anchor.diff:                      link(Pid),
                       Pid ! ?VECTOR_MSG(Lid, VC),
                       receive
  -                        ?VECTOR_MSG(PidsLid, ok) -> ok;
  +                        ?VECTOR_MSG(_PidsLid, ok) -> ok;
                           {'EXIT', Pid, _Reason} ->
                               %% Process may have been asked to exit.
                               ok                                                        
  
positive.code:                 end
          end,
      {ok, Pick, _Clock} = lists:foldl(Fold, none, Candidates),
      {one, Pick}.
  
  update_sleep_map(Procs, SleepThis, SleepMap) ->
      Update =
          fun(OldSleeps) ->
              ordsets:add_element(SleepThis, OldSleeps)
          end,
      Init = ordsets:from_list([SleepThis]),
      Fold =
          fun(P, Dict) ->
              dict:update(P, Update, Init, Dict)
          end,
      lists:foldl(Fold, SleepMap, Procs).
  
  %% - add new entry with new entry
  %% - wait any possible additional messages
  
negative.code:     #dpor_state{trace = [TraceTop|_] = Trace} = State,
      #trace_state{i = I, enabled = Enabled, blocked = Blocked,
                   nexts = Nexts, lid_trace = LidTrace,
                   clock_map = ClockMap, sleep_set = SleepSet} = TraceTop,
      NewN = I+1,
      ClockVector = lookup_clock(Lid, ClockMap),
      LidsClockVector = dict:store(Lid, NewN, ClockVector),
  