Author: Uri Blass
Date: 03:14:05 01/04/06
Go up one level in this thread
On January 04, 2006 at 04:33:37, Dann Corbit wrote: >On January 03, 2006 at 14:40:01, Tord Romstad wrote: > >>On January 03, 2006 at 13:22:57, Andreas Guettinger wrote: >> >>>On January 03, 2006 at 12:28:09, Robert Allgeuer wrote: >>> >>>> >>>>>It is possible that Sergei introduced the name "history pruning", but the >>>>>technique itself is very old; certainly much older than SmarThink. I no >>>>>longer remember where or when I heard about it for the first time, but it was >>>>>definitely not in this millennium. >>>> >>>>It would be really interesting where this technique came from, given that it is >>>>now in wide-spread use. Maybe a forum member knows... >>>> >>> >>> >>>Two papers were it was introduced (1989), probably found on Dann corbits FTP. >> >>As Stuart points out, these papers are about history-based move ordering, >>which is not the same thing at all. >> >>I don't think there are any papers to be found. History pruning/late move >>reductions must rather be considered as a part of the "oral tradition", and >>the origins seem to be lost in antiquity. Perhaps Bob or some other veterans >>can tell us more. > >I would be interested in pruning data for difference based pruning. > >For instance, if some move is the root node, and has a centipawn evaluation of >100 centipawns, then when a move fails low or has a hash table value of the >appropriate depth at -100 centipawns, can we reduce the depth of search? How >about 200 centipawns difference? 1000 centipawns? It is true, we will just have >a bound, but if it is an upper bound and it is 200 centipawns below the pv node, >can we reduce the depth of search by 1/2 ply? How about by 1 ply? > >The idea is sort of like null move, except that we scale reductions according to >how bad the move looks. We could have an additional parameter for maximum >reduction (e.g if we are supposed to look 12 plies deep, we will look at least 7 >plies deep even if we lose a queen and a rook). I think that this would play >more like most people. We tend to look harder at moves that look promising and >not so hard at moves that look bad. Same for computers because of null move pruning. If you are queen and rook down you usually threats nothing. Uri
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