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Subject: Re: Hashing is a complicated affair ?

Author: rasjid chan

Date: 17:11:41 04/05/04

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On April 05, 2004 at 19:48:12, Dann Corbit wrote:

ONE ENTRY PER HASH TABLE IS PROBLEM ENOUGH and sufficient to engage
me for some time. I will only take note of possibilities
just in case I need them later.

Rasjid




>On April 05, 2004 at 19:37:20, Ricardo Gibert wrote:
>
>>On April 05, 2004 at 19:23:48, Dann Corbit wrote:
>>
>>[...]
>>
>>>
>>>Complicated idea:
>>>First level hash table is large
>>>Second level hash table is log(big_table_size)
>>>Third level hash table is log(second_level_size)
>>>Fourth level hash table is log(third_level_size)
>>>Hash replacement scheme is a function that eats several parameters and decides
>>>heuristically which entries are the most important.
>>
>>I'm not understanding your use of the log() function above. How about pluging in
>>some concrete numbers to illustrate what you mean?
>e.g.:
>First level hash has 1048576 elements and index is 20 bits so tag=64-20=44 bits
>Second level hash has 32 elements and index is 5 bits so tag=64-5=59 bits
>3rd level hash has 2 elements and index is 2 bits so tag = 62 bits
>4th level hash has one element, no index and 64 bit tag.
>
>Second level index [in case of collision] is just (hash & (32-1))
>3rd level index is just (hash & 1)
>last level needs no index
>
>Collisions are pretty rare.  I think that the above is good enough, but maybe
>someone else has a better idea.



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