program TEST_RNPSSN

C  Author:  Glen Cowan
C  Date:    7-OCT-1997

C  Test program for CERNLIB routine RNPSSN (V136) for generating
C  Poisson distributed numbers.
C  Must be linked with the CERN Program Library (including PACKLIB for
C  HBOOK histogram routines).

      implicit        NONE

c  Needed for HBOOK routines

      integer         hsize
      parameter       (hsize = 100000)

      integer         hmemor (hsize)
      common  /pawc/  hmemor

c  Local variables

      character*80    outfile

      integer         i
      integer         icycle
      integer         ierror
      integer         istat
      integer         lun
      integer         n

      real            nu

c  Initialize HBOOK, open histogram file, book histograms.

      call HLIMIT (hsize)
      lun = 20
      outfile = 'test_rnpssn.his'
      call HROPEN (lun, 'histog', outfile, 'N', 1024, istat)
      if (istat .ne. 0) write (*, *) 'HROPEN error, istat = ', istat
      call HBOOK1 (1, 'Poisson n', 100, -0.5, 99.5, 0.)

C  Generate 10000 values and enter into histogram.

      write (*, *) 'enter Poisson mean nu'
      read (*, *) nu
      do i = 1, 10000
        call RNPSSN (nu, n, ierror)
        call HF1 (1, FLOAT(n), 1.)
      end do

c  Store histogram and close.

      call HROUT (0, icycle, ' ')
      call HREND ('histog')

      stop
      END