Author: Dieter Buerssner
Date: 08:21:17 11/25/01
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On November 24, 2001 at 21:59:44, Christophe Theron wrote: >On November 24, 2001 at 07:33:10, Dieter Buerssner wrote: > >>On November 23, 2001 at 08:30:08, Steve Maughan wrote: >> >>>I came across the YACE web site the other day (http://home1.stofanet.dk/Moq/). >>>Interestingly it explains some of the search techniques employed by YACE. >>> >>>One that I haven't come across before is explained as follows: >>> >>>"ALL_MOVES_IN_CHECK: When set, and a capture checks the opponent, essentially >>>one non capture search will be done. This will need a bit more time, but will >>>find mates earlier." >>> >>>Any idea what's meant? My guess is that when a capturing move also gives check >>>extend the search. >> >>More or less, yes. But as GCP has pointed out, this is not really and extension >>(but similar). The idea of quiescent search is to reach a quiet position. This >>is usually defined, as giving the player at move the choice to capture or not. >>But one thing does not really fit inside here: when we are in check already, >>this is not really quiet. But in deep qsearch, doing a lot of things may also >>hurt the performance. > > > >That's something that has already worried me: you do it when your King is >threatened, but not when your Queen is threatened. What's the logic here? > >The only answer that I have found is that if you do it when your Queen is >threatened, the search tree explodes! > >I don't like my answer because it has little to do with logic, but there is >nothing I can do about it... Interesting thought. Perhaps I will try out some experiments. Perhaps, threats to the Q are not so dangerous? To attack it with a Q/B/N/P, the attacker must be defended (of course this is oversimplifying things, and special cases, like a pinned Q might be very worthwhile to consider). Attacking it with a Q, and you can allways capture the Q. Usually the Q will have more moves, to find a better place. Of course, this is not allways true, and may lead to other problems. I think most chess programs do some sort of extension for (at least part of the) checks. Also, most time the check will not lead to immediate checkmate, but rather to other (material) advantage, when it is dangerous. About the search tree exploding. Often we have the K well defended, while the Q searches for an active place. I think, it is obvious, that there can be built many more threats to the Q, than to the K in such situation. Regards, Dieter
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