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Subject: Re: Efficient hash algorithm?

Author: James Robertson

Date: 16:32:37 09/21/98

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On September 21, 1998 at 18:56:46, John Coffey wrote:

>On September 21, 1998 at 18:12:36, Tom Kerrigan wrote:
>
>>Mostly correct, although maintaining two numbers to describe the position is
>>overkill. One 64 bit number should be enough.
>>
>
>Is one 64 bit number enough to uniquely identify a position?  Does this
>prevent two positions from getting the same hash key?

I sent a message to Robert Hyatt with the same question, and he said that the
odds of turning up two positions with the same number is almost nil.

>
>I assume that you convert your hash key into an index into the history.
>I assume that you take your 64 bit number and divide it by a constant
>(or right shift it) to get the number of entries available in your hash
>table?  i.e. 64 megs would be 4 million positions.

Yes. There are several ways to come up with the hash index, but I know a not a
few people who use the Zobrist algorithm.

>
>John Coffey



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