Author: Ricardo Gibert
Date: 16:55:08 11/09/02
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On November 09, 2002 at 18:40:44, Uri Blass wrote: >On November 09, 2002 at 18:13:35, Ricardo Gibert wrote: > >>Are there any chess engines that understand anything about strategic exchange >>sacs? >> >> >>The following is an instructive example of an exchange sac that yields a >>strategicly won position: >> >>[D]r3r1k1/1pqn1pbp/p2p2p1/3P4/1RP5/4B3/P3BPPP/3Q1RK1 b - - >> >>From Polugaevsky-Petrosian 50th USSR Ch Final 1958 >> >>19...Rxe3!! 20.fxe3 Nc5-+ 21.Qc2 Re8 22.Rf3 Bh6 23.Qc3 Qe7 24.Rb6? Na4 0-1 >> >>Neither Nimzo8 nor Ruffian 1.0.1 have a clue in the above position. > >Movei can see only a small positional compensation for white(score 1.30 at depth >11 and 1.20 at depth 12 after 19...Rxe3 20.fxe3 Nc5 when the material advantage >is considered as slightly more than 1.30) > >Maybe with bigger positional scores it can find it. > >depth=11 +1.30 f1f3 c7a5 d1b1 a8e8 b4b6 a5d2 g1f2 f7f5 f2f1 g7e5 g2g3 >Nodes: 24362368 NPS: 116907 >Time: 00:03:28.39 > >depth=11 +1.30 f1f3 c7a5 d1b1 a8e8 b4b6 a5d2 g1f2 f7f5 f2f1 g7e5 g2g3 >Nodes: 39418809 NPS: 118563 >Time: 00:05:32.47 > >depth=12 +1.20 f1f3 c7a5 d1b1 a8e8 g1h1 g7h6 b4b6 h6e3 b6d6 a5d2 b1f1 f7f5 >Nodes: 41103072 NPS: 118613 >Time: 00:05:46.53 > >Can you win Ruffian or Nimzo with black from the above position? > >Uri I'm too weak! Against Ruffian I tried several 2 minute games with a 6 sec increment and lost all of them. Then I put it in analysis mode tried to see if I could beat it by peeking at the analysis. This is a double edge procedure, because it does not really understand the position. I lost the first couple before deciding that winning White e-pawn is a strategic error. It allows White to exchange off a pair of Rooks. After that discovery I actually managed to win one by winning the exchange (Ne4-g5xRf3), but when I tried to repeat this success and giving Ruffian a bit more time, aI won the exchange again, but it then found a strong pawn sac idea c4-c5 to activate the White squared Bishop and I lost. That's enough for me today. However, I have the feeling that after about maybe a dozen more games I may learn enough about the position to be able to hold my own, but only by peaking at Ruffian's analysis. A tough and instructive position!
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