FAQ 3.15 How can I make my Perl program run faster?

Discussion in 'Perl Misc' started by PerlFAQ Server, Jan 1, 2011.

  1. This is an excerpt from the latest version perlfaq3.pod, which
    comes with the standard Perl distribution. These postings aim to
    reduce the number of repeated questions as well as allow the community
    to review and update the answers. The latest version of the complete
    perlfaq is at http://faq.perl.org .


    3.15: How can I make my Perl program run faster?

    The best way to do this is to come up with a better algorithm. This can
    often make a dramatic difference. Jon Bentley's book *Programming
    Pearls* (that's not a misspelling!) has some good tips on optimization,
    too. Advice on benchmarking boils down to: benchmark and profile to make
    sure you're optimizing the right part, look for better algorithms
    instead of microtuning your code, and when all else fails consider just
    buying faster hardware. You will probably want to read the answer to the
    earlier question "How do I profile my Perl programs?" if you haven't
    done so already.

    A different approach is to autoload seldom-used Perl code. See the
    AutoSplit and AutoLoader modules in the standard distribution for that.
    Or you could locate the bottleneck and think about writing just that
    part in C, the way we used to take bottlenecks in C code and write them
    in assembler. Similar to rewriting in C, modules that have critical
    sections can be written in C (for instance, the PDL module from CPAN).

    If you're currently linking your perl executable to a shared *libc.so*,
    you can often gain a 10-25% performance benefit by rebuilding it to link
    with a static libc.a instead. This will make a bigger perl executable,
    but your Perl programs (and programmers) may thank you for it. See the
    INSTALL file in the source distribution for more information.

    The undump program was an ancient attempt to speed up Perl program by
    storing the already-compiled form to disk. This is no longer a viable
    option, as it only worked on a few architectures, and wasn't a good
    solution anyway.


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    are not necessarily experts in every domain where Perl might show up,
    so please include as much information as possible and relevant in any
    corrections. The perlfaq-workers also don't have access to every
    operating system or platform, so please include relevant details for
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