Author: Miguel A. Ballicora
Date: 20:15:41 12/26/02
Go up one level in this thread
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. Don't you have any pruning/razoring/extension method that depends on the value of alpha? Hard to believe that any modern program has not any of those. Miguel > > > >>> >>>Hashing _can_ cause quirks, but it actually is more important to search _worse_ >>>moves first and then graft those search results on to better searches. That is >>>how we solve fine 70 faster than we should. If the tree were ordered >>>perfectly it takes 26 plies, period... >> >>IMHO, faster in plies does not mean faster in nodes (time). With terrible move >>ordering you could solve a position in less plies but it could be in more nodes >>than with good move ordering. > > >I am talking time to solution. Fine 70 takes 26 plies with perfect move >ordering. Most solve it at a considerably shallower depth, and there are no >extensions whatsoever to help, so it is simply an artifact of hashing. And >the only way hashing can help is as I explained earlier... > > > > >> >>Miguel
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