anchor.diff:  
       ! name list to drive model
       namelist /driver/ nloop, ntime, input_forcing, output, validation 
  +
  +#if MPI
  +    integer :: ierr, num_procs, my_id
  +
  +    ! MPI directives
  +    call MPI_INIT ( ierr )
  +    !     find out MY process ID, and how many processes were started.
  +
  +    call MPI_COMM_RANK (MPI_COMM_WORLD, my_id, ierr)
  +    call MPI_COMM_SIZE (MPI_COMM_WORLD, num_procs, ierr)
  +#endif
   
       write(*,*) "\x1B[32mrun_particles:\x1B[0m start particle calculation."
       prog_name = "run_particles"
  
positive.code:       
      use utils
      use surface_physics
  
      implicit none
  
  
negative.code: 
      write(*,*) "\x1B[32mrun_particle:\x1B[0m end particle calculation."
  
  #if MPI
      call MPI_FINALIZE ( ierr )
  #endif
  
  end program
  