improve factor() performance

Author: TilmanNeumann

src/main/java/de/tilman_neumann/jml/factor/tdiv/TDiv31Barrett.java

@@ -85,9 +85,13 @@ public void factor(BigInteger Nbig, int Nexp, SortedMultiset<BigInteger> primeFa
 		int q;
 		for (int i=1; ; i++) {
 			final int p = primes[i];
+			int exp = 0;
 			while ((q = (1 + (int) ((N*pinv[i])>>32))) * p == N) {
-				primeFactors.add(BigInteger.valueOf(p), Nexp);
-				N = q;
+				exp++;
+				N = q; // avoiding a division here by storing q benefits the int version but not the long version
+			}
+			if (exp > 0) {
+				primeFactors.add(BigInteger.valueOf(p), exp*Nexp);
 			}
 			// for random composite N, it is much much faster to check the termination condition after each p;
 			// for semiprime N, it would be ~40% faster to do it only after sucessful divisions

src/main/java/de/tilman_neumann/jml/factor/tdiv/TDiv31Inverse.java

@@ -76,10 +76,14 @@ public void factor(BigInteger Nbig, int Nexp, SortedMultiset<BigInteger> primeFa
 		int q;
 		for (int i=0; ; i++) {
 			final int p = primes[i];
+			int exp = 0;
 			while ((q = (int) (N*reciprocals[i] + DISCRIMINATOR)) * p == N) {
-				primeFactors.add(BigInteger.valueOf(p), Nexp);
+				exp++;
 				N = q; // avoiding a division here by storing q benefits the int version but not the long version
 			}
+			if (exp > 0) {
+				primeFactors.add(BigInteger.valueOf(p), exp*Nexp);
+			}
 			// for random composite N, it is much much faster to check the termination condition after each p;
 			// for semiprime N, it would be ~40% faster to do it only after sucessful divisions
 			if (((long)p) * p > N) { // move p as long into registers makes a performance difference