in reply to Re: Finding all substrings
in thread Finding all substrings

Um, cool! But it leaks memory at an insane rate on 5.6.1. Trying to run 100,000 iterations nearly made my computer explode.

-sam

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Re: Finding all substrings
by Dominus (Parson) on Apr 24, 2002 at 21:17 UTC
    Says samtregar:
    Um, cool! But it leaks memory at an insane rate on 5.6.1.
    Jeff Pinyan explained this one to me. The code in the regex captures the first instance of @ss, and keeps appending to it, 1023 new elements every time through the loop. You can fix the problem by using a static variable: 
    { my @ss;
  sub substrings {
    @ss = ();
    $_[0] =~ /.*?(.+?)(?{push @ss, $1})(?!)/;
    @ss;
  }
}

    [download]

    --
    Mark Dominus
    Perl Paraphernalia

[reply]
[d/l]
      Ah, much better. Now I can test it! Here are the results from my benchmark against /usr/dict/words, 100,000 iterations (my final code above is "new" and your code is "mjd"): 
      Benchmark: timing 100000 iterations of mjd, new, original...
       mjd: 17 wallclock secs (16.86 usr +  0.00 sys = 16.86 CPU) @ 59
+31.20/s (n=100000)
       new:  3 wallclock secs ( 2.70 usr +  0.01 sys =  2.71 CPU) @ 36
+900.37/s (n=100000)
  original: 17 wallclock secs (12.87 usr +  0.01 sys = 12.88 CPU) @ 77
+63.98/s (n=100000)
            Rate      mjd original      new
mjd       5931/s       --     -24%     -84%
original  7764/s      31%       --     -79%
new      36900/s     522%     375%       --

      [download]
      It looks like this solution is actually slower than the original...

      -sam

[reply]
[d/l]

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