table of contents
/home/abuild/rpmbuild/BUILD/lapack-3.12.0/SRC/zgeqlf.f(3) | Library Functions Manual | /home/abuild/rpmbuild/BUILD/lapack-3.12.0/SRC/zgeqlf.f(3) |
NAME¶
/home/abuild/rpmbuild/BUILD/lapack-3.12.0/SRC/zgeqlf.f
SYNOPSIS¶
Functions/Subroutines¶
subroutine ZGEQLF (m, n, a, lda, tau, work, lwork, info)
ZGEQLF
Function/Subroutine Documentation¶
subroutine ZGEQLF (integer m, integer n, complex*16, dimension( lda, * ) a, integer lda, complex*16, dimension( * ) tau, complex*16, dimension( * ) work, integer lwork, integer info)¶
ZGEQLF
Purpose:
!> !> ZGEQLF computes a QL factorization of a complex M-by-N matrix A: !> A = Q * L. !>
Parameters
M
!> M is INTEGER !> The number of rows of the matrix A. M >= 0. !>
N
!> N is INTEGER !> The number of columns of the matrix A. N >= 0. !>
A
!> A is COMPLEX*16 array, dimension (LDA,N) !> On entry, the M-by-N matrix A. !> On exit, !> if m >= n, the lower triangle of the subarray !> A(m-n+1:m,1:n) contains the N-by-N lower triangular matrix L; !> if m <= n, the elements on and below the (n-m)-th !> superdiagonal contain the M-by-N lower trapezoidal matrix L; !> the remaining elements, with the array TAU, represent the !> unitary matrix Q as a product of elementary reflectors !> (see Further Details). !>
LDA
!> LDA is INTEGER !> The leading dimension of the array A. LDA >= max(1,M). !>
TAU
!> TAU is COMPLEX*16 array, dimension (min(M,N)) !> The scalar factors of the elementary reflectors (see Further !> Details). !>
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 had an illegal value !>
Author
Univ. of Tennessee
Univ. of California Berkeley
Univ. of Colorado Denver
NAG Ltd.
Further Details:
!> !> The matrix Q is represented as a product of elementary reflectors !> !> Q = H(k) . . . H(2) H(1), where k = min(m,n). !> !> Each H(i) has the form !> !> H(i) = I - tau * v * v**H !> !> where tau is a complex scalar, and v is a complex vector with !> v(m-k+i+1:m) = 0 and v(m-k+i) = 1; v(1:m-k+i-1) is stored on exit in !> A(1:m-k+i-1,n-k+i), and tau in TAU(i). !>
Definition at line 137 of file zgeqlf.f.
Author¶
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