Author: Michael Neish
Date: 05:59:09 12/19/02
> ply time nodes score pv > 4( 0)& 0 154 110 d5c7 a4c6 e1e7 b7c5 > 4( 0). 0 202 110 d5c7 a4c6 e1e7 b7c5 > 5( 7)+ 0 3847 140 d5c7 > 5( 8)& 0 8482 151 d5c7 b8c8 e1e7 > 5(10). 0 25477 151 d5c7 b8c8 e1e7 > 6(11)& 0 45435 140 d5c7 a4c6 c7d5 c6c4 e1c1 c4e4 > 6(14). 1 100773 140 d5c7 a4c6 c7d5 c6c4 e1c1 c4e4 > 7(14)& 1 149416 119 d5c7 a4c6 e1e7 b7c5 d2d5 c6d5 c7d5 > 7(16)& 6 586252 120 f3g5 b8f8 d2d3 f7f5 d5c7 a4a2 d3d5 a2d5 c7d5 > 7(16). 6 656165 120 f3g5 b8f8 d2d3 f7f5 d5c7 a4a2 d3d5 a2d5 c7d5 > 8(18)+ 14 1414370 150 f3g5 > 8(18)+ 21 2119919 240 f3g5 > 8(18)& 28 3063718 301 f3g5 b8f8 d5e7 g8h8 d2f4 a4b3 e7g6 h8g8 g6f8 >g8f8 f2f1 > 8(18). 30 3349952 301 f3g5 b8f8 d5e7 g8h8 d2f4 a4b3 e7g6 h8g8 g6f8 >g8f8 f2f1 > 9(20)- 63 7327394 271 f3g5 b8f8 > 9(20)& 73 8444763 232 f3g5 b8f8 d5e7 g8h8 d2f4 a4b3 e7g6 h8g8 g6f8 >g8f8 g5h7 f8g8 f4e4 b3b2 > 9(20). 78 9244951 232 f3g5 b8f8 d5e7 g8h8 d2f4 a4b3 e7g6 h8g8 g6f8 >g8f8 g5h7 f8g8 f4e4 b3b2 > 10(21)+ 162 17746254 262 f3g5 > 10(21)+ 214 23044194 352 f3g5 > 10(21)& 399 45409923 458 f3g5 h7h6 d5e7 g8f8 b2b3 a4b5 g5h7 f8e8 e7c6 >e8d7 c6b8 d7c8 > 10(21). 452 51989903 458 f3g5 h7h6 d5e7 g8f8 b2b3 a4b5 g5h7 f8e8 e7c6 >e8d7 c6b8 d7c8 > 11(23)& 875 101778383 446 f3g5 h7h6 d5e7 g8f8 b2b3 a4b5 g5h7 f8e8 e7c6 >e8d7 c6b8 d7c8 > 11(23). 1118 132224180 446 f3g5 h7h6 d5e7 g8f8 b2b3 a4b5 g5h7 f8e8 e7c6 >e8d7 c6b8 d7c8 POSITION: [D]1r2q1k1/pnp2ppp/3p4/3N4/Pp6/5N1P/1P1Q1KP1/4R3 b - - Sorry to leave you waiting a couple of days for my reply. Well, I thought there was only one main line leading to fireworks at the end, but it looks like there are variations. The analysis below is with the help of HIARCS 7, by moving back and forth between variations to see what came up. Let's look at the line I was considering, which may be the most forceful. It starts with 24 ... Qxa4, which isn't the best move. There follows 25. Ng5 Rf8 26. Qd3 f5 27. Qc4 ... with at least a mate in 8 following. Black can hold the mate off longest by sacrificing the Queen with 27. ... Qc2+. There follows 28. Qxc2 Nc5 29. Qc4 g6 30. Nf4+ d5 31. Qxc5 Rf7 32. Qxd5 Kg7 33. Nfe6+ Kh6 34. Nxf7+ Kh5 35. Nf4+ Kh4 36. g3++ which is 24 ply from start to finish, although there might be a shorter mate that I didn't find. The position came up in a game between the shareware program Sigma Chess 5.1.1 for the Macintosh and my program, at 10 seconds per move. My program, as Black, played 24. ... Qxa4, Sigma found the continuation 25. Ng5 and 26. Qd3 and proceeded to plaster my program. I was very impressed by its tactical prowess but now think it was more of an accident that the checkmate fell into place the way it did. Some really strong programs appear to need some time (more than 10 seconds) to see that they should avoid 24. ... Qxa4. In the game itself, my program didn't see the need to sacrifice the Queen immediately. There followed 27. ... Kh8 28. Nf4 Qe8 29. Rxe8 Rxe8 30. Nf7+ Kg8 31. Nh6+ Kh8 32. Qg8+ Rxg8 33. Nf7++ !! With a beautiful smothered mate. Since there is a pattern to the last few moves I wondered whether some extensions might be able to handle it (at the time I though Sigma had seen through to the end, but I've changed my mind), hence my question. I see that Baron finds the 25. Ng5 Rf8 continuation, but prefers 26. Ne7+ which is weaker. Then it changes its mind to 25. Ng5 h6 26. Ne7+ Kf8 which is also winning very strongly for White. 25. ... h6 is weak, so I wonder why it switches to that move. I hope you don't think this is overkill in a position where most programs will avoid 24. ... Qxa4 anyway, but by taking things apart we might be able to find ways to improve our programs' thinking. So, are there any extensions which could deal with this position, i.e., to allow programs to see through to the end after 24. ... Qxa4? Cheers, Mike.
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