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Subject: Re: Hash Collisions

Author: William Bryant

Date: 10:23:24 02/21/99

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On February 21, 1999 at 10:21:50, Robert Hyatt wrote:

>On February 21, 1999 at 01:14:37, KarinsDad wrote:
>
>>I posted this the other day, but it may have been obscured (or not if nobody has
>>any information on it).
>>
>>I have been wondering if changing the Zobrist hash from a set of random number
>>to a set of non-random and very specific numbers could result in a more even
>>distribution in the hash table. Has anyone done any work in this area?
>>
>>KarinsDad
>
>
>Burt Wendroff and Tony Warnock published a paper in the JICCA a few years
>ago discussing this.  The main issue is to find the hamming distances between
>_all_ the random numbers, and maximize all of them.  Random numbers work fine
>if they have been tested (I ran all of mine thru a hamming distance analysis
>when I first started).
>
>As far as 'distribution' this is done by the low order N bits
>(N=log2(hash_size)) of the hash signature.  You _could_ do the hamming analysis
>on just those bits as well.

I check all my random numbers for uniqueness, ie no duplicates,and use
0xFFFFFFFFFFFFFFFF for the side to move (compliment the side to move),
but would appreciate information on 'hamming distance analysis' in not to
complicated to post or send via email.

Thank you,

William
wbryant@ix.netcom.com




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