anchor.diff:          error -> 0
       end.
   
  -add_from_E(P, Enabled, ForwardTrace, ClockVector, Backtrack) ->
  +add_from_E(P, Enabled, ForwardTrace, ClockVector) ->
     case lists:member(P, Enabled) of
       true ->
         ?f_debug("        Enabled.\n"),
  -      ordsets:add_element(P, Backtrack);
  +      {one, P};
       false ->
         ?f_debug("        Not Enabled.\n"),
         case find_one_from_E(P, ClockVector, Enabled, ForwardTrace) of
           {true, Q} ->
             ?f_debug("        ~p needs to happen\n", [Q]),
  -          ordsets:add_element(Q, Backtrack);
  +          {one, Q};
           false ->
  -          ?f_debug("        Adding all enabled: ~p\n", [Enabled]),
  -          ordsets:union(Backtrack, ordsets:from_list(Enabled))
  +          ?f_debug("        Adding all enabled: ~w\n", [Enabled]),
  +          {many, Enabled}
         end
     end.
   
  
positive.code:     [TraceTop|RestTrace] = Trace,
      Backtrack = TraceTop#trace_state.backtrack,
      Done = TraceTop#trace_state.done,
      case ordsets:subtract(Backtrack, Done) of
  	[SelectedLid|_RestLids] ->
              ?f_debug("Have to try ~p...\n",[SelectedLid]),
              State =
                  case MightNeedReplayState#dpor_state.must_replay of
  
negative.code:                     Next = wait_next(Lid, Cmd),
                      ?f_debug("Next: ~p\n",[Next]),
                      LocalAddState = add_local_backtracks(Selected, State),
                      %% ?f_debug("AAS: ~p\n",[AllAddState]),
                      UpdState = update_trace(Selected, Next, LocalAddState),
                      %% ?f_debug("LAS: ~p\n",[UpdState]),
                      AllAddState = add_all_backtracks({Lid, Next}, UpdState),
                      NewChildState = add_all_child_backtracks(Cmd, AllAddState),
                      %% ?f_debug("US : ~p\n",[UpdState]),
                      NewState = add_some_next_to_backtrack(NewChildState),
                      explore(NewState)
  