-module(pingpong).
-export([oneway/0, consumer/0, pingpong/0]).

oneway() ->
    N = 10000000,
    Pid = spawn(?MODULE, consumer, []),
    Start = erlang:now(),
    dotimes(N - 1, fun () -> Pid ! message end),
    Pid ! {done, self()},
    receive ok -> ok end,
    Stop = erlang:now(),
    N / time_diff(Start, Stop).

pingpong() ->
    N = 10000000,
    Pid = spawn(?MODULE, consumer, []),
    Start = erlang:now(),
    Message = {ping, self()},
    dotimes(N, fun () ->
                       Pid ! Message,
                       receive pong -> ok end
               end),
    Stop = erlang:now(),
    N / time_diff(Start, Stop).

consumer() ->
    receive
        message -> consumer();
        {done, Pid} -> Pid ! ok;
        {ping, Pid} ->
            Pid ! pong,
            consumer()
    end.

dotimes(0, _) -> done;
dotimes(N, F) ->
    F(),
    dotimes(N - 1, F).

time_diff({A1,A2,A3}, {B1,B2,B3}) ->
    (B1 - A1) * 1000000 + (B2 - A2) + (B3 - A3) / 1000000.0 .