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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) } } } }