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88 lines
2.2 KiB
Fortran
88 lines
2.2 KiB
Fortran
#include <sla_config.h>
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REAL FUNCTION sla_RANDOM (SEED)
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*+
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* - - - - - - -
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* R A N D O M
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* - - - - - - -
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*
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* Generate pseudo-random real number in the range 0 <= X < 1.
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* (single precision)
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*
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*
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* Given:
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* SEED real an arbitrary real number
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*
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* Notes:
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*
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* 1) The result is a pseudo-random REAL number in the range
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* 0 <= sla_RANDOM < 1.
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*
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* 2) SEED is used first time through only.
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*
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* Called: RAN or RAND (a REAL function returning a random variate --
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* the precise function which is called depends on which functions
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* are available when the library is built). If neither of these
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* is available, we use the local substitute RANDOM defined
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* in rtl_random.c
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*
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* P.T.Wallace Starlink 14 October 1991
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*
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* License:
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program (see SLA_CONDITIONS); if not, write to the
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* Free Software Foundation, Inc., 59 Temple Place, Suite 330,
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* Boston, MA 02111-1307 USA
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*-
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IMPLICIT NONE
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REAL SEED
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#if HAVE_RAND
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REAL RAND
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#elif HAVE_RANDOM
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REAL RANDOM
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#else
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error "Can't find random-number function"
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#endif
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REAL AS
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INTEGER ISEED
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LOGICAL FIRST
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SAVE FIRST
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DATA FIRST /.TRUE./
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* If first time, turn SEED into a large, odd integer
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IF (FIRST) THEN
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AS=ABS(SEED)+1.0
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ISEED=NINT(AS/10.0**(NINT(ALOG10(AS))-6))
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IF (MOD(ISEED,2).EQ.0) ISEED=ISEED+1
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FIRST=.FALSE.
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#if HAVE_RAND
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AS = RAND(ISEED)
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#endif
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ELSE
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ISEED=0
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END IF
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* Next pseudo-random number
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#if HAVE_RAND
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sla_RANDOM=RAND(0)
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#elif HAVE_RANDOM
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sla_RANDOM=RANDOM(ISEED)
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#endif
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END
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