From: Paolo Bonzini <paolo.bonzini@gmail.com>
To: Jeff King <peff@peff.net>
Cc: Junio C Hamano <gitster@pobox.com>, John Bito <jwbito@gmail.com>,
git <git@vger.kernel.org>
Subject: Re: git diff looping?
Date: Wed, 17 Jun 2009 13:02:11 +0200 [thread overview]
Message-ID: <4A38CD33.9020402@gmail.com> (raw)
In-Reply-To: <20090617102332.GA32353@coredump.intra.peff.net>
> system, orig: 0.22s
> system, paolo: 0.22s
> system, ".": 0.15s
> compat, orig: 150.88s
> compat, paolo: 0.43s
> compat, ".": 0.15s
>
> Besides the exponential behavior on the original regex, it is still
> about twice as slow as the system one.
The reason is that the glibc regex is a DFA-based matcher. It is much
slower on regexes with backreferences, but otherwise it is faster.
> 1. Replace the builtin diff.java.xfuncname pattern with what Paolo
> suggested (though I haven't verified its correctness beyond a
> cursory look at the results).
I checked it a bit harder, but still it is not easy to check because of
the false positives in the original regex. I'm pretty sure it's correct
though; I find it even easier to read (though longer) than the
original one.
> I haven't looked at how large or how portable the glibc
> implementation is.
Decently portable, but I don't think it's worth it. Users that write
regexes so complex should know of the exponential behavior, I think.
Paolo
next prev parent reply other threads:[~2009-06-17 11:02 UTC|newest]
Thread overview: 37+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-06-16 1:37 git diff looping? John Bito
2009-06-16 2:44 ` Jeff Epler
2009-06-16 2:53 ` John Bito
2009-06-16 11:47 ` Jeff King
2009-06-16 12:07 ` Jeff King
2009-06-16 12:11 ` [PATCH 1/2] Makefile: refactor regex compat support Jeff King
2009-06-16 18:47 ` Johannes Sixt
2009-06-16 19:05 ` Jeff King
2009-06-16 19:07 ` [PATCH v2 " Jeff King
2009-06-16 19:08 ` [PATCH v2 2/2] Makefile: use compat regex on Solaris Jeff King
2009-06-16 20:07 ` Brandon Casey
2009-06-17 13:15 ` Mike Ralphson
2009-06-17 13:55 ` Mike Ralphson
2009-06-16 12:14 ` [PATCH " Jeff King
2009-06-16 15:48 ` git diff looping? John Bito
2009-06-16 16:51 ` Junio C Hamano
2009-06-16 17:15 ` Jeff King
2009-06-16 17:35 ` Brandon Casey
2009-06-16 17:39 ` John Bito
2009-06-16 17:41 ` Jeff King
2009-06-16 20:22 ` Brandon Casey
2009-06-17 8:46 ` Paolo Bonzini
2009-06-17 10:23 ` Jeff King
2009-06-17 11:02 ` Paolo Bonzini [this message]
2009-06-17 11:31 ` Andreas Ericsson
2009-06-17 13:08 ` Paolo Bonzini
2009-06-17 13:16 ` Andreas Ericsson
2009-06-17 13:58 ` Paolo Bonzini
2009-06-17 14:26 ` [PATCH] avoid exponential regex match for java and objc function names Paolo Bonzini
2009-06-17 15:46 ` demerphq
2009-06-17 15:56 ` Jeff King
2009-06-17 16:00 ` demerphq
2009-06-17 16:04 ` Paolo Bonzini
2009-06-17 16:42 ` Junio C Hamano
2009-06-18 6:45 ` Paolo Bonzini
2009-06-16 17:16 ` git diff looping? John Bito
2009-06-16 17:24 ` Jeff King
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