Author: Bob Durrett
Date: 06:03:47 09/12/03
In comparing the top engines, I am finding that Shredder consistently gives White more favorable position evaluation scores than the rest of the top engines do. This is a problem for users of the software because the position evaluation scores given by Shredder must be "taken with a grain of salt." Position evaluation scores are important to the user of a chess engine when the engine is being used to evaluate lines and positions. For example, if Shredder indicates that White gets a big advantage by playing a certain opening move, then the unsuspecting user might mistakenly decide to use that move in his/her opening repertoire. Similarly, if an engine were to indicate that a good move were not good, the user might mistakenly reject that move and not use it in his future games. There is a computer programming issue here, too. Are the position evaluation scores displayed on the monitor actually used by the engine during the searches? It could be that the move searches are done independently and then the evaluation scores to be displayed to the user calculated subsequently. Suppose the displayed position evaluation scores are those actually used by the engine during search. In this case, a constant bias might not adversely impact the selection of the correct move. This might explain why Shredder is on the top of the rating list even though the displayed position evaluation scores are inconsistent with those displayed by the other top engines. Incidentally, I am finding that Shredder, Tiger, DJ, Fritz, and Crafty are all much more inconsistent in evaluation scores than I would have suspected. I had been putting much faith in the evaluation scores of Fritz 8, and now find that they could be off by as much as 1/2 pawn! Who is to say which engine is most right most of the time? Maybe Shredder's evaluation scores are usually correct and all the rest are off! [Everybody's out of step except Shredder]. Bob D.
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