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Subject: Re: programmers: pawn hash tables

Author: Ed Schröder

Date: 00:43:20 03/08/03

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On March 08, 2003 at 01:42:15, Robert Hyatt wrote:

>On March 08, 2003 at 01:29:46, Joel wrote:
>
>>Hey All,
>>
>>Just wondering what everyone thinks is the best way to implement a pawn hash
>>table?
>>
>>At the moment I am incrementally generating a seperate pair of pawn hash keys,
>>and using them to index a table - very similar to how my transposition table
>>works.
>>
>>Is it possible to do _significantly_ better than this? It seems to be somewhat
>>expensive to do, although having said that my NPS still went up at least 20% in
>>most situations.

>That is what everyone since chess 4.x has done.  Two signatures, one for
>all pieces and pawns, one just for pawns.

I don't use it, the problem is that you can not evaluate the coherence between
pawns and the other pieces. If you have stuff like that in your eval pawn
hashing is unusable and IMO that evaluation (coherence) is a must in a chess
program.

My best,

Ed



>
>
>>
>>I am not really worried about effeciency as much as some other people here, so I
>>guess I am really asking whether I am missing something major.
>
>Doesn't sound like it.  But you will end up storing more than just a score for
>the position.  IE passed pawn locations, weak pawn locations (or bitmaps that
>feature them).  Etc...
>
>>
>>Regards,
>>Joel



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