anchor.diff:  	    %% If that process is in the `active` set (i.e. has not blocked),
   	    %% remove it from the actives and make it next-to-run, else do
   	    %% that for another process from the actives.
  -	    {Next, NewActive} =
  -		case sets:is_element(LastLid, Active) of
  -		    true -> {LastLid,
  -			     sets:to_list(sets:del_element(LastLid, Active))};
  -		    false ->
  -			[INext|INewActive] = sets:to_list(Active),
  -			{INext, INewActive}
  -		end,
  -	    %% io:format("Search - NewActive: ~p~n", [NewActive]),
  -	    %% Store all other possible successor states for later exploration.
  -	    [state_save(state:extend(State, Lid)) || Lid <- NewActive],
  -	    Next
  +	    %% In the former case, all other possible successor states are
  +	    %% stored in the next state queue to be explored on the next
  +	    %% preemption bound.
  +	    %% In the latter case, all other possible successor states are
  +	    %% stored in the current state queue, because a non-preemptive
  +	    %% context switch is happening (the last process either exited
  +	    %% or blocked).
  +	    case sets:is_element(LastLid, Active) of
  +		true ->
  +		    NewActive = sets:del_element(LastLid, Active),
  +		    Fun = fun(L, Acc) ->
  +				  state_save_next(state:extend(State, L)),
  +				  Acc
  +			  end,
  +		    sets:fold(Fun, unused, NewActive),
  +		    LastLid;
  +		false ->
  +		    [Next|NewActive] = sets:to_list(Active),
  +		    [state_save(state:extend(State, L)) || L <- NewActive],
  +		    Next
  +	    end
       end.
   
   %%%----------------------------------------------------------------------
  
positive.code: 	State -> State
      end.
  
  %% Add a state to the `state` table.
  state_save(State) ->
      ets:insert(?NT_STATE2, {State}).
  
  %% Initialize state tables.
  state_start() ->
  
negative.code:             end
      end.
  
  %% Stores states for later exploration and returns the process to be run next.
  search(#context{active = Active, state = State}) ->
      case state:is_empty(State) of
  	%% Handle first call to search (empty state, one active process).
  