papermc/patches/server/0067-Use-a-Shared-Random-for-Entities.patch

From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: Aikar <aikar@aikar.co>
Date: Tue, 22 Mar 2016 00:33:47 -0400
Subject: [PATCH] Use a Shared Random for Entities

Reduces memory usage and provides ensures more randomness, Especially since a lot of garbage entity objects get created.

diff --git a/src/main/java/net/minecraft/world/entity/Entity.java b/src/main/java/net/minecraft/world/entity/Entity.java
index 0d8590368ed35bd95f3b8abcd34eb172ef8ae43b..9aa25ee1e4e3ad205e9e373bbf95d24bd305e078 100644
--- a/src/main/java/net/minecraft/world/entity/Entity.java
+++ b/src/main/java/net/minecraft/world/entity/Entity.java
@@ -153,6 +153,21 @@ public abstract class Entity implements Nameable, EntityAccess, CommandSource, n
         return tag.contains("Bukkit.updateLevel") && tag.getInt("Bukkit.updateLevel") >= level;
     }
 
+    // Paper start
+    public static Random SHARED_RANDOM = new Random() {
+        private boolean locked = false;
+        @Override
+        public synchronized void setSeed(long seed) {
+            if (locked) {
+                LogManager.getLogger().error("Ignoring setSeed on Entity.SHARED_RANDOM", new Throwable());
+            } else {
+                super.setSeed(seed);
+                locked = true;
+            }
+        }
+    };
+    // Paper end
+
     private CraftEntity bukkitEntity;
 
     public CraftEntity getBukkitEntity() {
@@ -324,7 +339,7 @@ public abstract class Entity implements Nameable, EntityAccess, CommandSource, n
         this.bb = Entity.INITIAL_AABB;
         this.stuckSpeedMultiplier = Vec3.ZERO;
         this.nextStep = 1.0F;
-        this.random = new Random();
+        this.random = SHARED_RANDOM; // Paper
         this.remainingFireTicks = -this.getFireImmuneTicks();
         this.fluidHeight = new Object2DoubleArrayMap(2);
         this.firstTick = true;
diff --git a/src/main/java/net/minecraft/world/entity/animal/Squid.java b/src/main/java/net/minecraft/world/entity/animal/Squid.java
index a24c05706ac8f088f1342ca947c5f1ff0fe80366..3093fc37c47bec1a6e884553809277fff1053d8e 100644
--- a/src/main/java/net/minecraft/world/entity/animal/Squid.java
+++ b/src/main/java/net/minecraft/world/entity/animal/Squid.java
@@ -50,7 +50,7 @@ public class Squid extends WaterAnimal {
 
     public Squid(EntityType<? extends Squid> type, Level world) {
         super(type, world);
-        this.random.setSeed((long) this.getId());
+        //this.random.setSeed((long) this.getId()); // Paper - we set the random to shared, do not clobber the seed
         this.tentacleSpeed = 1.0F / (this.random.nextFloat() + 1.0F) * 0.2F;
     }