• NAME
• SYNOPSIS
• F95 INTERFACE
• C INTERFACE
• PURPOSE
• ARGUMENTS

NAME

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

SYNOPSIS

  SUBROUTINE ZUNGQL( M, N, K, A, LDA, TAU, WORK, LWORK, INFO)
  DOUBLE COMPLEX A(LDA,*), TAU(*), WORK(*)
  INTEGER M, N, K, LDA, LWORK, INFO

  SUBROUTINE ZUNGQL_64( M, N, K, A, LDA, TAU, WORK, LWORK, INFO)
  DOUBLE 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(8), DIMENSION(:) :: TAU, WORK
  COMPLEX(8), DIMENSION(:,:) :: A
  INTEGER :: M, N, K, LDA, LWORK, INFO

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

C INTERFACE

#include <sunperf.h>

void zungql(int m, int n, int k, doublecomplex *a, int lda, doublecomplex *tau, int *info);

void zungql_64(long m, long n, long k, doublecomplex *a, long lda, doublecomplex *tau, long *info);

PURPOSE

zungql 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)
  

   = 0:  successful exit

   < 0:  if INFO  = -i, the i-th argument has an illegal value