FUNCTION ran2(idum) INTEGER idum,IM1,IM2,IMM1,IA1,IA2,IQ1,IQ2,IR1,IR2,NTAB,NDIV REAL ran2,AM,EPS,RNMX PARAMETER (IM1=2147483563,IM2=2147483399,AM=1./IM1,IMM1=IM1-1, *IA1=40014,IA2=40692,IQ1=53668,IQ2=52774,IR1=12211,IR2=3791, *NTAB=32,NDIV=1+IMM1/NTAB,EPS=1.2e-7,RNMX=1.-EPS) INTEGER idum2,j,k,iv(NTAB),iy SAVE iv,iy,idum2 DATA idum2/123456789/, iv/NTAB*0/, iy/0/ if (idum.le.0) then idum=max(-idum,1) idum2=idum do 11 j=NTAB+8,1,-1 k=idum/IQ1 idum=IA1*(idum-k*IQ1)-k*IR1 if (idum.lt.0) idum=idum+IM1 if (j.le.NTAB) iv(j)=idum 11 continue iy=iv(1) endif k=idum/IQ1 idum=IA1*(idum-k*IQ1)-k*IR1 if (idum.lt.0) idum=idum+IM1 k=idum2/IQ2 idum2=IA2*(idum2-k*IQ2)-k*IR2 if (idum2.lt.0) idum2=idum2+IM2 j=1+iy/NDIV iy=iv(j)-idum2 iv(j)=idum if(iy.lt.1)iy=iy+IMM1 ran2=min(AM*iy,RNMX) return END