Author: Dann Corbit
Date: 11:50:11 09/12/03
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On September 12, 2003 at 14:39:46, Dieter Buerssner wrote: >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). An n-bit SDBM hash scheme would be a good one, I bet. Perhaps 2^20 entries (1,048,576) and a simple and operation will finish the hash. (Or you could even have an unsigned:20 type). The SDBM hash is super simple and yet of high quality. http://www.cs.yorku.ca/~oz/hash.html
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