GNU bug report logs - #24009
[PATCH] grep: use fastmap in regex

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From: Norihiro Tanaka <noritnk <at> kcn.ne.jp>
To: 24009 <at> debbugs.gnu.org
Subject: bug#24009: [PATCH] grep: use fastmap in regex
Date: Sun, 17 Jul 2016 01:57:30 +0900

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

sed and gawk use fastmap in regex, but grep does not.  By using fastmap,
I expect that grep speeds up for patterns as regex is used.

before:
$ time -p env LC_ALL=ja_JP.eucjp src/grep '\([a-b]\)\1' k
real 7.83
user 7.62
sys 0.07

after:
$ time -p env LC_ALL=ja_JP.eucjp src/grep '\([a-b]\)\1' k
real 0.46
user 0.38
sys 0.07

However, if grep uses fastmap, fails in case-fold-titlecase test.  It
means that grep's behavior differ from sed and gawk, as they use fastmap,
although it seems to be a bug in regex.

[0001-grep-use-fastmap-in-regex.patch (text/plain, attachment)]

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