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zunm22.f(3) LAPACK zunm22.f(3)

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

Definition at line 164 of file zunm22.f.

Author

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Tue Nov 14 2017 Version 3.8.0