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Subject: Re: pawn hash tables

Author: Gerd Isenberg

Date: 13:49:10 08/01/03

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On August 01, 2003 at 16:01:51, Joshua Lee wrote:

>Would someone please explain pawn hash and how much of the whole hash tables it
>is when you set them to lets say 256MB?

Hi Joshua,

as Rick already mentioned, pawn hash tables are for pure pawn related eval
stuff. It requires a separate pawn hashkey, incrementally updated if pawn
formation changes, similar to main hash table.

The size depends on the size of your entries and the number of entries of
course. The number of entries should be much more less than in main hash table,
64K entries are quite enough IMHO. But the entry size may be bigger than in main
hash, depending on what you store (some aggregated eval score or several
bitbooards with some important properties).

If i think about my eval with a lot of pawn-king or piece interactions...
May be i throw out pawn hash table in future IsiChess. A lot of pawn patterns
like, isolated, backward, double, triple, candidates, passers, outside passers,
duos, rams etc. may be generated on the fly with bitboards and stored a while.

On the other hand, if you hash pawn eval, you may do a lot of really expensive
things with pawns - the hit rate is about 99%.

Regards,
Gerd

>
>Thankyou



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