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47 lines
1.3 KiB
47 lines
1.3 KiB
C Copyright(C) 1999-2020 National Technology & Engineering Solutions
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C of Sandia, LLC (NTESS). Under the terms of Contract DE-NA0003525 with
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C NTESS, the U.S. Government retains certain rights in this software.
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C
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C See packages/seacas/LICENSE for details
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REAL FUNCTION RAN1(idum)
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C This function returns a pseudo-random number for each invocation.
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C It is a FORTRAN 77 adaptation of the "Integer Version 2" minimal
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C standard number generator whose Pascal code appears in the article:
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C Park, Steven K. and Miller, Keith W., "Random Number Generators:
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C Good Ones are Hard to Find", Communications of the ACM,
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C October, 1988.
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PARAMETER (MPLIER=16807,MODLUS=2147483647,MOBYMP=127773,
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+ MOMDMP=2836)
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data jseed /123456789/
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data ifrst /0/
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INTEGER HVLUE, LVLUE, TESTV, NEXTN
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SAVE NEXTN
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IF (IFRST .EQ. 0) THEN
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if (idum .ne. 0) then
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nextn = idum
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else
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NEXTN = JSEED
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end if
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IFRST = 1
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ENDIF
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HVLUE = NEXTN / MOBYMP
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LVLUE = MOD(NEXTN, MOBYMP)
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TESTV = MPLIER*LVLUE - MOMDMP*HVLUE
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IF (TESTV .GT. 0) THEN
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NEXTN = TESTV
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ELSE
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NEXTN = TESTV + MODLUS
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ENDIF
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RAN1 = REAL(NEXTN)/REAL(MODLUS)
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RETURN
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END
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