Author: Uri Blass
Date: 12:30:57 12/25/02
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On December 25, 2002 at 15:18:29, Robert Hyatt wrote: >On December 25, 2002 at 10:46:17, Dieter Buerssner wrote: > >>On December 24, 2002 at 23:05:09, Robert Hyatt wrote: >> >>>[...] Why don't you go read Knuth/Moore's paper on >>>alpha beta. There you will find that move ordering does _not_ affect the >>>final score, only the size of the tree. Something every senion-level computer >>>science student should know. >> >>I think, in most modern chess programs, move ordering can affect the final >>score. Reasons can be extensions/pruning/hash tables. >> >>Regards, >>Dieter > >If move ordering affects extensions or pruning, _something_ is broken. As >that violates the basic premise of alpha/beta... Move ordering can effect pruning in every program that is using null move pruning. suppose that there are 2 good moves A and B that you did not search. A has a score of 1 pawn adavntage and B has a score of 1.5 pawns advantage with no pruning and the score that you have is 0. Suppose that you start with move A and get a score of 1 pawns advantage. You continue with B and find after null move no threat(you can find a threat only for scopres that are lower than 0.5 pawns and 1>0.5). B is pruned and you choose A. Suuppose that you start with B. now after a null move you can see a threat so B is not pruned and you discover that B has 1.5 pawns advantage. Uri
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