Rngs

- imoprted and fixed for java

src/main/java/net/berack/upo/valpre/rand/Rng.java

@@ -0,0 +1,99 @@
+package net.berack.upo.valpre.rand;
+
+/**
+ * This is an Java library for random number generation.  The use of this
+ * library is recommended as a replacement for the Java class Random,
+ * particularly in simulation applications where the statistical
+ * 'goodness' of the random number generator is important.
+ *
+ * The generator used in this library is a so-called 'Lehmer random number
+ * generator' which returns a pseudo-random number uniformly distributed
+ * between 0.0 and 1.0.  The period is (m - 1) where m = 2,147,483,647 and
+ * the smallest and largest possible values are (1 / m) and 1 - (1 / m)
+ * respectively.  For more details see:
+ *
+ *       "Random Number Generators: Good Ones Are Hard To Find"
+ *                   Steve Park and Keith Miller
+ *              Communications of the ACM, October 1988
+ *
+ * Note that as of 7-11-90 the multiplier used in this library has changed
+ * from the previous "minimal standard" 16807 to a new value of 48271.  To
+ * use this library in its old (16807) form change the constants MULTIPLIER
+ * and CHECK as indicated in the comments.
+ *
+ * Name              : Rng.java  (Random Number Generation - Single Stream)
+ * Authors           : Steve Park & Dave Geyer
+ * Translated by     : Jun Wang & Richard Dutton
+ * Language          : Java
+ * Latest Revision   : 6-10-04
+ *
+ * Program rng       : Section 2.2
+ */
+public class Rng {
+	public final static long CHECK = 399268537L; /* use 1043616065 for the "minimal standard" */
+	public final static long DEFAULT = 123456789L; /* initial seed, use 0 < DEFAULT < MODULUS */
+	public final static long MODULUS = 2147483647; /* DON'T CHANGE THIS VALUE */
+	public final static long MULTIPLIER = 48271; /* use 16807 for the "minimal standard" */
+
+	private long seed = DEFAULT; /* seed is the state of the generator */
+
+	public Rng() {
+	}
+
+	public Rng(long seed) {
+		this.putSeed(seed);
+	}
+
+	/**
+	 * Random is a Lehmer generator that returns a pseudo-random real number
+	 * uniformly distributed between 0.0 and 1.0. The period is (m - 1)
+	 * where m = 2,147,483,647 amd the smallest and largest possible values
+	 * are (1 / m) and 1 - (1 / m) respectively.
+	 */
+	public double random() {
+		this.seed = Rng.newSeed(MODULUS, MULTIPLIER, this.seed);
+		return ((double) this.seed / MODULUS);
+	}
+
+	/**
+	 * Use this (optional) procedure to initialize or reset the state of
+	 * the random number generator according to the following conventions:
+	 * if x > 0 then x is the initial seed (unless too large)
+	 * if x <= 0 then the initial seed is obtained from the system clock
+	 */
+	public void putSeed(long x) {
+		if (x > 0L) {
+			x = x % MODULUS; /* correct if x is too large */
+		} else {
+			x = System.currentTimeMillis();
+			// x = ((unsigned long) time((time_t *) NULL)) % MODULUS;
+		}
+
+		this.seed = x;
+	}
+
+	/**
+	 * Use this (optional) procedure to get the current state of the random
+	 * number generator.
+	 */
+	public long getSeed() {
+		return this.seed;
+	}
+
+	/**
+	 * Use this (optional) procedure to test for a correct implementation.
+	 */
+	public static boolean testRandom() {
+		Rng rng = new Rng(1); /* set initial state to 1 */
+		for (var i = 0; i < 10000; i++)
+			rng.random();
+		return rng.getSeed() == CHECK;
+	}
+
+	public static long newSeed(long modulus, long multiplier, long seed) {
+		var Q = modulus / multiplier;
+		var R = modulus % multiplier;
+		var t = multiplier * (seed % Q) - R * (seed / Q);
+		return t > 0 ? t : (t + modulus);
+	}
+}