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Re: [Bug-gnubg] Analysis of race rollouts

From: Joseph Heled
Subject: Re: [Bug-gnubg] Analysis of race rollouts
Date: Fri, 01 Nov 2002 07:28:34 +1300
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David Montgomery wrote:
The power (and limitation) of the OSR is that it is one sided, i.e. plays each side independently, so that it has no notion if it needs to make desperation plays or not. Even if it did, I doubt it is possible to find those moves cheaply.


It's true that one-sided racing databases that just have the mean rolls to bear off can't make desperation plays.

But one-sided racing databases with the probability distribution
of rolls to bear off *can and do* make desperation plays, if you
choose plays by convolving the two distributions.

But I am computing the probability distribution by playing out each side seperatly, ignoring desperation. After that it is too late.


I believe that it will be very rare for a rollout done in this
manner to differ noticably from the exact cpw from a two-sided database.

If a normal approximation is used, you can still get desperation
plays. Basically the trailer chooses high-variance plays, even those which might have a slightly higher mean rolls to bear off. This must be less accurate than using the actual single-sided distribution, but for positions far from the end of the race, it probably doesn't give up much.


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