Fix rare bug in MultivariateGCD#isGCDTriplet for polys over Z

PoslavskySV · Apr 4, 2018 · fe97345 · fe97345
1 parent 96ce09f
commit fe97345
Showing 1 changed file with 5 additions and 2 deletions.
diff --git a/rings/src/main/java/cc/redberry/rings/poly/multivar/MultivariateGCD.java b/rings/src/main/java/cc/redberry/rings/poly/multivar/MultivariateGCD.java
@@ -2135,8 +2135,11 @@ private static <E> boolean isGCDTriplet(MultivariatePolynomial<E> a, Multivariat
 
             UnivariatePolynomial<E> uniDiv = subsToUnivariate(gcd, powers);
             // fast check
-            if (!UnivariateDivision.remainder(subsToUnivariate(a, powers), uniDiv, false).isZero()
-                    || !UnivariateDivision.remainder(subsToUnivariate(b, powers), uniDiv, false).isZero())
+            UnivariatePolynomial<E> ra = UnivariateDivision.remainder(subsToUnivariate(a, powers), uniDiv, false);
+            if (ra == null || !ra.isZero())
+                return false;
+            UnivariatePolynomial<E> rb = UnivariateDivision.remainder(subsToUnivariate(b, powers), uniDiv, false);
+            if (rb == null || !rb.isZero())
                 return false;
         }