Re: [computer-go] Ko and transposition tables

[Peter Drake <drake@xxxxxxxxxx>]

On May 11, 2005, at 10:39 AM, Chris Fant wrote:

> You should always have the same number of factors in your board  
> hash, so...
>
> Move   Board hash      Cumulative hash
> 1      A^B^C^D         A^B^C^D
> 2      A^E^C^D         B^D^E
> 3      A^E^C^F         A^B^C^F
> 4      G^E^C^F         A^B^E^G
>
> In each move, I have changed one component of the board hash (but more
> will change when you capture).
Okay, I see part of the confusion.  In my Zobrist scheme, I only have  
numbers for black and white points, not for vacant points.  Thus, the  
Zobrist hash for the empty board is always zero.  I don't think this  
matters here;  it just happens that A, B, C, and D are zero.

Using your notation, notice that the value F (which presumably  
represents a stone at some location) is no longer a factor in the  
final cumulative hash.  This means that the cumulative hash will be  
the same no matter where move 3 is played.  Isn't this a problem?


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