From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: Spottedleaf <Spottedleaf@users.noreply.github.com>
Date: Wed, 14 Aug 2024 17:52:47 -0700
Subject: [PATCH] Moonrise: Optimise BiomeManager#getFiddle

Original license: GPLv3
Original project: https://github.com/Tuinity/Moonrise

https://github.com/Tuinity/Moonrise/commit/a83025a52f3284b597aabecb945cf37d3e377317

The floorMod and subtraction by 0.5 can be done before converting
to double, and the division by 1024 may be converted to a simple
multiplication. At this point, the result is exactly the same.

However, to remove the extra multiplication by 0.9, it can be
moved into the multiplication by 1/1024. This may affect
the result to one ULP, but I do not forsee that causing any problems.

diff --git a/src/main/java/net/minecraft/world/level/biome/BiomeManager.java b/src/main/java/net/minecraft/world/level/biome/BiomeManager.java
index b90a323c4fc9af141758a73a72e6918300caf470..db159843e16e29be897112d02e71e48377ab13ac 100644
--- a/src/main/java/net/minecraft/world/level/biome/BiomeManager.java
+++ b/src/main/java/net/minecraft/world/level/biome/BiomeManager.java
@@ -127,10 +127,15 @@ public class BiomeManager {
         return Mth.square(f + n) + Mth.square(e + h) + Mth.square(d + g);
     }
 
-    private static double getFiddle(long l) {
-        double d = (double)Math.floorMod(l >> 24, 1024) / 1024.0;
-        return (d - 0.5) * 0.9;
+    // Moonrise start - Optimise BiomeManager#getFiddle
+    /**
+     * @reason Replace floorMod and double division to optimise the function
+     * @author Spottedleaf
+     */
+    private static double getFiddle(long seed) {
+        return (double) (((seed >> 24) & (1024 - 1)) - (1024 / 2)) * (0.9 / 1024.0);
     }
+    // Moonrise end - Optimise BiomeManager#getFiddle
 
     public interface NoiseBiomeSource {
         Holder<Biome> getNoiseBiome(int biomeX, int biomeY, int biomeZ);