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Re: A (memory) poor man's <strike>hash</strike> lookup table.

by TimToady (Parson)
on Nov 22, 2003 at 00:07 UTC ( #309076=note: print w/ replies, xml ) Need Help??

in reply to A (memory) poor man's <strike>hash</strike> lookup table.

For another approach, look at Tie::SubstrHash. You'd have to recast your problem as keys of constant length though. Still, it'd be interesting to see a timing comparison.

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Re: Re: A (memory) poor man's <strike>hash</strike> lookup table.
by BrowserUk (Pope) on Nov 22, 2003 at 09:43 UTC

    The timing comes out to 10 minutes for the insertion and 9.6 minutes for iteration of the million keys.

    use Tie::SubstrHash; tie %hash, 'Tie::SubstrHash', 7, 1, 1_000_000; print time; $hash{ pack 'A7', $_ } = ' ' for 1 .. 1_000_000; print time; 1069489311 1069489911 $n = 0; print time; $n += defined $hash{ pack 'A7', $_ } for 1 .. 1_000_000; print time, $ +/, $n; 1069490448 1069491023 1000000

    I think that it may be possible to improve this a little by updating the module. It uses local several places where my would probably be quicker. Though, I suspect that the main performance hit is the cost of tie rather than the implementation. Part of my reasoning for liking the mechanism I described was that it was simple enough in it's implementation that it could be coded directly avoiding the need for tie.

    I also think that it would be possible to improve the user interface by having the module perform any padding required rather than the caller,

    Examine what is said, not who speaks.
    "Efficiency is intelligent laziness." -David Dunham
    "Think for yourself!" - Abigail

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