Author: John Hatcher
Date: 02:31:28 03/19/01
Go up one level in this thread
On March 19, 2001 at 05:27:10, John Hatcher wrote: >On March 19, 2001 at 05:23:02, John Hatcher wrote: > >>On March 19, 2001 at 05:21:08, John Hatcher wrote: >> >>>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 >> >>Sorry, here's the diagram: >> >>[D]wKc3,Bg6,Ph5/bKe7,Pg7,h6 w - - > >Geez, not my day.... > > >[D]8/4k1p1/6Bp/7P/8/8/2K5/8 w - - 0 1 > >JOHN Fourth time's a charm...... [D]8/4k1p1/6Bp/7P/8/2K5/8/8 w - - 0 1
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