more popular rngs

Author: TilmanNeumann

src/main/java/de/tilman_neumann/jml/random/SplitMix64.java

@@ -18,7 +18,8 @@
 /**
  * 64 bit random number generator adapted from https://rosettacode.org/wiki/Pseudo-random_numbers/Splitmix64.
  * 
- * Very fast.
+ * Very fast, but its statistical properties are poor.
+ * But according to https://en.wikipedia.org/wiki/Xorshift#Initialization, it is well-suited to initialize other random generators.
  * 
  * @author Tilman Neumann
  */

src/main/java/de/tilman_neumann/jml/random/Xoroshiro128Plus.java

@@ -0,0 +1,59 @@
+/*
+ * java-math-library is a Java library focused on number theory, but not necessarily limited to it. It is based on the PSIQS 4.0 factoring project.
+ * Copyright (C) 2018-2025 Tilman Neumann - tilman.neumann@web.de
+ *
+ * This program is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 3 of the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied
+ * warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along with this program;
+ * if not, see <http://www.gnu.org/licenses/>.
+ */
+package de.tilman_neumann.jml.random;
+
+import de.tilman_neumann.jml.base.Uint128;
+
+/**
+ * 64 bit random number generator.
+ * 
+ * @see https://nullprogram.com/blog/2017/09/21/
+. * 
+ * @author Tilman Neumann
+ */
+public class Xoroshiro128Plus {
+	
+	private long state0, state1;
+	
+	public Xoroshiro128Plus() {
+		SplitMix64 splitMix = new SplitMix64();
+		long seed = System.currentTimeMillis();
+		state0 = seed ^ splitMix.nextLong();
+		state1 = seed ^ splitMix.nextLong();
+	}
+	
+	public long nextLong() {
+	    long s0 = state0;
+	    long s1 = state1;
+	    long result = s0 + s1;
+	    s1 ^= s0;
+	    state0 = ((s0 << 55) | (s0 >>> 9)) ^ s1 ^ (s1 << 14);
+	    state1 = (s1 << 36) | (s1 >>> 28);
+	    return result;
+	}
+	
+	/**
+	 * @param max
+	 * @return a random long number N with 0 <= N <= max.
+	 */
+	public long nextLong(long max) {
+		final long l = nextLong(); // take it as unsigned
+		final Uint128 prod = Uint128.mul64_MH(l, max);
+	    return prod.getHigh();
+	}
+	
+	public long nextLong(long min, long max) {
+	    return min + nextLong(max - min);
+	}
+}

src/main/java/de/tilman_neumann/jml/random/Xoroshiro256StarStar.java

@@ -0,0 +1,70 @@
+/*
+ * java-math-library is a Java library focused on number theory, but not necessarily limited to it. It is based on the PSIQS 4.0 factoring project.
+ * Copyright (C) 2018-2025 Tilman Neumann - tilman.neumann@web.de
+ *
+ * This program is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 3 of the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied
+ * warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along with this program;
+ * if not, see <http://www.gnu.org/licenses/>.
+ */
+package de.tilman_neumann.jml.random;
+
+import de.tilman_neumann.jml.base.Uint128;
+
+/**
+ * 64 bit random number generator adapted from https://en.wikipedia.org/wiki/Xorshift.
+ * 
+ * This seems to be the best 64 bit pseudo-random number generator these days, see also https://nullprogram.com/blog/2017/09/21/
+ * 
+ * @author Tilman Neumann
+ */
+public class Xoroshiro256StarStar {
+	
+	private long state0, state1, state2, state3;
+	
+	public Xoroshiro256StarStar() {
+		SplitMix64 splitMix = new SplitMix64();
+		long seed = System.currentTimeMillis();
+		state0 = seed ^ splitMix.nextLong();
+		state1 = seed ^ splitMix.nextLong();
+		state2 = seed ^ splitMix.nextLong();
+		state3 = seed ^ splitMix.nextLong();
+	}
+	
+	public long nextLong() {
+		final long result = rol64(state1 * 5, 7) * 9;
+		final long t = state1 << 17;
+
+		state2 ^= state0;
+		state3 ^= state1;
+		state1 ^= state2;
+		state0 ^= state3;
+
+		state2 ^= t;
+		state3 = rol64(state3, 45);
+
+		return result;
+	}
+	
+	private static long rol64(long x, int k) {
+		return (x << k) | (x >>> (64 - k));
+	}
+	
+	/**
+	 * @param max
+	 * @return a random long number N with 0 <= N <= max.
+	 */
+	public long nextLong(long max) {
+		final long l = nextLong(); // take it as unsigned
+		final Uint128 prod = Uint128.mul64_MH(l, max);
+	    return prod.getHigh();
+	}
+	
+	public long nextLong(long min, long max) {
+	    return min + nextLong(max - min);
+	}
+}

