Author: Howard Exner
Date: 04:25:00 02/16/98
Go up one level in this thread
On February 15, 1998 at 17:41:13, Amir Ban wrote: > >The group ECM 601 thru 700 is the most difficult part of the suite, >though the remaining part till the end is almost as hard. I solve only >60 out of 100 of these in under 60 seconds on P6/200. > >The first half is mostly endgame positions, some of them pretty and very >difficult (e.g. 603,605,607,608,615,621,626,640). The second half is >mostly "routine" sacrifices on h7/h2. > >Since I had to go through many positions, I decided to break at 680 and >post this: > > >No. 601 (g4): > >This is a draw assignment. I don't know about this one, and I don't find >any clear line here. It seems to be a positional test: If 1...g4 2.h4 >and then white can make many different tries to win, and maybe they all >fail. It looks like g4 is intented to prevent g4 by white, but I'm not >convinced that failing to play g4 loses. E.g. 1...Kg6 2.g4 how does >white win ? > >Recommend: Someone explain what this position is about. > > >No. 617 (Rxa6): > >The idea is clear: 1.Rxa6 Rxa6 2.d6! Qxe5 3.fxe5, but is it good enough >to win ? > >Recommend: Investigate. > > >No. 623 (Rc4): > >After 1...Rc4 white mustn't take on c4, but the continuation 2.Rc1 Bc5 >3.Kg2 Bxf2 4.Kxf2 is not an obvious win. I find Bc5 which is also not >decisive. > >Recommend: Investigate. [Event ""] [Site " Black to move "] [Date "1997.06.11"] [Round ""] [White "Pos 623"] [Black "ECM.EPD"] [Result "*"] [BlackElo ""] [WhiteElo ""] [FEN "6k1/p3b1pp/4p3/4Pp2/Pp1r1P1P/1P4P1/2p2R2/5RK1 b - - 0 1"] 1... Rc4 2. Rc1 Bc5 3. Kg2 Bxf2 4. Kxf2 Rc3 At this juncture there is not much white can do. If the black king approaches the c2 pawn black can march his king up the kingside. If white trys to prevent the king march with say h5 then black advances g6 and swaps to make room to advance. Finally if white shuffles the king around gurding the g3 pawn then again black can move the king up the d file. The key in all of this is to not worry about losing the c2 pawn as it will cost white too much time. Black should avoid plans like Rxb3 which needlessly lets the white rook play Rxc2. Here is the continuation of a sample analysis: 5. h5 g6 6. hxg6 hxg6 7. a5 Kf7 8. Kg2 g5 9. Kf2 Kg6 10. fxg5 Kxg5 11. Kg2 Kg4 and so on. > > >No. 624 (Qe6): > >1.Qe6 Qe3 and I cannot find the win. Instead, I think 1.Kh2 wins. This >is a complicated position to be sure. The book only gives the wrong reply Rxe6 so Qe6 is not the correct key. > >Recommend: Change key to Kh2. Will 1.Kh2 Rge3 2.Qxd7 h5! hold on? There may be a drawing perpetual here. I'll investigate this line further also. I'll reply to the rest of your post later. This is fun stuff!
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