dorgql

NAME

dorgql - generate an M-by-N real matrix Q with orthonormal columns,

SYNOPSIS

  SUBROUTINE DORGQL( M, N, K, A, LDA, TAU, WORK, LDWORK, INFO)
  INTEGER M, N, K, LDA, LDWORK, INFO
  DOUBLE PRECISION A(LDA,*), TAU(*), WORK(*)
 
  SUBROUTINE DORGQL_64( M, N, K, A, LDA, TAU, WORK, LDWORK, INFO)
  INTEGER*8 M, N, K, LDA, LDWORK, INFO
  DOUBLE PRECISION A(LDA,*), TAU(*), WORK(*)

F95 INTERFACE

  SUBROUTINE ORGQL( M, [N], [K], A, [LDA], TAU, [WORK], [LDWORK], 
 *       [INFO])
  INTEGER :: M, N, K, LDA, LDWORK, INFO
  REAL(8), DIMENSION(:) :: TAU, WORK
  REAL(8), DIMENSION(:,:) :: A
 
  SUBROUTINE ORGQL_64( M, [N], [K], A, [LDA], TAU, [WORK], [LDWORK], 
 *       [INFO])
  INTEGER(8) :: M, N, K, LDA, LDWORK, INFO
  REAL(8), DIMENSION(:) :: TAU, WORK
  REAL(8), DIMENSION(:,:) :: A

C INTERFACE

#include <sunperf.h>

void dorgql(int m, int n, int k, double *a, int lda, double *tau, int *info);

void dorgql_64(long m, long n, long k, double *a, long lda, double *tau, long *info);

PURPOSE

dorgql generates an M-by-N real 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 SGEQLF.

ARGUMENTS

* M (input)

The number of rows of the matrix Q. M >= 0.

* N (input)

The number of columns of the matrix Q. M >= N >= 0.

* K (input)

The number of elementary reflectors whose product defines the matrix Q. N >= K >= 0.

* A (input/output)

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 SGEQLF in the last k columns of its array argument A. On exit, the M-by-N matrix Q.

* LDA (input)

The first dimension of the array A. LDA >= max(1,M).

* TAU (input)

TAU(i) must contain the scalar factor of the elementary reflector H(i), as returned by SGEQLF.

* WORK (workspace)

On exit, if INFO = 0, WORK(1) returns the optimal LDWORK.

* LDWORK (input)

The dimension of the array WORK. LDWORK >= max(1,N). For optimum performance LDWORK >= N*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)