28 lines
772 B
Fortran
28 lines
772 B
Fortran
FUNCTION ran1(idum)
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INTEGER idum,IA,IM,IQ,IR,NTAB,NDIV
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REAL ran1,AM,EPS,RNMX
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PARAMETER (IA=16807,IM=2147483647,AM=1./IM,IQ=127773,IR=2836,
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*NTAB=32,NDIV=1+(IM-1)/NTAB,EPS=1.2e-7,RNMX=1.-EPS)
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INTEGER j,k,iv(NTAB),iy
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SAVE iv,iy
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DATA iv /NTAB*0/, iy /0/
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if (idum.le.0.or.iy.eq.0) then
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idum=max(-idum,1)
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do 11 j=NTAB+8,1,-1
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k=idum/IQ
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idum=IA*(idum-k*IQ)-IR*k
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if (idum.lt.0) idum=idum+IM
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if (j.le.NTAB) iv(j)=idum
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11 continue
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iy=iv(1)
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endif
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k=idum/IQ
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idum=IA*(idum-k*IQ)-IR*k
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if (idum.lt.0) idum=idum+IM
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j=1+iy/NDIV
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iy=iv(j)
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iv(j)=idum
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ran1=min(AM*iy,RNMX)
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return
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END
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