module ran

contains

  function ranf()

!.....Replaces cray routine ranf(). What follows is the
!     same as FUNCTION RAN1(idum) of numerical recipes p196,
!     except idum is set explicitly below.

!.....RAN1(idum):
!.....Returns a uniform deviate between 0.0 and 1.0.
!     Set idum to any negative value to initialize
!     or reinitialize the sequence

    real :: ranf
    parameter (ia=16807,im=2147483647,am=1./im,iq=127773,ir=2836, &
         ntab=32,ndiv=1+(im-1)/ntab,eps=1.2e-7,rnmx=1.-eps)
    integer j,k,iv(ntab),iy
    save iv,iy
    data iv /ntab*0/, iy /0/

!.....To conform to cray, do not pass idum
    idum=1
    
    if (idum <= 0.or.iy == 0) then
       idum=max(-idum,1)
       do j=NTAB+8,1,-1
          k=idum/IQ
          idum=IA*(idum-k*IQ)-IR*k
          if (idum < 0) idum=idum+IM
          if (j <= NTAB) iv(j)=idum
       enddo
       iy=iv(1)
    endif
    k=idum/IQ
    idum=IA*(idum-k*IQ)-IR*k
    if (idum < 0) idum=idum+IM
    j=1+iy/NDIV
    iy=iv(j)
    iv(j)=idum
!     ran1=min(AM*iy,RNMX) (change name to ranf)
    ranf=min(AM*iy,RNMX)
    
  end function ranf
!  (C) Copr. 1986-92 Numerical Recipes Software n2'%).

end module ran