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Re: [Bug-gnubg] Question About Rollout


From: Massimiliano Maini
Subject: Re: [Bug-gnubg] Question About Rollout
Date: Tue, 13 Nov 2007 11:14:40 +0100


address@hidden wrote on 13/11/2007 09:53:12:

> Hi Mochy,
>
> the winning chances reported by a rollout are in a sense cubeless. What
> actually goes on is the following. If a game is played to the end the
> actual result is recorded, i.e. 1 lost backgammon counts as one game in
> that column. However, many games are truncated, either by using the race
> database, or at cash point. In these cases the evaluation values at the
> truncation point is added to the individual columns. For example,
> suppose that you double out when winning 60% games and 40% gammons. Then
>
> 0.60 0.40 0.00 - 0.40 0.00 0.00
>
> would be added.

Hmmm I'm confused:

1- When you say "cubeless", do you mean that the game will be truncated
right after the very first double decision, if any? I understand your
example of a double/pass, but what about a double/take situation?

2- At the end of the trials, the computed "cubeless" figures will
lead to a "cubeless" equity that will be translated into a cubefull
equity via the janowski formula, right? In Mochy's example, the W/G/BG%
are the "cubeless" results of the rollout, the CL is the "cubeless"
equity and CF is comuted via Janowski formula?

> > Rollout details:
> > Centered 1-cube:
> >   0.669 0.146 0.002 - 0.331 0.078 0.003 CL  +0.405 CF  +0.621
> > Player player owns 2-cube:
> >   0.670 0.152 0.001 - 0.330 0.077 0.003 CL  +0.854 CF  +0.574


3- Any idea why a simple "full cubefull rollout" approach is not implemented ?
I mean letting gnubg play against himeself cubefull and record the outcome.
I suspect this comes from the fact that its result would not be a W/G/BG%
but more an equity (for money) or a MWC (for match), but hey, these
are what matters ...
Another reason is that the current method, truncating at double decisions,
should/could "reduce the variance" (provided the evaluation is good).

MaX.
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