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Date: Tue, 28 Apr 2009 23:37:09 -0400
Message-ID: <f8560b80904282037t61b27ce7lbe532b0f2dd54ee9@mail.gmail.com>
Subject: Re: [Caml-list] Strange performance bug
From: Markus Mottl <markus.mottl@gmail.com>
To: Brighten Godfrey <pbg@cs.berkeley.edu>
Cc: caml-list@yquem.inria.fr
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X-Spam: no; 0.00; bug:01 markus:01 mottl:01 markus:01 mottl:01 bug:01 compiler:01 pcre:01 pcre:01 regexp:01 ocaml:01 28,:98 2009:98 wrote:01 pat:01 

On Tue, Apr 28, 2009 at 22:43, Brighten Godfrey <pbg@cs.berkeley.edu> wrote=
:
> I've encountered a very odd performance problem which I suspect is not a =
bug
> in my code. =A0Could it be the compiler, or maybe PCRE?

I'm not sure it solves your problem (haven't tried the example), but
just looking at the code there is clearly a performance bug: the
pattern is passed to Pcre.pmatch "on the fly" using label "~pat".
This is ok and convenient if it is used only once, but is bad if it
happens in a loop.  Precompile the regular expression outside of the
loop (let rex =3D Pcre.regexp "...") and pass it in with label "~rex" to
solve this problem.

Regards,
Markus

--=20
Markus Mottl        http://www.ocaml.info        markus.mottl@gmail.com