Re: hash tables

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Article #2104

#2104

From: Simon Waters
Date: Sat, 05 May 2001 14:36

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Dan Oetting wrote:
> 
> GNU Chess 5 has two hash tables. One for general evaluations and the
> other for pawn evaluations. The available ram needs to be divided
> between the two tables but the optimum split needs to be determined by
> experimentation.

I've experimented a fair bit. Generally make the normal hash
as large as possible. 

Since in Gnuchess the hash table has to be a power of 2, you
usually get an odd sized chunk to fill up with Pawn hash.

IIRC (check the source) the hash table can be configured at
the command, but not the pawn hash (or was that fixed in
5.02?), so edit the header file...

32Mb of RAM - Hmm - this would be cheap to change and make
the average PC much more usable.

Since GNU chess uses the same pseudo random hash codes
everytime it is run, you can make the pawn hash table
permanent by saving it to disk. Alas the other hash table is
cleared between moves, but simply stopping the reset seems
to cause problems I never completely understood.

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From: Simon Waters <Simon@wretched.demon.co.uk>
Newsgroups: gnu.chess
Subject: Re: hash tables
Date: Sat, 05 May 2001 15:36:28 +0100
Organization: Eighth Layer Limited
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