mirror of
https://github.com/gonum/gonum.git
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17ea55aedb
Apply (with manual curation after the fact):
* s/^T/U+1d40/g
* s/^H/U+1d34/g
* s/, {2,3}if / $1/g
Some additional manual editing of odd formatting.
102 lines
2.7 KiB
Go
102 lines
2.7 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 gonum
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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 = Qᵀ * 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 * Qᵀ 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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left := side == blas.Left
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switch {
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case !left && side != blas.Right:
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panic(badSide)
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case trans != blas.Trans && trans != blas.NoTrans:
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panic(badTrans)
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case m < 0:
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panic(mLT0)
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case n < 0:
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panic(nLT0)
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case k < 0:
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panic(kLT0)
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case left && k > m:
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panic(kGTM)
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case !left && k > n:
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panic(kGTN)
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case lda < max(1, k):
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panic(badLdA)
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case ldc < max(1, n):
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panic(badLdC)
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}
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// Quick return if possible.
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if m == 0 || n == 0 || k == 0 {
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return
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}
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switch {
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case left && len(a) < (m-1)*lda+k:
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panic(shortA)
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case !left && len(a) < (n-1)*lda+k:
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panic(shortA)
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case len(c) < (m-1)*ldc+n:
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panic(shortC)
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case len(tau) < k:
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panic(shortTau)
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case left && len(work) < n:
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panic(shortWork)
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case !left && len(work) < m:
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panic(shortWork)
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}
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if left {
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if trans == blas.NoTrans {
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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 trans == blas.NoTrans {
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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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