Fortran example: PI

program main 
 
include "mpif.h" 
 
double precision  PI25DT 
      parameter        (PI25DT = 3.141592653589793238462643d0) 
 
double precision  mypi, pi, h, sum, x, f, a 
      integer n, myid, numprocs, i, rc 
c                                 function to integrate 
      f(a) = 4.d0 / (1.d0 + a*a) 
 
call MPI_INIT( ierr ) 
      call MPI_COMM_RANK( MPI_COMM_WORLD, myid, ierr ) 
      call MPI_COMM_SIZE( MPI_COMM_WORLD, numprocs, ierr ) 
 
10   if ( myid .eq. 0 ) then 
         write(6,98) 
 98      format('Enter the number of intervals: (0 quits)') 
         read(5,99) n 
 99      format(i10) 
      endif 
      
 
call MPI_BCAST(n,1,MPI_INTEGER,0,MPI_COMM_WORLD,ierr)