Re: Re: Re: Idiomatic optimizations

[thelenm]

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.