lapack/testlapack: add implementation comment to Dlarfx test
@@ -21,6 +21,7 @@ type Dlarfxer interface {
func DlarfxTest(t *testing.T, impl Dlarfxer) {
rnd := rand.New(rand.NewSource(1))
for _, side := range []blas.Side{blas.Right, blas.Left} {
+ // For m and n greater than 10 we are testing Dlarf, so avoid unnecessary work.
for m := 1; m < 12; m++ {
for n := 1; n < 12; n++ {
for _, extra := range []int{0, 1, 11} {
@@ -36,22 +37,28 @@ func DlarfxTest(t *testing.T, impl Dlarfxer) {
func testDlarfx(t *testing.T, impl Dlarfxer, side blas.Side, m, n, extra int, rnd *rand.Rand) {
const tol = 1e-13
- c := randomGeneral(m, n, n+extra, rnd)
- cWant := randomGeneral(m, n, n+extra, rnd)
+ // Generate random input data.
+ var v []float64
+ if side == blas.Left {
+ v = randomSlice(m, rnd)
+ } else {
+ v = randomSlice(n, rnd)
+ }
tau := rnd.NormFloat64()
+ ldc := n + extra
+ c := randomGeneral(m, n, ldc, rnd)
- var (
- v []float64
- h blas64.General
- )
+ // Compute the matrix H explicitly as H := I - tau * v * v^T.
+ var h blas64.General
if side == blas.Left {
- v = randomSlice(m, rnd)
h = eye(m, m+extra)
} else {
- v = randomSlice(n, rnd)
h = eye(n, n+extra)
}
blas64.Ger(-tau, blas64.Vector{Inc: 1, Data: v}, blas64.Vector{Inc: 1, Data: v}, h)
+
+ // Compute the product H * C or C * H explicitly.
+ cWant := nanGeneral(m, n, ldc)
if side == blas.Left {
blas64.Gemm(blas.NoTrans, blas.NoTrans, 1, h, c, 0, cWant)
} else {
