lapack/gonum: require exact length of tau in QR routines

lapack/testlapack/dgeqrf.go

@@ -62,8 +62,9 @@ func DgeqrfTest(t *testing.T, impl Dgeqrfer) {
 
 		// Allocate a slice for scalar factors of elementary reflectors
 		// and fill it with random numbers.
-		tau := make([]float64, n)
-		for i := 0; i < n; i++ {
+		k := min(m, n)
+		tau := make([]float64, k)
+		for i := range tau {
 			tau[i] = rnd.Float64()
 		}
 

lapack/testlapack/dlarfb.go

@@ -84,7 +84,7 @@ func DlarfbTest(t *testing.T, impl Dlarfber) {
 						}
 
 						// Use dgeqr2 to find the v vectors
-						tau := make([]float64, na)
+						tau := make([]float64, k)
 						work := make([]float64, na)
 						impl.Dgeqr2(ma, k, a, lda, tau, work)
 

lapack/testlapack/dlarft.go

@@ -52,7 +52,8 @@ func DlarftTest(t *testing.T, impl Dlarfter) {
 					}
 				}
 				// Use dgeqr2 to find the v vectors
-				tau := make([]float64, n)
+				k := min(m, n)
+				tau := make([]float64, k)
 				work := make([]float64, n)
 				impl.Dgeqr2(m, n, a, lda, tau, work)
 
@@ -64,7 +65,6 @@ func DlarftTest(t *testing.T, impl Dlarfter) {
 
 				h := constructH(tau, vMat, store, direct)
 
-				k := min(m, n)
 				ldt := test.ldt
 				if ldt == 0 {
 					ldt = k

lapack/testlapack/dorg2r.go

@@ -59,7 +59,7 @@ func Dorg2rTest(t *testing.T, impl Dorg2rer) {
 		q := constructQK("QR", m, n, k, a, lda, tau)
 
 		// Compute the matrix Q using Dorg2r.
-		impl.Dorg2r(m, n, k, a, lda, tau, work)
+		impl.Dorg2r(m, n, k, a, lda, tau[:k], work)
 
 		// Check that the first n columns of both results match.
 		same := true

lapack/testlapack/dorgqr.go

@@ -57,7 +57,7 @@ func DorgqrTest(t *testing.T, impl Dorgqrer) {
 			a[i] = rnd.Float64()
 		}
 		work := make([]float64, 1)
-		tau := make([]float64, n)
+		tau := make([]float64, min(m, n))
 		for i := range tau {
 			tau[i] = math.NaN()
 		}
@@ -71,12 +71,12 @@ func DorgqrTest(t *testing.T, impl Dorgqrer) {
 		for i := range work {
 			work[i] = math.NaN()
 		}
-		impl.Dorg2r(m, n, k, aUnblocked, lda, tau, work)
+		impl.Dorg2r(m, n, k, aUnblocked, lda, tau[:k], work)
 		// make sure work isn't used before initialized
 		for i := range work {
 			work[i] = math.NaN()
 		}
-		impl.Dorgqr(m, n, k, a, lda, tau, work, len(work))
+		impl.Dorgqr(m, n, k, a, lda, tau[:k], work, len(work))
 		if !floats.EqualApprox(a, aUnblocked, 1e-10) {
 			t.Errorf("Q Mismatch. m = %d, n = %d, k = %d, lda = %d", m, n, k, lda)
 		}