| // 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" |
| "math/rand" |
| "testing" |
| ) |
| |
| 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 |
| } |
