Author: Dieter Buerssner
Date: 15:22:16 10/10/02
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On October 10, 2002 at 17:51:17, Peter Fendrich wrote: >On October 10, 2002 at 17:17:43, Dieter Buerssner wrote: >>You are correct, and the example I gave was bad. Other posters explained it >>better. To my excuse, I might say: For my engine the example was mor or less >>correct, because I also update "PVs" (which may be be called refutation >>variation) when outside of the alpha-beta window (so for a fail low node, >>whatever the fail soft alpha beta loop reported as best move, for fail high >>node, the move that returns a score >= beta). I use this "refutation PV" to help >>moveordering, for example in the case where a reasearch from zero window search >>is needed. > >Will this really help? In my experience, it did help a bit. >The fail low node will not produce anything useful and the fail high node move >will be kept in the hash table so when researching it will be there anyway. wont Yes (but I think even the fail low, can give a bit of info, when using fail soft search at least.). But for my engine, there is often the situation (in games with longer TC) that the hash tables are overcrowded, and some of the essential info can be overwritten. The "refutation-variations" should give a persistent source for the move ordering in this case. Note, that this idea is from old days with a 396SX-16 and little memory (I started with 1MB). Perhaps, I didn't have a hash table at that time (I cannot remember). I certainly tested it later with HTs, and it still gave slightly smaller tree sizes in the situations I tried. Regards, Dieter
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