GNU bug report logs - #21763
poor performance since grep 2.19 when comparing files with grep

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From: Jim Meyering <jim <at> meyering.net>
To: Norihiro Tanaka <noritnk <at> kcn.ne.jp>
Cc: Paul Eggert <eggert <at> cs.ucla.edu>, 21763-done <at> debbugs.gnu.org, Bruce Dubbs <bruce.dubbs <at> gmail.com>, 22357-done <at> debbugs.gnu.org, sur-behoffski <sur_behoffski <at> grouse.com.au>, "L.A. Walsh" <law <at> tlinx.org>, "Bennett, Steve" <S.Bennett <at> lancaster.ac.uk>, JQK <jquan <at> redhat.com>, Aharon Robbins <arnold <at> skeeve.com>, 22239 <at> debbugs.gnu.org, Trevor Cordes <gnu <at> tecnopolis.ca>, Paul Jackson <pj <at> usa.net>, Bruno Haible <bruno <at> clisp.org>, Ond?ej Cifka <ondra <at> cifka.com>
Subject: bug#21763: bug#22357: grep -f not only huge memory usage, but also huge time cost
Date: Thu, 22 Dec 2016 03:14:16 -0800

On Wed, Dec 21, 2016 at 3:04 PM, Norihiro Tanaka <noritnk <at> kcn.ne.jp> wrote:
>   yes $(printf %040d 0) | head -10000000 >inp
>   printf '0\n1\n' >pat
>   env LC_ALL=C src/grep -w -f pat inp

Thanks for mentioning that.
Here is some actual data (Fedora 25 on an i7-4770S):

for i in $(env ls -1dv /p/p/grep-*/bin/grep) src/grep; do env LC_ALL=C
time -f "%e $i" $i -w -f pat inp; done
1.05 /p/p/grep-2.3/bin/grep
0.91 /p/p/grep-2.4.1/bin/grep
0.91 /p/p/grep-2.4.2/bin/grep
0.91 /p/p/grep-2.4/bin/grep
0.94 /p/p/grep-2.5.1/bin/grep
0.94 /p/p/grep-2.5.3/bin/grep
0.94 /p/p/grep-2.5.4/bin/grep
0.95 /p/p/grep-2.5/bin/grep
0.90 /p/p/grep-2.6.1/bin/grep
1.03 /p/p/grep-2.6.2/bin/grep
0.90 /p/p/grep-2.6.3/bin/grep
0.90 /p/p/grep-2.6/bin/grep
0.90 /p/p/grep-2.7/bin/grep
0.90 /p/p/grep-2.8/bin/grep
0.90 /p/p/grep-2.9/bin/grep
0.90 /p/p/grep-2.10/bin/grep
0.89 /p/p/grep-2.11/bin/grep
0.90 /p/p/grep-2.12/bin/grep
0.90 /p/p/grep-2.13/bin/grep
0.89 /p/p/grep-2.14/bin/grep
0.90 /p/p/grep-2.15/bin/grep
0.90 /p/p/grep-2.16/bin/grep
0.89 /p/p/grep-2.17/bin/grep
0.90 /p/p/grep-2.18/bin/grep
0.90 /p/p/grep-2.19/bin/grep
0.90 /p/p/grep-2.20/bin/grep
0.86 /p/p/grep-2.21/bin/grep
0.90 /p/p/grep-2.22/bin/grep
0.91 /p/p/grep-2.23/bin/grep
0.91 /p/p/grep-2.24/bin/grep
0.91 /p/p/grep-2.25/bin/grep
0.25 /p/p/grep-2.26/bin/grep
13.07 /p/p/grep-2.27/bin/grep
37.49 src/grep

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