# Regexp-engine: ruby vs. perl **URL:** \ **Category:** Ruby\ **Created:** [July 6, 2009, 5:07pm UTC](https://www.ruby-forum.com/t/regexp-engine-ruby-vs-perl/171611 "2009-07-06T17:07:12Z")\ **Posts on this page:** 2\ **Page:** 1
**Author:** ![Axel\_S](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/a/6bbea6/32.png) [@Axel\_S](https://www.ruby-forum.com/u/Axel_S)\ **Post date:** [July 6, 2009, 5:07pm UTC](https://www.ruby-forum.com/t/regexp-engine-ruby-vs-perl/171611/1 "2009-07-06T17:07:12Z")
-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 Hello list, I’ve got a question about ruby’s regexp-engine: I’m wondering why ruby’s regexp-engine is soo much slower than perl’s. My test file looks like this (status.dat from nagios): { key=value … ~20 further key=value pairs } This file’s size is about 100MB. [perl – v5.8.8] time perl -wnl -00 -e ‘print if /host\_name=monslave\d+/ and /service\_description=load/ and /servicestatus\s+{[^}]+}/m’ /tmp/status.dat \>/dev/null perl -wnl -00 -e /tmp/status.dat \> /dev/null 0.90s user 0.11s system 51% cpu 1.946 total [ruby19 – ruby 1.9.1p129 (2009-05-12 revision 23412) [i686-linux]] time ruby19 -wnl -00 -e ‘print if /host\_name=monslave\d+/ and /service\_description=load/ and /servicestatus\s+{[^}]+}/m’ /tmp/status.dat \>/dev/null ruby19 -wnl -00 -e /tmp/status.dat \> /dev/null 5.13s user 0.15s system 50% cpu 10.449 total [ruby18 – ruby 1.8.7p5000 (2009-02-19) [i686-linux]] time ruby18 -wnl -00 -e ‘print if /host\_name=monslave\d+/ and /service\_description=load/ and /servicestatus\s+{[^}]+}/m’ /tmp/status.dat \>/dev/null ruby18 -wnl -00 -e /tmp/status.dat \> /dev/null 3.93s user 0.05s system 48% cpu 8.153 total So, both versions of ruby are slower than perl and I’m wondering why. I’d like to integrate ruby in my daily work (it’s actually a wonderful/beatiful language) it’s hard to justify when things like the trivial regexp above is about a factor of 4-5 slower than in perl. And writing/using regexps is part of my daily work. Thanks * * * Freundliche Grüße / Kind regards Axel S. Platform Engineer * * * domainfactory GmbH Oskar-Messter-Str. 33 85737 Ismaning Germany Mobil: +49 (0)176 / 10246727 Telefon: +49 (0)89 / 55266-356 Telefax: +49 (0)89 / 55266-222 E-Mail: removed\_email\_address@domain.invalid Internet: www.df.eu Registergericht: Amtsgericht München HRB-Nummer 150294, Geschäftsführer: Tobia Sara Marburg, Jochen Tuchbreiter -----BEGIN PGP SIGNATURE----- Version: GnuPG v2.0.10 (MingW32) Comment: Using GnuPG with Mozilla - [http://enigmail.mozdev.org](http://enigmail.mozdev.org) iEYEARECAAYFAkpSEsIACgkQsuqpduCyZM1hdgCguZab/bhqUBpyCLbEKvIoM2nj NigAn1pvoVHCzGNIUve+0NgcYprlKCeZ =tZ+c -----END PGP SIGNATURE----- ---
**Author:** ![Axel\_S](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/a/6bbea6/32.png) [@Axel\_S](https://www.ruby-forum.com/u/Axel_S)\ **Post date:** [July 6, 2009, 9:29pm UTC](https://www.ruby-forum.com/t/regexp-engine-ruby-vs-perl/171611/2 "2009-07-06T21:29:40Z")
On 7/6/09, Axel S. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote: > I’ve got a question about ruby’s regexp-engine: I’m wondering why ruby’s > regexp-engine is soo much slower than perl’s. Just guessing here, but usually when regexes are slow it’s because of backtracking. Since it looks like you don’t need any backtracking in this little script, you might try throwing in some (?\> ) around your repetitions. (And yes, perl doesn’t require this hack to be fast. Perl’s probably applying it for you automatically… perl’s regex is smarter than ruby’s; what can I say?) HTH