anchor.diff:    ! declarations
     use UserData
     implicit none
  +  include "mpif.h"
     real*8,  intent(in)  :: t, rpar
     integer, intent(in)  :: ipar
     integer, intent(out) :: ierr
  
positive.code:   !---------------------------------------------------------------
    subroutine InitUserData()
      implicit none
      nx = 0
      ny = 0
      is = 0
  
negative.code: ! Main driver program
  !-----------------------------------------------------------------
  program driver
  
    ! inclusions
    use UserData
    implicit none
    include "mpif.h"
  
    ! Declarations
    ! general problem parameters
    real*8,    parameter :: pi = 3.1415926535897932d0
    real*8,    parameter :: T0 = 0.d0     ! initial time 
  