Author: Uri Blass
Date: 08:25:03 12/07/02
Go up one level in this thread
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
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