Author: Robert Hyatt
Date: 07:03:49 02/05/00
Go up one level in this thread
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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