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dgeqp3.go
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/
dgeqp3.go
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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 (
"testing"
"golang.org/x/exp/rand"
"gonum.org/v1/gonum/blas"
"gonum.org/v1/gonum/blas/blas64"
)
type Dgeqp3er interface {
Dlapmter
Dgeqp3(m, n int, a []float64, lda int, jpvt []int, tau, work []float64, lwork int)
}
func Dgeqp3Test(t *testing.T, impl Dgeqp3er) {
rnd := rand.New(rand.NewSource(1))
for c, test := range []struct {
m, n, lda int
}{
{1, 1, 0},
{2, 2, 0},
{3, 2, 0},
{2, 3, 0},
{1, 12, 0},
{2, 6, 0},
{3, 4, 0},
{4, 3, 0},
{6, 2, 0},
{12, 1, 0},
{1, 1, 20},
{2, 2, 20},
{3, 2, 20},
{2, 3, 20},
{1, 12, 20},
{2, 6, 20},
{3, 4, 20},
{4, 3, 20},
{6, 2, 20},
{12, 1, 20},
{129, 256, 0},
{256, 129, 0},
{129, 256, 266},
{256, 129, 266},
} {
n := test.n
m := test.m
lda := test.lda
if lda == 0 {
lda = test.n
}
const (
all = iota
some
none
)
for _, free := range []int{all, some, none} {
// Allocate m×n matrix A and fill it with random numbers.
a := make([]float64, m*lda)
for i := range a {
a[i] = rnd.Float64()
}
// Store a copy of A for later comparison.
aCopy := make([]float64, len(a))
copy(aCopy, a)
// Allocate a slice of column pivots.
jpvt := make([]int, n)
for j := range jpvt {
switch free {
case all:
// All columns are free.
jpvt[j] = -1
case some:
// Some columns are free, some are leading columns.
jpvt[j] = rnd.Intn(2) - 1 // -1 or 0
case none:
// All columns are leading.
jpvt[j] = 0
default:
panic("bad freedom")
}
}
// Allocate a slice for scalar factors of elementary
// reflectors and fill it with random numbers. Dgeqp3
// will overwrite them with valid data.
k := min(m, n)
tau := make([]float64, k)
for i := range tau {
tau[i] = rnd.Float64()
}
// Get optimal workspace size for Dgeqp3.
work := make([]float64, 1)
impl.Dgeqp3(m, n, a, lda, jpvt, tau, work, -1)
lwork := int(work[0])
work = make([]float64, lwork)
for i := range work {
work[i] = rnd.Float64()
}
// Compute a QR factorization of A with column pivoting.
impl.Dgeqp3(m, n, a, lda, jpvt, tau, work, lwork)
// Compute Q based on the elementary reflectors stored in A.
q := constructQ("QR", m, n, a, lda, tau)
// Check that Q is orthogonal.
if !isOrthogonal(q) {
t.Errorf("Case %v, Q not orthogonal", c)
}
// Copy the upper triangle of A into R.
r := blas64.General{
Rows: m,
Cols: n,
Stride: n,
Data: make([]float64, m*n),
}
for i := 0; i < m; i++ {
for j := i; j < n; j++ {
r.Data[i*n+j] = a[i*lda+j]
}
}
// Compute Q * R.
got := nanGeneral(m, n, lda)
blas64.Gemm(blas.NoTrans, blas.NoTrans, 1, q, r, 0, got)
// Compute A * P: rearrange the columns of A based on the permutation in jpvt.
want := blas64.General{Rows: m, Cols: n, Stride: lda, Data: aCopy}
impl.Dlapmt(true, want.Rows, want.Cols, want.Data, want.Stride, jpvt)
// Check that A * P = Q * R.
if !equalApproxGeneral(got, want, 1e-13) {
t.Errorf("Case %v, Q*R != A*P\nQ*R=%v\nA*P=%v", c, got, want)
}
}
}
}