another rng (experimental)

Author: TilmanNeumann

src/main/java/de/tilman_neumann/jml/random/Xorshf32.java

@@ -0,0 +1,56 @@
+/*
+ * 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 org.apache.logging.log4j.Logger;
+import org.apache.logging.log4j.LogManager;
+
+import de.tilman_neumann.util.ConfigUtil;
+
+/**
+ * Java port of Marsaglia's xorshf generator.
+ * @see https://stackoverflow.com/questions/1640258/need-a-fast-random-generator-for-c<br/><br/>
+ * 
+ * <strong>WARNING: This class is experimental!</strong> SpRand32 looks faster for numbers close to 31 bit.
+ * Maybe I need to improve the conversion from C "unsigned long" to Java int (shifts, masks etc.).
+ * 
+ * @author Tilman Neumann
+ */
+public class Xorshf32 {
+	private static final Logger LOG = LogManager.getLogger(Xorshf32.class);
+	
+	int x=123456789, y=362436069, z=521288629;
+	
+	public int nextInt(int max) {
+		int t;
+	    x ^= x << 16;
+	    x ^= x >> 5;
+	    x ^= x << 1;
+
+	    t = x;
+	    x = y;
+	    y = z;
+	    z = t ^ x ^ y;
+
+	    return Math.abs(z%max);
+	}
+	
+	public static void main(String[] args) {
+		ConfigUtil.initProject();
+		Xorshf32 rng = new Xorshf32();
+		for (int i=0; i<1000; i++) {
+			LOG.info("rand(" + i + ") = " + rng.nextInt(10));
+		}
+	}
+}