Author: Robert Hyatt
Date: 14:49:35 12/26/02
Go up one level in this thread
On December 26, 2002 at 11:09:16, Uri Blass wrote: >On December 26, 2002 at 10:55:55, Robert Hyatt wrote: > >>On December 26, 2002 at 01:34:46, Miguel A. Ballicora wrote: >> >>>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... >>> >>>I am really surprised by this statement. Any pruning or extension that depends >>>on alpha will be affected by the move ordering. With different move ordering, >>>the same position might face different bounds, hence, different extensions could >>>be triggered. >>> >>That is the point. Do you want to find something by serendipity? I don't. >>I want consistent behavior every time. And if something is dependent on move >>ordering, it is dependent on luck. IE do you overwrite a position that >>eliminates a hash move which eliminates an extensions? >> >>_not_ a good design, IMHO. > >Ok >You say in other words: >It is not a good design to make programs use null move pruning. >It is not a good design to make programs better. > >For some reason I prefer to be dependent on move ordering and better. >I do not care about instability if it makes my program better. > >Uri In my testing, null-move changes the _score_ so infrequently that it simply doesn't matter. IE in the typical case, the score is the same with or without, as is the best move, etc. Which is as it should be. So for me, in the general case, changing move ordering only changes the size of the tree, not the score or best move.
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