Author: Dave Gomboc
Date: 23:57:15 10/07/00
Go up one level in this thread
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
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