Author: Tony Werten
Date: 00:45:23 08/27/03
Go up one level in this thread
On August 27, 2003 at 00:38:05, Christophe Theron wrote: >On August 26, 2003 at 21:02:37, Tom Kerrigan wrote: > >>On August 26, 2003 at 19:34:59, Ricardo Gibert wrote: >> >>>On August 26, 2003 at 19:25:39, Steve Maughan wrote: >>> >>>>Ricardo, >>>> >>>>>"For example I have never used capture searches and rely instead on a static >>>>>swap off routine." >>>>> >>>>>This seems to indicate that CG does not employ a qsearch. I also understand >>>>>that Junior does something similar. I wonder how this is done? I would >>>>>presume some type of accuracy tradeoff must be involved, but I wonder what? >>>>>I'm very curious about how this is all done and why doesn't everybody do it >>>>>this way? >>>> >>>>I guess it's either some sort of SEE or a routine to resolve the effect of >>>>attack tables. >>>> >>>>>How is all the effort that goes into creating a good eval compatible with >>>>>such a handling of non-quiescent positions? It just seems kind of wacky to me. >>>> >>>>It's different - and it clearly did work well in the 80s and 90s. >>>> >>>>Regards, >>>> >>>>Steve >>> >>>It's working pretty well right now in Junior too. >>> >>>I haven't been able to find anything on this using google or citeseer. I guess >>>how to make this work is being kept secret? It would be nice if RL could be >>>persuaded to reveal this. >> >>I don't think this is any secret. I remember reading a BYTE (?) article about >>the exchange evaluator in early versions of Sargon which they said they used >>instead of a quiescence search because micros weren't fast enough for the >>latter. If that was the case for Sargon, I imagine it was also the case for any >>other program from that era, including predecessors of Fritz, WChess, Genius, >>and Rebel. > > > >One of the first thing you come up when you start to think about a chess program >is a way to "terminate" the search for the sake of simplicity, or in other words >you want to "evaluate" the leaf positions and to include in this evaluation the >exchange that can happen from here. > >You want to do - for example - a three plies search and do not want to go any >deeper. So you want a SEE to apply to all the positions three plies deep. > >When you actually write a chess program and experiment more, you realize - and >this is counter intuitive - that it is possible to search the tree of all the >captures at the point where you normally would like to call your SEE, and that >it is only marginally more expensive while being more reliable. Chess and Sargon >(from version II and on) are exemple of successful programs that have used this >method (full QSearch). > >After a number of years thinking about it and experimenting with it, I believe >that it is possible to achieve even better results by sometimes doing a full >QSearch and sometimes just calling the SEE. > >That's what I do in Chess Tiger. > > > > > >>Right now there are programs (e.g., HIARCS) with eval terms for en prise pieces >>which isn't that much of a leap. >> >>Another thing is that Genius was very selective, so it may have run its eval >>function on positions that it considered quiescent through some other means. In >>practice not much different from a Q search. >> >>There may be a trade-off with accracy, but really, the accuracy of Q searches is >>shit anyway. It may be BETTER to evaluate things as they are than figure that a >>brain-dead sequence of captures may occur. I've been working on ways to keep my >>program from returning (inaccurate) evaluations from positions that are very >>active (e.g., hanging pieces all over) but the Q search decides are legitimate >>stopping points. Eliminating the Q search doesn't seem like a bad idea at all. > > > >Maybe using a SEE when you know that doing a full QSearch is going to be >expensive, doing a full QSearch when you know that the SEE is not going to >return a reliable result...? Hmm, I would guess that they positions where SEE isn't going to be accurate are the expensive ones .... Tony > > > > > > Christophe
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