Author: Ricardo Gibert
Date: 01:09:00 10/08/00
Go up one level in this thread
On October 08, 2000 at 02:57:15, Dave Gomboc wrote: >On October 08, 2000 at 02:07:37, Ricardo Gibert wrote: > >>On October 08, 2000 at 02:00:25, Dave Gomboc wrote: >> >>>On October 08, 2000 at 01:37:20, Ricardo Gibert wrote: >>> >>>>On October 08, 2000 at 01:27:15, Dave Gomboc wrote: >>>> >>>>>On October 07, 2000 at 22:29:44, Ricardo Gibert wrote: >>>>> >>>>>>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. >>>>> >>>>>Your opinion notwithstanding, Murray Campbell did it over ten years ago. :-) >>>>> >>>>>Dave >>>> >>>>Very interesting. Is there a download article on this? I'm curious if this a >>>>practical algorithm, why it is not being used in programs. Does it include >>>>positions where pawns can move forward? Or only positions where they are >>>>blocked? >>> >>>In fact, there's an entire Ph.D. thesis on it. :-) I imagine it isn't being >>>used in (at least most) programs because it's not perfect either, and the >>>brute-force method worked somewhat better overall than it did. However, it did >>>handle some positions much better than a brute forcer. The pawns didn't have to >>>be blocked, but of course that makes it easier (mind you, that makes it easier >>>for a brute force program too!) >>> >>>Dave >> >>Then I seem to have guessed right about its practicality. > >I don't think so... after all, ten years is a long time. The technique might be >effective now, or it might not. I think it's probably worth checking out, >though. > >Dave Brute-force has certainly gotten more effective with the speed up of cpus, but whether the technique you refer to has kept pace (or outpaced) is an open question I suppose. Worth looking into as you said.
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