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Re: Re: Re: Idiomatic optimizations

by thelenm (Vicar)
on Apr 30, 2002 at 16:59 UTC ( #163127=note: print w/replies, xml ) Need Help??

in reply to Re: Re: Idiomatic optimizations
in thread Idiomatic optimizations

Nah, no castigation here. When I whipped up my test, I had thought that the alphabet x 500 was a pretty big string, but now that I'm thinking clearly that's not very big at all.

To test out a really big string, I replicated Romeo and Juliet 500 times, read the whole thing into a string, then ran the same regular expressions almost the same regular expressions. I removed /o from the 'chars' sub, which actually made it a little faster. The string was about 70 MB. Here is my new test code:

use strict; use Benchmark qw(cmpthese); local $/ = undef; open IN, "romeo-and-juliet-500-times.txt"; my $text = <IN>; close IN; # Ten iterations is enough with a 70 MB string! cmpthese(10, { 'i' => sub { $text =~ /abc/ig }, 'chars' => sub { $text =~ /[Aa][Bb][Cc]/g }, });
To my surprise (again!), the /i version ran in about 1/3 the time as the character-class version. Here is the output on my machine:
Benchmark: timing 10 iterations of chars, i... chars: 40 wallclock secs (38.37 usr + 0.04 sys = 38.41 CPU) @ 0 +.26/s (n=10) i: 12 wallclock secs (11.43 usr + 0.01 sys = 11.44 CPU) @ 0 +.87/s (n=10) s/iter chars i chars 3.84 -- -70% i 1.14 236% --
I'm amazed. Am I not testing the right thing? Or has /i really been cleaned up in recent versions of Perl? I'm running 5.6.1.

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