GNU bug report logs - #17700
[PATCH] dfa: speed-up for a pattern that many atoms are catenated

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From: Norihiro Tanaka <noritnk <at> kcn.ne.jp>
To: Paul Eggert <eggert <at> cs.ucla.edu>
Cc: Aharon Robbins <arnold <at> skeeve.com>, 17700 <at> debbugs.gnu.org
Subject: bug#17700: [PATCH] dfa: speed-up for a pattern that many atoms are catenated
Date: Fri, 06 Jun 2014 07:49:22 +0900

Thanks.

Paul Eggert wrote:
> It seems to me that much of the performance benefit comes from using a
> faster implementation of strstr, and that the DFA code will be better
> off if it simply uses the system strstr rather than rolling its own.

`lookfor' isn't terminated by `\-'\0' in istrstr(), but strstr() requires
it.  So I wasn't replace it to strstr();

after `grep: undo part of previous change', no longer faster.

$ printf '%02048d\n' 0 | time -p src/grep -f - /dev/null

master  : real 5.74  user 5.40  sys 0.17
my patch: real 0.08  user 0.04  sys 0.04

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