[Computer-go] evaluating number of wins versus looses

Petr Baudis pasky at ucw.cz
Mon Mar 30 07:09:35 PDT 2015

On Mon, Mar 30, 2015 at 09:11:52AM -0400, Jason House wrote:
> The complex formula at the end is for a lower confidence bound of a
> Bernoulli distribution with independent trials (AKA biased coin flip) and
> no prior knowledge. At a leaf of your search tree, that is the most correct
> distribution. Higher up in a search tree, I'm not so sure that's the
> correct distribution. For a sufficiently high number of samples, most
> averaging processes converge to a Normal distribution (due to central limit
> theorem). For a Bernoulli distribution with a mean near 50% the required
> number of samples is ridiculously low.
> I believe a lower confidence bound is probably best for final move
> selection, but UCT uses an upper confidence bound for tree exploration. I
> recommend reading the paper, but it uses a gradually increasing confidence
> interval which was shown to be an optimal solution for the muli-armed
> bandit problem. I don't think that's the best model for computer go, but
> the success of the method cannot be denied.
> The strongest programs have good "prior knowledge" to initialize wins and
> losses. My understanding is that they use average win rate directly
> (incorrect solution #2) instead of any kind of confidence bound.
> TL;DR: Use UCT until your program natures

The strongest programs often use RAVE or LGRF or something like that,
with or without the UCB for tree exploration.

For selecting the final move, the move with most simulations is used.
(Using the product reviews analogy - assume all your products go on sale
at once, have the same price, shipping etc., then with number of buyers
going to infinity, the best product should get the most buyers and
ratings even if some explore other products.)  I think trying the Wilson
lower bound could be also interesting, but the inconvenience is that you
need to specify some arbitrary confidence level.

> On Mar 30, 2015 8:06 AM, "folkert" <folkert at vanheusden.com> wrote:
> > --
> > Finally want to win in the MegaMillions lottery? www.smartwinning.info

funny in the context :)

				Petr Baudis
	If you do not work on an important problem, it's unlikely
	you'll do important work.  -- R. Hamming

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