anchor.diff:  
   start_link() ->
       gen_server:start_link({local, ?SERVER}, ?MODULE, [], []).
  +
  +stop() ->
  +    gen_server:call(?SERVER, stop).
   
   reset() ->
       gen_server:call(?SERVER, reset).
  
positive.code: 
  collect(Duration, Nodes) ->
      gen_server:call(?SERVER, {collect, Duration,  Nodes}).
  
  %% Return the trace
  results() ->
  
negative.code: -record(state, {trace=[],
                  filters=[],
                  mfs=[],
                  stop_tref,
                  stop_from,
                  tracing=false}).
  
  %%===================================================================
  %% API
  