anchor.diff:       stop "Usage: bin/rt input_file output_file"
     end if
   
  +  ! Start up multi-processing if needed
  +  call mp_initialize()
  +
     if(main_process()) then
        write(*,*) repeat('-',60)
        write(*,'(" Started on ",A)') trim(now())
  
positive.code:   end if
  
    ! Display message
    if(main_process()) call message(1,' [main] exiting final iteration')
  
    if(use_raytracing) then
  
       ! Display message
       if(main_process()) call message(1,' [main] starting raytracing iteration')
  
       ! Do the raytracing
       call do_raytracing(n_raytracing_photons_star,n_raytracing_photons_dust, n_stats)
  
       ! Display message
       if(main_process()) call message(1,' [main] exiting raytracing iteration')
  
    end if
  
  
negative.code:   do iter=1,n_lucy_iter
  
       ! Display message
       if(main_process()) write(*,'(" [main] starting Lucy iteration ", I0)') iter
  
       ! Do the RT
       call do_lucy(n_lucy_photons, n_stats)
  