This fixes #47

PoslavskySV · Sep 16, 2018 · e960bcd · e960bcd
1 parent b438f93
commit e960bcd
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Showing 2 changed files with 16 additions and 3 deletions.
diff --git a/rings/src/main/java/cc/redberry/rings/poly/univar/UnivariateFactorization.java b/rings/src/main/java/cc/redberry/rings/poly/univar/UnivariateFactorization.java
@@ -388,7 +388,10 @@ private static int next32BitPrime(int val) {
             return SmallPrimes.nextPrime(val);
     }
 
-    final static int N_MODULAR_FACTORIZATION_TRIALS = 2;
+    final static int
+            N_MIN_MODULAR_FACTORIZATION_TRIALS = 2, // minimal number of modular trials
+            N_SIMPLE_MOD_PATTERN_FACTORS = 12, // number of modular factors sufficient small enough to proceed to reconstruction
+            N_MODULAR_FACTORIZATION_TRIALS = 4; // maximal number of modular trials
 
     /**
      * Factors primitive square-free polynomial using Hensel lifting
@@ -412,6 +415,9 @@ static PolynomialFactorDecomposition<UnivariatePolynomial<BigInteger>> FactorSqu
         PolynomialFactorDecomposition<UnivariatePolynomialZp64> lModularFactors = null;
 
         for (int attempt = 0; attempt < N_MODULAR_FACTORIZATION_TRIALS; attempt++) {
+            if (attempt >= N_MIN_MODULAR_FACTORIZATION_TRIALS && lModularFactors.size() <= N_SIMPLE_MOD_PATTERN_FACTORS)
+                break;
+
             long tmpModulus;
             do {
                 tmpModulus = SmallPrimes.nextPrime(randomModulusInf());
@@ -421,6 +427,7 @@ static PolynomialFactorDecomposition<UnivariatePolynomial<BigInteger>> FactorSqu
 
             // do modular factorization
             PolynomialFactorDecomposition<UnivariatePolynomialZp64> tmpFactors = FactorInGF(moduloImage.monic());
+
             if (tmpFactors.size() == 1)
                 return PolynomialFactorDecomposition.of(poly);
 

diff --git a/rings/src/test/java/cc/redberry/rings/poly/univar/UnivariateFactorizationTest.java b/rings/src/test/java/cc/redberry/rings/poly/univar/UnivariateFactorizationTest.java
@@ -20,8 +20,8 @@
 
 import java.util.function.Supplier;
 
-import static cc.redberry.rings.Rings.Q;
-import static cc.redberry.rings.Rings.UnivariateRing;
+import static cc.redberry.rings.Rings.*;
+import static cc.redberry.rings.poly.univar.UnivariateFactorization.Factor;
 import static cc.redberry.rings.poly.univar.UnivariateFactorization.FactorInNumberField;
 import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertTrue;
@@ -547,4 +547,10 @@ public void testNumberField3_random() {
             }
         }
     }
+
+    @Test(timeout = 100_000)
+    public void test7() {
+        UnivariatePolynomial<BigInteger> poly = UnivariatePolynomial.parse("x^259 - 1", Z, "x");
+        assertEquals(4, Factor(poly).size());
+    }
 }