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Subject: Re: A fast hash -- assuming you are not planning to do incremental updates

Author: Dann Corbit

Date: 02:19:42 06/15/01

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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.




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