NAME

       zunm22.f -

SYNOPSIS

   Functions/Subroutines
       subroutine zunm22 (SIDE, TRANS, M, N, N1, N2, Q, LDQ, C, LDC, WORK, LWORK, INFO)
           ZUNM22 multiplies a general matrix by a banded unitary matrix.

Function/Subroutine Documentation

   subroutine zunm22 (character SIDE, character TRANS, integer M, integer N, integer N1, integer
       N2, complex*16, dimension( ldq, * ) Q, integer LDQ, complex*16, dimension( ldc, * ) C,
       integer LDC, complex*16, dimension( * ) WORK, integer LWORK, integer INFO)
       ZUNM22 multiplies a general matrix by a banded unitary matrix.

       Purpose

             ZUNM22 overwrites the general complex M-by-N matrix C with

                             SIDE = 'L'     SIDE = 'R'
             TRANS = 'N':      Q * C          C * Q
             TRANS = 'C':      Q**H * C       C * Q**H

             where Q is a complex unitary matrix of order NQ, with NQ = M if
             SIDE = 'L' and NQ = N if SIDE = 'R'.
             The unitary matrix Q processes a 2-by-2 block structure

                    [  Q11  Q12  ]
                Q = [            ]
                    [  Q21  Q22  ],

             where Q12 is an N1-by-N1 lower triangular matrix and Q21 is an
             N2-by-N2 upper triangular matrix.

       Parameters:
           SIDE

                     SIDE is CHARACTER*1
                     = 'L': apply Q or Q**H from the Left;
                     = 'R': apply Q or Q**H from the Right.

           TRANS

                     TRANS is CHARACTER*1
                     = 'N':  apply Q (No transpose);
                     = 'C':  apply Q**H (Conjugate transpose).

           M

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

           N

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

           N1
           N2

                     N1 is INTEGER
                     N2 is INTEGER
                     The dimension of Q12 and Q21, respectively. N1, N2 >= 0.
                     The following requirement must be satisfied:
                     N1 + N2 = M if SIDE = 'L' and N1 + N2 = N if SIDE = 'R'.

           Q

                     Q is COMPLEX*16 array, dimension
                                         (LDQ,M) if SIDE = 'L'
                                         (LDQ,N) if SIDE = 'R'

           LDQ

                     LDQ is INTEGER
                     The leading dimension of the array Q.
                     LDQ >= max(1,M) if SIDE = 'L'; LDQ >= max(1,N) if SIDE = 'R'.

           C

                     C is COMPLEX*16 array, dimension (LDC,N)
                     On entry, the M-by-N matrix C.
                     On exit, C is overwritten by Q*C or Q**H*C or C*Q**H or C*Q.

           LDC

                     LDC is INTEGER
                     The leading dimension of the array C. LDC >= max(1,M).

           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.
                     If SIDE = 'L', LWORK >= max(1,N);
                     if SIDE = 'R', LWORK >= max(1,M).
                     For optimum performance LWORK >= M*N.

                     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 had an illegal value

       Author:
           Univ. of Tennessee

           Univ. of California Berkeley

           Univ. of Colorado Denver

           NAG Ltd.

       Date:
           January 2015

Author

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