diff --git a/native/dormhr.go b/native/dormhr.go new file mode 100644 index 00000000..28ba0796 --- /dev/null +++ b/native/dormhr.go @@ -0,0 +1,117 @@ +// Copyright ©2016 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 native + +import "github.com/gonum/blas" + +// Dormhr multiplies an m×n general matrix C with an nq×nq orthogonal matrix Q +// Q * C, if side == blas.Left and trans == blas.NoTrans, +// Q^T * C, if side == blas.Left and trans == blas.Trans, +// C * Q, if side == blas.Right and trans == blas.NoTrans, +// C * Q^T, if side == blas.Right and trans == blas.Trans, +// where nq == m if side == blas.Left and nq == n if side == blas.Right. +// +// Q is defined implicitly as the product of ihi-ilo elementary reflectors, as +// returned by Dgehrd: +// Q = H_{ilo} H_{ilo+1} ... H_{ihi-1}. +// Q is equal to the identity matrix except in the submatrix +// Q[ilo+1:ihi+1,ilo+1:ihi+1]. +// +// ilo and ihi must have the same values as in the previous call of Dgehrd. It +// must hold that +// 0 <= ilo <= ihi < m, if m > 0 and side == blas.Left, +// ilo = 0 and ihi = -1, if m = 0 and side == blas.Left, +// 0 <= ilo <= ihi < n, if n > 0 and side == blas.Right, +// ilo = 0 and ihi = -1, if n = 0 and side == blas.Right. +// +// a and lda represent an m×m matrix if side == blas.Left and an n×n matrix if +// side == blas.Right. The matrix contains vectors which define the elementary +// reflectors, as returned by Dgehrd. +// +// tau contains the scalar factors of the elementary reflectors, as returned by +// Dgehrd. tau must have length m-1 if side == blas.Left and n-1 if side == +// blas.Right. +// +// c and ldc represent the m×n matrix C. On return, c is overwritten by the +// product with Q. +// +// work must have length at least max(1,lwork), and lwork must be at least +// max(1,n), if side == blas.Left, and max(1,m), if side == blas.Right. For +// optimum performance lwork should be at least n*nb if side == blas.Left and +// m*nb if side == blas.Right, where nb is the optimal block size. On return, +// work[0] will contain the optimal value of lwork. +// +// If lwork == -1, instead of performing Dormhr, only the optimal value of lwork +// will be stored in work[0]. +// +// If any requirement on input sizes is not met, Dormhr will panic. +// +// Dormhr is an internal routine. It is exported for testing purposes. +func (impl Implementation) Dormhr(side blas.Side, trans blas.Transpose, m, n, ilo, ihi int, a []float64, lda int, tau, c []float64, ldc int, work []float64, lwork int) { + var ( + nq int // The order of Q. + nw int // The minimum length of work. + ) + switch side { + case blas.Left: + nq = m + nw = n + case blas.Right: + nq = n + nw = m + default: + panic(badSide) + } + checkMatrix(m, n, c, ldc) + checkMatrix(nq, nq, a, lda) + switch { + case trans != blas.NoTrans && trans != blas.Trans: + panic(badTrans) + case ilo < 0 || max(1, nq) <= ilo: + panic(badIlo) + case ihi < min(ilo, nq-1) || nq <= ihi: + panic(badIhi) + case nq > 0 && len(tau) != nq-1: + panic(badTau) + case lwork < max(1, nw) && lwork != -1: + panic(badWork) + case len(work) < max(1, lwork): + panic(shortWork) + } + + nh := ihi - ilo + var nb int + if side == blas.Left { + opts := "LN" + if trans == blas.Trans { + opts = "LT" + } + nb = impl.Ilaenv(1, "DORMQR", opts, nh, n, nh, -1) + } else { + opts := "RN" + if trans == blas.Trans { + opts = "RT" + } + nb = impl.Ilaenv(1, "DORMQR", opts, m, nh, nh, -1) + } + lwkopt := max(1, nw) * nb + if lwork == -1 { + work[0] = float64(lwkopt) + return + } + + if m == 0 || n == 0 || nh == 0 { + work[0] = 1 + return + } + if side == blas.Left { + impl.Dormqr(side, trans, nh, n, nh, a[(ilo+1)*lda+ilo:], lda, + tau[ilo:ihi], c[(ilo+1)*ldc:], ldc, work, lwork) + } else { + impl.Dormqr(side, trans, m, nh, nh, a[(ilo+1)*lda+ilo:], lda, + tau[ilo:ihi], c[ilo+1:], ldc, work, lwork) + } + work[0] = float64(lwkopt) +}