Author: Uri Blass
Date: 08:30:16 09/19/01
Go up one level in this thread
On September 19, 2001 at 11:04:38, Robert Hyatt wrote: >On September 19, 2001 at 10:16:36, Uri Blass wrote: > >>On September 19, 2001 at 09:52:52, Robert Hyatt wrote: >> >>>On September 19, 2001 at 05:20:31, Bernhard Bauer wrote: >>> >>>>>>>>Here is a simple attempt: >>>>>>>> >>>>>>>>[D]2k5/1r6/3p1p2/n2p1p2/P2PpP2/R3P3/1BK5/8 b - - >>>>>>>> >>>>>>>>Here black has several moves to try, one which liquidates into a pawn up >>>>>>>>(but dead lost) ending. Rxb2 Kxb2 Nc4+ Ka2 Nxa3 Kxa3 and white is a pawn >>>>>>>>down, but winning easily. >>>>>>>> >>>>>>>>Once you start with Rxb2, you are committed. As if you try to back out and >>>>>>>>not play Nc4 and Nxa3, you are an exchange down. And if you do recover the >>>>>>>>material, you are dead lost. Add another such forced capture/recapture and >>>>>>>>you have burned 6 plies. You won't see white winning all the black pawns >>>>>>>>and winning. >>>>>>> >>>>>>> >>>>>>>Note that I don't say there are not better moves for black here. The point >>>>>>>was to show a move choice that commits you to a course of action that gets >>>>>>>worse and worse as you go deeper and deeper. >>>>>> >>>>>>I think that this is not a good example because white has an obvious positional >>>>>>advantage for programs(white has a passed pawn when black has 2 pawns on the >>>>>>same file for file d,f >>>>>> >>>>>>Uri >>>>> >>>>> >>>>>Pick any such position you want, where one side is a pawn up but the other is >>>>>winning. I have seen many. That is one example where if you trade, you lose. >>>>>And it is one example of where one extra pawn does _not_ mean you are winning. >>>>>Here it means you are losing and badly. >>>>> >>>> >>>>From a players point of view *white*is a pawn up, the a-pawn and therefor >>>>winning, just like Ed said. >>>>A player would not count the additional blocked black pawns. >>>>Kind regards >>>>Bernhard >>> >>> >>>Human, right. But set the position up and ask your favorite program which side >>>is winning with a simple static eval... >> >>I asked few program to give me their evaluation at depth 1 for this position >>[D]2k5/8/3p1p2/3p1p2/P2PpP2/n3P3/K7/8 w - - 0 3 >> >> >>CometB27 0.53 for white >>Junior7 0.20 for black. >>shredder5.32 0.18 for black. >> >>They clearly can see white's positional advantage by static evaluation and do >>not give +1 for black. > >The two commercial programs say black is