[erlang-questions] How do I elegantly check many conditions?

Hynek Vychodil <>
Fri Mar 20 18:40:21 CET 2009


I forgot, it is on 2.2GHz Intel Core2 Duo CPU - it means exception handling
takes less than thousand CPU cycles in byte-code and  less than 300 in
native code.

On Fri, Mar 20, 2009 at 6:33 PM, Hynek Vychodil <>wrote:

> One benchmark is worth of thousand questions ;-)
>
> -module(exceptiontest).
>
> -export([test/2, success/0, fail/0]).
>
> test(0, _)-> ok;
> test(N, F)->
>     try
>         ok = ?MODULE:F()
>     catch
>         error:{badmatch, fail} -> fail
>     end,
>     test(N-1, F).
>
> success()->ok.
>
> fail()->fail.
>
> Byte code:
>
> 9> timer:tc(exceptiontest,test,[1000000, fail]).
> {469954,ok}
> 10> timer:tc(exceptiontest,test,[1000000, success]).
> {164390,ok}
>
> Native:
>
> 11> c(exceptiontest, native).
> {ok,exceptiontest}
> 12> timer:tc(exceptiontest,test,[1000000, fail]).
> {146526,ok}
> 13> timer:tc(exceptiontest,test,[1000000, success]).
> {21573,ok}
>
> It means about roughly 2 millions exceptions in one second (0.47us)
> compared to 6 millions success (external) function calls (0.146us) - one can
> guess that exception handling takes about 0.32us.
> In native code it is 6.8 vs 47 millions per second and handling can take
> about 0.125us. There can be some additional cost for try-catch construct
> which I haven't measured this way. (Is very low how I remember from past.)
>
>
> On Fri, Mar 20, 2009 at 3:43 PM, ryeguy <> wrote:
>
>> I actually like that one the best. It's cleanest, and simplest. I
>> actually thought about something like this, but my mind is still
>> clouded from other evil languages, where exceptions should be used for
>> "exceptional" situations (exluding Python).
>>
>> Is exception handling cheap in Erlang?
>>
>> On Mar 20, 10:34 am, Paul Fisher <> wrote:
>> > Hynek Vychodil wrote:
>> > > One of Joe's suggestion: program success case code separated from
>> error
>> > > handling. You can make it in this way
>> >
>> > > create_user(Email, UserName, Password) ->
>> > >   try
>> > >     ok = new_email(Email),
>> > >     ok = valid_user_name(UserName),
>> > >     ok = new_user(UserName),
>> > >     ok = strong_password(Password),
>> > >     ...
>> > >     _create_user(Email, UserName, Password)
>> > >   catch
>> > >     error:{badmatch, email_in_use} -> do_something();
>> > >     error:{badmatch, invalid_user_name} -> do_something();
>> > >     error:{badmatch, user_exists} -> do_something();
>> > >     error:{badmatch, weak_password} -> do_something();
>> > >     ...
>> > >   end.
>> >
>> > +1 Bravo!
>> >
>> > --
>> > paul
>> >
>> > _______________________________________________
>> > erlang-questions mailing list
>> > ://
>> www.erlang.org/mailman/listinfo/erlang-questions
>> _______________________________________________
>> erlang-questions mailing list
>> 
>> http://www.erlang.org/mailman/listinfo/erlang-questions
>>
>
>
>
> --
> --Hynek (Pichi) Vychodil
>
> Analyze your data in minutes. Share your insights instantly. Thrill your
> boss.  Be a data hero!
> Try Good Data now for free: www.gooddata.com
>



-- 
--Hynek (Pichi) Vychodil

Analyze your data in minutes. Share your insights instantly. Thrill your
boss.  Be a data hero!
Try Good Data now for free: www.gooddata.com
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://erlang.org/pipermail/erlang-questions/attachments/20090320/96d5133d/attachment.html>


More information about the erlang-questions mailing list