Author: Uri Blass
Date: 06:40:41 12/19/02
Go up one level in this thread
On December 19, 2002 at 08:59:09, Michael Neish wrote: > > > >> 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. check exensions are used for the last plies. I do not know if there are programs that use extensions for patterns(for example extend Nf7+ Kg8 Nh6+ Kh8 Qg8+ Rxg8 when these moves are possible) The main problem is to see the quiet moves Qc4 and Nf4 and after the program can see a big advantage in other lines null move may prune the things that happen after these moves. > >I see that Baron finds the 25. Ng5 Rf8 continuation, but prefers 26. Ne7+ which >is weaker. 26.Ne7+ is strong enough to convince programs to avoid Qxa4 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. It probably finds that Rf8 is not good. It is possible that it even finds 26.Qd3 and decides to change the main line to 25...h6 because it does not like the result of 26.Qd3. Not all the calculation of programs can be seen in the pv. Movei also changes it's pv from Ng5 Rf8 Ne7+ to Ng5 h6 and the reason is seeing that Qd3 is strong. Note that it does not see Qc4 in it's main line but prefer Ne7+ that is also winning Uri
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