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Re: [gnugo-devel] Semeai node limits


From: David G Doshay
Subject: Re: [gnugo-devel] Semeai node limits
Date: Fri, 17 Mar 2006 10:59:41 -0800

My view, from seeing the kinds of troubles SlugGo has with doing
global look ahead over the top of the GNU Go engine, is that a
new dragon amalgamation algorithm would make a huge difference.
As the number of thrashing dragons grows, the probability of a
mistake that lets them connect together increases. After they connect
the probability of loosing a capturing race similarly increases.

But perhaps I see this clearly in SlugGo due to effects that do not
happen inside a pure GNU Go engine.

Cheers,
David



On 17, Mar 2006, at 5:40 AM, Gunnar Farnebäck wrote:

Terry wrote:
Regressions are not run often ...

On the contrary regressions are run frequently to try out new patches.
It may not be run often, or at all, by ordinary users but for
developers the regression run time has a big impact on the
productivity. This does not mean that it's automatically wrong to slow
down the regressions but we need to be careful about it.

it would be more pertinent to ask a) whether gnugo picks better
moves with a higher node limit,

In general it can be expected not to do worse on average, at least.
But as long we are doing selective search with heuristic evaluation of
the leaf nodes there will always be anomalies where a deeper search
gives a worse result.

More important here is the fact that the semeai reading tends to have
a high branching factor. My feeling is that for the simpler semeais,
the node limit is not much of a problem, while for complex semeais the
node limit can be increased a lot and still be insufficient. There's
certainly a class of semeais where changes in the 500-2000 range are
significant but the question is how often we encounter those.

and b) whether the cost time-wise is acceptable for ordinary usage.

I'm more interested in the question which ways to slow down the engine
have most impact on the playing strength. Maybe large-scale (ticket
#29), a new dragon amalgamation algorithm (#97) or Alain's twin option
(#104) are better places to spend time. Or maybe just increasing some
depth parameter (e.g. ko_depth).

/Gunnar


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