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