FAQ 3.6 How do I profile my Perl programs?

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3.6: How do I profile my Perl programs?

    You should get the Devel::DProf module from the standard distribution
    (or separately on CPAN) and also use Benchmark.pm from the standard
    distribution. The Benchmark module lets you time specific portions of
    your code, while Devel::DProf gives detailed breakdowns of where your
    code spends its time.

    Here's a sample use of Benchmark:

      use Benchmark;

      @junk = `cat /etc/motd`;
      $count = 10_000;

      timethese($count, {
                'map' => sub { my @a = @junk;
                               map { s/a/b/ } @a;
                               return @a },
                'for' => sub { my @a = @junk;
                               for (@a) { s/a/b/ };
                               return @a },

    This is what it prints (on one machine--your results will be dependent
    on your hardware, operating system, and the load on your machine):

      Benchmark: timing 10000 iterations of for, map...
             for:  4 secs ( 3.97 usr  0.01 sys =  3.98 cpu)
             map:  6 secs ( 4.97 usr  0.00 sys =  4.97 cpu)

    Be aware that a good benchmark is very hard to write. It only tests the
    data you give it and proves little about the differing complexities of
    contrasting algorithms.


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