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Re: [Bug-gnubg] Re: Bug? Pruning On/Pruning Off gives significantly dif

From: Joseph Heled
Subject: Re: [Bug-gnubg] Re: Bug? Pruning On/Pruning Off gives significantly different results at 4ply
Date: Tue, 1 Sep 2009 08:40:24 +1200

I am not sure what you mean by "sigmoid has changed" but any change to the way it is evaluated means the net will suffer - it is not recommended without re-training.


On Tue, Sep 1, 2009 at 7:24 AM, Michael Petch <address@hidden> wrote:

On 31/08/09 1:09 PM, "address@hidden"
<address@hidden> wrote:

> Hi Michael
> I'm almost certain the problem arises when at the 2-ply stage gnubg thinks the
> move is an error it simply references the 0-ply evals but reports them as
> 4-ply.
> This would explain why it takes longer with pruning on than off.
> The problem doesn't occur when the move played is the best move at 2-ply.
> Gnubg then reports the correct 4-ply evals.
> I've checked quite a few positions and they all confirm my findings.
I am CC'ing this back to the list to provide others that information.

> On a separate note I'm using build Aug 3 2007 because I can't get the latest
> build to stop crashing. I noticed a lot of the times the evals will differ but
> I've never seen more than 0.001. Do you know why that is?

With regards to the crashing. What happens if you remove gnubgautorc (make a
backup somewhere else) from the .gnubg directory (Its a subfolder of your
home directory), and then reenter all of your settings. Does it crash? If it
continues to crash, what are you doing when it does crash?

As for evals being different, yes there is a reason. Since 2007 we have
added two things. SSE vector support. This changed the evals slightly. More
recently we added SSE2 vector support and a new sigmoid function in the
neural net. The evals will be slightly different yet again. Since 2007 there
have been a number of bug fixes, some of which may alter rollout results as

You can not rely on evaluations to always be the same from release to
release. When you install Gnugb there is a file installed called Changelog.
It contains a list of the bigger changes that have been committed (and the


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