Author: Uri Blass
Date: 13:20:20 12/07/02
Go up one level in this thread
On December 07, 2002 at 14:09:48, Uri Blass wrote: >On December 07, 2002 at 11:36:03, Ingo Lindam wrote: > >>On December 07, 2002 at 11:25:03, Uri Blass wrote: >> >>>On December 07, 2002 at 05:04:33, Ingo Lindam wrote: >>> >>>>Hello all, >>>> >>>>concerning the current discussion about testing positional skills >>>>I like to add the following: >>>> >>>>I think to evaluate/test positional skills of an chess engine you don't need to >>>>have positions without tactics (what I think is impossible, because for >>>>everything true in a chess position there is a tactical proof if you are just >>>>able to look deep enough into the tree). >>>> >>>>We agree that also in a nearly 'tactical solution free' (within a certain scope) >>>>position with a one and only best move it could happen that the engine plays the >>>>right move for the wrong reason. >>>> >>>>So why not test the other direction? Assume that you have a true evaluation for >>>>a position. This true evaluation doesn't need to be exact it can also be: "White >>>>is atleast equal (or better)." So as long as the engine claims a clear advantage >>>>for black, it fails the test. If the score corresponds with your own evaluation >>>>you are ofcourse not able to judge about the engine as long as you not checked >>>>the reason, why it gives this evaluation. Ofcourse your test positions prefers >>>>the engine to give the wrong evaluation instantly because of e.g. being a pawn >>>>up. The deeper the engine goes into the search tree keeps to give the wrong >>>>evaluation the worse is the positional evaluation of the maschine (at least at >>>>this special kind of positions). And because you know at least one reason, why >>>>the position shouldn't be judge that worse as the engine does, you should also >>>>be able to name some/a positional feature/s the engine doesn't evaluate right. >>>> >>>>Giving an example: >>>> >>>>[D] r3kb1r/1p1q1ppp/p1n1p3/3pN1B1/3Pb3/1Q2P3/PP2BPPP/2R1K2R b Kkq - 0 1 >>>> >>>>position after 12.Se5 >>>> >>>>Analysis by Fritz 7: >>>>(sorry for the german letters: S=N,L=B,D=Q,T=R and K=K) >>>> >>>>12...Sxe5 13.f3 Sg6 14.fxe4 h6 15.Lf4 Sxf4 16.exf4 dxe4 >>>>³ (-0.69) Tiefe: 8/21 00:00:00 151kN >>>>12...Sxe5 13.dxe5 Lxg2 14.Tg1 Le4 15.f3 h6 16.Lh4 Lf5 17.Kf1 >>>>³ (-0.69) Tiefe: 9/24 00:00:00 400kN >>>>12...Sxe5 13.f3 Sg6 14.fxe4 h6 15.Lf4 Sxf4 16.exf4 dxe4 17.De3 Lb4+ >>>>µ (-0.78) Tiefe: 10/27 00:00:01 935kN >>>>12...Sxe5 13.dxe5 Lxg2 14.Tg1 Le4 15.f3 h6 16.Lf4 Lf5 17.Kf1 Tc8 18.Kg2 >>>>µ (-0.75) Tiefe: 11/29 00:00:04 2493kN >>>>12...Sxe5 13.dxe5 Lxg2 14.Tg1 Le4 15.f3 h6 16.Lf4 Lg6 17.Kf1 Le7 18.Ld3 