Author: Robert Hyatt
Date: 21:03:09 05/28/99
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On May 28, 1999 at 18:07:17, vitor wrote: >as far as i can tell, zobrist hashing seems to be an imperfect(but fast) hashing >scheme, meaning it is possible that your program will mistake position X as >position Y. > >so my question is: >is zobrist hashing the current standard in computer chess? is it just an >accepted risk or are there any perfect hashing schemes that are used? The term "perfect hashing scheme" is an oxymoron. There is no such animal, _by definition_. Because you are reducing an N-bit quantity (if I recall, from a mathematical discussion a few years ago, a chess board can be represented in something just over 160 bits [I have not followed the discussion here as this isn't a burning issue with me]) to an M-bit quantity, where N >> M. IE I hash using 64 bits everywhere... which means there is _no_ way to represent a chess board accurately in only 64 bits... since the original is > 64 bits...
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