Author: Ricardo Gibert
Date: 19:29:44 10/07/00
Go up one level in this thread
On October 07, 2000 at 19:32:18, Vincent Diepeveen wrote: >On October 07, 2000 at 15:16:17, Peter McKenzie wrote: > >>The position where the solution is most in doubt: >> >>[D]2k2K2/8/pp6/2p5/2P5/PP6/8/8 w - - >> >>The authors say that after 1.Ke8 Kc7 2.Ke7, black draws by 2...b5 with a >>stalemate motif after 3.Ke6 b4 4.a4 Kb6. > >nice motif for humans. peanut for the computer to see. >however, after 1.a4 i get a 0.00 score from diep initially, >now there are sure some bugs in this version, as i'm busy rewriting >its hashing to 64 bits (which asks for bugs of course), but 0.00 is >pretty hard. it is basically doubting between 0.50 and 0.00 on most >plies. where the stalemate position is 50 moves of shuffling around >with king and score +1.31. this version not showing +3.x scores weirdly. > >what is the win with a4 which i'm missing? and 20 plies of search too, >which is hard to believe in this position. with all 3 vs 2 egtb attached >and 20 plies of search with the white king already penetrated i either >expect to see +mateXX or see many pawns go or see draw score if it's >a draw. Now i get a slight draw score depending upon depth it is 0.00 or >+0.50 for white. That's not very convincing. > >>Of course white can vary, and they quote: 4.axb4 cxb4 5.Kd5 a5 6.Kc5 a4= >> >>Or: 2.a4 b5 which is supposed to be drawn too. > >>I haven't checked these lines thoroughly, but quickly playing some of them vs my >>program suggests they are probably correct. Certainly its possible there is a >>mistake though. >> >>The other controversial positon: >> >>[D]8/1k6/p4p2/2p2P2/p1P2P2/2P5/P1K5/8 w - - >> >>Kc1 is analysed using the 'theory of corresponding squares', something I don't >>really understand :-) I haven't analysed this one at all, I will just quote the >>main variation: > >i have wasted a full evening to go to a meeting where the writers >about the 'corresponding square' theory were there. > >it's all big nonsense. the problem is to figure out what the corresponding >squares are. it's like saying: "find best move M and play perfect >chess". Now the problem is to find move M. So is the problem to >find the corresponding squares. There is no algorithm for it at all. >After wasting hours of talk to the authors who themselves aren't strong >chessplayers at all, they couldn't give any algorithm for it, and it >all appeared to come down to how well you can define squares as being >the corresponding square! > >>1.Kc1! Kc7 2.Kd1! Kd7 3.Ke1 Kc7 4.Kf2 Kd8 5.Ke2 Ke8 6.Kd3 Kd7 7.Ke3 Kd6 8.Ke4 >>"(forcing the pawn to advance)" a3 9.Kd3 a5 10.Kc2! a4 "The posiiton on the >>Q-side is blocked; a quadratic system with non-ambiguous rear (711) now >>operates." Go figure! 11.Kc2! Ke7 12.Kd3 Kc6 13.Ke2 Kd6 14.Kf2 Kd7 15.Ke3 Ke7 >>16.Kf3 and wins > >that's 16 moves. I'm searching 40 plies. that's 20 moves. So i see >4 moves deeper as this. Also i have made afew moves and then also searched >40 plies. that's like 23 ply in the diagram position. So obviously this >trick isn't the problem here! > >>I didn't play thru. that variation, but clearly its at least 31ply and white >>hasn't even captured a pawn yet! Let me see, finished with white K on f3, so it >>needs another 3 moves at the very least to capture c5 so this problem looks like >>it is at the VERY least 34ply deep and probably more. > >I searched if i count the moves made first with it 44 plies or something >and don't see a win at all. > >>cheers, >>Peter If you are really interested in the theory of corresponding squares, you may want to have a look at the book, "The Final Countdown" by Willem Hajenius & Herman van Riemsdijk. As for translating it into a computer comprehensible algorithm, I don't think it is practical. I think it all comes down to what is "obvious to a human player" and what is "obvious to a computer" not being the same. In any case, with hash tables, computers do quite well with these type of positions generally, so I don't think it is really worthwhile to try to get computers to to analyze these positions the same way a human does...unless maybe your idea is to have the computer explain these positions to humans?
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