table of contents
/home/abuild/rpmbuild/BUILD/lapack-3.12.0/SRC/dormbr.f(3) | Library Functions Manual | /home/abuild/rpmbuild/BUILD/lapack-3.12.0/SRC/dormbr.f(3) |
NAME¶
/home/abuild/rpmbuild/BUILD/lapack-3.12.0/SRC/dormbr.f
SYNOPSIS¶
Functions/Subroutines¶
subroutine DORMBR (vect, side, trans, m, n, k, a, lda, tau,
c, ldc, work, lwork, info)
DORMBR
Function/Subroutine Documentation¶
subroutine DORMBR (character vect, character side, character trans, integer m, integer n, integer k, double precision, dimension( lda, * ) a, integer lda, double precision, dimension( * ) tau, double precision, dimension( ldc, * ) c, integer ldc, double precision, dimension( * ) work, integer lwork, integer info)¶
DORMBR
Purpose:
!> !> If VECT = 'Q', DORMBR overwrites the general real M-by-N matrix C !> with !> SIDE = 'L' SIDE = 'R' !> TRANS = 'N': Q * C C * Q !> TRANS = 'T': Q**T * C C * Q**T !> !> If VECT = 'P', DORMBR overwrites the general real M-by-N matrix C !> with !> SIDE = 'L' SIDE = 'R' !> TRANS = 'N': P * C C * P !> TRANS = 'T': P**T * C C * P**T !> !> Here Q and P**T are the orthogonal matrices determined by DGEBRD when !> reducing a real matrix A to bidiagonal form: A = Q * B * P**T. Q and !> P**T are defined as products of elementary reflectors H(i) and G(i) !> respectively. !> !> Let nq = m if SIDE = 'L' and nq = n if SIDE = 'R'. Thus nq is the !> order of the orthogonal matrix Q or P**T that is applied. !> !> If VECT = 'Q', A is assumed to have been an NQ-by-K matrix: !> if nq >= k, Q = H(1) H(2) . . . H(k); !> if nq < k, Q = H(1) H(2) . . . H(nq-1). !> !> If VECT = 'P', A is assumed to have been a K-by-NQ matrix: !> if k < nq, P = G(1) G(2) . . . G(k); !> if k >= nq, P = G(1) G(2) . . . G(nq-1). !>
Parameters
VECT
!> VECT is CHARACTER*1 !> = 'Q': apply Q or Q**T; !> = 'P': apply P or P**T. !>
SIDE
!> SIDE is CHARACTER*1 !> = 'L': apply Q, Q**T, P or P**T from the Left; !> = 'R': apply Q, Q**T, P or P**T from the Right. !>
TRANS
!> TRANS is CHARACTER*1 !> = 'N': No transpose, apply Q or P; !> = 'T': Transpose, apply Q**T or P**T. !>
M
!> M is INTEGER !> The number of rows of the matrix C. M >= 0. !>
N
!> N is INTEGER !> The number of columns of the matrix C. N >= 0. !>
K
!> K is INTEGER !> If VECT = 'Q', the number of columns in the original !> matrix reduced by DGEBRD. !> If VECT = 'P', the number of rows in the original !> matrix reduced by DGEBRD. !> K >= 0. !>
A
!> A is DOUBLE PRECISION array, dimension !> (LDA,min(nq,K)) if VECT = 'Q' !> (LDA,nq) if VECT = 'P' !> The vectors which define the elementary reflectors H(i) and !> G(i), whose products determine the matrices Q and P, as !> returned by DGEBRD. !>
LDA
!> LDA is INTEGER !> The leading dimension of the array A. !> If VECT = 'Q', LDA >= max(1,nq); !> if VECT = 'P', LDA >= max(1,min(nq,K)). !>
TAU
!> TAU is DOUBLE PRECISION array, dimension (min(nq,K)) !> TAU(i) must contain the scalar factor of the elementary !> reflector H(i) or G(i) which determines Q or P, as returned !> by DGEBRD in the array argument TAUQ or TAUP. !>
C
!> C is DOUBLE PRECISION array, dimension (LDC,N) !> On entry, the M-by-N matrix C. !> On exit, C is overwritten by Q*C or Q**T*C or C*Q**T or C*Q !> or P*C or P**T*C or C*P or C*P**T. !>
LDC
!> LDC is INTEGER !> The leading dimension of the array C. LDC >= max(1,M). !>
WORK
!> WORK is DOUBLE PRECISION array, dimension (MAX(1,LWORK)) !> On exit, if INFO = 0, WORK(1) returns the optimal LWORK. !>
LWORK
!> LWORK is INTEGER !> The dimension of the array WORK. !> If SIDE = 'L', LWORK >= max(1,N); !> if SIDE = 'R', LWORK >= max(1,M). !> For optimum performance LWORK >= N*NB if SIDE = 'L', and !> LWORK >= M*NB if SIDE = 'R', where NB is the optimal !> blocksize. !> !> If LWORK = -1, then a workspace query is assumed; the routine !> only calculates the optimal size of the WORK array, returns !> this value as the first entry of the WORK array, and no error !> message related to LWORK is issued by XERBLA. !>
INFO
!> INFO is INTEGER !> = 0: successful exit !> < 0: if INFO = -i, the i-th argument had an illegal value !>
Author
Univ. of Tennessee
Univ. of California Berkeley
Univ. of Colorado Denver
NAG Ltd.
Definition at line 193 of file dormbr.f.
Author¶
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