better. White is winning. You don't >see a problem with that kind of incorrect evaluation? IE as black they would >go for this position rather than a repetition draw. there is a problem with the evaluation but it does not contradict my claim that it is usually safe to evaluate as +2 when there is no positional reason to prefer the weaker side in material. I meant that changing scores of 1.xx in pawn endgames to 2.xx if the side with material advantage has an 1.xx evaluation is usually safe I did not say that changing 0.xx to 1.xx is usually safe and I also did not say that improving the evaluation function is a bad idea. > >That was my point. If you say "a pawn ahead is winning" you are going to lose >many games by doing so. Particularly when your opponent notices that you are >doing this and steers the game into such positions. I will be happy to give >you a similar position where the pawns are not isolated if you think that is >the problem... > >Keep the pieces at the same squares. Pub black pawns at h7, g6, e7 and d6. >put white pawns at g5, d5 and a4. What does your engines think now? Black >is a pawn up. no isolated pawns... Shredder5.32 can see positive score at depthes that are at least 7 and positional advantage for white at depth 4. [D]2k5/4p2p/3p2p1/3P2P1/P7/n7/K7/8 w - - 0 1 Analysis by Shredder 5.32: 1.Kxa3 h5 -+ (-1.84) Depth: 1/2 00:00:00 1.Kxa3 h5 2.gxh6 -+ (-2.88) Depth: 1/2 00:00:00 1.Kxa3 Kd7 2.Ka2 -+ (-1.84) Depth: 2/4 00:00:00 1.Kxa3 Kb7 2.Ka2 µ (-1.22) Depth: 2/4 00:00:00 1.Kxa3 Kb7 2.Kb4 ³ (-0.35) Depth: 2/4 00:00:00 1.Kxa3 Kb7 2.Kb4 h5 3.gxh6 -+ (-3.22) Depth: 3/6 00:00:00 1.Kxa3 Kd8 2.Ka2 h5 -+ (-1.87) Depth: 3/6 00:00:00 1.Kxa3 Kb7 2.Kb4 Ka8 3.Ka3 -+ (-1.56) Depth: 4/8 00:00:00 1.Kxa3 Kd8 2.Ka2 Kd7 3.Ka1 µ (-1.00) Depth: 4/8 00:00:00 1.Kxa3 Kc7 2.Kb4 Kb7 3.Kc4 = (-0.13) Depth: 4/8 00:00:00 1.Kxa3 e5 2.dxe6 Kd8 3.e7+ Kxe7 ³ (-0.43) Depth: 5/10 00:00:00 1.Kxa3 Kd8 2.Kb4 e5 3.Kc4 Ke7 ³ (-0.64) Depth: 5/10 00:00:00 1.Kxa3 Kd8 2.Kb4 Kc7 3.Kc4 Kb6 4.Kd3 ³ (-0.38) Depth: 6/12 00:00:00 2kN 1.Kxa3 Kc7 2.a5 Kb7 3.Kb3 Ka6 4.Kb4 Kb7 5.Kc4 = (-0.02) Depth: 6/12 00:00:00 3kN 1.Kxa3 Kc7 2.a5 Kb7 3.Kb3 Ka6 4.Kb4 Ka7 5.Kc4 h6 = (0.04) Depth: 7/14 00:00:00 6kN 1.Kxa3 Kc7 2.a5 Kb7 3.Kb3 Ka6 4.Kb4 Kb7 5.Kc4 Kc7 6.Kb4 Kd8 7.Kc4 Kc7 8.Kb4 = (0.04) Depth: 8/16 00:00:00 9kN 1.Kxa3 Kc7 2.a5 Kb7 3.Ka4 Ka6 4.Kb4 Kb7 5.Kb5 Kb8 6.Kc6 e6 ² (0.29) Depth: 9/18 00:00:00 14kN 1.Kxa3 Kc7 2.a5 Kb7 3.Ka4 Ka6 4.Kb4 Kb7 5.Kb5 Kb8 