Author: Ratko V Tomic
Date: 13:42:47 05/25/00
Go up one level in this thread
> I can't think of any reason why the result of X:X matches (between > the same engine) would vary with depth. > > What could possibly cause this? The same thing which causes X+1 to win more against X i.e. the existence of shallow terminal (or practically terminal) nodes. What test X:X for X=7,8,9... would assure is that the sample set of positions is fair in distributing such shallow terminal nodes. One can illustrate the problem with an extremely skewed sample: suppose that all positions have a tempting trap with a reward, say, 9 plies ahead. Your sample fairness test 8:8 would not show the problem here, yet the 9:8 play would allow 9 ply program to win every game (with right colors) against the 8 ply program which would always fall for the trap. While the positions you used are likely not anywhere near as skewed in this regard, it is conceivable that a few percent variation may occur in X:X play with variable X (your data does show some non-uniformity of X+1 effects with depth). So the result X:X+1 should be normalized to X:X and X+1:X+1 results and not to 8:8 results for all X. Or the positions should be prefiltered to those yielding approximately 50:50 for all X:X matches. In any case, the results are still quite interesting and useful. One possible future test not mentioned in the preprint would be to try X+Y:X, where Y can vary as 1,2,3.... Such test would provide the idea of degree of stability (across the strength differences) of the diminishing returns effect.
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