Author: Jesper Antonsson
Date: 17:04:06 05/05/01
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On May 05, 2001 at 10:58:36, Robert Hyatt wrote: >Don't forget that there are programs and there are programs. Ernst used >Dark Thought. Monty and I used Crafty. Nothing says those two will behave >the same way. IE a more speculative program will gain more from another ply >(because it will help to make the speculative eval more accurate) than a >conservative program will... True, but perhaps even more so for "bad" than "speculative". I would say that the better the eval, the more diminishing gains you will see. This is quite obvious when you think about it, if you get a correct best move early (which will happen with better eval) the best move won't likely change after that. This means that a steeper diminishing gains curve is a sign of quality. In fact, the diminishing gains curve could be used for evaluating eval/extensions or even comparing different programs respective eval functions in an objective, scientific way. One problem is that it takes a lot of time to conduct the experiments, of course, but perhaps low ply searches would be good enough given a better and larger test set, which would make the method somewhat feasible anyway. :-) As an observation along those lines, I would say that it is likely that Craftys eval were better than Dark Thoughts at the time the experiments were conducted, since Crafty seems to have a somewhat steeper diminishing gains curve. Some further calculations I've done indicate that at ply 14, DT may have the correct move 18% of the time, while crafty is correct 22% of the time, which would make your ply 14 as good as DT ply 15. Unfortunately, the number of positions in the experiment were probably too few to conclude the above with any real statistical significance, but it's an interesting thought nevertheless, that such comparisons are possible. >Today we are doing about 12-14 plies. To get to 20 will require a machine >roughly 3^6-3^8 times faster. We won't see that in 10 years, which was my >point. For the forseeable future, the "diminishing returns" isn't going to >be a factor. Yes, as I said, the gains taper off very slowly. On the other hand, for each additional ply, trading speed for eval will be more productive, which is something that can be considered a factor if you compare with the situation, say, 15 years ago. If you consider just one or two years, however, I agree that it isn't a big deal. Jesper
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