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Re: [computer-go] Ko and transposition tables

On May 10, 2005, at 11:04 AM, Chris Fant wrote:


One option is to XOR all previous-board Zobrist hashes and store that
value in the table as well.  This would take care of #1 and #2 below.
I may have some misconceptions about Zobrist hashes, but this doesn't seem like it would work. Suppose I play the move sequence A, B, C, D. This produces the following sequence of Zobrist hashes:

A
A xor B
A xor B xor C
A xor B xor C xor D

If I xor these four bit patterns together, I'll get B xor D. In other words, only the stones that are on the board for an odd number of moves in the sequence will be taken into account. Thus, an alternate sequence like E, B, F, D will look exactly the same.

I also don't see how this would take depth into account.

Peter Drake
Assistant Professor of Computer Science
Lewis & Clark College
http://www.lclark.edu/~drake/
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