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