gonum.org/v1/gonum@v0.14.0/lapack/testlapack/dlapmr.go (about)

     1  // Copyright ©2022 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  	"fmt"
     9  	"testing"
    10  
    11  	"golang.org/x/exp/rand"
    12  	"gonum.org/v1/gonum/blas"
    13  	"gonum.org/v1/gonum/blas/blas64"
    14  )
    15  
    16  type Dlapmrer interface {
    17  	Dlapmr(forwrd bool, m, n int, x []float64, ldx int, k []int)
    18  }
    19  
    20  func DlapmrTest(t *testing.T, impl Dlapmrer) {
    21  	rnd := rand.New(rand.NewSource(1))
    22  	for _, fwd := range []bool{true, false} {
    23  		for _, m := range []int{0, 1, 2, 3, 4, 5, 10} {
    24  			for _, n := range []int{0, 1, 4} {
    25  				for _, ldx := range []int{max(1, n), n + 3} {
    26  					dlapmrTest(t, impl, rnd, fwd, m, n, ldx)
    27  				}
    28  			}
    29  		}
    30  	}
    31  }
    32  
    33  func dlapmrTest(t *testing.T, impl Dlapmrer, rnd *rand.Rand, fwd bool, m, n, ldx int) {
    34  	name := fmt.Sprintf("forwrd=%v,m=%d,n=%d,ldx=%d", fwd, m, n, ldx)
    35  
    36  	bi := blas64.Implementation()
    37  
    38  	// Generate a random permutation and simultaneously apply it to the rows of the identity matrix.
    39  	k := make([]int, m)
    40  	for i := range k {
    41  		k[i] = i
    42  	}
    43  	p := eye(m, m)
    44  	for i := 0; i < m-1; i++ {
    45  		j := i + rnd.Intn(m-i)
    46  		k[i], k[j] = k[j], k[i]
    47  		bi.Dswap(m, p.Data[i*p.Stride:], 1, p.Data[j*p.Stride:], 1)
    48  	}
    49  	kCopy := make([]int, len(k))
    50  	copy(kCopy, k)
    51  
    52  	// Generate a random matrix X.
    53  	x := randomGeneral(m, n, ldx, rnd)
    54  
    55  	// Applying the permutation k with Dlapmr is the same as multiplying X with P or Pᵀ from the left:
    56  	//  - forward permutation:  P * X
    57  	//  - backward permutation: Pᵀ* X
    58  	trans := blas.NoTrans
    59  	if !fwd {
    60  		trans = blas.Trans
    61  	}
    62  	want := zeros(m, n, n)
    63  	bi.Dgemm(trans, blas.NoTrans, m, n, m, 1, p.Data, p.Stride, x.Data, x.Stride, 0, want.Data, want.Stride)
    64  
    65  	// Apply the permutation in k to X.
    66  	impl.Dlapmr(fwd, m, n, x.Data, x.Stride, k)
    67  	got := x
    68  
    69  	// Check that k hasn't been modified in Dlapmr.
    70  	var kmod bool
    71  	for i, ki := range k {
    72  		if ki != kCopy[i] {
    73  			kmod = true
    74  			break
    75  		}
    76  	}
    77  	if kmod {
    78  		t.Errorf("%s: unexpected modification of k", name)
    79  	}
    80  
    81  	// Check that Dlapmr yields the same result as multiplication with P.
    82  	if !equalGeneral(got, want) {
    83  		t.Errorf("%s: unexpected result", name)
    84  	}
    85  }