Lxd3+ >>>>19.Dxd3 >>>>µ (-0.78) Tiefe: 12/31 00:00:10 5134kN >>>>12...Sxe5 13.dxe5 Lxg2 14.Tg1 Le4 15.f3 h6 16.Lf4 Lf5 17.Kf1 Tc8 18.Txc8+ Dxc8 >>>>µ (-0.84) Tiefe: 13/36 00:00:28 15940kN >>>>12...Sxe5 13.dxe5 Lxg2 14.Tg1 Le4 15.f3 h6 16.Lf4 Lf5 17.Kf1 Tc8 18.Txc8+ Dxc8 >>>>µ (-0.78) Tiefe: 14/38 00:01:06 39095kN >>>>12...Sxe5 13.dxe5 Lxg2 14.Tg1 Le4 15.f3 Lf5 16.Kf2 b5 17.Lf4 Tc8 18.Txc8+ Dxc8 >>>>µ (-0.84) Tiefe: 15/42 00:02:47 102460kN >>>>12...Sxe5 13.dxe5 Lxg2 14.Tg1 Le4 15.Db6 Tc8 16.Txc8+ Dxc8 17.Kd2 d4 18.Dxd4 >>>>Dc2+ >>>>µ (-0.72) Tiefe: 16/46 00:08:08 293734kN >>>> >>>>Still at ply 16 the machine evaluates (in my opinion wrongly) an advantage for >>>>black, although the PV contains th ebest moves for white in the beginning. >>>>(going one move back in the position you will see that the engine will not play >>>>Ne5 within 17 plys). >>>> >>>>Giving the engine some more (white) moves towards 16. Kd2 the evaluation will >>>>change into the right direction. >>>> >>>>in the game it follows: >>>> >>>>12... Nxe5 13. dxe5 Bxg2 14. Rg1 >>>>Be4 15. Qb6 Rc8 >>> >>> >>>The question is if 12.Ne5 was the only best move. >>>I doubt it >>> >>>Movei prefers 15...h6 >>> >>>Is there a win for white after 15...h6? >>> >>>A possible line is 16.Rc7 Qa4 17.a3 hxg5 18.Qxb7 Bb4+ 19.Kf1 0-0 20.Qxb4 Qxb4 >>>21.axb4 and the endgame seems to be equal. >>> >>>Uri >> >>My question was not whether Ne5 is doubtless the one and only best move. I am >>sure...that black is not better here, after white plays Ne5 and nevertheless the >>engine (Fritz 8) gives a clear advantage to black. And (if I am right) that >>should be a sign that the positional evaluation of the engine is not optimal is >>this position here, shouldn't it? > >I am not so sure about it. > >The moves of Fritz in the pv may not be the best moves for black(I suspect that >13...Bxg2 is a mistake). > > >I guess that the fact that 15.Qb6 can force a draw is a tactical observation >that Fritz is not able to see. > >I checked with movei and here is analysis 2 plies later > >Movei is unable to see the problem at depth 12 and wants to take g2. >The problem is lack of important extensions >Bxg2 should trigger an extension because Rg1 is forced but movei does not know >it. >Movei can see at depth 13 that Bxg2 Rg1 Be4 is not good and the pv is changed to >Bxg2 Rg1 h6 > >You can see by the score that it is tactics(the score dropped from 0.89 to >0.13). > >Movei fails high on h6 later > > >depth=12 +0.89 e4g2 h1g1 g2e4 f2f3 e4f5 b3b6 a8c8 e1d2 c8c1 g1c1 h7h6 c1c7 f8b4 >d2c1 >Nodes: 17303621 NPS: 161068 >Time: 00:01:47.43 > >depth=13 +0.13 e4g2 h1g1 h7h6 g5h6 h8h6 g1g2 a8c8 c1d1 d7c7 b3a4 e8d8 a4f4 