lapack/testlapack: add sameLowerTri and sameUpperTri helpers

lapack/testlapack/dlauu2.go

@@ -38,7 +38,6 @@ func dlauuTest(t *testing.T, dlauu func(blas.Uplo, int, []float64, int), uplo bl
 	rnd := rand.New(rand.NewSource(1))
 
 	for _, n := range ns {
-	loop:
 		for _, lda := range []int{max(1, n), n + 11} {
 			prefix := fmt.Sprintf("n=%v,lda=%v", n, lda)
 
@@ -59,27 +58,27 @@ func dlauuTest(t *testing.T, dlauu func(blas.Uplo, int, []float64, int), uplo bl
 				continue
 			}
 
-			// * Check that the triangle opposite to uplo has not been modified.
+			// * Check that the triangle of A opposite to uplo has not been modified.
 			// * Convert the result of Dlauu? into a dense symmetric matrix.
 			// * Zero out the triangle in aCopy opposite to uplo.
 			if uplo == blas.Upper {
+				if !sameLowerTri(n, aCopy, lda, a, lda) {
+					t.Errorf("%v: unexpected modification in lower triangle", prefix)
+					continue
+				}
 				for i := 1; i < n; i++ {
 					for j := 0; j < i; j++ {
-						if aCopy[i*lda+j] != a[i*lda+j] {
-							t.Errorf("%v: unexpected modification in lower triangle", prefix)
-							break loop
-						}
 						a[i*lda+j] = a[j*lda+i]
 						aCopy[i*lda+j] = 0
 					}
 				}
 			} else {
+				if !sameUpperTri(n, aCopy, lda, a, lda) {
+					t.Errorf("%v: unexpected modification in upper triangle", prefix)
+					continue
+				}
 				for i := 0; i < n-1; i++ {
 					for j := i + 1; j < n; j++ {
-						if aCopy[i*lda+j] != a[i*lda+j] {
-							t.Errorf("%v: unexpected modification in upper triangle", prefix)
-							break loop
-						}
 						a[i*lda+j] = a[j*lda+i]
 						aCopy[i*lda+j] = 0
 					}

lapack/testlapack/general.go

@@ -1489,3 +1489,35 @@ func isIdentity(n int, a []float64, lda int, tol float64) bool {
 	}
 	return true
 }
+
+func sameFloat64(a, b float64) bool {
+	return a == b || math.IsNaN(a) && math.IsNaN(b)
+}
+
+// sameLowerTri returns whether n×n matrices A and B are same under the diagonal.
+func sameLowerTri(n int, a []float64, lda int, b []float64, ldb int) bool {
+	for i := 1; i < n; i++ {
+		for j := 0; j < i; j++ {
+			aij := a[i*lda+j]
+			bij := b[i*ldb+j]
+			if !sameFloat64(aij, bij) {
+				return false
+			}
+		}
+	}
+	return true
+}
+
+// sameUpperTri returns whether n×n matrices A and B are same above the diagonal.
+func sameUpperTri(n int, a []float64, lda int, b []float64, ldb int) bool {
+	for i := 0; i < n-1; i++ {
+		for j := i + 1; j < n; j++ {
+			aij := a[i*lda+j]
+			bij := b[i*ldb+j]
+			if !sameFloat64(aij, bij) {
+				return false
+			}
+		}
+	}
+	return true
+}