implement more methods for Xorshf64

Author: TilmanNeumann

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

@@ -45,8 +45,8 @@ public int nextInt() {
 	 */
 	public int nextInt(int max) {
 		final long i = nextInt();
-		final long l = i<0 ? -i : i;  // up to unsigned 2^32 - 1
-		final long prod = l * max; // up to max * (2^32 - 1)
+		final long l = i<0 ? -i : i;  // up to unsigned 2^31 - 1
+		final long prod = l * max; // up to max * (2^31 - 1)
 	    return (int) (prod >>> 32);
 	}
 

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

@@ -13,6 +13,8 @@
  */
 package de.tilman_neumann.jml.random;
 
+import de.tilman_neumann.jml.base.Uint128;
+
 /**
  * <strong>Experimental</strong> 64 bit random number generator computing longs from three consecutive 32 bit random numbers.
  * 
@@ -36,4 +38,19 @@ public long nextLong() {
 	    i2 = i3;
 	    return result;
 	}
+	
+	/**
+	 * @param max
+	 * @return a random long number N with 0 <= N <= max.
+	 */
+	public long nextLong(long max) {
+		final long i = nextLong();
+		final long l = i<0 ? -i : i;  // up to unsigned 2^63 - 1
+		final Uint128 prod = Uint128.mul64_MH(l, max);
+	    return prod.getHigh();
+	}
+	
+	public long nextLong(long min, long max) {
+	    return min + nextLong(max - min);
+	}
 }

src/test/java/de/tilman_neumann/jml/random/RngPerformanceTest.java

@@ -171,5 +171,19 @@ public static void main(String[] args) {
 			xorshf64.nextLong();
 		}
 		LOG.debug("Xorshf64.nextLong() took " + timer.capture() + " ms");
+		
+		// test nextLong(long upper)
+		long upperLong = 1L<<55;
+		for (int i=0; i<NCOUNT; i++) {
+			xorshf64.nextLong(upperLong);
+		}
+		LOG.debug("Xorshf64.nextLong(upper) took " + timer.capture() + " ms");
+
+		// test nextLong(long lower, long upper)
+		long lowerLong = 1L<<20;
+		for (int i=0; i<NCOUNT; i++) {
+			xorshf64.nextLong(lowerLong, upperLong);
+		}
+		LOG.debug("Xorshf64.nextLong(lower, upper) took " + timer.capture() + " ms");
 	}
 }