SRC/zunm22.f(3) Library Functions Manual SRC/zunm22.f(3)

SRC/zunm22.f


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.

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