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BGonline.org Forums
Losing your market at 2a2a
Posted By: Rick Janowski In Response To: Losing your market at 2a2a (Timothy Chow)
Date: Tuesday, 16 September 2014, at 3:00 a.m.
One good reason to be happy about not doubling is where subsequently game winning chances reduce to the extent that you are pleased to be able to concede only a single point by dropping the cube. This seems to be a more likely reason than those from scenarios where the position suddenly becomes to good.
Such a situation occurs where the game winning chances fall below about 40%, where doubling would nullify the damage limitation insurance policy.
Incidentally, I am convinced that the anomalies from the evaluations and rollouts resulting from the -2-2 position that Dmitri posted relate to an inconsistency in the methodology used by XG in evaluating game winning chances and associated normal equities. For no-double equities, evaluations incorporate opening book rollouts, whereas for double-take equities they do not.
I checked this possibility out by carrying out the full range of evaluations but setting XG to ignore the opening book to create consistency. For the n-ply evaluations (from 1-ply to 7-ply) the maximum difference in normalised equity is only 0.0001! For XGR+ and XGR++ the difference is a little higher, but still less than 0.0010. I think the greater variance probably relates to the use of mini-rollouts for these evaluation types.
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