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SUBROUTINE MA02BZ( SIDE, M, N, A, LDA )
C
C SLICOT RELEASE 5.0.
C
C Copyright (c) 2002-2009 NICONET e.V.
C
C This program is free software: you can redistribute it and/or
C modify it under the terms of the GNU General Public License as
C published by the Free Software Foundation, either version 2 of
C the License, or (at your option) any later version.
C
C This program is distributed in the hope that it will be useful,
C but WITHOUT ANY WARRANTY; without even the implied warranty of
C MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
C GNU General Public License for more details.
C
C You should have received a copy of the GNU General Public License
C along with this program. If not, see
C <http://www.gnu.org/licenses/>.
C
C PURPOSE
C
C To reverse the order of rows and/or columns of a given matrix A
C by pre-multiplying and/or post-multiplying it, respectively, with
C a permutation matrix P, where P is a square matrix of appropriate
C order, with ones down the secondary diagonal.
C
C ARGUMENTS
C
C Mode Parameters
C
C SIDE CHARACTER*1
C Specifies the operation to be performed, as follows:
C = 'L': the order of rows of A is to be reversed by
C pre-multiplying A with P;
C = 'R': the order of columns of A is to be reversed by
C post-multiplying A with P;
C = 'B': both the order of rows and the order of columns
C of A is to be reversed by pre-multiplying and
C post-multiplying A with P.
C
C Input/Output Parameters
C
C M (input) INTEGER
C The number of rows of the matrix A. M >= 0.
C
C N (input) INTEGER
C The number of columns of the matrix A. N >= 0.
C
C A (input/output) COMPLEX*16 array, dimension (LDA,N)
C On entry, the leading M-by-N part of this array must
C contain the given matrix whose rows and/or columns are to
C be permuted.
C On exit, the leading M-by-N part of this array contains
C the matrix P*A if SIDE = 'L', or A*P if SIDE = 'R', or
C P*A*P if SIDE = 'B'.
C
C LDA INTEGER
C The leading dimension of the array A. LDA >= max(1,M).
C
C CONTRIBUTOR
C
C A. Varga, German Aerospace Center,
C DLR Oberpfaffenhofen, March 1998.
C Complex version: V. Sima, Research Institute for Informatics,
C Bucharest, Nov. 2008.
C
C REVISIONS
C
C -
C
C ******************************************************************
C
C .. Scalar Arguments ..
CHARACTER SIDE
INTEGER LDA, M, N
C .. Array Arguments ..
COMPLEX*16 A(LDA,*)
C .. Local Scalars ..
LOGICAL BSIDES
INTEGER I, J, K, M2, N2
C .. External Functions ..
LOGICAL LSAME
EXTERNAL LSAME
C .. External Subroutines ..
EXTERNAL ZSWAP
C .. Executable Statements ..
C
BSIDES = LSAME( SIDE, 'B' )
C
IF( ( LSAME( SIDE, 'L' ) .OR. BSIDES ) .AND. M.GT.1 ) THEN
C
C Compute P*A.
C
M2 = M/2
K = M - M2 + 1
DO 10 J = 1, N
CALL ZSWAP( M2, A(1,J), -1, A(K,J), 1 )
10 CONTINUE
END IF
IF( ( LSAME( SIDE, 'R' ) .OR. BSIDES ) .AND. N.GT.1 ) THEN
C
C Compute A*P.
C
N2 = N/2
K = N - N2 + 1
DO 20 I = 1, M
CALL ZSWAP( N2, A(I,1), -LDA, A(I,K), LDA )
20 CONTINUE
END IF
C
RETURN
C *** Last line of MA02BZ ***
END
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