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Diffstat (limited to 'Utilib/src/RANDF.f')
| -rw-r--r-- | Utilib/src/RANDF.f | 65 |
1 files changed, 65 insertions, 0 deletions
diff --git a/Utilib/src/RANDF.f b/Utilib/src/RANDF.f new file mode 100644 index 0000000..9b9e6de --- /dev/null +++ b/Utilib/src/RANDF.f @@ -0,0 +1,65 @@ +*DECK RANDF + SUBROUTINE RANDF(ISEED,IFIRST,RAND) +* +*----------------------------------------------------------------------- +* +*Purpose: +* This subroutine returns a pseudo-random number for each invocation. +* It is a FORTRAN 77 adaptation of the "Integer Version 2" minimal +* standard number generator whose Pascal code appears in reference. +* +*Copyright: +* Copyright (C) 2008 Ecole Polytechnique de Montreal +* This library is free software; you can redistribute it and/or +* modify it under the terms of the GNU Lesser General Public +* License as published by the Free Software Foundation; either +* version 2.1 of the License, or (at your option) any later version +* +*Author(s): R. Chambon +* +*Parameters: input +* ISEED the seed for the generation of random numbers. +* IFIRST set to 1 to indicate that the seed is being generated. +* +*Parameters: ouput +* IFIRST set to 1 to indicate that the seed is being generated. +* RAND random number between 0 and 1. +* +*Reference: +* Park, Steven K. and Miller, Keith W., "Random Number Generators: +* Good Ones are Hard to Find", Communications of the ACM, October 1988. +* +*----------------------------------------------------------------------- +* + IMPLICIT NONE +*---- +* SUBROUTINE ARGUMENTS +*---- + INTEGER ISEED,IFIRST + REAL RAND + DOUBLE PRECISION D1,D2 +*---- +* LOCAL VARIABLES +*---- + INTEGER MPLIER,MODLUS,MOBYMP,MOMDMP + PARAMETER (MPLIER=16807,MODLUS=2147483647,MOBYMP=127773, + + MOMDMP=2836) + INTEGER HVLUE, LVLUE, TESTV, NEXTN +* + IF (IFIRST .EQ. 0) IFIRST = 1 + NEXTN = ISEED +* + HVLUE = NEXTN / MOBYMP + LVLUE = MOD(NEXTN, MOBYMP) + TESTV = MPLIER*LVLUE - MOMDMP*HVLUE + IF (TESTV .GT. 0) THEN + NEXTN = TESTV + ELSE + NEXTN = TESTV + MODLUS + ENDIF + D1=DBLE(NEXTN) + D2=DBLE(MODLUS) + RAND=REAL(D1/D2) + ISEED= NEXTN + RETURN + END |