src/main/java/de/tilman_neumann/jml/random/Xorshift128Plus.java

@@ -0,0 +1,67 @@
+/*
+ * java-math-library is a Java library focused on number theory, but not necessarily limited to it. It is based on the PSIQS 4.0 factoring project.
+ * Copyright (C) 2018-2025 Tilman Neumann - tilman.neumann@web.de
+ *
+ * This program is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 3 of the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied
+ * warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along with this program;
+ * if not, see <http://www.gnu.org/licenses/>.
+ */
+package de.tilman_neumann.jml.random;
+
+import de.tilman_neumann.jml.base.Uint128;
+
+/**
+ * 64 bit random number generator adapted from https://nullprogram.com/blog/2017/09/21/.
+. * 
+ * @author Tilman Neumann
+ */
+public class Xorshift128Plus {
+	
+	private long state0, state1;
+	
+	/**
+	 * Standard constructor.
+	 * 
+	 * Note https://nullprogram.com/blog/2017/09/21/: There’s one important caveat: That 16-byte state must be well-seeded.
+	 * Having lots of zero bytes will lead terrible initial output until the generator mixes it all up. Having all zero bytes will completely break the generator.
+	 * If you’re going to seed from, say, the unix epoch, then XOR it with 16 static random bytes.
+	 * 
+	 * And https://en.wikipedia.org/wiki/Xorshift#Initialization: In the xoshiro paper, it is recommended to initialize the state of the generators using a generator
+	 * which is radically different from the initialized generators, as well as one which will never give the "all-zero" state; for shift-register generators,
+	 * this state is impossible to escape from. The authors specifically recommend using the SplitMix64 generator, from a 64-bit seed.
+	 */
+	public Xorshift128Plus() {
+		SplitMix64 splitMix = new SplitMix64();
+		long seed = System.currentTimeMillis();
+		state0 = seed ^ splitMix.nextLong();
+		state1 = seed ^ splitMix.nextLong();
+	}
+	
+	public long nextLong() {
+	    long x = state0;
+	    long y = state1;
+	    state0 = y;
+	    x ^= x << 23;
+	    state1 = x ^ y ^ (x >>> 17) ^ (y >>> 26);
+	    return state1 + y;
+	}
+
+	/**
+	 * @param max
+	 * @return a random long number N with 0 <= N <= max.
+	 */
+	public long nextLong(long max) {
+		final long l = nextLong(); // take it as unsigned
+		final Uint128 prod = Uint128.mul64_MH(l, max);
+	    return prod.getHigh();
+	}
+	
+	public long nextLong(long min, long max) {
+	    return min + nextLong(max - min);
+	}
+}

src/main/java/de/tilman_neumann/jml/random/Xorshift64Star.java

@@ -0,0 +1,57 @@
+/*
+ * java-math-library is a Java library focused on number theory, but not necessarily limited to it. It is based on the PSIQS 4.0 factoring project.
+ * Copyright (C) 2018-2025 Tilman Neumann - tilman.neumann@web.de
+ *
+ * This program is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 3 of the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied
+ * warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along with this program;
+ * if not, see <http://www.gnu.org/licenses/>.
+ */
+package de.tilman_neumann.jml.random;
+
+import de.tilman_neumann.jml.base.Uint128;
+
+/**
+ * 64 bit random number generator adapted from https://nullprogram.com/blog/2017/09/21/.
+. * 
+ * @author Tilman Neumann
+ */
+public class Xorshift64Star {
+	
+	private static final long multiplier = 0x2545f4914f6cdd1dL;
+	
+	private long state0;
+	
+	public Xorshift64Star() {
+		SplitMix64 splitMix = new SplitMix64();
+		long seed = System.currentTimeMillis();
+		state0 = seed ^ splitMix.nextLong();
+	}
+	
+	public long nextLong() {
+	    long x = state0;
+	    x ^= x >>> 12;
+	    x ^= x << 25;
+	    x ^= x >>> 27;
+	    state0 = x;
+	    return x * multiplier;
+	}
+	
+	/**
+	 * @param max
+	 * @return a random long number N with 0 <= N <= max.
+	 */
+	public long nextLong(long max) {
+		final long l = nextLong(); // take it as unsigned
+		final Uint128 prod = Uint128.mul64_MH(l, max);
+	    return prod.getHigh();
+	}
+	
+	public long nextLong(long min, long max) {
+	    return min + nextLong(max - min);
+	}
+}