From: Wai-Sun Chia <waisun.chia@...>
Date: 2002-10-07T17:30:15+09:00
Subject: Re: regex speed

Here's my take:

RH7.3 box, Perl 5.6.1, Ruby 1.7.3 (2002-09-13)

$ perl -0 -ne'print 1 if /A.+\n+B/s' str      # 0m0.517s
$ ruby -0 -ne'print 1 if /A.+\n+B/m' str      # 0m5.715s
$ perl -0 -ne'print 1 if /A.+\n.+\nB/s' str   # 0m5.854s
$ ruby -0 -ne'print 1 if /A.+\n.+\nB/m' str   # 0m3.574s

Heh. So Ruby 1.7.3 overtakes Perl for complex regexes??!! ;-)

This is a Xeon 1.8GHz/512MB box.


David Garamond wrote:
> i am noticing ruby is much slower than perl when matching patterns with 
> two or more quantifier (+ or *). consider this string:
> 
>  $ ruby -0 -ne 'print "A"*3,"\n"*10000,"B"*10,"\n"*10000' > str
> 
> and matching this string:
> 
>  $ perl -0 -ne'print 1 if /A.+\n+B/s' str   # 0m1.682s
>  $ ruby -0 -ne'print 1 if /A.+\n+B/m' str   # 0m12.468s
>  $ perl -0 -ne'print 1 if /A.+\n.+\nB/s' str   # 0m1.368s
>  $ ruby -0 -ne'print 1 if /A.+\n.+\nB/m' str   # 0m11.427s
> 
> php (pcre) speed is somewhere in between.
> 
> of course, with patterns like /A.+\n+.+B/ or those with more quantifiers 
> both become very slow, but i suspect perl is still faster then ruby 
> especially when there are fewer ".+" and more "SINGLECHAR+" subpatterns. 
>  i even have one case where perl takes less than a second and ruby takes 
> more than five minutes (i don't know for sure, i interrupted the process 
> so ruby never finished).
> 
> note that i'm not implying anything though, because i understand perl's 
> regex engine has undergone a long period of tweaking and optimization.
> 


-- 
Wai-Sun "Squidster" Chia <waisun.chia@ac-ac.org>
Sr. OpenSource Consultant, M.Sc., RHCE
Advanced Computing & Application Center
Universiti Teknologi Malaysia