Re^5: question about reg exp engine

I have a feeling I may be about to learn something... ;-)

use strict;
use warnings;


use Benchmark   qw( cmpthese );

my $results = cmpthese( -10, {
                              'r3' => sub {
                                  my $string = "  stuff  ";
                                  $string =~ s/^\s//g;
                                  $string =~ s/\s$//g;
                                  $string =~ s/\s+$//g;
                              },
                              'r1' => sub {
                                  my $string = "  stuff  ";
                                  $string =~ s/^\s|\s$|\s+$//g;
                              },
                             }
                      );
[download]

       Rate  r1  r3
r1 295926/s  -- -1%
r3 299980/s  1%  --
[download]

Updated: Now that I see GrandFather's detailed Benchmark below, I see that my error was to use a short string. When I change to

my $string = (' ' x 1000) . 'x' . (' ' x 1000);
[download]

matching GrandFather's, I get the following:

       Rate   r3   r1
r3  61890/s   -- -79%
r1 297607/s 381%   --
[download]

So Lies, damn lies, and benchmarks (with the wrong data), indeed.

Comment on Re^5: question about reg exp engine Select or Download Code

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Re^6: question about reg exp engine by GrandFather (Saint) on Aug 04, 2008 at 00:24 UTC
Changing `" stuff "` to `(' ' x 1000) . 'x' . (' ' x 1000)` gives: `Rate r1 r3 r1 1849/s -- -99% r3 166166/s 8888% --` [download] It is important that a benchmark test what you think it is testing so what you think is being tested must entail a significant portion of the benchmark's processing time. Update: BTW, my result for your original benchmark was: `Rate r1 r3 r1 767220/s -- -10% r3 855450/s 11% --` [download] Perl reduces RSI - it saves typing	[reply] [d/l] [select]
Re^7: question about reg exp engine by broomduster (Priest) on Aug 04, 2008 at 00:43 UTC
I didn't see this reply before I Updated above, but now we're in the same direction, even if the magnitude of difference is off. As I said earlier, the largest difference I saw for the short string was 3% (about a dozen runs, looking back). BTW, I can confirm your observation about the penalty associated with 'nibble' vs. 'swallow' vs. both.	[reply]


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