dormhr3
Part of dormhr.f(3).
Usage
Functions/Subroutines
subroutine dormhr (side, trans, m, n, ilo, ihi, a, lda, tau, c, ldc, work, lwork, info)
DORMHR
Function/Subroutine Documentation
subroutine dormhr (character side, character trans, integer m, integer n, integer ilo, integer ihi, 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)
DORMHR
Purpose:
!> !> DORMHR 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 !> !> where Q is a real orthogonal matrix of order nq, with nq = m if !> SIDE = 'L' and nq = n if SIDE = 'R'. Q is defined as the product of !> IHI-ILO elementary reflectors, as returned by DGEHRD: !> !> Q = H(ilo) H(ilo+1) . . . H(ihi-1). !>
Parameters
SIDE
!> SIDE is CHARACTER*1 !> = 'L': apply Q or Q**T from the Left; !> = 'R': apply Q or Q**T from the Right. !>
TRANS
!> TRANS is CHARACTER*1 !> = 'N': No transpose, apply Q; !> = 'T': Transpose, apply Q**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. !>
ILO
!> ILO is INTEGER !>
IHI
!> IHI is INTEGER !> !> ILO and IHI must have the same values as in the previous call !> of DGEHRD. Q is equal to the unit matrix except in the !> submatrix Q(ilo+1:ihi,ilo+1:ihi). !> If SIDE = 'L', then 1 <= ILO <= IHI <= M, if M > 0, and !> ILO = 1 and IHI = 0, if M = 0; !> if SIDE = 'R', then 1 <= ILO <= IHI <= N, if N > 0, and !> ILO = 1 and IHI = 0, if N = 0. !>
A
!> A is DOUBLE PRECISION array, dimension !> (LDA,M) if SIDE = 'L' !> (LDA,N) if SIDE = 'R' !> The vectors which define the elementary reflectors, as !> returned by DGEHRD. !>
LDA
!> LDA is INTEGER !> The leading dimension of the array A. !> LDA >= max(1,M) if SIDE = 'L'; LDA >= max(1,N) if SIDE = 'R'. !>
TAU
!> TAU is DOUBLE PRECISION array, dimension !> (M-1) if SIDE = 'L' !> (N-1) if SIDE = 'R' !> TAU(i) must contain the scalar factor of the elementary !> reflector H(i), as returned by DGEHRD. !>
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. !>
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 176 of file dormhr.f.
Releases
14 releases since Debian 1.3 (Bo); the text changed 11 times.