Author: Robert Hyatt
Date: 07:55:55 12/26/02
Go up one level in this thread
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. >> >>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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