From 3f01e45b67a4913f94435c65d02132053c51b4b3 Mon Sep 17 00:00:00 2001
From: asiekierka <kontakt@asie.pl>
Date: Tue, 5 May 2015 09:51:42 +0200
Subject: [PATCH] replace randomness algorith with Xorshift128+, both more
 efficient and better quality

---
 common/buildcraft/BuildCraftCore.java         |  3 +-
 common/buildcraft/core/BlockSpring.java       |  3 +-
 .../core/lib/block/BlockBuildCraft.java       |  3 +-
 common/buildcraft/core/lib/utils/Utils.java   |  2 +-
 .../core/lib/utils/XorShift128Random.java     | 42 +++++++++++++++++++
 5 files changed, 49 insertions(+), 4 deletions(-)
 create mode 100644 common/buildcraft/core/lib/utils/XorShift128Random.java

diff --git a/common/buildcraft/BuildCraftCore.java b/common/buildcraft/BuildCraftCore.java
index 45463bae..d66c286b 100644
--- a/common/buildcraft/BuildCraftCore.java
+++ b/common/buildcraft/BuildCraftCore.java
@@ -95,6 +95,7 @@ import buildcraft.core.lib.engines.TileEngineBase;
 import buildcraft.core.lib.network.ChannelHandler;
 import buildcraft.core.lib.utils.ColorUtils;
 import buildcraft.core.lib.utils.NBTUtils;
+import buildcraft.core.lib.utils.XorShift128Random;
 import buildcraft.core.network.PacketHandlerCore;
 import buildcraft.core.properties.WorldPropertyIsDirt;
 import buildcraft.core.properties.WorldPropertyIsFarmland;
@@ -142,7 +143,7 @@ public class BuildCraftCore extends BuildCraftMod {
 		Full, NoDynamic
 	}
 
-	public static Random random = new Random();
+	public static XorShift128Random random = new XorShift128Random();
 	public static RenderMode render = RenderMode.Full;
 	public static boolean debugWorldgen = false;
 	public static boolean modifyWorld = false;
diff --git a/common/buildcraft/core/BlockSpring.java b/common/buildcraft/core/BlockSpring.java
index b0f83047..c56f6140 100644
--- a/common/buildcraft/core/BlockSpring.java
+++ b/common/buildcraft/core/BlockSpring.java
@@ -20,10 +20,11 @@ import net.minecraft.item.ItemStack;
 import net.minecraft.world.World;
 import cpw.mods.fml.relauncher.Side;
 import cpw.mods.fml.relauncher.SideOnly;
+import buildcraft.core.lib.utils.XorShift128Random;
 
 public class BlockSpring extends Block {
 
-	public static final Random rand = new Random();
+	public static final XorShift128Random rand = new XorShift128Random();
 
 	public enum EnumSpring {
 
diff --git a/common/buildcraft/core/lib/block/BlockBuildCraft.java b/common/buildcraft/core/lib/block/BlockBuildCraft.java
index 51d3d837..8a663e18 100644
--- a/common/buildcraft/core/lib/block/BlockBuildCraft.java
+++ b/common/buildcraft/core/lib/block/BlockBuildCraft.java
@@ -32,6 +32,7 @@ import buildcraft.api.tiles.IHasWork;
 import buildcraft.core.BCCreativeTab;
 import buildcraft.core.lib.utils.ResourceUtils;
 import buildcraft.core.lib.utils.Utils;
+import buildcraft.core.lib.utils.XorShift128Random;
 
 public abstract class BlockBuildCraft extends BlockContainer {
 	protected static boolean keepInventory = false;
@@ -45,7 +46,7 @@ public abstract class BlockBuildCraft extends BlockContainer {
 	@SideOnly(Side.CLIENT)
 	public IIcon[][] icons;
 
-	protected final Random rand = new Random();
+	protected final XorShift128Random rand = new XorShift128Random();
 	protected int renderPass;
 
 	protected int maxPasses = 1;
diff --git a/common/buildcraft/core/lib/utils/Utils.java b/common/buildcraft/core/lib/utils/Utils.java
index c28455d7..5a3ecc7d 100644
--- a/common/buildcraft/core/lib/utils/Utils.java
+++ b/common/buildcraft/core/lib/utils/Utils.java
@@ -50,7 +50,7 @@ import buildcraft.core.proxy.CoreProxy;
 
 public final class Utils {
 
-	public static final Random RANDOM = new Random();
+	public static final XorShift128Random RANDOM = new XorShift128Random();
 	private static final List<ForgeDirection> directions = new ArrayList<ForgeDirection>(Arrays.asList(ForgeDirection.VALID_DIRECTIONS));
 
 	/**
diff --git a/common/buildcraft/core/lib/utils/XorShift128Random.java b/common/buildcraft/core/lib/utils/XorShift128Random.java
new file mode 100644
index 00000000..6c42cb65
--- /dev/null
+++ b/common/buildcraft/core/lib/utils/XorShift128Random.java
@@ -0,0 +1,42 @@
+package buildcraft.core.lib.utils;
+
+import java.util.Random;
+
+/**
+ * Based on http://xorshift.di.unimi.it/xorshift128plus.c
+ */
+public class XorShift128Random {
+	private static final Random seed = new Random();
+	private static final double DOUBLE_UNIT = 0x1.0p-53;
+	private long[] s = new long[2];
+
+	public XorShift128Random() {
+		s[0] = seed.nextLong();
+		s[1] = seed.nextLong();
+	}
+
+	public long nextLong() {
+		long s1 = s[0];
+		long s0 = s[1];
+		s[0] = s0;
+		s1 ^= (s1 << 23);
+		s[1] = (s1 ^ s0 ^ (s1 >> 17) ^ (s0 >> 26)) + s0;
+		return s[1];
+	}
+
+	public int nextInt() {
+		return (int) (nextLong() & 0xFFFFFFFF);
+	}
+
+	public boolean nextBoolean() {
+		return (nextLong() & 0x1) != 0;
+	}
+
+	public int nextInt(int size) {
+		return (int) (nextLong() % size);
+	}
+
+	public double nextDouble() {
+		return (double) (long) (nextLong() & 0x1FFFFFFFFFFFFFL) * DOUBLE_UNIT;
+	}
+}