Author: Vincent Diepeveen
Date: 06:48:42 03/01/01
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On February 28, 2001 at 17:35:48, Sune Larsson wrote: >On February 28, 2001 at 16:47:27, Bertil Eklund wrote: > >>On February 28, 2001 at 16:23:35, Sune Larsson wrote: >> >>> >>> [D]8/5b2/p2k4/1p1p1p1p/1P1K1P1P/2P1PB2/8/8 w - - 0 1 >>> >>> >>> This is one of Averbakh's positions from 1954. >>> It's a typical winning position in a good versus bad bishop ending. >>> The black pawns on h5, f5, d5 and a6 are vulnerable and curtail the >>> movements of the black bishop. To seal black's fate, all white need to do >>> is lose a move. That is - repeat the initial position with black to move. >>> This may be accomplished as follows: >>> >>> 1.Be2 Be8 [1.-Bg6 2.Bd3 Bh7 3.Bf1 leads to instant zugzwang, be it after >>> 3.-Bg6 4.Bg2 Bf7 5.Bf3 or after 3.-Bg8 4.Be2 Bf7 5.Bf3] >>> >>> 2.Bd3 Bg6 3.Bc2 Bh7 4.Bb3! Bg8 5.Bd1 Bf7 6.Bf3! and so on >>> >>> >>> Test: The above position is won for white so your program should be able >>> to win it. The evals should differ distinctly between white and black. >>> >>> Sune >> >>Hej! >> >>Nimzo8 sees it immediately with a score of more then +2. >>It also sees 1.Bg2 as winning with about the same score. >> >>Bertil > > Okej, it's a bit hard to find a good balance, when choosing these positions. > If they are too easy some people just complain - if they are too hard > almost noone answers...;) > > Sune The big problem is to find correct positions. Every position i always get i have to double check things. Majority of all positions a few tactical extensions find it already 100x faster. Your rook position was very cool though. The bad bishop on g3 i had already implemented quite some time ago :) The problem here is that in a normal position a single bad placed pawn can lose, nearly all programs realize that now. however this position is more complicated from human viewpoint as the black king is doing a great job, so you need more weaknesses and need a zugzwang here. How to tell my program that it only wins this position if it can create a zugzwang? So the basic fault here of the chessplayer is the assumption that it is a bad bishop position. it's in fact a zugzwang position. for a single zugzwang you need a few plies of search that's it. Cool for my double nullmove to show its correctness, but no big deal really :)
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