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// Copyright ©2016 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"
"gonum.org/v1/gonum/blas"
"gonum.org/v1/gonum/blas/blas64"
)
type Dlacn2er interface {
Dlacn2(n int, v, x []float64, isgn []int, est float64, kase int, isave *[3]int) (float64, int)
}
func Dlacn2Test(t *testing.T, impl Dlacn2er) {
rnd := rand.New(rand.NewSource(1))
for _, n := range []int{1, 2, 3, 4, 5, 7, 10, 15, 20, 100} {
for cas := 0; cas < 10; cas++ {
a := randomGeneral(n, n, n, rnd)
// Compute the 1-norm of A explicitly.
var norm1 float64
for j := 0; j < n; j++ {
var sum float64
for i := 0; i < n; i++ {
sum += math.Abs(a.Data[i*a.Stride+j])
}
if sum > norm1 {
norm1 = sum
}
}
// Compute the estimate of 1-norm using Dlanc2.
x := make([]float64, n)
work := make([]float64, n)
v := make([]float64, n)
isgn := make([]int, n)
var (
kase int
isave [3]int
got float64
)
loop:
for {
got, kase = impl.Dlacn2(n, v, x, isgn, got, kase, &isave)
switch kase {
default:
panic("Dlacn2 returned invalid value of kase")
case 0:
break loop
case 1:
blas64.Gemv(blas.NoTrans, 1, a, blas64.Vector{Data: x, Inc: 1}, 0, blas64.Vector{Data: work, Inc: 1})
copy(x, work)
case 2:
blas64.Gemv(blas.Trans, 1, a, blas64.Vector{Data: x, Inc: 1}, 0, blas64.Vector{Data: work, Inc: 1})
copy(x, work)
}
}
// Check that got is either accurate enough or a
// lower estimate of the 1-norm of A.
if math.Abs(got-norm1) > 1e-8 && got > norm1 {
t.Errorf("Case n=%v: not lower estimate. 1-norm %v, estimate %v", n, norm1, got)
}
}
}
}
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