Author: martin fierz
Date: 18:58:06 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? i suggest 1.a4 and 2.a5 against more or less any move of black, except 1...a5 of course :-) and seriously, also not against b5. but against any king move. taking the pawn loses for black as your computer will quickly find, once you play it out, and if black doesn't take the pawn, white will take b6 and win against the weak black pawns. white must take a little care to do this in the right moment, as there is the other stalemate trick for black with a recapture on b6 and playing ka5 when kxc5 for white is again stalemate. so white just uses the opposition to get black's king further in the corner before taking the material. >>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 >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. i disagree strongly based on the fact that I suggested... >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. ...before he posted this line: >>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 so as you can see there was a way for me to figure out what was in his book, and yes! it IS the theory of the corresponding squares. of course the line in the book is wrong because it misses the stalemate trick with a3-kb6-ka5-ka4-a5. it takes some time getting used to, but once you do, it's rather easy. the problem with this position is that it's a very hard example and you shouldn't try a newly-learned theory on the hard examples, but on the easy ones first. so you say it's hard to figure out the corresponding squares? let me try: take the black king off the board. look for possible routes of entry for the white king in the black camp. you will see: 1) b2-a3xa4 2) d3-e4-d5xc5 3) d3-e4-f3-g4-h5-g6xf6 now, black is not allowed to let this happen. so you have to see where black must stop the white king: for 1) it is enough that the black king is on a5 when wk is on a3 2) the black king must already stop wk-d5, else it's over, so after wk-e4 black MUST play ke6 (or ke6) and 3) the wk is not allowed to be on g6 so after kh5 the black king MUST appear on g7 (or h7) for us humans this is simple to see - and also to describe to another human. how you want to tell this to your program is another story, of course, but it is really easy to see the first 3 pairs of corresponding squares. the way the side with the advantage wins is usually a moving around with the king to attack two squares simultaneously where the opponent cannot attack the same two corresponding squares at the same time, thereby the attacker will be able to move to one of them without the defender being able to. now in this example we only have 3 squares designated yet, and i don't want to go into the whole rest, but you have to establish more corresponding squares and find those which white can attack simultaneously and black can't. cheers martin
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