Author: Peter McKenzie
Date: 16:27:26 08/27/03
Go up one level in this thread
On August 27, 2003 at 14:01:18, Robert Hyatt wrote: >On August 26, 2003 at 18:42:59, Ricardo Gibert wrote: > >>In the Richard Lang interview at: >> >>http://www.beepworld.de/members37/computerschach/ >>(Just click on the link "ChessGenius Classic 7" in the leftmost column. The >>interview also appears in *English*) >> >>"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? >> >>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. > > >I can tell you what I did in the 1970's. > >The issue is that the _last_ move in the search path is "iffy". IE if you >just do a pure 4 ply search, no extensions, no q-search, the last move in your >pv will _always_ be a capture of the most valuable piece that can be taken, >whether it is protected or not (IE in a worst case, you end the PV with QxP, >where in a real game, the opponent would the reply PxQ.) Yes, this is really funny to watch :-) > >If you apply a SEE type exchange evaluation to the last piece moved, you >stop this nonsense. Of course, that misses overloaded pieces and the like, >but it is certainly possible that the errors that produces are not frequent >enough to cause a problem. I did something similar to this in the early days of LambChop. I did a capture search but only on the destination square of the last moved piece. It seemed to work reasonably well (much better than nothing of course), and had very little overhead. > The tree is far more robust than I would have >thought possible, until some recent testing has produced some amazing results. We're all ears...
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