anchor.diff:  
   #ifndef useExtSolver
     myid = 0
  +  num_procs = 1
  +  allocate(ilower(0:num_procs-1, 2))
  +  allocate(iupper(0:num_procs-1, 2))
   #endif
   
   
  
positive.code:       hypre_grid)
    print *, 'Execution ended normally'
    
    ! Finalize MPI
    call MPI_Finalize(ierr)
    
    stop 0
  end program aronnax
  
  
negative.code:   ! unless the external solver is used.
    integer :: nProcX, nProcY
  
  #ifndef useExtSolver
    ! if we don't call mpi, then this needs to be expicitly defined
    integer :: MPI_COMM_WORLD
  #endif
    integer :: ierr
    integer :: num_procs, myid
  
  