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73 lines
1.4 KiB
Go
73 lines
1.4 KiB
Go
// Copyright ©2017 The gonum Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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package native
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import "gonum.org/v1/gonum/blas/blas64"
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// Dlapmt rearranges the columns of the m×n matrix X as specified by the
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// permutation k_0, k_1, ..., k_n-1 of the integers 0, ..., n-1.
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//
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// If forward is true a forward permutation is performed:
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//
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// X[0:m, k[j]] is moved to X[0:m, j] for j = 0, 1, ..., n-1.
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//
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// otherwise a backward permutation is performed:
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//
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// X[0:m, j] is moved to X[0:m, k[j]] for j = 0, 1, ..., n-1.
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//
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// k must have length n, otherwise Dlapmt will panic. k is zero-indexed.
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func (impl Implementation) Dlapmt(forward bool, m, n int, x []float64, ldx int, k []int) {
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checkMatrix(m, n, x, ldx)
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if len(k) != n {
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panic(badKperm)
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}
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if n <= 1 {
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return
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}
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for i, v := range k {
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v++
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k[i] = -v
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}
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bi := blas64.Implementation()
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if forward {
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for j, v := range k {
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if v >= 0 {
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continue
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}
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k[j] = -v
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i := -v - 1
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for k[i] < 0 {
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bi.Dswap(m, x[j:], ldx, x[i:], ldx)
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k[i] = -k[i]
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j = i
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i = k[i] - 1
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}
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}
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} else {
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for i, v := range k {
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if v >= 0 {
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continue
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}
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k[i] = -v
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j := -v - 1
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for j != i {
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bi.Dswap(m, x[j:], ldx, x[i:], ldx)
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k[j] = -k[j]
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j = k[j] - 1
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}
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}
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}
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for i := range k {
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k[i]--
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}
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}
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