NAME

       zungrq.f -

SYNOPSIS

   Functions/Subroutines
       subroutine zungrq (M, N, K, A, LDA, TAU, WORK, LWORK, INFO)
           ZUNGRQ

Function/Subroutine Documentation

   subroutine zungrq (integer M, integer N, integer K, complex*16, dimension( lda, * ) A, integer
       LDA, complex*16, dimension( * ) TAU, complex*16, dimension( * ) WORK, integer LWORK,
       integer INFO)
       ZUNGRQ

       Purpose:

            ZUNGRQ generates an M-by-N complex matrix Q with orthonormal rows,
            which is defined as the last M rows of a product of K elementary
            reflectors of order N

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

            as returned by ZGERQF.

       Parameters:
           M

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

           N

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

           K

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

           A

                     A is COMPLEX*16 array, dimension (LDA,N)
                     On entry, the (m-k+i)-th row must contain the vector which
                     defines the elementary reflector H(i), for i = 1,2,...,k, as
                     returned by ZGERQF in the last k rows of its array argument
                     A.
                     On exit, the M-by-N matrix Q.

           LDA

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

           TAU

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

           WORK

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

           LWORK

                     LWORK is INTEGER
                     The dimension of the array WORK. LWORK >= max(1,M).
                     For optimum performance LWORK >= M*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

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

       Author:
           Univ. of Tennessee

           Univ. of California Berkeley

           Univ. of Colorado Denver

           NAG Ltd.

       Date:
           November 2011

Author

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