rng clean up

Author: TilmanNeumann

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

@@ -25,11 +25,10 @@ public class Xorshf32 {
 
 	private int x=123456789, y=362436069, z=521288629;
 
+	/**
+	 * @return a random long number N with Integer.MIN_VALUE <= N <= Integer.MAX_VALUE.
+	 */
 	public int nextInt() {
-	    return nextInt(Integer.MAX_VALUE);
-	}
-
-	public int nextInt(int max) {
 		int t;
 	    x ^= x << 16;
 	    x ^= x >> 5;
@@ -40,9 +39,19 @@ public int nextInt(int max) {
 	    y = z;
 	    z = t ^ x ^ y;
 
-	    return Math.abs(z % max);
+	    return z;
 	}
-
+	
+	/**
+	 * @param max
+	 * @return a random int number N with 0 <= N <= max.
+	 */
+	public int nextInt(int max) {
+		final long l = nextInt() & 0xFFFFFFFFL; // take it as unsigned
+		final long prod = l * max;
+	    return (int) (prod >>> 32);
+	}
+	
 	public int nextInt(int min, int max) {
 	    return min + nextInt(max - min);
 	}

src/main/java/de/tilman_neumann/jml/random/Xorshf32b.java

@@ -43,15 +43,18 @@ public class RngPerformanceTest {
 	private static final long LOWER_LONG = 1L<<20;
 	private static final long UPPER_LONG = 1L<<50;
 
+	// any-size generators
 	private static final SecureRandom secureRandom = new SecureRandom();
 	private static final Random random = new Random();
 	private static final Rng rng = new Rng();
+	
+	// pure int generators
 	private static final SpRand32 spRand32 = new SpRand32();
 	private static final Xorshf32 xorshf32 = new Xorshf32();
-	private static final Xorshf32b xorshf32b = new Xorshf32b();
+	
+	// pure long generators
 	private static final LehmerRng64 lehmer64 = new LehmerRng64();
 	private static final LehmerRng64MH lehmer64MH = new LehmerRng64MH();
-	private static final Xorshf64 xorshf64 = new Xorshf64();
 	private static final SplitMix64 splitMix64 = new SplitMix64();
 	private static final Xorshift64Star xorshift64Star = new Xorshift64Star();
 	private static final Xorshift128Plus xorshift128Plus = new Xorshift128Plus();
@@ -82,10 +85,6 @@ private static void testNextInt() {
 			xorshf32.nextInt();
 		}
 		LOG.debug("Xorshf32.nextInt() took " + timer.capture() + " ms");
-		for (int i=0; i<NCOUNT; i++) {
-			xorshf32b.nextInt();
-		}
-		LOG.debug("Xorshf32b.nextInt() took " + timer.capture() + " ms");
 	}
 
 	private static void testNextIntWithUpperBound() {
@@ -112,10 +111,6 @@ private static void testNextIntWithUpperBound() {
 			xorshf32.nextInt(UPPER_INT);
 		}
 		LOG.debug("Xorshf32.nextInt(" + UPPER_INT + ") took " + timer.capture() + " ms");
-		for (int i=0; i<NCOUNT; i++) {
-			xorshf32b.nextInt(UPPER_INT);
-		}
-		LOG.debug("Xorshf32b.nextInt(" + UPPER_INT + ") took " + timer.capture() + " ms");
 	}
 
 	private static void testNextIntWithLowerUpperBound() {
@@ -144,10 +139,6 @@ private static void testNextIntWithLowerUpperBound() {
 			xorshf32.nextInt(LOWER_INT, UPPER_INT);
 		}
 		LOG.debug("Xorshf32.nextInt(" + LOWER_INT + ", " + UPPER_INT + ") took " + timer.capture() + " ms");
-		for (int i=0; i<NCOUNT; i++) {
-			xorshf32b.nextInt(LOWER_INT, UPPER_INT);
-		}
-		LOG.debug("Xorshf32b.nextInt(" + LOWER_INT + ", " + UPPER_INT + ") took " + timer.capture() + " ms");
 	}
 
 	private static void testNextLong() {
@@ -174,10 +165,6 @@ private static void testNextLong() {
 			lehmer64MH.nextLong();
 		}
 		LOG.debug("LehmerRng64MH.nextLong() took " + timer.capture() + " ms");
-		for (int i=0; i<NCOUNT; i++) {
-			xorshf64.nextLong();
-		}
-		LOG.debug("Xorshf64.nextLong() took " + timer.capture() + " ms");
 		for (int i=0; i<NCOUNT; i++) {
 			splitMix64.nextLong();
 		}
@@ -202,10 +189,6 @@ private static void testNextLong() {
 
 	private static void testNextLongWithUpperBound() {
 		Timer timer = new Timer();
-		for (int i=0; i<NCOUNT; i++) {
-			xorshf64.nextLong(UPPER_LONG);
-		}
-		LOG.debug("Xorshf64.nextLong(" + UPPER_LONG + ") took " + timer.capture() + " ms");
 		for (int i=0; i<NCOUNT; i++) {
 			splitMix64.nextLong(UPPER_LONG);
 		}
@@ -230,10 +213,6 @@ private static void testNextLongWithUpperBound() {
 
 	private static void testNextLongWithLowerUpperBound() {
 		Timer timer = new Timer();
-		for (int i=0; i<NCOUNT; i++) {
-			xorshf64.nextLong(LOWER_LONG, UPPER_LONG);
-		}
-		LOG.debug("Xorshf64.nextLong(" + LOWER_LONG + ", " + UPPER_LONG + ") took " + timer.capture() + " ms");
 		for (int i=0; i<NCOUNT; i++) {
 			splitMix64.nextLong(LOWER_LONG, UPPER_LONG);
 		}

src/main/java/de/tilman_neumann/jml/random/Xorshf64.java

@@ -57,7 +57,7 @@ public void testNextIntNoArgs() {
 		}
 		LOG.debug("First 100 elements: " + Arrays.toString(firstElements));
 		LOG.debug(NCOUNT + " numbers from " + rng.getClass().getSimpleName() + ".nextInt() gave min = " + min + ", max = " + max);
-		assertTrue(min >= 0);
+		assertTrue(min < 0);
 		assertTrue(generatesEven);
 		assertTrue(generatesOdd);
 	}