Programming Erlang: Chapter 8 Problem 2

'Tis an odd title, I know.  My puppy is prancing around the kitchen trying to get me interested in his chew toy, dropping it near me so I can see that it bounces and wiggles.

Do you want to see Erlang bounce and wiggle? The code below creates a circular linked list of Erlang N processes, then sends a Message around it M times. Pretty cool, huh? Well, it was meant to be used by readers of "Programming Erlang" to compare their favorite language to Erlang. I didn't bother doing this with C# threads, though it would be interesting to try it out with the concurrency and co-ordination runtime.

Here's the out put of the code (time is in milliseconds):

Sent 30000000 messages in 27453 / 29186

-module(problem2).
-compile(export_all).

start(N, M, Message) when is_integer(N), is_integer(M) ->
  statistics(runtime),
  statistics(wall_clock),
  FirstPid = spawn(?MODULE,loop,[[]]),
  LastPid = create(1, N, FirstPid),
  FirstPid ! LastPid, %% the ring is closed
  send(0, M, FirstPid, Message),
  {_, Time1} = statistics(runtime),
  {_, Time2} = statistics(wall_clock),
  io:format("Sent ~p messages in ~p / ~p~n", [N * M, Time1, Time2]).
  
send(C, C, _Pid,  _Message) -> void;
send(I, C, Pid, Message) ->
  Pid ! {self(), Message},
  receive
    finished -> void
  end,
  send(I+1, C, Pid, Message).

create(C, C, Pid) -> Pid; 
create(I, C, Pid) -> 
  create(I+1, C, spawn(?MODULE, loop, [Pid])).

loop(Next) ->
  receive
    {Caller, FirstPid, Message} ->
      if
        FirstPid =:= self() -> Caller ! finished;
        true -> Next ! {Caller, FirstPid, Message}
      end,
      loop(Next);
    {Caller, Message} ->
      Next ! {Caller, self(), Message},
      loop(Next);
    NewNext when Next =:= [] ->
      loop(NewNext)
  end.