cungql

NAME

cungql - generate an M-by-N complex matrix Q with orthonormal columns,

SYNOPSIS 

  SUBROUTINE CUNGQL( M, N, K, A, LDA, TAU, WORK, LWORK, INFO)
  COMPLEX A(LDA,*), TAU(*), WORK(*)
  INTEGER M, N, K, LDA, LWORK, INFO
 
  SUBROUTINE CUNGQL_64( M, N, K, A, LDA, TAU, WORK, LWORK, INFO)
  COMPLEX A(LDA,*), TAU(*), WORK(*)
  INTEGER*8 M, N, K, LDA, LWORK, INFO

F95 INTERFACE 

  SUBROUTINE UNGQL( M, [N], [K], A, [LDA], TAU, [WORK], [LWORK], [INFO])
  COMPLEX, DIMENSION(:) :: TAU, WORK
  COMPLEX, DIMENSION(:,:) :: A
  INTEGER :: M, N, K, LDA, LWORK, INFO
 
  SUBROUTINE UNGQL_64( M, [N], [K], A, [LDA], TAU, [WORK], [LWORK], 
 *       [INFO])
  COMPLEX, DIMENSION(:) :: TAU, WORK
  COMPLEX, DIMENSION(:,:) :: A
  INTEGER(8) :: M, N, K, LDA, LWORK, INFO

C INTERFACE

#include <sunperf.h>

void cungql(int m, int n, int k, complex *a, int lda, complex *tau, int *info);

void cungql_64(long m, long n, long k, complex *a, long lda, complex *tau, long *info);

PURPOSE

cungql generates an M-by-N complex 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 CGEQLF.

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 CGEQLF 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 CGEQLF.

* WORK (workspace)
On exit, if INFO = 0, WORK(1) returns the optimal LWORK.

* LWORK (input)
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 (output)