dgelqf
dgelqf - compute an LQ factorization of a real M-by-N matrix A
SUBROUTINE DGELQF( M, N, A, LDA, TAU, WORK, LDWORK, INFO)
INTEGER M, N, LDA, LDWORK, INFO
DOUBLE PRECISION A(LDA,*), TAU(*), WORK(*)
SUBROUTINE DGELQF_64( M, N, A, LDA, TAU, WORK, LDWORK, INFO)
INTEGER*8 M, N, LDA, LDWORK, INFO
DOUBLE PRECISION A(LDA,*), TAU(*), WORK(*)
SUBROUTINE GELQF( [M], [N], A, [LDA], TAU, [WORK], [LDWORK], [INFO])
INTEGER :: M, N, LDA, LDWORK, INFO
REAL(8), DIMENSION(:) :: TAU, WORK
REAL(8), DIMENSION(:,:) :: A
SUBROUTINE GELQF_64( [M], [N], A, [LDA], TAU, [WORK], [LDWORK],
* [INFO])
INTEGER(8) :: M, N, LDA, LDWORK, INFO
REAL(8), DIMENSION(:) :: TAU, WORK
REAL(8), DIMENSION(:,:) :: A
#include <sunperf.h>
void dgelqf(int m, int n, double *a, int lda, double *tau, int *info);
void dgelqf_64(long m, long n, double *a, long lda, double *tau, long *info);
dgelqf computes an LQ factorization of a real M-by-N matrix A:
A = L * Q.
-
* M (input)
-
The number of rows of the matrix A. M >= 0.
-
* N (input)
-
The number of columns of the matrix A. N >= 0.
-
* A (input/output)
-
On entry, the M-by-N matrix A.
On exit, the elements on and below the diagonal of the array
contain the m-by-min(m,n) lower trapezoidal matrix L (L is
lower triangular if m <= n); the elements above the diagonal,
with the array TAU, represent the orthogonal matrix Q as a
product of elementary reflectors (see Further Details).
-
* LDA (input)
-
The leading dimension of the array A. LDA >= max(1,M).
-
* TAU (output)
-
The scalar factors of the elementary reflectors (see Further
Details).
-
* WORK (workspace)
-
On exit, if INFO = 0, WORK(1) returns the optimal LDWORK.
-
* LDWORK (input)
-
The dimension of the array WORK. LDWORK >= max(1,M).
For optimum performance LDWORK >= M*NB, where NB is the
optimal blocksize.
If LDWORK = -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 LDWORK is issued by XERBLA.
-
* INFO (output)
-