181 lines
4.8 KiB
Fortran
181 lines
4.8 KiB
Fortran
LOGICAL FUNCTION MA02HD( JOB, M, N, DIAG, 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 check if A = DIAG*I, where I is an M-by-N matrix with ones on
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C the diagonal and zeros elsewhere.
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C
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C FUNCTION VALUE
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C
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C MA02HD LOGICAL
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C The function value is set to .TRUE. if A = DIAG*I, and to
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C .FALSE., otherwise.
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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 JOB CHARACTER*1
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C Specifies the part of the matrix A to be checked out,
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C as follows:
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C = 'U': Upper triangular/trapezoidal part;
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C = 'L': Lower triangular/trapezoidal part.
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C Otherwise: All of the matrix A.
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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 DIAG (input) DOUBLE PRECISION
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C The scalar DIAG.
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C
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C A (input) DOUBLE PRECISION array, dimension (LDA,N)
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C The leading M-by-N part of this array must contain the
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C matrix A. If JOB = 'U', only the upper triangle or
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C trapezoid is accessed; if JOB = 'L', only the lower
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C triangle or trapezoid is accessed.
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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 METHOD
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C
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C The routine returns immediately after detecting a diagonal element
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C which differs from DIAG, or a nonzero off-diagonal element in the
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C searched part of A.
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C
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C CONTRIBUTORS
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C
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C V. Sima, Research Institute for Informatics, Bucharest, May 2001.
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C A. Varga, German Aerospace Center, Oberpfaffenhofen, May 2001.
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C
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C REVISIONS
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C
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C V. Sima, Research Institute for Informatics, Bucharest, Jan. 2003.
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C
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C KEYWORDS
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C
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C Elementary operations.
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C
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C ******************************************************************
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C
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C .. Parameters ..
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DOUBLE PRECISION ZERO
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PARAMETER ( ZERO = 0.0D0 )
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C .. Scalar Arguments ..
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CHARACTER JOB
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INTEGER LDA, M, N
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DOUBLE PRECISION DIAG
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C .. Array Arguments ..
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DOUBLE PRECISION A(LDA,*)
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C .. Local Scalars ..
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INTEGER I, J
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C .. External Functions
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LOGICAL LSAME
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EXTERNAL LSAME
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C .. Intrinsic Functions ..
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INTRINSIC MIN
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C
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C .. Executable Statements ..
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C
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C Do not check parameters, for efficiency.
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C
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IF( LSAME( JOB, 'U' ) ) THEN
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C
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DO 20 J = 1, N
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C
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DO 10 I = 1, MIN( J-1, M )
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IF( A(I,J).NE.ZERO ) THEN
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MA02HD = .FALSE.
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RETURN
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END IF
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10 CONTINUE
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C
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IF( J.LE.M ) THEN
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IF( A(J,J).NE.DIAG ) THEN
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MA02HD = .FALSE.
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RETURN
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END IF
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END IF
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20 CONTINUE
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C
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ELSE IF( LSAME( JOB, 'L' ) ) THEN
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C
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DO 40 J = 1, MIN( M, N )
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IF( A(J,J).NE.DIAG ) THEN
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MA02HD = .FALSE.
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RETURN
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END IF
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C
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IF ( J.NE.M ) THEN
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C
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DO 30 I = MIN( J+1, M ), M
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IF( A(I,J).NE.ZERO ) THEN
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MA02HD = .FALSE.
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RETURN
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END IF
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30 CONTINUE
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C
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END IF
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40 CONTINUE
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C
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ELSE
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C
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DO 70 J = 1, N
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C
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DO 50 I = 1, MIN( J-1, M )
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IF( A(I,J).NE.ZERO ) THEN
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MA02HD = .FALSE.
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RETURN
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END IF
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50 CONTINUE
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C
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IF( J.LE.M ) THEN
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IF( A(J,J).NE.DIAG ) THEN
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MA02HD = .FALSE.
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RETURN
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END IF
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END IF
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C
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IF ( J.LT.M ) THEN
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C
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DO 60 I = MIN( J+1, M ), M
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IF( A(I,J).NE.ZERO ) THEN
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MA02HD = .FALSE.
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RETURN
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END IF
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60 CONTINUE
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C
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END IF
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70 CONTINUE
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C
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END IF
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C
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MA02HD = .TRUE.
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C
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RETURN
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C *** Last line of MA02HD ***
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END
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