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Subject: Re: KQ vs kr position

Author: Robert Hyatt

Date: 13:34:40 08/04/99

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On August 04, 1999 at 16:24:58, Ricardo Gibert wrote:

>I think I figured out what the problem is.
>
>Consider W: Kf2, Re2, Pa2; B: Kh2.
>
>Distance to mate will return:
>1 Re3 Kh1 2 Rh3#
>
>Distance to mate or winning pawn move or winning capture will return:
>1 a4 Kh3 2 a5 Kg4, etc.
>
>The pawn move is a 1 mover that leads to a winning position, while the rook move
>is a 2 mover to lead to mate. To avoid this idiotic behavior, distance to mate
>must be used at the expense of extremely rare positions that will instead of win
>due to the 50 move rule. The rest of the program must deal with 3-fold
>repetition (easy) and the 50 move rule as best as it can.


you say "deal repetition (easy)".  I don't see how it is possible, much less
easy.  Unless the program plays the whole game from start to finish.  Because
tablebases are positions that say "mate in N moves from this position" and that
is a reference to a path of moves that if followed, end up with mate in the
number of moves given...  But if someone has played some non-optimal moves,
this won't work, because between "here" and "mate" lies a whole lot of other
positions that have to be stepped over.  And it is just possible that one of
those positions has already been hit twice before the computer gets a chance to
do the lookup.  And I don't see _any_ way to repair this.

of course, it isn't a problem if the computer plays from the beginning.  But
the lack of path information from the tablebase hit to the final tablebase
mate position is a killer, otherwise...



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