Author: Jeremiah Penery
Date: 02:45:18 10/07/01
Go up one level in this thread
On October 06, 2001 at 23:45:19, Slater Wold wrote: >Bruce and I have disagreed in the past that DJ7 can "solve" Nolot #3. He >believes that DJ7 simply "prefers" Nxg5, because it doesn't have an impressive >eval. Well, I believe I have found the reason! > >Here is the position: >[D]r2qk2r/ppp1b1pp/2n1p3/3pP1n1/3P2b1/2PB1NN1/PP4PP/R1BQK2R w KQkq - 0 1 > >Here are Baudot's words: > >Smaguine - Sahovic, Bienne 1990 > >White wins with a queen sac but black has several ways to defend 12.Nxg5!! Bxd1 >13.Nxe6 Qb8 14.Nxg7!! Kf8 15.Bh6! Bg4 16.0-0+ 17.Kg8 17.Rf4 +- > >It should take between a few months and a few years for a program to find >12.Nxg5!! > >Here was DJ7's original solution: > >Deep Junior 7 - W,S >r2qk2r/ppp1b1pp/2n1p3/3pP1n1/3P2b1/2PB1NN1/PP4PP/R1BQK2R w KQkq - 0 1 > >Analysis by Deep Junior 7: > <snip> >1.Nxg5 Bxd1 2.Nxe6 Qb8 3.Nxg7+ Kd8 4.Kxd1 b5 5.Bf5 b4 6.Kc2 a5 7.Ne6+ Kd7 8.Bh6 >a4 9.cxb4 > ± (0.72) Depth: 20 00:07:17 757031kN > >Look at the mainline though. Baudot's line is a *tad* different. Instead of >Kf8, DJ7 believe (and therefore evaluates) Kd8. > >I played through, with DJ7, and here's what I got: <snip> >Here is a recap: > >Deep Junior 7 - W,S >Level=180"av. , 06.10.2001 > >1.Nxg5 0.68/18 3:48 Bxd1 2.Nxe6 0.72/20 3:26 Qb8 3.Nxg7+ 0.54/19 2:44 >Kf8 4.Bh6 1.16/17 2:09 Bg4 5.0-0+ 1.96/17 2:13 Kg8 6.Rf4 2.08/17 1:00 >1-0 > >It choose, step by step, each move. With _no_ problem. > >But what about Kf8? Is it the best move? Here is what I get: > >W,S - Deep Junior 7 >rq2k2r/ppp1b1Np/2n5/3pP3/3P4/2PB2N1/PP4PP/R1BbK2R b KQkq - 0 1 > >Analysis by Deep Junior 7: > <snip> >3...Kd8 4.Kxd1 b5 5.Bf5 b4 6.Kc2 Qb5 7.Ne6+ Kd7 8.b3 Qa6 9.cxb4 > ² (0.70) Depth: 15 00:00:08 14218kN >3...Kd8 4.Kxd1 b5 5.Bf5 b4 6.Kc2 Rg8 7.Ne6+ Kc8 > ² (0.57) Depth: 18 00:03:19 325791kN >3...Kd8 4.Kxd1 b5 5.Bf5 b4 6.Kc2 Rg8 7.Ne6+ Kc8 > ² (0.57) Depth: 18 00:03:40 363183kN You didn't give the full commentary from the DT team. They pretty much agree with you, and here's what they had to say (edited slightly by me): Smaguine - Sahovic, Bienne 1990 12. Nxg5!! Bxd1 13. Nxe6 Qb8 14. Nxg7!! Kf8 15. Bh6! Bg4 16. 0-0+ 17. Kg8 17. Rf4 +- Solution move is 1. Nxg5!. Verified that the move is sound by following the published analysis, but could not play it within one hour time. This is more a positional sac than what would be normally called tactics. We took a closer look at this position. 12. Nxg5 is a sound positional sac, but depending on the temperament of the player, it might not be the best move. The published annotation gives 12. Bxg5 Bxg5 13. O-O as +=, but white could play 13. h3 instead and white appears to have a simple positional squeeze. The critical line in the 12. Nxg5 variation turns out to be 12. Nxg5 Bxd1 13. Nxe6 Qb8 14. Nxg7 Kd8 15. Kxd1. Black's queen and rooks are temporarily out of play, black is up a pawn, but white has a protected passed pawn, and lots of pressure. (The annotator gave one line that ended "with the attack":). From DT-2's point of view, The Bxg5 line was gaining 0.20 pawn after each iteration, and so was the Nxg5 line. Except that the Bxg5 line has about a 0.20 pawn lead at the same depth. There appears to be no kill in the Nxg5 line when black king goes to d8 instead of the f file. Black would have to give up the extra pawn to activate the queen and the rooks, and while white is definitely better, black is not without counter play. On the deepest search that we checked out, black's evaluation stopped dropping at around -1.4 pawns, and black's pieces were becoming active.
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