[erlang-questions] Ring Benchmark Problem

[Robert Virding]

Your ring loop becomes something like:

ring(Next) ->
    receive
        {_From,Msg} ->
            Next ! {self(),Msg},
            loop(Next);
        stop ->
            Next ! stop,
            ok
    end.

where we include the sender in the message (might be useful) and a stop
message which it sends to the next process and then dies. Starting the
processes can be done in a number of ways, for example "backwards" around
the ring or each process spawning its successor.

Robert


On 12 January 2015 at 19:25, Harit Himanshu <harit.subscriptions@REDACTED>
wrote:

> That sounds like a good idea Robert, could you please guide me how to
> achieve this?
>
> Thanks
>
> On Mon, Jan 12, 2015 at 10:00 AM, Robert Virding <rvirding@REDACTED>
> wrote:
>
>> A much better way than sending the path around is for every process to
>> keep track for itself the next process in the ring so you just need to send
>> the message between the processes. At least if you are after speed. If you
>> do do need to be able to dynamically restructure the ring it would be easy
>> to add an extra message where you tell a process its new next process.
>>
>> Robert
>>
>>
>> On 11 January 2015 at 20:48, Harit Himanshu <
>> harit.subscriptions@REDACTED> wrote:
>>
>>> Hello there,
>>>
>>> I need help with code review on my attempt to following problem
>>>
>>>  Write a ring benchmark. Create N processes in a ring. Send a message
>>> round the ring M times so that a total of N * M messages get sent. Time
>>> how long this takes for different values of N and M.
>>>
>>> I have not timed this yet, and guidance on recommended ways to time is
>>> very much appreciated.
>>>
>>> For now, following is the code for ring that I wrote. Please let me know
>>> if there are any shortcomings or code could be written in an much idiomatic
>>> way.
>>>
>>> Thanks a lot
>>> + Harit
>>>
>>> *Code*
>>>
>>> -module(ring).
>>> -author("harith").
>>>
>>> %% API
>>> -export([message/2]).
>>>
>>> % create ring of N processes and
>>> % send M messages between them
>>> message(N, M) when is_integer(N), is_integer(M), N > 0, M > 0 ->
>>>   Ring = create_ring(N),
>>>   [Start | T] = Ring,
>>>   Start ! {T, Ring, 1, M}.
>>>
>>> create_ring(N) ->
>>>   Processes = [spawn(fun() -> loop() end) || _ <- lists:seq(1, N)],
>>>   [H | _] = Processes,
>>>   lists:append(Processes, [H]).
>>>
>>> loop() ->
>>>   receive
>>>     {[H | T], _L, CurrentMessage, M} ->
>>>       io:format("~p received ~p~n", [self(), CurrentMessage]),
>>>       H ! {T, _L, CurrentMessage, M},
>>>       loop();
>>>     {[], Ring, CurrentMessage, M} ->
>>>       io:format("~p received ~p with empty list~n", [self(),
>>> CurrentMessage]),
>>>       case CurrentMessage < M of
>>>         true ->
>>>           [_ | [Next | T]] = Ring,
>>>           NewMessage = CurrentMessage + 1,
>>>           io:format("sending message ~p to ~p~n", [NewMessage, Next]),
>>>           Next ! {T, Ring, NewMessage, M};
>>>         false -> io:format("done sending ~p messages in ~p ring, taking
>>> rest now.~n",[M, Ring])
>>>       end,
>>>       loop()
>>>   end.
>>>
>>> *Output*
>>> 1> ring:message(4, 3).
>>> <0.33.0> received 1
>>> {[<0.34.0>,<0.35.0>,<0.36.0>,<0.33.0>],
>>>  [<0.33.0>,<0.34.0>,<0.35.0>,<0.36.0>,<0.33.0>],
>>>  1,3}
>>> <0.34.0> received 1
>>> <0.35.0> received 1
>>> 2> <0.36.0> received 1
>>> 2> <0.33.0> received 1 with empty list
>>> 2> sending message 2 to <0.34.0>
>>> 2> <0.34.0> received 2
>>> 2> <0.35.0> received 2
>>> 2> <0.36.0> received 2
>>> 2> <0.33.0> received 2 with empty list
>>> 2> sending message 3 to <0.34.0>
>>> 2> <0.34.0> received 3
>>> 2> <0.35.0> received 3
>>> 2> <0.36.0> received 3
>>> 2> <0.33.0> received 3 with empty list
>>> 2> done sending 3 messages in
>>> [<0.33.0>,<0.34.0>,<0.35.0>,<0.36.0>,<0.33.0>] ring, taking rest now.
>>> 2>
>>>
>>> _______________________________________________
>>> erlang-questions mailing list
>>> erlang-questions@REDACTED
>>> http://erlang.org/mailman/listinfo/erlang-questions
>>>
>>>
>>
>
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