minor performance improvement +++ comment on Xorshf64

Author: TilmanNeumann

src/main/java/de/tilman_neumann/jml/factor/pollardRho/PollardRhoBrentMontgomery32.java

@@ -20,7 +20,7 @@
 
 import de.tilman_neumann.jml.factor.FactorAlgorithm;
 import de.tilman_neumann.jml.gcd.Gcd31;
-import de.tilman_neumann.jml.random.SpRand32;
+import de.tilman_neumann.jml.random.Xorshf32;
 import de.tilman_neumann.util.Ensure;
 
 /**
@@ -47,7 +47,7 @@ public class PollardRhoBrentMontgomery32 extends FactorAlgorithm {
 	private static final Logger LOG = LogManager.getLogger(PollardRhoBrentMontgomery32.class);
 	private static final boolean DEBUG = false;
 
-	private static final SpRand32 RNG = new SpRand32();
+	private static final Xorshf32 RNG = new Xorshf32(); // looks slightly faster than SpRand32 here
 
 	// The reducer R is 2^32, but the only constant still required is the half of it.
 	private static final int R_HALF = 1 << 31;

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

@@ -18,6 +18,9 @@
 /**
  * <strong>Experimental</strong> 64 bit random number generator computing longs from three consecutive 32 bit random numbers.
  * 
+ * It is fast, but the quality of the generated numbers seems to be insufficient to improve the performance of
+ * factoring algorithms like PollardRhoBrentMontgomery64.
+ * 
  * @author Tilman Neumann
  */
 public class Xorshf64 {