[32971] in Perl-Users-Digest
Perl-Users Digest, Issue: 4247 Volume: 11
daemon@ATHENA.MIT.EDU (Perl-Users Digest)
Tue Jul 8 06:09:15 2014
Date: Tue, 8 Jul 2014 03:09:02 -0700 (PDT)
From: Perl-Users Digest <Perl-Users-Request@ruby.OCE.ORST.EDU>
To: Perl-Users@ruby.OCE.ORST.EDU (Perl-Users Digest)
Perl-Users Digest Tue, 8 Jul 2014 Volume: 11 Number: 4247
Today's topics:
Re: Cost of qr// vs m// <hjp-usenet3@hjp.at>
Digest Administrivia (Last modified: 6 Apr 01) (Perl-Users-Digest Admin)
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Date: Tue, 8 Jul 2014 11:57:42 +0200
From: "Peter J. Holzer" <hjp-usenet3@hjp.at>
Subject: Re: Cost of qr// vs m//
Message-Id: <slrnlrng4m.9c4.hjp-usenet3@hrunkner.hjp.at>
On 2014-07-06 23:08, Ilya Zakharevich <nospam-abuse@ilyaz.org> wrote:
> On 2014-03-28, Rainer Weikusat <rweikusat@mobileactivedefense.com> wrote:
>> This mystery is easily explained when looking the the decompiled/
>> disassembled internal represention (I've omitted everything except the
>> actual loop). 'live' becomes
>
> I do not see how it explains anything…
[...]
>> For the qr'ed case, it actually calls into the top-level regexp compiler
>> routine (pp_regcomp) on each iteration which gets the already compiled
>> regexp out of the passed argument in case contained a (reference) to an
> ^^^^ it
>> already compiled regexp instead of calling the 'real' regexp compiler.
>> Judging from the (5.10.1) C-code, the compiled regexp is also copied to
>> 'a temporary object' for each match.
>
> With 5.8.8 (the last version for which I bear some responsibility),
> the timing is
> qr 2.28
> q 2.19
> inline 1.78
[...]
> *This* is reasonable, and matches what I intended with qr//.
It's much better than the current behaviour, but reusing the precompiled
regex is still *slower* than just recompiling the regex every time. I
thought the intention was to be faster - ideally almost as fast an
inline regexp.
(Of course /some/ is an atypically simple regex, the results may be
different with a more complex regex).
hp
--
_ | Peter J. Holzer | Fluch der elektronischen Textverarbeitung:
|_|_) | | Man feilt solange an seinen Text um, bis
| | | hjp@hjp.at | die Satzbestandteile des Satzes nicht mehr
__/ | http://www.hjp.at/ | zusammenpaßt. -- Ralph Babel
------------------------------
Date: 6 Apr 2001 21:33:47 GMT (Last modified)
From: Perl-Users-Request@ruby.oce.orst.edu (Perl-Users-Digest Admin)
Subject: Digest Administrivia (Last modified: 6 Apr 01)
Message-Id: <null>
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End of Perl-Users Digest V11 Issue 4247
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