Author: Will Singleton
Date: 19:33:48 06/04/99
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On June 04, 1999 at 22:08:18, Dave Gomboc wrote: >On June 04, 1999 at 21:54:16, vitor wrote: > >>theyre basically the same except negascout has the extra depth>2 condition. >>their performance numbers are near equal too. negascout searches maybe 0.1% >>fewer nodes. another thing is ,if you're using extensions, doesnt it get more >>complicated to properly detect depth>2? so is it worth it to include the extra >>condition? > >PVS can be enhanced with the depth_remaining<=2 test too. PVS and NegaScout are >different, but this is not the difference. > >Using the depth_remaining<=2 early exit is bad if you use extensions. It is a >subtle bug, and to my knowledge, this has not been mentioned in the literature. >Jonathan Schaeffer found this one the hard way many years ago, debugging a >search that gave incorrect results. :-) Considering that the complete special >condition for early termination of the search line occurs next to never, it is >probably faster to not do the check at all, even if you don't extend, that is, >the depth_remaining<=2 refinement is not really worthwhile. > >Dave I could never get that to work properly, always got bad results. Don't know why it affected the search negatively. Will
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