GNU bug report logs - #21696
[PATCH 1/2] grep: improvement of performance of grep -Fw

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From: help-debbugs <at> gnu.org (GNU bug Tracking System)
To: Paul Eggert <eggert <at> cs.ucla.edu>
Cc: tracker <at> debbugs.gnu.org
Subject: bug#21696: closed ([PATCH 1/2] grep: improvement of performance
 of grep -Fw)
Date: Sat, 17 Oct 2015 05:49:01 +0000

[Message part 1 (text/plain, inline)]

Your message dated Fri, 16 Oct 2015 22:48:07 -0700
with message-id <5621E117.8040201 <at> cs.ucla.edu>
and subject line Re: bug#21696: [PATCH 1/2] grep: improvement of performance of grep -Fw
has caused the debbugs.gnu.org bug report #21696,
regarding [PATCH 1/2] grep: improvement of performance of grep -Fw
to be marked as done.

(If you believe you have received this mail in error, please contact
help-debbugs <at> gnu.org.)


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21696: http://debbugs.gnu.org/cgi/bugreport.cgi?bug=21696
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From: Norihiro Tanaka <noritnk <at> kcn.ne.jp>
To: <bug-grep <at> gnu.org>
Subject: [PATCH 1/2] grep: improvement of performance of grep -Fw
Date: Sat, 17 Oct 2015 10:13:36 +0900

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I found that grep -Fw is extremely slow in spite of whether in
multibyte locales or not.

$ yes 'abcdefg hijklmn opqrstu vwxyz' | head -100000 >k
$ time -p env LC_ALL=C grep -Fw vwxy k
real 14.03
user 12.51
sys 0.74
$ time -p env LC_ALL=ja_JP.eucJP grep -Fw vwxy k
real 14.29
user 12.67
sys 0.50

$ time -p env LC_ALL=C grep -w vwxy k
real 0.11
user 0.01
sys 0.09
$ time -p env LC_ALL=ja_JP.eucJP grep -w vwxy k
real 0.89
user 0.71
sys 0.15

First patch fixes the problem.  Second patch changes as using grep
matcher for grep -Fw in single byte locales.

In single byte locales, DFA (not regex) is also used for words matching,
and it is very fast as above result.

[0001-grep-improvement-of-performance-of-grep-Fw.patch (text/plain, attachment)]

[0002-grep-use-grep-matcher-for-grep-Fw-in-single-byte-loc.patch (text/plain, attachment)]

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From: Paul Eggert <eggert <at> cs.ucla.edu>
To: Norihiro Tanaka <noritnk <at> kcn.ne.jp>, 21696-done <at> debbugs.gnu.org
Subject: Re: bug#21696: [PATCH 1/2] grep: improvement of performance of grep
 -Fw
Date: Fri, 16 Oct 2015 22:48:07 -0700

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Thanks for those performance improvements. I installed them, with some minor 
changes to commentary. I also installed a couple of minor tweaks to the code, to 
use memrchr and to simplify the multibyte test. Attached are the revised set of 
patches.

[0001-grep-improve-performance-of-grep-Fw.patch (text/plain, attachment)]

[0002-grep-use-memchr-memrchar.patch (text/plain, attachment)]

[0003-grep-use-grep-matcher-for-grep-Fw-when-unibyte.patch (text/plain, attachment)]

[0004-grep-simplify-previous-change.patch (text/plain, attachment)]

[0005-maint-add-news-item.patch (text/plain, attachment)]

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