SRC/zungql.f(3) | Library Functions Manual | SRC/zungql.f(3) |
NAME
SRC/zungql.f
SYNOPSIS
Functions/Subroutines
subroutine zungql (m, n, k, a, lda, tau, work, lwork, info)
ZUNGQL
Function/Subroutine Documentation
subroutine zungql (integer m, integer n, integer k, complex*16, dimension( lda, * ) a, integer lda, complex*16, dimension( * ) tau, complex*16, dimension( * ) work, integer lwork, integer info)
ZUNGQL
Purpose:
!> !> ZUNGQL generates an M-by-N complex matrix Q with orthonormal columns, !> which is defined as the last N columns of a product of K elementary !> reflectors of order M !> !> Q = H(k) . . . H(2) H(1) !> !> as returned by ZGEQLF. !>
Parameters
M
!> M is INTEGER !> The number of rows of the matrix Q. M >= 0. !>
N
!> N is INTEGER !> The number of columns of the matrix Q. M >= N >= 0. !>
K
!> K is INTEGER !> The number of elementary reflectors whose product defines the !> matrix Q. N >= K >= 0. !>
A
!> A is COMPLEX*16 array, dimension (LDA,N) !> On entry, the (n-k+i)-th column must contain the vector which !> defines the elementary reflector H(i), for i = 1,2,...,k, as !> returned by ZGEQLF in the last k columns of its array !> argument A. !> On exit, the M-by-N matrix Q. !>
LDA
!> LDA is INTEGER !> The first dimension of the array A. LDA >= max(1,M). !>
TAU
!> TAU is COMPLEX*16 array, dimension (K) !> TAU(i) must contain the scalar factor of the elementary !> reflector H(i), as returned by ZGEQLF. !>
WORK
!> WORK is COMPLEX*16 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. LWORK >= max(1,N). !> For optimum performance LWORK >= N*NB, 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 has an illegal value !>
Author
Univ. of Tennessee
Univ. of California Berkeley
Univ. of Colorado Denver
NAG Ltd.
Definition at line 127 of file zungql.f.
Author
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