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// Copyright ©2015 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"
)
type Dlasv2er interface {
Dlasv2(f, g, h float64) (ssmin, ssmax, snr, csr, snl, csl float64)
}
func Dlasv2Test(t *testing.T, impl Dlasv2er) {
rnd := rand.New(rand.NewSource(1))
for i := 0; i < 100; i++ {
f := rnd.NormFloat64()
g := rnd.NormFloat64()
h := rnd.NormFloat64()
ssmin, ssmax, snr, csr, snl, csl := impl.Dlasv2(f, g, h)
// tmp =
// [ csl snl] [f g]
// [-snl csl] [0 h]
tmp11 := csl * f
tmp12 := csl*g + snl*h
tmp21 := -snl * f
tmp22 := -snl*g + csl*h
// lhs =
// [tmp11 tmp12] [csr -snr]
// [tmp21 tmp22] [snr csr]
ans11 := tmp11*csr + tmp12*snr
ans12 := tmp11*-snr + tmp12*csr
ans21 := tmp21*csr + tmp22*snr
ans22 := tmp21*-snr + tmp22*csr
lhs := []float64{ans11, ans12, ans21, ans22}
rhs := []float64{ssmax, 0, 0, ssmin}
if !floats.EqualApprox(rhs, lhs, 1e-12) {
t.Errorf("SVD mismatch. f = %v, g = %v, h = %v.\nLHS: %v\nRHS: %v", f, g, h, lhs, rhs)
}
}
}
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