lapack/testlapack: add implementation comments to Dlanst test
@@ -23,15 +23,19 @@ func DlanstTest(t *testing.T, impl Dlanster) {
for _, norm := range []lapack.MatrixNorm{lapack.MaxAbs, lapack.MaxColumnSum, lapack.MaxRowSum, lapack.Frobenius} {
for _, n := range []int{1, 3, 10, 100} {
for cas := 0; cas < 100; cas++ {
+ // Generate randomly the main diagonal of the
+ // symmetric tridiagonal matrix A.
d := make([]float64, n)
for i := range d {
d[i] = rnd.NormFloat64()
}
+ // Generate randomly the off-diagonal of A.
e := make([]float64, n-1)
for i := range e {
e[i] = rnd.NormFloat64()
}
+ // Create A in dense representation.
m := n
lda := n
a := make([]float64, m*lda)
@@ -42,8 +46,12 @@ func DlanstTest(t *testing.T, impl Dlanster) {
a[i*lda+i+1] = e[i]
a[(i+1)*lda+i] = e[i]
}
+
work := make([]float64, n)
+ // Compute a norm of A using Dlanst.
syNorm := impl.Dlanst(norm, n, d, e)
+ // Compute a reference value for the norm using
+ // Dlange and the dense representation of A.
geNorm := impl.Dlange(norm, m, n, a, lda, work)
if math.Abs(syNorm-geNorm) > 1e-12 {
t.Errorf("Norm mismatch: norm = %v, cas = %v, n = %v. Want %v, got %v.", string(norm), cas, n, geNorm, syNorm)
