Author: Ed Schröder
Date: 12:02:46 08/28/01
Go up one level in this thread
On August 28, 2001 at 11:58:02, Dieter Buerssner wrote:
>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
It will depend how king safety is programmed. In Rebel's case the black king
gets a huge penalty for walking into the center while white has so many pieces
to attack the black king.
Another example of this: 1.e4 Nf6 2.Bc4 Nxe4 3.Bxf7+ Kxf7 4.Qh5+
and now black has 2 choices: a) to defend the knight with 4..Ke6 or (b) safely
move to g8. Rebel immediately moves to g8 as Ke6 is suicide.
Ed
This page took 0 seconds to execute
Last modified: Thu, 15 Apr 21 08:11:13 -0700
Current Computer Chess Club Forums at Talkchess. This site by Sean Mintz.