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[Bug-gnubg] gnubg defends poorly against outer primes

From: Misja Alma
Subject: [Bug-gnubg] gnubg defends poorly against outer primes
Date: Sun, 23 Nov 2003 20:01:24 +0100


I finally managed to analyse a position where a gnubg rollout gave strange
results: ObsdAAhi2zYQEA
Although gnubg evaluates this as a clear take, its rollout (level: world
class) evaluates this as a pass and almost no double. At first I thought
this was a bug in gnubg, but I believe it was Joern Thyssen who told me that
the result might be due to gnubg's poor understanding of this position.
So I saved the rollout trials and managed to import them into Snowie (I read
in your excellent manual that JellyFish export format is most suitable for
that purpose, and it was!). It turned out that Joern was right: gnubg plays
the side that is defending against the outer prime in the position mentioned
above very poorly.
For instance, in positions like YttuAQDb7BoACA it does not come up to the
edge of the prime. Not doubling in the initial position does not cost very
much in the rollout, because gnubg will take always later on, even with one
checker against a six prime: 69wVAAhi23YQAA
So I guess gnubg needs some more training in positions with outer primes..
Those positions don't come up so much, so that's why it has not had enough
practice I suppose.


PS: importing the rollout trials into Snowie was quite a hassle, because the
JellyFish .gam format does not support
    games which do not start from the initial position. So I had to create a
fake start of the game where finally
    my position would come up, and this start I had to paste at the start of
every saved rollout trial.
    As far as I can see the only solution would be to implement an export to
Snowie format? I read in an earlier post
    that Snowie .swm format is just a zipped Paradox database. So I tried to
unzip such a file and open it in MS Access,
    but this gave an error message.
    So does anybody know which kind of a Paradox database this is? Then I
could perhaps make an attempt to write an
    export/ import function in Delphi..

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