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Subject: Re: Pawn hashing without Zobrist keys

Author: Omid David Tabibi

Date: 13:33:13 09/12/03

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On September 12, 2003 at 16:20:22, Gian-Carlo Pascutto wrote:

>On September 12, 2003 at 16:19:11, Omid David Tabibi wrote:
>
>>On September 12, 2003 at 14:13:55, Gerd Isenberg wrote:
>>
>>>Hi,
>>>
>>>i never used Zobrist keys for pawn hashing in IsiChess,
>>>but 64-bit difference of white and black pawn-bitboards
>>>modulus some odd tablesize.
>>>
>>>Not for speed reasons, but simply because i didn't knew
>>>it better a few years ago.
>>>
>>>Recently i played with some modulus by fixed point
>>>approximation methods to get rid of the slow 64-bit mod:
>>
>>Why do you need the modulus operation?
>
>Because a pawnhash of 2^64 entries is rather large, and
>you can't AND since that just means you cancel out part
>of the board.

I still don't understand why modulus is needed, and I have a pawn hash of 2^17
entries. What is so special about pawn hash that you need the modulus operation
there while you don't need it in the normal hash table?


>
>--
>GCP



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