anchor.diff:      use feval_module
       use hooks_module
       use transfer_module
  -    use pf_mod_rkstepper
       use pf_mod_parallel
       use pf_mod_mpi
       use pfasst
  
positive.code:         allocate(sweet_level_t::pf%levels(level)%ulevel)
          allocate(sweet_data_factory_t::pf%levels(level)%ulevel%factory)
          allocate(sweet_sweeper_t::pf%levels(level)%ulevel%sweeper)
          
          ! check the number of nodes for RK stepper
          if (pf%use_rk_stepper .eqv. .true.) then
              if (pf%levels(level)%ulevel%stepper%order      == 5 .and. nnodes(level) /= 9) then
                  stop "invalid number of nodes for the RK stepper"
              else if (pf%levels(level)%ulevel%stepper%order == 4 .and. nnodes(level) /= 7) then
                  stop "invalid number of nodes for the RK stepper"
              else if (pf%levels(level)%ulevel%stepper%order == 3 .and. nnodes(level) /= 5) then
                  stop "invalid number of nodes for the RK stepper"
              else if (pf%levels(level)%ulevel%stepper%order == 2 .and. nnodes(level) /= 4) then
                  stop "invalid number of nodes for the RK stepper"
              end if
          end if
  
          ! cast the object into sweet data objects
          sd_factory_ptr    => as_sweet_data_factory(pf%levels(level)%ulevel%factory)
  
negative.code:                          PF_POST_BLOCK,       &
                           fecho_output_invariants)
          
          call pf_print_options(pf,un_opt=6)
          
          ! advance in time with libpfasst
          level = nlevs
  
  