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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 ( "math" "testing" "golang.org/x/exp/rand" ) type Dlaev2er interface { Dlaev2(a, b, c float64) (rt1, rt2, cs1, sn1 float64) } func Dlaev2Test(t *testing.T, impl Dlaev2er) { rnd := rand.New(rand.NewSource(1)) for trial := 0; trial < 100; trial++ { a := rnd.NormFloat64() b := rnd.NormFloat64() c := rnd.NormFloat64() rt1, rt2, cs1, sn1 := impl.Dlaev2(a, b, c) tmp := mul2by2([2][2]float64{{cs1, sn1}, {-sn1, cs1}}, [2][2]float64{{a, b}, {b, c}}) ans := mul2by2(tmp, [2][2]float64{{cs1, -sn1}, {sn1, cs1}}) if math.Abs(ans[0][0]-rt1) > 1e-14 { t.Errorf("Largest eigenvalue mismatch. Returned %v, mul %v", rt1, ans[0][0]) } if math.Abs(ans[1][0]) > 1e-14 || math.Abs(ans[0][1]) > 1e-14 { t.Errorf("Non-zero off diagonal. ans[1][0] = %v, ans[0][1] = %v", ans[1][0], ans[0][1]) } if math.Abs(ans[1][1]-rt2) > 1e-14 { t.Errorf("Smallest eigenvalue mismatch. Returned %v, mul %v", rt2, ans[1][1]) } } } func mul2by2(a, b [2][2]float64) [2][2]float64 { var c [2][2]float64 c[0][0] = a[0][0]*b[0][0] + a[0][1]*b[1][0] c[0][1] = a[0][0]*b[0][1] + a[0][1]*b[1][1] c[1][0] = a[1][0]*b[0][0] + a[1][1]*b[1][0] c[1][1] = a[1][0]*b[0][1] + a[1][1]*b[1][1] return c }