For Large Dictionaries Could One Use Separate Dictionaries Where Each Dictionary Covers an Interval of the Input Range?

skip at pobox.com skip at pobox.com
Wed May 17 02:48:14 CEST 2006


    bob> If you have the same number of entries as buckets, and you have a
    bob> good hash function, then if you have n buckets your longest chain
    bob> should have length around ln(n).  The average length of a nonempty
    bob> bucket would be somewhere around 1 1/2.

Yes, and it achieves that nice short chain length by consuming gobs of
memory.  A dictionary with 10**7 keys is going to chew up lots of memory.
There's nothing particularly magical about dictionaries in this respect.
They are good examples of a classic time-space tradeoff.

Skip




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