Author: Thorsten Greiner
Date: 05:09:02 01/28/00
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On January 28, 2000 at 07:39:17, Mark Taylor wrote: >My question is this - being forced to make a move in Chess can be disastrous in >certain positions (esp. in the endgame), and in this type of position misleading >results would be obtained. Yes, a well known problem of null move pruning. This is why most programs switch the nullmove off in the endgame. > >It seems to me that a better approach would be to make a single move (any move) >rather than no move at all - the resulting tree would be the same size and >therefore the overheads should not be that much greater. Actually the tree resulting from a null move is searched with reduced search depth, nowadays a reduction of 2 plies is standard, but brave people like Vincent Diepeenven (sp?) will use R=3 (or more?). So if the null move results in a beta cutoff we have searched only 1/(bf*bf) of the nodes we usually need, with a typical branching factor of 3 this saves 90% of the effort. And in the case of no cutoff we introduced only a small overhead. > >Can anyone help me with an explanation? Hope that helps... -Thorsten > >Thanks, > >Mark Taylor.
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