zunm22.f - Man Page

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.

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.

Definition at line 160 of file zunm22.f.