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RE: [Bug-gnubg] Some Questions about rollouts.

From: David Montgomery
Subject: RE: [Bug-gnubg] Some Questions about rollouts.
Date: Sun, 3 Nov 2002 16:49:16 -0800

> There is still one thing I don't understand, even though I have read the
> several times: Which seven rolls does it pick? How does it make the
choice? It
> doesn't pick random as I understand. And as I understand this it doesn't
> the order in respect of how good the rolls are either. Please explain.

I haven't looked at this code in a long time, but it came from
my program, so I think I remember how it works.  My recollection
is that it rotates among three groups of 7 rolls, so that all 21
rolls are represented.    That is, 1/3 of the 1-ply continuations
are evaluated at 2-ply with one set of 7 rolls, another 1/3 are
evaluated with a *different* 7 rolls, and the remaining 1/3 are
evaluated with the remaining 7 rolls.

The partitioning of the rolls into three groups was done with some
effort toward evening up the luck.  For example, I tried to roughly
balance the number of doublets and the number of individual sixes,
fives, fours, threes, twos, and ones.

It does not, however, do any analysis of which rolls are likely to
be good or bad in the current board situation.  You can think of
it as a "random" sample of the continuations, with a little effort
to make it better (on average) than a truly random sample.


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