| // 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 gonum |
| |
| import ( |
| "gonum.org/v1/gonum/blas" |
| "gonum.org/v1/gonum/blas/blas64" |
| ) |
| |
| // Dorgl2 generates an m×n matrix Q with orthonormal rows defined by the |
| // first m rows product of elementary reflectors as computed by Dgelqf. |
| // Q = H_0 * H_1 * ... * H_{k-1} |
| // len(tau) >= k, 0 <= k <= m, 0 <= m <= n, len(work) >= m. |
| // Dorgl2 will panic if these conditions are not met. |
| // |
| // Dorgl2 is an internal routine. It is exported for testing purposes. |
| func (impl Implementation) Dorgl2(m, n, k int, a []float64, lda int, tau, work []float64) { |
| checkMatrix(m, n, a, lda) |
| if len(tau) < k { |
| panic(badTau) |
| } |
| if k > m { |
| panic(kGTM) |
| } |
| if k > m { |
| panic(kGTM) |
| } |
| if m > n { |
| panic(nLTM) |
| } |
| if len(work) < m { |
| panic(badWork) |
| } |
| if m == 0 { |
| return |
| } |
| bi := blas64.Implementation() |
| if k < m { |
| for i := k; i < m; i++ { |
| for j := 0; j < n; j++ { |
| a[i*lda+j] = 0 |
| } |
| } |
| for j := k; j < m; j++ { |
| a[j*lda+j] = 1 |
| } |
| } |
| for i := k - 1; i >= 0; i-- { |
| if i < n-1 { |
| if i < m-1 { |
| a[i*lda+i] = 1 |
| impl.Dlarf(blas.Right, m-i-1, n-i, a[i*lda+i:], 1, tau[i], a[(i+1)*lda+i:], lda, work) |
| } |
| bi.Dscal(n-i-1, -tau[i], a[i*lda+i+1:], 1) |
| } |
| a[i*lda+i] = 1 - tau[i] |
| for l := 0; l < i; l++ { |
| a[i*lda+l] = 0 |
| } |
| } |
| } |