durand.f

      FUNCTION ran1(idum)
      INTEGER idum,IA,IM,IQ,IR,NTAB,NDIV
      DOUBLE PRECISION ran1,AM,EPS,RNMX
      PARAMETER (IA=16807,IM=2147483647,AM=1.d0/IM,IQ=127773,IR=2836,
     *NTAB=32,NDIV=1+(IM-1)/NTAB,EPS=3.d-16,RNMX=1.d0-EPS)
      INTEGER j,k,iv(NTAB),iy
      SAVE iv,iy
      DATA iv /NTAB*0/, iy /0/
      if (idum.le.0.or.iy.eq.0) then
        idum=max(-idum,1)
        do 11 j=NTAB+8,1,-1
          k=idum/IQ
          idum=IA*(idum-k*IQ)-IR*k
          if (idum.lt.0) idum=idum+IM
          if (j.le.NTAB) iv(j)=idum
11      continue
        iy=iv(1)
      endif
      k=idum/IQ
      idum=IA*(idum-k*IQ)-IR*k
      if (idum.lt.0) idum=idum+IM
      j=1+iy/NDIV
      iy=iv(j)
      iv(j)=idum
      ran1=min(AM*iy,RNMX)
      return
      END

      subroutine durand(seed, npts, x)
      implicit none
      integer npts, i, idum
      real*8  seed, ran1,  x(npts)
      if (seed .lt. 0.0d0  .or. seed .gt. 2147483648.0) then
         write(6,*) 'seed must be a positive integer < 2.1474*10**9'
         seed = 135791113.0
      end if
      idum = -int(seed)
      do i = 1, npts
           x(i) = ran1(idum)
      end do
      seed = dble(idum)
      end