dgeqpf(3P) Sun Performance Library dgeqpf(3P)NAMEdgeqpf - routine is deprecated and has been replaced by routine DGEQP3
SYNOPSIS
SUBROUTINE DGEQPF(M, N, A, LDA, JPIVOT, TAU, WORK, INFO)
INTEGER M, N, LDA, INFO
INTEGER JPIVOT(*)
DOUBLE PRECISION A(LDA,*), TAU(*), WORK(*)
SUBROUTINE DGEQPF_64(M, N, A, LDA, JPIVOT, TAU, WORK, INFO)
INTEGER*8 M, N, LDA, INFO
INTEGER*8 JPIVOT(*)
DOUBLE PRECISION A(LDA,*), TAU(*), WORK(*)
F95 INTERFACE
SUBROUTINE GEQPF([M], [N], A, [LDA], JPIVOT, TAU, [WORK], [INFO])
INTEGER :: M, N, LDA, INFO
INTEGER, DIMENSION(:) :: JPIVOT
REAL(8), DIMENSION(:) :: TAU, WORK
REAL(8), DIMENSION(:,:) :: A
SUBROUTINE GEQPF_64([M], [N], A, [LDA], JPIVOT, TAU, [WORK], [INFO])
INTEGER(8) :: M, N, LDA, INFO
INTEGER(8), DIMENSION(:) :: JPIVOT
REAL(8), DIMENSION(:) :: TAU, WORK
REAL(8), DIMENSION(:,:) :: A
C INTERFACE
#include <sunperf.h>
void dgeqpf(int m, int n, double *a, int lda, int *jpivot, double *tau,
int *info);
void dgeqpf_64(long m, long n, double *a, long lda, long *jpivot, dou‐
ble *tau, long *info);
PURPOSEdgeqpf routine is deprecated and has been replaced by routine DGEQP3.
DGEQPF computes a QR factorization with column pivoting of a real M-by-
N matrix A: A*P = Q*R.
ARGUMENTS
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 upper triangle
of the array contains the min(M,N)-by-N upper triangular
matrix R; the elements below the diagonal, together with the
array TAU, represent the orthogonal matrix Q as a product of
min(m,n) elementary reflectors.
LDA (input)
The leading dimension of the array A. LDA >= max(1,M).
JPIVOT (input/output)
On entry, if JPIVOT(i) .ne. 0, the i-th column of A is per‐
muted to the front of A*P (a leading column); if JPIVOT(i) =
0, the i-th column of A is a free column. On exit, if
JPIVOT(i) = k, then the i-th column of A*P was the k-th col‐
umn of A.
TAU (output)
The scalar factors of the elementary reflectors.
WORK (workspace)
dimension(3*N)
INFO (output)
= 0: successful exit
< 0: if INFO = -i, the i-th argument had an illegal value
FURTHER DETAILS
The matrix Q is represented as a product of elementary reflectors
Q = H(1)H(2) . . . H(n)
Each H(i) has the form
H = I - tau * v * v'
where tau is a real scalar, and v is a real vector with
v(1:i-1) = 0 and v(i) = 1; v(i+1:m) is stored on exit in A(i+1:m,i).
The matrix P is represented in jpvt as follows: If
jpvt(j) = i
then the jth column of P is the ith canonical unit vector.
6 Mar 2009 dgeqpf(3P)
