Author: blass uri
Date: 17:33:38 05/03/00
Go up one level in this thread
On May 03, 2000 at 18:29:24, Robert Hyatt wrote: >On May 02, 2000 at 09:07:42, Stefan Meyer-Kahlen wrote: > >> >>In my set of tactical test positions there is the following example: >> >>[D] 2rqk2r/pb1nbp1p/4p1p1/1B1n4/Np1N4/7Q/PP3PPP/R1B1R1K1 w k - bm Rxe6 >> >>I can?t remember where I have found this position, but the solution is supposed >>to be Rxe6. Until know every version of Shredder has found this move sooner or >>later and kept it as a best move until the end of my test time. >> >>Last night I have tested my latest version and found something interesting. >>Shredder played Rxe6 after a while as usual, but got a terrible fail low for >>that move at ply 11. >> >>So here is my question: >>Is Rxe6 really the best move and I have introduced a bug somewhere in my code or >>is Rxe6 a mistake? I didn?t find an improvement for white after 1. Rxe6 fxe6, >>but this can be due to my limited chess knowledge. >> >>Here is Shredder?s output: >> >> 6.01 0:00.71 -0.23 1.Bh6 a6 2.Bd3 Bf6 3.Nf3 a5 (63.557) 88.3 >> 6 -> 0:01.76 -0.23 1.Bh6 a6 2.Bd3 Bf6 3.Nf3 a5 (159.299) 90.2 >> 7.01 0:02.71 -0.09 1.Bh6 a6 2.Bd3 Bf6 3.Nb3 N5b6 4.Nxb6 Qxb6 >> (240.167) 88.3 >> 7 -> 0:04.90 -0.09 1.Bh6 a6 2.Bd3 Bf6 3.Nb3 N5b6 4.Nxb6 Qxb6 >> (435.029) 88.6 >> 8.01 0:07.96 -0.01 1.Bh6 a6 2.Bf1 N7f6 3.Rad1 Qa5 4.Bg7 Nf4 >> (704.124) 88.3 >> 8 -> 0:10.15 -0.01 1.Bh6 a6 2.Bf1 N7f6 3.Rad1 Qa5 4.Bg7 Nf4 (911.624) 89.7 >> 9.01 0:17.93 -0.17 1.Bh6 a6 2.Be2 Bg5 3.Bf3 Nf4 4.Qg3 Bxh6 5.Bxb7 >> (1.594.580) 88.8 >> 9 -> 0:32.29 -0.17 1.Bh6 a6 2.Be2 Bg5 3.Bf3 Nf4 4.Qg3 Bxh6 5.Bxb7 >> (2.918.536) 90.3 >>10.01 0:42.76 -0.14 1.Bh6 a6 2.Be2 Qa5 3.b3 e5 4.Nf3 e4 5.Nd2 f5 >> (3.876.621) 90.6 >>10.08 2:02.76 -0.13++ 1.Rxe6 fxe6 2.Nxe6 Qa5 3.Bxd7+ Kxd7 4.Nec5+ Ke8 5.Qd7+ >> Kf8 6.Nxb7 (11.210.309) 91.3 >>10.08 2:26.60 +0.22++ 1.Rxe6 fxe6 2.Nxe6 Qa5 3.Bxd7+ Kxd7 4.Nec5+ Ke8 5.Qd7+ >> Kf8 6.Bh6+ Kf7 7.Nxb7 a6 8.Nxa5 Rc1+ 9.Rxc1 >> (13.366.273) 91.1 >>10.08 3:25.78 +0.40 1.Rxe6 Rc7 2.Re2 O-O 3.Bh6 Re8 4.Rae1 a6 5.Bd3 a5 6.b3 >> (18.827.259) 91.4 >>10 -> 3:45.35 +0.40 1.Rxe6 Rc7 2.Re2 O-O 3.Bh6 Re8 4.Rae1 a6 5.Bd3 a5 6.b3 >> (20.541.368) 91.1 >>11.01 5:35.76 +0.15-- 1.Rxe6 fxe6 2.Nxe6 Qa5 3.Bxd7+ Kxd7 4.Nec5+ Ke8 5.Qd7+ >> Kf7 6.Nxb7 Rc7 7.Nd6+ Kg7 8.Ne8+ Rxe8 9.b3 Rxc1+ >> (31.352.209) 93.3 >>11.01 9:18.76 -0.35-- 1.Rxe6 fxe6 2.Nxe6 Qa5 3.Bxd7+ Kxd7 4.Nec5+ Ke8 5.Qd7+ >> Kf7 6.Nxb7 Rc7 7.Nd6+ Kg7 8.Ne8+ Rxe8 9.Qxe8 Nf6 >> 10.Qb8 Bd6 (54.470.299) 97.4 >>11.01 14:41.53 -1.36 1.Rxe6 fxe6 2.Nxe6 Qa5 3.Bxd7+ Kxd7 4.Nec5+ Ke8 5.Qd7+ >> Kf7 6.Nxb7 Rc7 7.Nxa5 Rxd7 8.Nc6 Rc7 9.Nxe7 >> (86.129.099) 97.7 >>11.02 14:52.57 -1.35++ 1.Bh6 a6 2.Be2 Qa5 3.b3 Nf4 4.Bxf4 Bxg2 5.Qxg2 >> (87.133.005) 97.6 >>11.02 15:07.65 -1.00++ 1.Bh6 a6 2.Bxd7+ Qxd7 3.Nxe6 Qxa4 4.Ng7+ Kd8 5.Qd7+ >> Qxd7 (88.458.785) 97.4 >>11.02 16:23.21 -0.10 1.Bh6 a6 2.Bxd7+ Qxd7 3.b3 e5 4.Qxd7+ Kxd7 5.Rxe5 Bf6 >> 6.Rxd5+ Bxd5 7.Nb6+ Kd6 8.Nxc8+ Kd7 9.Re1 >> (95.283.049) 96.9 >> >>(I have formatted it a bit, hopefully it helps...) >> >>Stefan > > >I had a chance to study this... Crafty likes Re6 from about one second on. It >isn't a tactical thing, it is more of a positional issue. I let it search to >15+ plies and the score didn't change much, being right around zero. I didn't >get any fail low, but in looking at your analysis, I think your fail low is >also a positional issue where you suddenly don't like the position after you see >deep enough, even though it isn't losing or winning material. > >The move may or may not be good... Crafty sees it as materially equal, as a >piece and 2 pawns for the rook. The position is unbalanced, which it >particularly seems to favor against humans... 1.Rxe6 fxe6 2.Nxe6 Qa5 3.Bxd7+ Kxd7 4.Nec5+ Ke8 5.Qd7+ Kf7 6.Nxb7 Rc7 is winning material for black(black has rook for knight and a pawn and not rook for knight and 2 pawns) Crafty17.10 admits that the final position in this line is clearly better for black and not close to equality. I do not see a logical way for white to avoid this line except 2.Bh6 and I guess that crafty does not want to play this move in the main line. I read that modified Crafty found 2.Bh6 after a long time but I do not trust this version and I guess that it can find also wrong sacrifices. Uri
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