Author: martin fierz
Date: 11:49:16 10/07/00
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On October 07, 2000 at 10:41:27, Vincent Diepeveen wrote: >On October 07, 2000 at 04:31:09, Peter McKenzie wrote: > >>I've been browsing 'Comprehensive Chess Endings, Pawn Endings' by Averbakh & >>Maiselis, picking out a few interesting looking positions to test my program >>with. Here is the little test suite I came up with: >> >>8/1p4kP/5pP1/3p4/8/4P3/7K/8 w - - bm e4; id "CCE4 479"; >>8/1pp5/3k3p/PP6/2P2K2/8/8/8 b - - bm Kd7; id "CCE 491a"; >>2k2K2/8/pp6/2p5/2P5/PP6/8/8 w - - bm a4; id "CCE4 530"; >>8/pp3p2/8/6kp/8/3K1PP1/PP6/8 b - - bm f5; id "CCE4 608"; >>8/pp2k1pp/2p5/2P1p3/2P1P2P/6P1/P7/2K5 b - - bm g5; id "CCE4 679"; >>8/1p6/p1p5/P1Pp2pp/1P1P1p1k/5P1P/6PK/8 w - - bm g3 g4; id "CCE 680"; >>8/1k6/p4p2/2p2P2/p1P2P2/2P5/P1K5/8 w - - bm Kc1; id "CCE 765"; > >all peanuts except #7 kc1 under 1 minute single cpu, >i have to checkout Kc1 position 7. i'm at 40 ply now, but it doesn't >see how to win with Kc1. all moves are +1.96 position 7 looks wrong to me. i analysed it a bit - it's one of those 'corresponding squares' studies - the author's intention is this: there are 3 special squares on the board: a3, e4 and h6. whenever the white king appears on one of these, the black king MUST be on a5, d6 and g7, respectively. you call a3 and a5 'corresponding squares' (CS). the point of all of these studies is this: once you have identified the primary CS, you can go on and identify secondary CS - for instance f3 corresponds to e7, because from f3 the white king threatens to move both to e4 and to h5 very quickly, so black must be ready for this. b2 corresponds to b6, and so on. to win you must find a square for which the other side has no corresponding square. i see the author's intention in this study, but i suppose he forgot something. the reasoning seems to be that black must do something about his f6-pawn, but black has a stalemate trick with ...a3,Kb6,Ka5,Ka4 and a5. so white cannot go after the f6 pawn and the position is a draw. i'm pretty sure that the main line in peter's book goes 1.Kc1 Kc7 2.Kd1 Kd7 3.Ke1 Kc7 4.Kf2 but here 4 ...a3 is a draw. (but of course it's rather dangerous to critizice averbakh :-) ) for a position with corresponding squares which really works and is hard for computers, check my chess puzzle page, www.fierz.ch/pontresina.htm, position number 2. the solution is Kb6 or Kc6 followed by Kc7 - fritz doesnt really see it's winning in this position, just a small +1 or so. cheers martin
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