Author: Robert Hyatt
Date: 07:03:49 02/05/00
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On February 05, 2000 at 04:04:06, Dann Corbit wrote: >On February 05, 2000 at 03:51:24, Gian-Carlo Pascutto wrote: > >>On February 05, 2000 at 01:05:13, Dann Corbit wrote: >> >>>It uses NegaScout() rather than NegaMax() like {for instance} Crafty. >> >> >>Hahaha...Crafty (and every other half-decent chessprogram) uses >>Principal Variantion Search, which is essentially identical to >>NegaScout. >> >>If it were to use pure NegaMax, you'd see the search depth nearly >>halved. > >Shows you what I know, which is not much. I was just going by the comments in >search.c that say this: > There is no "negamax" search that I know of, by itself. negamax is just a odd formulation of a minimax search that turns it into a "maximax" search for simpler program, by negating things at every ply. IE alpha/beta and negamax alpha/beta are identical, since both use minimax... only the negamax code is simpler to write (it can be recursive where straight minimax can't be without a lot of extra tests for min or max nodes... Crafty uses PVS as the basic search strategy, coded in the 'negamax' framework of recursive alpha/beta. >******************************************************************************** >* * >* Search() is the recursive routine used to implement the alpha/beta * >* negamax search (similar to minimax but simpler to code.) Search() is * >* called whenever there is "depth" remaining so that all moves are subject * >* to searching, or when the side to move is in check, to make sure that this * >* side isn't mated. Search() recursively calls itself until depth is ex- * >* hausted, at which time it calls Quiesce() instead. * >* * >******************************************************************************** > >What (exactly) is the modification that turns a negamax search into a Principal >Variantion Search? > >In what way does this cause identical search performance?
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