Author: Antonio Dieguez
Date: 07:32:30 08/23/00
Go up one level in this thread
On August 23, 2000 at 03:57:00, Christophe Theron wrote: >On August 23, 2000 at 03:42:09, Dieter Buerssner wrote: > >>On August 22, 2000 at 21:57:58, Antonio Dieguez wrote: >> >>>can a kind person explain me Negascout? >>>what it does in addition of pvsing? >> >>I think there are two differences between Negascout and PVS. >> >>Both use zero window searches with -alpha-1, -alpha for the recursive call. >>If the score returned from the recursive call is > alpha and < beta, Negascout >>will research with -beta, -score while PVS will research with -beta, -alpha. > > >This is a subtle difference and actually one should try both versions and see >which one works better. but that doesnt work properly too anyway. >>Also Negascout will not research, when the depth is the final depth - 1 or >>the final depth - 2. >> >>I believe, this last point won't work, when you have pruning decisons in >>qsearch, >>that depend on the window (i.e. you skip capturing moves, that look, as if they >>could not bring back the score to alpha), or when you use futility pruning close >>to the leaves of the tree. > > >I have never understood this "not re-search in the last plies" trick. Obviously >it does not work for the reasons you have given, but I think it also simply does >not work if you use a QSearch. I suspect this optimization works only when you >do not have a QSearch, and you consider the nodes at the horizon to be terminal >nodes. Because in this case the score you have got with the null window cannot >change after the re-search with the full window. > >If somebody understands it in a different way, I'm interested to hear about the >explanation... > > > Christophe thanks for replaying, yep i also didnt believe in the no-research at the last wide ply. But the idea is interesting anyway, to think *when* something like that could work, or also when a score>beta is really a lower bound(not picking just beta as the lower bound for the hash) etc etc bye bye.
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