Author: Ingo Lindam
Date: 02:04:33 12/07/02
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 16. Kd2! d4 17. Rxc8+ Qxc8 18. Rc1 dxe3+ 19.fxe3 Bc6??
(better is 19... Qd7+ 20. Ke1 h6 21. Rc7 Qxc7 22. Qxc7 hxg5 23. Qc8+ Ke7 24. h3
with the idea e.g. 24... Rxh3 25. Qc7+ Ke8 26. Qb8+ Ke7 27. Bxa6 bxa6 28. Qb4+
Ke8 29. Qxe4 )
20. Bxa6?
(20. Ke1 {with threat Rxc6.} 20... h6 (20...
Be7 21. Bxe7 Kxe7 22. Bxa6 Qd8 23. Qb4+ Ke8 24. Bxb7 Bd7 25. Qd6 $18) 21. Rxc6
bxc6 22. Bxa6 Bb4+ 23. Qxb4) (20. Rxc6 $2 bxc6 21. Bf3 (21. Bxa6 Qd7+ $17)
21... f6 $13)
20... Be7
(20... Qd7+ 21. Ke1 f6 $8 (21... Be7 22. Rd1 Qc8 23.
Bxe7 Kxe7 24. Qc5+ Ke8 25. Bb5 $16) 22. exf6 Qd5 23. fxg7 (23. Rxc6 $2 bxc6 24.
Qb8+ Kf7 $15) (23. Bf4 $2 gxf6 24. Bc4 Qe4 $15) 23... Bxg7 24. Qc5 Qxc5 25.
Rxc5 $11)
21. Rxc6 Qd7+ 22. Rd6 Bxd6 23. exd6 f6
(23... O-O 24. Bb5 Qc8 25. d7 $18)
24. Bb5 1-0
Internette Gruesse,
Ingo
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