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89 lines
2.4 KiB
Go
89 lines
2.4 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 "gonum.org/v1/gonum/blas"
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// Dorm2r multiplies a general matrix C by an orthogonal matrix from a QR factorization
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// determined by Dgeqrf.
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// C = Q * C if side == blas.Left and trans == blas.NoTrans
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// C = Q^T * C if side == blas.Left and trans == blas.Trans
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// C = C * Q if side == blas.Right and trans == blas.NoTrans
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// C = C * Q^T if side == blas.Right and trans == blas.Trans
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// If side == blas.Left, a is a matrix of size m×k, and if side == blas.Right
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// a is of size n×k.
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//
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// tau contains the Householder factors and is of length at least k and this function
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// will panic otherwise.
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//
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// work is temporary storage of length at least n if side == blas.Left
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// and at least m if side == blas.Right and this function will panic otherwise.
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//
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// Dorm2r is an internal routine. It is exported for testing purposes.
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func (impl Implementation) Dorm2r(side blas.Side, trans blas.Transpose, m, n, k int, a []float64, lda int, tau, c []float64, ldc int, work []float64) {
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if side != blas.Left && side != blas.Right {
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panic(badSide)
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}
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if trans != blas.Trans && trans != blas.NoTrans {
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panic(badTrans)
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}
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left := side == blas.Left
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notran := trans == blas.NoTrans
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if left {
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// Q is m x m
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checkMatrix(m, k, a, lda)
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if len(work) < n {
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panic(badWork)
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}
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} else {
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// Q is n x n
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checkMatrix(n, k, a, lda)
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if len(work) < m {
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panic(badWork)
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}
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}
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checkMatrix(m, n, c, ldc)
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if m == 0 || n == 0 || k == 0 {
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return
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}
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if len(tau) < k {
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panic(badTau)
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}
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if left {
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if notran {
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for i := k - 1; i >= 0; i-- {
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aii := a[i*lda+i]
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a[i*lda+i] = 1
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impl.Dlarf(side, m-i, n, a[i*lda+i:], lda, tau[i], c[i*ldc:], ldc, work)
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a[i*lda+i] = aii
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}
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return
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}
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for i := 0; i < k; i++ {
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aii := a[i*lda+i]
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a[i*lda+i] = 1
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impl.Dlarf(side, m-i, n, a[i*lda+i:], lda, tau[i], c[i*ldc:], ldc, work)
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a[i*lda+i] = aii
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}
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return
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}
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if notran {
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for i := 0; i < k; i++ {
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aii := a[i*lda+i]
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a[i*lda+i] = 1
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impl.Dlarf(side, m, n-i, a[i*lda+i:], lda, tau[i], c[i:], ldc, work)
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a[i*lda+i] = aii
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}
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return
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}
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for i := k - 1; i >= 0; i-- {
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aii := a[i*lda+i]
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a[i*lda+i] = 1
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impl.Dlarf(side, m, n-i, a[i*lda+i:], lda, tau[i], c[i:], ldc, work)
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a[i*lda+i] = aii
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}
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}
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