seenBy); // CraftBukkit