6.Kc6 e6 = (0.18) Depth: 9/18 00:00:00 15kN 1.Kxa3 Kc7 2.a5 Kb7 3.Ka4 Ka7 4.Kb3 Kb7 5.Ka4 Ka7 = (0.04) Depth: 10/20 00:00:00 25kN 1.Kxa3 Kc7 2.a5 Kb7 3.Ka4 Ka6 4.Kb4 h5 5.gxh6 e5 6.dxe6 d5 = (0.04) Depth: 11/22 00:00:01 45kN 1.Kxa3 Kc7 2.a5 Kb7 3.Kb4 Ka7 4.Kb5 Kb7 5.a6+ Kb8 6.Kc4 Ka8 7.Kb5 e5 8.dxe6 h5 9.gxh6 ² (0.29) Depth: 12/24 00:00:01 66kN 1.Kxa3 Kc7 2.a5 Kb7 3.Kb4 Ka7 4.Kb5 Kb7 5.a6+ Ka7 6.Ka5 Kb8 7.Kb6 Ka8 8.a7 ² (0.33) Depth: 12/24 00:00:01 73kN 1.Kxa3 Kc7 2.a5 Kb7 3.Kb4 Ka7 4.Kc4 Ka6 5.Kb4 h5 6.gxh6 e5 7.dxe6 d5 ² (0.33) Depth: 13/25 00:00:02 113kN 1.Kxa3 Kc7 2.a5 Kb7 3.Kb4 Ka7 4.Kb5 Kb7 5.Ka4 Ka6 6.Kb4 h5 7.gxh6 e5 8.dxe6 d5 ² (0.33) Depth: 14/26 00:00:03 154kN 1.Kxa3 Kc7 2.a5 Kb7 3.Kb4 Ka7 4.Kb5 Kb7 5.Ka4 Ka6 6.Kb4 h5 7.gxh6 e5 8.dxe6 d5 ² (0.33) Depth: 15/27 00:00:04 203kN, tb=4 1.Kxa3 Kc7 2.a5 Kb7 3.Kb4 Ka7 4.Kb5 Kb7 5.Ka4 Ka6 6.Kb4 h5 7.gxh6 e5 8.dxe6 d5 ² (0.33) Depth: 16/28 00:00:05 277kN, tb=9 1.Kxa3 Kc7 2.a5 Kb7 3.Kb4 Ka7 4.Kb5 Kb7 5.Ka4 Ka6 6.Kb4 h5 7.gxh6 e5 8.dxe6 d5 ² (0.33) Depth: 17/29 00:00:08 379kN, tb=42 1.Kxa3 Kc7 2.a5 Kb7 3.Kb4 Ka7 4.Kb5 Kb7 5.a6+ Kc7 6.Ka5 Kc8 7.Kb6 e6 8.dxe6 ² (0.58) Depth: 18/30 00:00:16 805kN, tb=72 1.Kxa3 Kc7 2.a5 Kb7 3.Kb4 Ka7 4.Kb5 e5 5.dxe6 h5 6.gxh6 Kb7 ± (1.08) Depth: 18/30 00:00:17 892kN, tb=72 1.Kxa3 Kc7 2.a5 Kb7 3.Kb4 Ka7 4.Kb5 Kb7 5.a6+ Ka7 6.Ka5 Ka8 7.Kb5 h5 8.gxh6 Kb8 9.h7 Kc7 +- (6.40) Depth: 18/30 00:00:39 1615kN, tb=380 Junior7 needs more time to see positive score but it still can see a positive positional score from the first iteration. Junior 7 - ,M 2k5/4p2p/3p2p1/3P2P1/P7/n7/K7/8 w - - 0 1 Analysis by Junior 7: 1.a5 Nc4 -+ (-2.98) Depth: 3 00:00:00 1.Kb3 Nb1 -+ (-2.24) Depth: 3 00:00:00 1.Kxa3 Kd7 2.Kb4 e5 3.dxe6+ ³ (-0.69) Depth: 3 00:00:00 1.Kxa3 Kb7 2.Kb3 Kb6 3.Kb4 ³ (-0.47) Depth: 6 00:00:00 1kN 1.Kxa3 Kd7 2.Kb4 e5 3.Ka5 Ke7 4.Kb5 ³ (-0.29) Depth: 9 00:00:00 9kN 1.Kxa3 Kb7 2.Kb3 Kb6 3.Kc4 Ka5 4.Kb3 Ka6 5.Kb4 = (-0.02) Depth: 12 00:00:01 50kN 1.Kxa3 Kd7 2.Kb4 e5 3.dxe6+ Kxe6 4.a5 Kd7 5.Kb5 Kc7 6.a6 Kb8 7.Kb6 = (-0.22) Depth: 15 00:00:03 302kN 1.Kxa3! = (0.08) Depth: 18 00:00:08 778kN 1.Kxa3! Kd7 2.a5 Kc8 3.Kb4 Kc7 4.Kb5 Kb7 5.a6+ Ka7 6.Ka5 Ka8 7.Kb6 = (0.13) Depth: 18 00:00:11 1065kN 1.Kxa3! ² (0.43) Depth: 20 00:00:17 1680kN 1.Kxa3 Kd7 2.a5 Kc8 3.Kb4 Kc7 4.Kb5 Kb7 5.a6+ Ka7 6.Ka5 Ka8 7.Kb6 Kb8 8.a7+ ² (0.43) Depth: 22 00:00:35 3489kN, tb=2 1.Kxa3! ± (0.73) Depth: 23 00:00:52 4936kN, tb=8 Uri
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