fix test and work out Squ

Author: TilmanNeumann

src/main/java/de/tilman_neumann/jml/factor/squfof/SquFoF63.java

@@ -1,6 +1,6 @@
 /*
  * java-math-library is a Java library focused on number theory, but not necessarily limited to it. It is based on the PSIQS 4.0 factoring project.
- * Copyright (C) 2018-2024 Tilman Neumann - tilman.neumann@web.de
+ * Copyright (C) 2018-2025 Tilman Neumann - tilman.neumann@web.de
  *
  * This program is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License
  * as published by the Free Software Foundation; either version 3 of the License, or (at your option) any later version.
@@ -22,14 +22,13 @@
 import de.tilman_neumann.jml.sequence.SquarefreeSequence;
 
 /**
- * Shanks' SQUFOF algorithm, 63-bit version.<br/>
+ * Shanks' SQUFOF algorithm, "63-bit version", which means that the core is implemented in signed longs.<br/>
  * Implemented according to <link>http://en.wikipedia.org/wiki/Shanks'_square_forms_factorization</link>.
  * 
  * Final choice with self-initialization of parameters.
  * Stopping criterion: after a maximum number of iterations.
  * 
- * Works for all numbers <= 63 bit.
- * Starting from 64 bit, there may be numbers the algorithm can't factor.
+ * Works stable for all numbers <= 87 bit.
  * 
  * @author Tilman Neumann
  */

src/test/java/de/tilman_neumann/jml/factor/squfof/SquFoF63Test.java

@@ -29,6 +29,8 @@
 import de.tilman_neumann.util.ConfigUtil;
 import de.tilman_neumann.util.SortedMultiset;
 
+import static de.tilman_neumann.jml.base.BigIntConstants.I_1;
+
 public class SquFoF63Test {
 
 	private static final Logger LOG = LogManager.getLogger(SquFoF63Test.class);
@@ -49,30 +51,41 @@ public void testSomeParticularNumbers() {
 	}
 
 	/**
-	 * Tests random composite numbers in the range where SquFoF63 should work correctly, i.e. up to 63 bit.
+	 * Tests smaller random composite numbers.
+	 */
+	@Test
+	public void testSmallRandomComposites() {
+		testRange(50, 69, 1000);
+	}
+
+	/**
+	 * Tests random composite numbers in the upper range where SquFoF63 works stable, i.e. up to 87 bit.
 	 */
 	@Test
-	public void testRandomComposites() {
-		int count = 10000;
-		for (int bits=50; bits<64; bits++) { // 64 bit numbers are not completely safe
+	public void testLargerRandomComposites() {
+		testRange(70, 86, 100);
+		testRange(87, 87, 1000);
+	}
+
+	private void testRange(int minBits, int maxBits, int count) {
+		for (int bits=minBits; bits<=maxBits; bits++) {
 			BigInteger[] testNumbers = TestsetGenerator.generate(count, bits, TestNumberNature.RANDOM_ODD_COMPOSITES);
 			LOG.info("Testing " + count + " random numbers with " + bits + " bit...");
 			int failCount = 0;
 			for (int i=0; i<count; i++) {
-				BigInteger NBig = testNumbers[i];
-				long N = NBig.longValue();
-				long squfofFactor = squfof63.findSingleFactor(N);
-				if (squfofFactor < 2) {
-					long correctFactor = testFactorizer.findSingleFactor(NBig).longValue();
-					if (correctFactor > 1 && correctFactor<N) {
+				BigInteger N = testNumbers[i];
+				BigInteger squfofFactor = squfof63.findSingleFactor(N);
+				if (squfofFactor.compareTo(I_1) <= 0) {
+					BigInteger correctFactor = testFactorizer.findSingleFactor(N);
+					if (correctFactor.compareTo(I_1)>0 && correctFactor.compareTo(N)<0) {
 						LOG.debug("N=" + N + ": SquFoF31 failed to find factor " + correctFactor);
 						failCount++;
 					} else {
 						LOG.error("The reference factorizer failed to factor N=" + N + " !");
 						fail();
 					}
 				} else {
-					if (N % squfofFactor != 0) {
+					if (N.mod(squfofFactor).signum() != 0) {
 						failCount++;
 					}
 				}