Author: Dieter Buerssner
Date: 08:58:02 08/28/01
Go up one level in this thread
On August 27, 2001 at 19:19:13, Peter Berger wrote:
>Just came across this one:
>
>[D] 7r/Q2k1ppp/2b1p3/8/6q1/2B5/5PPP/2R3K1 b - - 0 1 am Ke8
>
>Here black has to play Kd6 and this should take not much time. Ke8 loses without
>any resistance.
Thanks for pointing out this position.
As you have found out, Yace needs some minutes to avoid Ke8.
However, I don't totally agree, that this is a King safety problem. For many
depths, Kd6 and Ke8 have almost the same score (or have the same score). Sure,
fiddling a little bit at KS-values will make Yace "find" the correct move
muchearlier. I actually lowered some time ago some "K-advance-penalty". But I
had the feeling, that this makes Yace weaker after some time, so I put back the
old values.
Also, this position may be a bit unusual, and not fitting some heuristics used
in many chess programs. Usually programs come out of book, in castled position,
or with a closed center. Neither is the case here.
BTW. An material only eval, never switches away from Kd6.
I think, this position tests more the search of the engine. When Yace sees the
problem, it gets a fail low to a score < -3. I wondered, why this is seen so
late.
First of all, after 1...Ke8, 2.f3 must be found. To see, that f3 is really good,
probably (after 2...Bxf3, which is no problem of course), 3. g3 must be found.
All those moves (and more in the mainline) don't trigger any extensions in Yace.
OTOH in other lines many extensions are triggered (and are mainly useless). So
the search depth increases too slowly, and Yace needs too much time.
I think, perhaps finding f3 after Ke8 would be another good test position.
And - Yace thinks even after Kd6, it will be difficult to hold the game.
After I have analyzed some lines, and gone back (what you called "cheating" :-)
I get the following after Kd6:
16702914 1:27.8 1.55 10t 2.f3 Bxf3 3.Rc2 Bxg2 4.Be1H Be4+H 5.Bg3+H
Qxg3+H 6.hxg3H Bxc2H 7.Qd4+H Ke7H 8.Qc5+H Kf6H
9.Qxc2H h5H 10.Qd1H g5H 11.Kf2H Rh7H 12.Qd8+H
Kg6H 13.Qd3+H Kg7H 14.Qd4+H {HT} {261}
29572054 2:33.8 1.55 10. 2.f3 Bxf3 3.Rc2 Bxg2 4.Be1 Be4+ 5.Bg3+ Qxg3+
6.hxg3 Bxc2 7.Qd4+ Ke7 8.Qc5+ Kf6 9.Qxc2 h5
10.Qd1 g5 11.Kf2 Rh7 12.Qd8+ Kg6 13.Qd3+ Kg7
14.Qd4+ {HT} {261}
Regards,
Dieter
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