====================================================================
zungqr examples
====================================================================

====================================================================
Man Page Details
====================================================================

 Online html documentation available at 
            http://www.netlib.org/lapack/explore-html/ 

 Definition:
 ===========

       SUBROUTINE ZUNGQR( M, N, K, A, LDA, TAU, WORK, LWORK, INFO )
 
       .. Scalar Arguments ..
       INTEGER            INFO, K, LDA, LWORK, M, N
       ..
       .. Array Arguments ..
       COMPLEX*16         A( LDA, * ), TAU( * ), WORK( * )
       ..
  

 Purpose:
 =============

 ZUNGQR generates an M-by-N complex 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 ZGEQRF.

 Arguments:
 ==========

  [in] M

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

  [in] N

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

  [in] K

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

  [in,out] A

          A is COMPLEX*16 array, dimension (LDA,N)
          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 ZGEQRF in the first k columns of its array
          argument A.
          On exit, the M-by-N matrix Q.

  [in] LDA

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

  [in] TAU

          TAU is COMPLEX*16 array, dimension (K)
          TAU(i) must contain the scalar factor of the elementary
          reflector H(i), as returned by ZGEQRF.

  [out] WORK

          WORK is COMPLEX*16 array, dimension (MAX(1,LWORK))
          On exit, if INFO = 0, WORK(1) returns the optimal LWORK.

  [in] LWORK

          LWORK is INTEGER
          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.

  [out] INFO

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

 Authors:
 ========

  Univ. of Tennessee 
  Univ. of California Berkeley 
  Univ. of Colorado Denver 
  NAG Ltd. 

 November 2011

