Author: Ricardo Gibert
Date: 14:00:03 08/04/99
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On August 04, 1999 at 16:34:40, Robert Hyatt wrote: >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. Yes, I see what you mean now. You can deal with some cases, but not others. The "winning" line can be quite long and a search can be prohibitive to avoid the 3-fold repetition. > >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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