Author: Robert Hyatt
Date: 20:17:45 03/31/00
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On March 31, 2000 at 12:53:43, Stephen Ham wrote: >Dear Readers, > >I know many of you are actively following my ongoing match games versus Fritz 6a >and Nimzo 7.32. For those of you not familiar with the event, please visit: > >http://correspondencechess.com/campbell/index.htm > >Anyway, a frequent poster here (name is withheld) wrote to Mr. Campbell stating >that since the chess engines are displaying their top 3 choices, they are being >weakened "a lot". No explanation was given for that claim. > >Would somebody here please provide a detailed explanation regarding whether this >claim is correct and why? It depends on how they compute these variations. Done correctly, it is _horribly_ inefficient. If you watch a normal search, the first move will usually take over 50% of the total time. The remaining N-1 moves take the remaining 50% of the time. If you have it display two 'best'moves, you increase the total search time by roughly 50%. The first move takes the same time as before. The second move also takes the same time as before, and the final N-2 moves take just a tad less than before. Net loss is ugly. If you have it display the best 3 moves, you slow it down by exactly a factor of two... > >The chess engines are on settings recommended by ChessBase USA as their optimal >settings for this event. My extremly limited understanding is that displaying >the top 3 choices does indeed affect the chess engines, but it causes them to >spend more time on what it believes to be the 3 best moves. As such, this sounds >like an enhancement to me. Given that the chess engines are allowed about 24 >hours calculation time on weekdays and are searching to 16-18 ply, I can't >imagine that this weakens them in any way. Each iteration will take about 2x longer than the previous. Rather than a branching factor of 3x, you raise it to 6x. This will cost several plies over 24 hours. > >Please advise. We sincerely want the chess engines to play at peak performance. >I also think we all learn more about computers in Correspondence Chess when we >can see their 2-3 choices and understand what it caclculates and DOESN'T >calculate in certain positions. Often, it seems they make the correct choices >for the wrong reasons. > >Since I am the computer's opponent, I don't have access to the chess engine >manuals where this may be explained. Thanks in advance for any information you >can provide. > >Stephen Ham If the computer is really playing the match, turn N-best _off_ and just play the best move it finds... this is far better...
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