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62 lines
1.3 KiB
Go
62 lines
1.3 KiB
Go
// Copyright ©2015 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 (
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"github.com/gonum/blas"
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"github.com/gonum/blas/blas64"
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)
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// Dorgl2 generates an m×n matrix Q with orthonormal rows defined by the
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// first m rows product of elementary reflectors as computed by Dgelqf.
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// Q = H(0) * H(2) * ... * H(k-1)
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// len(tau) >= k, 0 <= k <= m, 0 <= m <= n, len(work) >= m.
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// Dorgl2 will panic if these conditions are not met.
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func (impl Implementation) Dorgl2(m, n, k int, a []float64, lda int, tau, work []float64) {
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checkMatrix(m, n, a, lda)
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if len(tau) < k {
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panic(badTau)
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}
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if k > m {
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panic(kGTM)
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}
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if k > m {
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panic(kGTM)
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}
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if m > n {
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panic(nLTM)
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}
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if len(work) < m {
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panic(badWork)
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}
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if m == 0 {
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return
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}
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bi := blas64.Implementation()
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if k < m {
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for i := k; i < m; i++ {
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for j := 0; j < n; j++ {
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a[i*lda+j] = 0
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}
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}
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for j := k; j < m; j++ {
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a[j*lda+j] = 1
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}
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}
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for i := k - 1; i >= 0; i-- {
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if i < n-1 {
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if i < m-1 {
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a[i*lda+i] = 1
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impl.Dlarf(blas.Right, m-i-1, n-i, a[i*lda+i:], 1, tau[i], a[(i+1)*lda+i:], lda, work)
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}
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bi.Dscal(n-i-1, -tau[i], a[i*lda+i+1:], 1)
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}
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a[i*lda+i] = 1 - tau[i]
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for l := 0; l < i; l++ {
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a[i*lda+l] = 0
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}
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}
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}
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