Author: Robert Hyatt
Date: 19:33:14 12/02/02
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On December 02, 2002 at 18:01:00, Bob Durrett wrote: > >Fritz will display second best, third best, etc. moves and give a line for each. > But the Fritz manual says doing so requires extra computation when compared to >calculating only one move and displaying a line for it. > >I do not know what other chess-playing programs have to offer insofar as display >of alternate moves with there lines is concerned. > >A few questions: > >(1) If other programs offer this same feature, how do these chess engines >produce the alternate moves and lines? Differently from the way the first move >and it's line is produced? There are two ways to do this. 1. Search all legal moves and get the best and display it. Delete this from the list of legal movs and search again for the best. This will take about as long as the first search. Total cost to find two moves is 2x the cost. 2. search the first move and get the PV. Then as you search others, you may get a new PV. This PV is clearly the best, and the old best is now _Probably_ second-best. To do it right is expensive. > >(2) If a chess-playing program were optimized to display multiple lines, would >the search algorithms and position evaluation code be any different from those >of a chess engine optimized for one move [and it's line] only? Probably not. But alpha/beta is not designed to produce anything other than the "bst" move... > >(3) If an engine is not optimized for this application, how much will the engine >performance be handicapped if it is forced to display alternate moves and their >lines? 5 lines is roughly 5x slower, but it can be better or worse... > >There may not be any simple answers to these questions? : ( > >My motive for asking these questions is obtain preliminary information which I >might use for an idea, having to do with trees of "best move sequences," I would >like to think more about. > >Bob D.
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