[erlang-questions] Erlang vs IO
Alpár Jüttner
alpar@REDACTED
Thu Sep 4 14:14:57 CEST 2008
> Greetings,
>
> If you are reading a file (as opposed to stdin) you can use
> file:read_file/2 (if you have enough RAM) or file:read/2 (after using
> the flag 'raw' when doing file:open/2).
>
Could you explain it a little bit more?
I'm very interested to see how to transform the code example of the
original question to use file:read_file/2 or file:read/2.
Best regards,
Alpar
>
> bengt
>
> On Wed, 2008-09-03 at 17:27 +0300, Imre Palik wrote:
> > Hi,
> >
> > It is me messing up something, or the IO in erlang is quite slow? I run the following program on a largish file:
> >
> > -module(intest).
> > -export([run/0]).
> >
> > problem_loop(0, _, Acc) ->
> > io:fwrite("~w~n", [Acc]),
> > void;
> > problem_loop(I, D, A) ->
> > {ok, [V]} = io:fread([], "~d"),
> > if
> > 0 == V rem D ->
> > problem_loop(I - 1, D, A + 1);
> > true ->
> > problem_loop(I - 1, D, A)
> > end.
> >
> >
> > run() ->
> > {ok, [Iter, Div]} = io:fread([], "~d ~d"),
> > problem_loop(Iter, Div, 0).
> >
> > Then both of my cores started to run at 100%, which I find weird in itself with an IO bound problem. Also, I compared the runtime with the following program written in scheme
> >
> > #!/usr/bin/guile -s
> > !#
> >
> > (define (intest iter div acc)
> > (if (= iter 0)
> > (display acc)
> > (if (= 0 (remainder (read) div))
> > (intest (- iter 1) div (+ acc 1))
> > (intest (- iter 1) div acc))))
> >
> > (intest (read) (read) 0)
> >
> >
> > The scheme implementation was 10 times as fast as the erlang, and it only used one of the cores.
> >
> > How can I get a decent IO performance out of erlang? Am I making some mistakes in my erlang code? Should I upgrade my erlang system? (I am running R12B on windows)
> >
> > Thx.
> >
> > ImRe
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