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## zunm22()

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.

Download ZUNM22 + dependencies [TGZ] [ZIP] [TXT]

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

  [in]

  SIDE

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

  [in]

  TRANS

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

  [in]

  M

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

  [in]

  N

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

  [in] | N1 |

  [in]

  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'.
      !>

  [in]

  Q

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

  [in]

  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'.
      !>

  [in,out]

  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.
      !>

  [in]

  LDC

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

  [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.
      !>          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.
      !>

  [out]

  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.