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Unlimited Game - Cube Action - XGR+ Evaluation

Posted By: Daniel Murphy
Date: Wednesday, 13 October 2010, at 8:16 p.m.

In Response To: Unlimited Game - Cube Action - XGR+ Evaluation (Stick)

You should of course always have a minimum number of trials before you stop a rollout. I think 324 trials as a minimum is a must.

If that means that 324 trials is a reasonable minimum number of trials for a wide range of positions for which rollouts are done, I'll go along with that. But if that meant that 324 trials was truly a "must" for all rollouts, that'd be absurd. For many positions, 324 trial would be a big a waste of time. It can't possibly be a minimum "must" for all positions. With variance reduction, just one trial might be enough!

This is right:

[the number of trials needed depends on] "how close the decisions are and the amount of variance left in the rollout."

And it also depends on how certain we want to be of the result, and (as Stick mentions) on how much time we have or want to devote to the problem. Depending on the closeness of the decision and the desired degree of certainty, an acceptable number of trials might be 1295, or 46655, or 323, or 107, or 35, or 1. Or impractically more than 46656.

Usually what you want out of a rollout is for the decision (here the cube action) to be 100%.

No, that is not what we usually want. We want results that are acceptably reliable given the fact that our time is not unlimited. That's why we talk, for example, of "joint standard deviations" and "95% confidence intervals," and pay attention (as Stick did mention) to the closeness and the variance of our results. 100% certainty is an extremely high standard of certainty that many rollouts posted on this site (and elsewhere) don't meet. And yet they're still useful.

I reveal no secrets here, but if one were to walk away from this thread thinking that all rollouts must be at least 324 trials long and provide 100% certain answers, one would be wrong.

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