Author: Simon Finn
Date: 13:52:25 09/28/01
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On September 28, 2001 at 14:32:28, Roy Eassa wrote: >On September 28, 2001 at 14:27:32, Simon Finn wrote: > >>On September 28, 2001 at 12:36:55, Dieter Buerssner wrote: >> >>[snip] >> >>>I think, often in this type of positions (only few pawns), chess programs are >>>usually very good. There are only few pawn moves possible, and programs reach a >>>high search depth fast, and of course, because of the TBs. Without TBs I get: >> >>I would be very impressed if any program can solve the following >>innocent-looking position (Grigoriev 1933) in a reasonable time. By "solve" I >>mean find most of the PV (up to 13. Ka8, say) with a winning score. >> >>[D]k7/8/pp6/2p4K/8/PPP5/8/8 w - - bm c4;c0 "Grigoriev 1933";pv "1. c4 Kb7 2. a4 >>Kc6 3. Kg5 Kc7 4. Kf6 Kd7 5. a5 Kd6 6. Kf5 Kc7 7. Ke6 Kc6 8. Ke7 Kc7 9. Ke8 Kf8 >>10. axb6 Kb7 11. Kd7 Kxb6 12. Kc8 Kb6 13. Ka8 a5 14. Kb8 a4 15. bxa4 Ka5 16. Kb7 >>Kxa4 17. Kc6 Kb4 18. Kd5"; >> >>Pawn endings are difficult! >> > > >Are there any words that go along with this to explain why each is the best >move, and what happens on other plausible lines? It's very difficult to annotate such a masterpiece, but I'll try to sketch out what's going on. Black has two defensive ideas: (1) Lock the pawns while he has (and can keep) the opposition. 3. Kg6?, 4. Kf5? and 5. Kf7? are all refuted by ...a5 for example. (2) Play for a stalemate trap with his king on a5. This refutes 2. Kg5? b5 3. Kf6 b4 4. a4 Kb6 and 6. axb6? Kc6 7. Ke6 Kxb6 8. Kd6 Ka5 White can only play axb6 when he can answer Kxb6 with Kc8. On the other hand, if Black touches his pawns he loses even more quickly. ...a5 allows White to grab the opposition ...b5 and ...bxa5 both allow White to win the c-pawn As for the mysterious king moves, all I can say is that anything else either worse or (occasionally) no better. White is trying to find a good opportunity for axb6 and Black is trying to prevent this. Simon
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