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Subject: Re: pawn hash tables

Author: Omid David Tabibi

Date: 14:07:07 08/01/03

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On August 01, 2003 at 16:49:10, Gerd Isenberg wrote:

>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%.

That's about the hit rate I get in closed positions, but for example searching
from the start position, I only get a hit rate of of slightly over 90%.


>
>Regards,
>Gerd
>
>>
>>Thankyou



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