Author: blass uri
Date: 03:18:47 08/06/00
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On August 06, 2000 at 05:19:33, Colin Frayn wrote: >On August 05, 2000 at 06:47:04, Ricardo Gibert wrote: > >>>This position came up in a game I just played between ColChess (Development >>>version) and Sjeng v7.1. >>> >>>[D]8/R7/8/8/7P/6P1/3k2K1/2q5 b - - >>> >>>ColChess, as Black, has to move, having just promoted a pawn to a queen, and >>>then white played a rook move (Ra5-a7). >>> >>>This looks like it should be an easy win for black, but in the game ColChess >>>just moved its pieces around aimlessly and drew by repetition. This annoyed me >>>quite a bit so I tried this position at longer time controls and sure enough it >>>still couldn't see anything. Then I tried it with Crafty and still nothing. >>> >>>Is this one of those positions where it's drawn and humans (if they're better >>>than me) can see it easily but a computer can't? If so then I'd better fix >>>ColChess' evaluation function before release so that it doesn't exchange off >>>(from a stronger position it sac'd its rook to promote the pawn) >> >>On the other hand, there may be another reason why your program should not have >>played into this line that _is_ fixable. Why not post the position before the >>sac and see how other programs handle it? > >OK I couldn't find the game, but I think this was the position 2 moves before, >followed by Ra5 Rxa5 c1=Q Ra7. > >[D]8/8/8/2R5/7P/6P1/r1pk2K1/8 b - - > >It looks almost better to have a lone rook against the 2 pawns, i.e. by playing >c1=Q Rxc1 Rxc1 or something. Crafty certainly prefers this. Of course, I might >have the position wrong, but it was certainly very similar. I think, as was >said, it may be that ColChess values queens too highly in certain endgame >situations. However, in general I value a queen as better than 2 rooks in an >endgame, which I think is justified. > >Cheers, >Col I think that the 5 piece tablebases can help you. Unfortunately I have not the KR vs KPP tablebases. Uri
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