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Re: (Ovid) Re: Comparing two hash tables

by Rajiv (Initiate)
on Mar 28, 2002 at 22:01 UTC ( #155131=note: print w/ replies, xml ) Need Help??


in reply to (Ovid) Re: Comparing two hash tables
in thread Comparing two hash tables

Thanks for your reply The reason why i am trying to delete the similar keys is that gradually the the search for the next similar would become faster owing to lesser number of keys left. I will also try calculating the time taken using Benchmark module.


Comment on Re: (Ovid) Re: Comparing two hash tables
Re: Re: (Ovid) Re: Comparing two hash tables
by PrakashK (Pilgrim) on Mar 29, 2002 at 04:43 UTC
    The reason why i am trying to delete the similar keys is that gradually the the search for the next similar would become faster owing to lesser number of keys left
    The time to access a hash member does not depend on the number of keys, but on whether the distribution of the hash keys into the buckets is uniform or not.

    /prakash

      So how can i ensure whether the distribution of keys in the buckets is uniform or not ? Please suggest Thanks

        The following will give you some information about the hashing:     print scalar %hash;
        See perldata for information: search for "bucket":

        This is pretty much useful only to find out whether Perl's internal hashing algorithm is performing poorly on your data set. For example, you stick 10,000 things in a hash, but evaluating %HASH in scalar context reveals `"1/16"', which means only one out of sixteen buckets has been touched, and presumably contains all 10,000 of your items. This isn't supposed to happen.

        However, this probably won't help you because you have no control over the hashing mechanism.

        Ultimately, the only way for you to answer your question is to use Benchmark.

        --
        John.

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