Author: John Hatcher
Date: 02:21:08 03/19/01
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On March 19, 2001 at 04:27:48, Steffen Jakob wrote: >Hi, > >in a game between Hossa and Crafty the following position occured: > >[D]8/8/8/8/p7/Pb6/1P6/K2k4 w - - > >White gets mated in 6 moves: > >1.Kb1 Bc2+ 2.Ka1 Kc1 3.Ka2 Bb3+ >4.Ka1 Bc4 5.b4 a4xb3 6.a4 b2# > >Hossa sees this very fast of course, but when I looked at his analysis I saw >that he evaluated the first few plies as a draw. The reason for this is that >e.g. the position above matches an eval term where Hossa "sees" that black has a >wrong bishop (the extra white pawns are included in that term). And in fact >white's position seems to be very unlucky here. E.g. I think if white's king is >somewhere else than on a1 or b1 then it is a draw. Also if the b2 pawn wouldnt >be there or somewhere else it looks like a draw. I think that even if in the >same position the pawn a3 wouldnt be on the board it is a draw (?). > >So it seems as if this is a very rare exception to my rule that the maximum >score for the side with the bishop is a draw if one side has "a" or "h" pawns >and a wrong bishop and the other side has 1 or two pawns. > >Do other engines who have some knowledge in such positions have the same problem >in the static evaluation of that position? > >Can you think of extra conditions to handle this problem? > >Can you think of other positions where >- one side has only a or h pawns >- has the wrong bishop >- the weaker side has 2 pawns >- no pawn of the weak side is attacked by a pawn of the side with the bishop >- the a/h passers dont run in a trivial way >- it is a win for the bishop side??? > >Best wishes, >Steffen. This position arose, with colors reversed, in an old endgame study (Walker 1841), which can be found in Rueben Fine's "Basic Chess Endings" as diagram No. 153. The starting position of the study is: [D]wKc3,Bg6,Ph5/bKe7,Pg7,h6 By the way, Fritz finds the mate instantly. Regards, John
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