#!/bin/sh
# grep-2.21 would incur a 100x penalty for 10x increase in regexp length

# Copyright 2015-2023 Free Software Foundation, Inc.

# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.

# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.

# You should have received a copy of the GNU General Public License
# along with this program.  If not, see <https://www.gnu.org/licenses/>.

. "${srcdir=.}/init.sh"; path_prepend_ ../src

fail=0

# This test is susceptible to failure due to differences in
# system load during the two test runs, so we'll mark it as
# "expensive", making it less likely to be run by regular users.
expensive_
require_perl_

echo x > in || framework_failure_
# Note that we want 10x the byte count (not line count) in the larger file.
seq 10000 50000 | tr -d '\012' > r || framework_failure_
cat r r r r r r r r r r > re-10x || framework_failure_
mv r re || framework_failure_

returns_ 0 user_time_ 1 grep -f re in > base-ms \
    || framework_failure_ 'failed to compute baseline timing'
base_ms=$(cat base-ms)

# This test caused trouble on at least two types of fringe hosts: those
# with very little memory (a 1.5GB RAM Solaris host) and a Linux/s390x
# (emulated with qemu-system-s390x). The former became unusable due to
# mem requirements of the 2nd test, and the latter ended up taking >35x
# more time than the base case. Skipping this test for any system using
# more than this many milliseconds for the first case should avoid those
# false-positive failures while skipping the test on few other systems.
test 800 -lt "$base_ms" && skip_ "this base-case test took too long"

returns_ 0 user_time_ 1 grep -f re-10x in > b10x-ms \
    || framework_failure_ 'failed to compute 10x timing'
b10x_ms=$(cat b10x-ms)

# Increasing the length of the regular expression by a factor
# of 10 should cause no more than a 10x increase in duration.
# However, we'll draw the line at 20x to avoid false-positives.
returns_ 1 expr $base_ms '<' $b10x_ms / 20 || fail=1

Exit $fail