in reply to Re^3: question about reg exp engine
in thread question about reg exp engine

Show your benchmark. I see about a 75x difference between the single regex and the multiple regex solutions offered by the OP.

Note that benchmarks are rather like statistics: Lies, damn lies and benchmarks.

Perl reduces RSI - it saves typing

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Re^5: question about reg exp engine
by broomduster (Priest) on Aug 04, 2008 at 00:11 UTC
    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.
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      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
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[d/l]
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        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.

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