c-----------------------------------------------------------
c     Demonstration program for Fortran use of C routines
c     'drand48' and 'srand48' which provide the same 
c     functionality as 'rand' and 'srand' on the SGI 
c     machines, but which are more portable. In particular, 
c     these routines are available on Linux systems.
c
c     See the source code 'drand48.c'  for the implementation 
c     of the Fortran interface to the C routines, as well as 
c     the 'Makefile' for compilation and linking information.
c
c     This program generates 'nrand' random numbers on the 
c     unit interval, bins them into 'nbin' uniform-subintervals, 
c     then outputs the fraction of numbers generated in each
c     bin.
c-----------------------------------------------------------
      program      trand48

      implicit     none

c-----------------------------------------------------------
c     Declaration of random number generator
c-----------------------------------------------------------
      real*8       drand48

c-----------------------------------------------------------
c     Control parameters and bin array
c-----------------------------------------------------------
      integer      nrand
      parameter  ( nrand = 100 000 )
      integer      nbin
      parameter  ( nbin  = 10 )
      integer      bin(nbin)

c-----------------------------------------------------------
c     Locals
c-----------------------------------------------------------
      integer      i,  ibin

c-----------------------------------------------------------
c     Random number generator can be 'seeded' (initialized)
c     via 'srand48' which takes a single integer argument
c     (the seed).
c-----------------------------------------------------------
      call srand48(2**20-1)

      write(0,*) 'Generating ', nrand, ' random numbers'
      write(0,*) 'Using ', nbin, ' bins'
      write(0,*) 'Relative frequencies:'
      do i = 1 , nbin
         bin(i) = 0.0d0
      end do
      do i = 1 , nrand
         ibin = max(1,min(nbin * drand48() + 1,nbin))
         bin(ibin) = bin(ibin) + 1
      end do
      do i = 1 , nbin
        write(*,fmt='(f6.3)') bin(i) / (1.0d0 * nrand)
      end do

      stop

      end