dorgqr

NAME

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

SYNOPSIS 

  SUBROUTINE DORGQR( M, N, K, A, LDA, TAU, WORK, LDWORK, INFO)
  INTEGER M, N, K, LDA, LDWORK, INFO
  DOUBLE PRECISION A(LDA,*), TAU(*), WORK(*)
 
  SUBROUTINE DORGQR_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 ORGQR( 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 ORGQR_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 dorgqr(int m, int n, int k, double *a, int lda, double *tau, int *info);

void dorgqr_64(long m, long n, long k, double *a, long lda, double *tau, long *info);

PURPOSE

dorgqr generates an M-by-N real matrix Q with orthonormal columns, which is defined as the first N columns of a product of K elementary reflectors of order M 

      Q  =  H(1) H(2) . . . H(k)

as returned by SGEQRF.

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 i-th column must contain the vector which defines the elementary reflector H(i), for i = 1,2,...,k, as returned by SGEQRF in the first 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 SGEQRF.

* 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)