h6h3 >f4g5 d8e8 e1f1 >Nodes: 47304313 NPS: 159569 >Time: 00:04:56.45 >depth=13 +0.14 h7h6 >Nodes: 69727812 NPS: 160422 >Time: 00:07:14.65 >depth=13 +0.43 h7h6 >Nodes: 77614594 NPS: 159585 >Time: 00:08:06.35 >depth=13 +0.58 h7h6 f2f3 e4f3 e2f3 h6g5 e3e4 d5d4 f3e2 f8e7 b3b6 d4d3 c1d1 e7d8 >b6b4 >Nodes: 95817407 NPS: 158874 >Time: 00:10:03.10 > >Uri It seems that Bxg2 is simply a tactical mistake also based on yace only material and it seems that after h6 black has the advantage. New position [D]r3kb1r/1p1q1ppp/p3p3/3pP1B1/4b3/1Q2P3/PP2BPPP/2R1K2R b Kkq - 0 1 Analysis by Yace 0.99.56(only material): 2...Be4xg2 µ (-0.80) Depth: 1 00:00:02 2...Be4xg2 3.Rh1-g1 µ (-0.80) Depth: 2 00:00:02 2...Be4xg2 3.Rh1-g1 Bg2-e4 µ (-0.80) Depth: 3 00:00:02 2...Be4xg2 3.Rh1-g1 Bg2-e4 4.Bg5-h4 µ (-0.80) Depth: 4 00:00:02 2...Be4xg2 3.Rh1-g1 Bg2-e4 4.Bg5-h4 b7-b5 µ (-0.80) Depth: 5 00:00:02 5kN 2...Be4xg2 3.Rh1-g1 Bg2-e4 4.Bg5-h4 b7-b5 5.Qb3-d1 µ (-0.80) Depth: 6 00:00:02 21kN 2...Be4xg2 3.Rh1-g1 Bg2-e4 4.Bg5-h4 b7-b5 5.Qb3-d1 g7-g6 µ (-0.80) Depth: 7 00:00:02 68kN 2...Be4xg2 3.Rh1-g1 Bg2-e4 4.Bg5-h4 b7-b5 5.Qb3-d1 g7-g6 6.Ke1-f1 µ (-0.80) Depth: 8 00:00:02 171kN 2...Be4xg2 3.Rh1-g1 Bg2-e4 4.Bg5-h4 b7-b5 5.Qb3-d1 g7-g6 6.Ke1-f1 Be4-f5 µ (-0.80) Depth: 9 00:00:03 443kN 2...Be4xg2 3.Rh1-g1 Bg2-e4 4.Bg5-h4 b7-b5 5.Qb3-d1 g7-g6 6.Ke1-f1 Be4-f5 7.Bh4-g3 µ (-0.80) Depth: 10 00:00:05 1318kN 2...Be4xg2 3.Rh1-g1 Bg2-e4 4.Bg5-h4 b7-b5 5.Qb3-d1 g7-g6 6.Ke1-f1 Be4-f5 7.Bh4-g3 Ke8-e7 µ (-0.80) Depth: 11 00:00:09 3017kN 2...Be4xg2 3.Rh1-g1 Bg2-e4 4.Bg5-h4 b7-b5 5.Qb3-d1 g7-g6 6.Ke1-f1 Be4-f5 7.Qd1-d2 Bf5-h3+ 8.Kf1-e1 Rh8-g8 µ (-0.80) Depth: 12 00:00:19 8520kN 2...Be4xg2 3.Rh1-g1 Bg2-e4 4.Qb3-b6 Ra8-c8 5.Rc1xc8+ Qd7xc8 6.Ke1-d2 Be4-f5 7.Rg1-c1 Qc8-d7 8.Be2xa6 b7xa6 9.Qb6-b8+ Qd7-c8 10.Rc1xc8+ Ke8-d7 ³ (-0.40) Depth: 13 00:00:53 26420kN 2...Be4xg2 3.Rh1-g1 Bg2-e4 4.Qb3-b6 Ra8-c8 5.Rc1xc8+ Qd7xc8 6.Ke1-d2 Bf8-e7 7.Bg5xe7 Ke8xe7 8.Rg1xg7 Ke7-e8 9.Rg7-g5 Be4-f5 10.Be2-d1 = (0.00) Depth: 13 00:01:12 35615kN 2...h7-h6 3.Bg5-h4 Be4xg2 4.Rh1-g1 Bg2-e4 5.Rg1-g2 = (-0.01) Depth: 13 00:02:57 90360kN 2...h7-h6 3.Bg5-h4 Be4xg2 4.Rh1-g1 Bg2-e4 5.Ke1-f1 b7-b5 6.Bh4-g3 Ra8-c8 7.Rc1xc8+ Qd7xc8 8.Be2-d1 Ke8-d8 9.f2-f3 Be4-f5 µ (-0.80) Depth: 13 00:03:29 106018kN 2...h7-h6 3.Bg5-h4 Be4xg2 4.Rh1-g1 Bg2-e4 5.Ke1-f1 b7-b5 6.Bh4-g3 Ra8-c8 7.Rc1xc8+ Qd7xc8 8.Be2-d1 Ke8-d8 9.f2-f3 Be4-f5 10.Rg1-g2 µ (-0.80) Depth: 14 00:06:10 187313kN 2...h7-h6 3.Bg5-h4 Be4xg2 4.Rh1-g1 Bg2-e4 5.Ke1-f1 b7-b5 6.Bh4-g3 Ra8-c8 7.Rc1xc8+ Qd7xc8 8.Be2-d1 Ke8-d8 9.f2-f3 Be4-f5 10.Rg1-g2 g7-g6 µ (-0.80) Depth: 15 00:14:12 435953kN (Blass, Tel-aviv 07.12.2002) Uri
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