Author: martin fierz
Date: 03:00:23 06/15/01
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On June 15, 2001 at 05:19:42, Dann Corbit wrote: >On June 15, 2001 at 05:09:35, martin fierz wrote: > >>On June 15, 2001 at 02:40:15, Dann Corbit wrote: >> >>>Suppose that you have a chessboard represented as 64 characters, and you want to >>>make a hash from it. This works well, if you make a 64 bit hash by hashing the >>>first 32 characters and then the second 32 characters to make two 32 bit chunks. >>> It was quite a bit faster than Zobrist hashing. On the other hand, it cannot >>>be used to do incremental updates, so you might be sorry you used it if you >>>decide to go that route. >> >>one of the best checkers programs (kingsrow by ed gilbert) uses this hash >>function. ed wrote me once that this was faster than zobrist. i have >>never tried it myself. > >I can verify that it is faster than Zobrist hashing if you hash the whole board >at once. However, if you do incremental updates, then Zobrist once again >becomes faster and by a goodly margin. With Zobrist hashing, you can >make/unmake for a single piece. i am using zobrist with incremental updates, ed gilbert is using this jenkins hash. his program is a lot faster than mine, but probably just because he is generally a better programmer than i am :-) anyway, he wrote me that this hash was faster than zobrist incremental... of course, in checkers you have a smaller board and only 4 kinds of pieces, so there is a difference to chess there - in chess and checkers, you have about the same incremental update difference with zobrist, but in checkers you have a much smaller effort to generate a whole new hashkey because of the smaller board and less piece types. cheers martin
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