vendor/gonum.org/v1/gonum/lapack/testlapack/dlacn2.go

   1 // Copyright ©2016 The Gonum Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style
   3 // license that can be found in the LICENSE file.
   4
   5 package testlapack
   6
   7 import (
   8         "math"
   9         "testing"
  10
  11         "golang.org/x/exp/rand"
  12
  13         "gonum.org/v1/gonum/blas"
  14         "gonum.org/v1/gonum/blas/blas64"
  15 )
  16
  17 type Dlacn2er interface {
  18         Dlacn2(n int, v, x []float64, isgn []int, est float64, kase int, isave *[3]int) (float64, int)
  19 }
  20
  21 func Dlacn2Test(t *testing.T, impl Dlacn2er) {
  22         rnd := rand.New(rand.NewSource(1))
  23         for _, n := range []int{1, 2, 3, 4, 5, 7, 10, 15, 20, 100} {
  24                 for cas := 0; cas < 10; cas++ {
  25                         a := randomGeneral(n, n, n, rnd)
  26
  27                         // Compute the 1-norm of A explicitly.
  28                         var norm1 float64
  29                         for j := 0; j < n; j++ {
  30                                 var sum float64
  31                                 for i := 0; i < n; i++ {
  32                                         sum += math.Abs(a.Data[i*a.Stride+j])
  33                                 }
  34                                 if sum > norm1 {
  35                                         norm1 = sum
  36                                 }
  37                         }
  38
  39                         // Compute the estimate of 1-norm using Dlanc2.
  40                         x := make([]float64, n)
  41                         work := make([]float64, n)
  42                         v := make([]float64, n)
  43                         isgn := make([]int, n)
  44                         var (
  45                                 kase  int
  46                                 isave [3]int
  47                                 got   float64
  48                         )
  49                 loop:
  50                         for {
  51                                 got, kase = impl.Dlacn2(n, v, x, isgn, got, kase, &isave)
  52                                 switch kase {
  53                                 default:
  54                                         panic("Dlacn2 returned invalid value of kase")
  55                                 case 0:
  56                                         break loop
  57                                 case 1:
  58                                         blas64.Gemv(blas.NoTrans, 1, a, blas64.Vector{1, x}, 0, blas64.Vector{1, work})
  59                                         copy(x, work)
  60                                 case 2:
  61                                         blas64.Gemv(blas.Trans, 1, a, blas64.Vector{1, x}, 0, blas64.Vector{1, work})
  62                                         copy(x, work)
  63                                 }
  64                         }
  65
  66                         // Check that got is either accurate enough or a
  67                         // lower estimate of the 1-norm of A.
  68                         if math.Abs(got-norm1) > 1e-8 && got > norm1 {
  69                                 t.Errorf("Case n=%v: not lower estimate. 1-norm %v, estimate %v", n, norm1, got)
  70                         }
  71                 }
  72         }
  73 }