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// Copyright ©2017 The Gonum Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package testlapack
import (
"testing"
"golang.org/x/exp/rand"
"gonum.org/v1/gonum/floats/scalar"
"gonum.org/v1/gonum/lapack"
)
type Dlapller interface {
Dgesvder
Dlapll(n int, x []float64, incX int, y []float64, incY int) float64
}
func DlapllTest(t *testing.T, impl Dlapller) {
rnd := rand.New(rand.NewSource(1))
for i, m := range []int{5, 6, 9, 300, 400, 600} {
n := 2
lda := n
// Allocate m×2 matrix A and fill it with random numbers.
a := make([]float64, m*lda)
for i := range a {
a[i] = rnd.NormFloat64()
}
// Store a copy of A for later comparison.
aCopy := make([]float64, len(a))
copy(aCopy, a)
// Compute the smallest singular value of A.
got := impl.Dlapll(m, a[0:], lda, a[1:], lda)
// Compute singular values of A independently by Dgesvd.
s := make([]float64, min(m, n))
work := make([]float64, 1)
impl.Dgesvd(lapack.SVDNone, lapack.SVDNone, m, n, aCopy, lda, s, nil, 1, nil, 1, work, -1)
work = make([]float64, int(work[0]))
impl.Dgesvd(lapack.SVDNone, lapack.SVDNone, m, n, aCopy, lda, s, nil, 1, nil, 1, work, len(work))
// Take the smallest singular value.
want := s[len(s)-1]
if !scalar.EqualWithinAbsOrRel(got, want, 1e-14, 1e-14) {
t.Errorf("Case %d: unexpected smallest singular value, got:%f want:%f", i, got, want)
}
}
}
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