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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"
"gonum.org/v1/gonum/floats"
)
type Drscler interface {
Drscl(n int, a float64, x []float64, incX int)
}
func DrsclTest(t *testing.T, impl Drscler) {
for _, test := range []struct {
x []float64
a float64
}{
{
x: []float64{1, 2, 3, 4, 5},
a: 4,
},
{
x: []float64{1, 2, 3, 4, 5},
a: math.MaxFloat64,
},
{
x: []float64{1, 2, 3, 4, 5},
a: 1e-307,
},
} {
xcopy := make([]float64, len(test.x))
copy(xcopy, test.x)
// Cannot test the scaling directly because of floating point scaling issues
// (the purpose of Drscl). Instead, check that scaling and scaling back
// yields approximately x. If overflow or underflow occurs then the scaling
// won't match.
impl.Drscl(len(test.x), test.a, xcopy, 1)
if floats.Equal(xcopy, test.x) {
t.Errorf("x unchanged during call to drscl. a = %v, x = %v.", test.a, test.x)
}
impl.Drscl(len(test.x), 1/test.a, xcopy, 1)
if !floats.EqualApprox(xcopy, test.x, 1e-14) {
t.Errorf("x not equal after scaling and unscaling. a = %v, x = %v.", test.a, test.x)
}
}
}
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