Re^2: Regex, capturing variables vs. speed

Thanks to all for feedback. I did get much more than 2x speed increase for greedy vs. not because my line to match is quite long. Taking what I've learned from the thread, I did some comparisons.

use Benchmark qw/cmpthese/;
                                                  
my $line = 'rs11502186 C/G Chr11 170472 + ncbi_b34 perlegen urn:lsid:p
+erlegen.hapmap.org:Protocol:Genotyping_1.0.0:2 urn:lsid:perlegen.hapm
+ap.org:Assay:25763.7541533:1 urn:lsid:dcc.hapmap.org:Panel:CEPH-30-tr
+ios:1 QC+ GG GG GG NN GG GG GG GG GG GG GG GG GG GG GG GG GG GG GG GG
+ GG GG GG GG GG GG GG GG GG GG GG GG GG GG GG GG GG GG GG GG GG GG NN
+ GG GG GG NN GG GG GG GG GG GG GG GG GG GG GG GG GG NN GG GG GG GG NN
+ GG GG GG GG GG GG GG GG GG GG GG GG GG GG GG GG GG GG GG GG GG GG GG
+ GG GG GG GG GG GG';


cmpthese(-1, 
     {                             
            'Greedy' => sub {$line =~ /(chr.*?)\s.*urn:lsid:(.*?)\s.*p
+anel:(.*?):/i},             
            'Non' => sub {$line =~ /(chr.*?)\s.*?urn:lsid:(.*?)\s.*?pa
+nel:(.*?):/i},              
            'Sep' => sub {$line =~ /(chr.*?)\s/i;
                          $line =~ /urn:lsid:(.*?)\s/i;
                          $line =~ /panel:(.*?):/i;
                      },                          
            'Death_star' => sub {$line =~ /(chr[^\s]+)/i;
                          $line =~ /urn:lsid:([^\s]+)/i;
                          $line =~ /panel:([^:]+)/i; 
                     } 
      }
);
[download]

Giving the following results:

               Rate     Greedy        Sep        Non Death_star
Greedy       8650/s         --       -95%       -95%       -97%
Sep        157827/s      1725%         --        -6%       -41%
Non        167020/s      1831%         6%         --       -38%
Death_star 267963/s      2998%        70%        60%         --
[download]

Killing the star is clearly the way to go. Thanks to the Monks which helped me learn something.

-albert

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Re^3: Regex, capturing variables vs. speed by robin (Chaplain) on Oct 30, 2005 at 20:31 UTC
Even faster is to use a single match, but to be explicit about what you're looking for, i.e. `'Better' => sub { $line =~ /(chr\S).?urn:lsid:(\S).?panel:([^:])/i }` [download] It's always better to write `(\S)\s` than `(.*?)\s`, because you're making it clear to the matching engine exactly what you're looking for (non-space characters in this case).	[reply] [d/l]
Re^4: Regex, capturing variables vs. speed by albert (Monk) on Oct 30, 2005 at 21:06 UTC
Thanks. Speed yet better as you say.... `Rate Sep Non Death_star Better Sep 158510/s -- -10% -23% -65% Non 175363/s 11% -- -15% -61% Death_star 206769/s 30% 18% -- -54% Better 449757/s 184% 156% 118% --` [download] -albert	[reply] [d/l]
Re^3: Regex, capturing variables vs. speed by GrandFather (Saint) on Oct 30, 2005 at 23:42 UTC
Interesting, there must be Perl differences too. The spread is not as great with Active State Perl v5.8.7. In particular, Better is not as much better. `Rate Greedy Sep Death_star Non Be +tter Greedy 9965/s -- -90% -94% -94% +-97% Sep 102700/s 931% -- -34% -37% +-66% Death_star 155342/s 1459% 51% -- -5% +-48% Non 164099/s 1547% 60% 6% -- +-46% Better 301485/s 2925% 194% 94% 84% + --` [download] The results above used OP's benchmark code (with the addition of Better). Perl is Huffman encoded by design.	[reply] [d/l]