bug#22357: grep -f not only huge memory usage, but also huge time cost

[Jim Meyering]

On Wed, Dec 21, 2016 at 3:04 PM, Norihiro Tanaka <address@hidden> 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