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Subject: Re: Pawn hashing without Zobrist keys

Author: Dieter Buerssner

Date: 11:39:46 09/12/03

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Hi Gerd,

my answer is not exactly referring to your post, but an idea I always had.
Instead of Zorbrist type hashing, one could use some "classical" hashing
function: See all the position data (or pawn pos data) as a string, and
calculate a hash - perhaps a 32 bit hash. Many schemes don't need any modulo.
One could use a (32-bit) modulo in the last step. Perhaps one could try the
typical CRC scheme (source available for example in zip). Crypto experts
certainly could suggest even better schemes. Incremental updates would perhaps
be difficult or impossible, but might be possible in some schemes. For pawn
hashing, storing the whole pawn structure as 2 bitboards, plus perhaps 12 bytes
for the KK pos for verification of clashes might be no problem (I guess, most
that use pawn hashing already store lot's of things about the pawnstructure
anyway, so the size overhead should not be too bad, and would have the
advantage, that one really has certainty).

Regards,
Dieter



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