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Re: [Bug-gnubg] GNUBG gammon bug

From: Ned Cross
Subject: Re: [Bug-gnubg] GNUBG gammon bug
Date: Sun, 20 Jul 2003 22:51:09 -0700

Possibly related, I'm not sure...I just did a rollout today of the attached
position, and strangely GNU reported a 0.0% chance of losing a gammon.
GNU's 2-ply eval showed gammon percentages around 2-3% for each of the top
two plays, as did Snowie 4 evals and rollouts.

Interestingly enough, I originally decided to rollout the position because
GNU 2-ply eval listed 5/2 as the top move (10/7 as second best, but a
significant error), while Snowie 4 listed 10/7 as best, with 5/2 far down
the list.  Performing a rollout with both bots gave the result that they
BOTH changed their minds...Snowie rollout (2-ply with 3-ply cube, 324 trials
with VR), preferred 5/2 and GNU rollout preferred 10/7.

I don't know if the gammon percentages would make a difference in GNU's
choice of "best move", but it seems like a problem in either the rollouts or
the reporting of rollout results.


----- Original Message ----- 
From: "Jim Segrave" <address@hidden>
To: <address@hidden>
Cc: <address@hidden>
Sent: Sunday, July 20, 2003 3:57 PM
Subject: Re: [Bug-gnubg] GNUBG gammon bug
> I'm very glad you raised this, it caused me to find and fix a rather
> stupid bug in the new rollout code. Having fixed it, the answer is:

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