PaperMC/Remapped-Spigot-Server-Patches/0069-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 93d3408231a177cf6d2086594756adffe3efa702..61048140cf0adca03bfb57193ada0adaee73b1bb 100644
--- a/src/main/java/net/minecraft/world/entity/Entity.java
+++ b/src/main/java/net/minecraft/world/entity/Entity.java
@@ -142,6 +142,21 @@ public abstract class Entity implements Nameable, CommandSource, net.minecraft.s
         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() {
@@ -271,7 +286,7 @@ public abstract class Entity implements Nameable, CommandSource, net.minecraft.s
         this.stuckSpeedMultiplier = Vec3.ZERO;
         this.nextStep = 1.0F;
         this.nextFlap = 1.0F;
-        this.random = new Random();
+        this.random = SHARED_RANDOM; // Paper
         this.remainingFireTicks = -this.getFireImmuneTicks();
         this.fluidHeight = new Object2DoubleArrayMap(2);
         this.firstTick = true;