use java.util.Random.nextLong(bound) - it's good!

Author: TilmanNeumann

src/main/java/de/tilman_neumann/jml/factor/pollardRho/PollardRhoBrentMontgomery64.java

@@ -1,6 +1,6 @@
 /*
  * 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) 2018-2024 Tilman Neumann - tilman.neumann@web.de
+ * 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.
@@ -14,14 +14,14 @@
 package de.tilman_neumann.jml.factor.pollardRho;
 
 import java.math.BigInteger;
+import java.util.Random;
 
 import org.apache.logging.log4j.Logger;
 import org.apache.logging.log4j.LogManager;
 
 import de.tilman_neumann.jml.base.Uint128;
 import de.tilman_neumann.jml.factor.FactorAlgorithm;
 import de.tilman_neumann.jml.gcd.Gcd63;
-import de.tilman_neumann.jml.random.Rng;
 import de.tilman_neumann.util.Ensure;
 
 /**
@@ -46,7 +46,7 @@ public class PollardRhoBrentMontgomery64 extends FactorAlgorithm {
 	private static final Logger LOG = LogManager.getLogger(PollardRhoBrentMontgomery64.class);
 	private static final boolean DEBUG = false;
 
-	private static final Rng RNG = new Rng();
+	private static final Random RNG = new Random(); // the numbers produced by Random.nextLong(bound) seem to have very good random number qualities
 
 	// The reducer R is 2^64, but the only constant still required is the half of it.
 	private static final long R_HALF = 1L << 63;

src/main/java/de/tilman_neumann/jml/factor/pollardRho/PollardRhoBrentMontgomery64MH.java

@@ -1,6 +1,6 @@
 /*
  * 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) 2018-2024 Tilman Neumann - tilman.neumann@web.de
+ * 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.
@@ -14,14 +14,14 @@
 package de.tilman_neumann.jml.factor.pollardRho;
 
 import java.math.BigInteger;
+import java.util.Random;
 
 import org.apache.logging.log4j.Logger;
 import org.apache.logging.log4j.LogManager;
 
 import de.tilman_neumann.jml.base.Uint128;
 import de.tilman_neumann.jml.factor.FactorAlgorithm;
 import de.tilman_neumann.jml.gcd.Gcd63;
-import de.tilman_neumann.jml.random.Rng;
 import de.tilman_neumann.util.Ensure;
 
 /**
@@ -50,7 +50,7 @@ public class PollardRhoBrentMontgomery64MH extends FactorAlgorithm {
 	private static final Logger LOG = LogManager.getLogger(PollardRhoBrentMontgomery64MH.class);
 	private static final boolean DEBUG = false;
 
-	private static final Rng RNG = new Rng();
+	private static final Random RNG = new Random(); // the numbers produced by Random.nextLong(bound) seem to have very good random number qualities
 
 	// The reducer R is 2^64, but the only constant still required is the half of it.
 	private static final long R_HALF = 1L << 63;

src/main/java/de/tilman_neumann/jml/factor/pollardRho/PollardRhoBrentMontgomery64MHInlined.java

@@ -1,6 +1,6 @@
 /*
  * 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) 2018-2024 Tilman Neumann - tilman.neumann@web.de
+ * 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.
@@ -14,14 +14,14 @@
 package de.tilman_neumann.jml.factor.pollardRho;
 
 import java.math.BigInteger;
+import java.util.Random;
 
 import org.apache.logging.log4j.Logger;
 import org.apache.logging.log4j.LogManager;
 
 import de.tilman_neumann.jml.base.Uint128;
 import de.tilman_neumann.jml.factor.FactorAlgorithm;
 import de.tilman_neumann.jml.gcd.Gcd63;
-import de.tilman_neumann.jml.random.Rng;
 import de.tilman_neumann.util.Ensure;
 
 /**
@@ -50,7 +50,7 @@ public class PollardRhoBrentMontgomery64MHInlined extends FactorAlgorithm {
 	private static final Logger LOG = LogManager.getLogger(PollardRhoBrentMontgomery64MHInlined.class);
 	private static final boolean DEBUG = false;
 
-	private static final Rng RNG = new Rng();
+	private static final Random RNG = new Random(); // the numbers produced by Random.nextLong(bound) seem to have very good random number qualities
 
 	// The reducer R is 2^64, but the only constant still required is the half of it.
 	private static final long R_HALF = 1L << 63;

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

@@ -57,33 +57,7 @@ public Rng(long seed) {
 	 * @return random int in the desired range
 	 */
 	public int nextInt(int minValue, int maxValue) {
-		int diff = maxValue - minValue;
-		if (diff < 1) throw new IllegalArgumentException("maxValue=" + maxValue + " must be bigger than minValue=" + minValue);
-		int rand = nextInt(diff); // 0...(diff-1)
-		return minValue + rand;
-	}
-
-	/**
-	 * Creates a random long from the uniform distribution U[0, maxValue-1].
-	 * The only requirement is maxValue > 0.
-	 * @param maxValue
-	 * @return random long in the desired range
-	 */
-	public long nextLong(long maxValue) {
-		if (maxValue < 1) {
-			throw new IllegalArgumentException("maxValue = " + maxValue + " is not positive");
-		}
-		
-		long rand = nextLong(); // Long.MIN_VALUE...Long.MAX_VALUE
-		long normalized; // shall become 0...(max-1)
-		if (rand >= 0) {
-			normalized = rand % maxValue;
-		} else if (rand > Long.MIN_VALUE) {
-			normalized = (-rand) % maxValue;
-		} else { // special treatment because -Long.MIN_VALUE == Long.MIN_VALUE
-			normalized = Long.MAX_VALUE % maxValue;
-		}
-		return normalized;
+		return minValue + nextInt(maxValue - minValue);
 	}
 
 	/**
@@ -94,10 +68,7 @@ public long nextLong(long maxValue) {
 	 * @return random long in the desired range
 	 */
 	public long nextLong(long minValue, long maxValue) {
-		long diff = maxValue - minValue;
-		if (diff < 1) throw new IllegalArgumentException("maxValue=" + maxValue + " must be bigger than minValue=" + minValue);
-		long rand = nextLong(diff); // 0...(diff-1)
-		return minValue + rand;
+		return minValue + nextLong(maxValue - minValue);
 	}
 
 	/**