[Computer-go] Progressive Bias, progressive widening

David Fotland fotland at smart-games.com
Sun Jan 20 11:07:03 PST 2013


Many Faces uses Progressive widening only.  I think they are pretty similar,
with progressive bias perhaps a little better when well-tuned (from private
communications with people who have tried both).  On 19x19 I think
progressive widening is faster and less memory, but I only did few small
experiments with progressive bias, so I may not have found an efficient
implementation.

David

> -----Original Message-----
> From: computer-go-bounces at dvandva.org [mailto:computer-go-
> bounces at dvandva.org] On Behalf Of Brian Sheppard
> Sent: Sunday, January 20, 2013 8:45 AM
> To: computer-go at dvandva.org
> Subject: Re: [Computer-go] Progressive Bias, progressive widening
> 
> I started with just progressive bias, and I have not seen any reason to
> add progressive widening.
> 
> My experiments are on 9x9. Like you, I wonder whether additional
> concepts will be necessary when the board is larger.
> 
> Brian
> 
> -----Original Message-----
> From: computer-go-bounces at dvandva.org
> [mailto:computer-go-bounces at dvandva.org] On Behalf Of ds
> Sent: Sunday, January 20, 2013 10:51 AM
> To: computer-go at dvandva.org
> Subject: [Computer-go] Progressive Bias, progressive widening
> 
> Hi,
> 
> I know, this topic was in the list a while ago. My problem is, as in all
> science, nobody publishes negative results:)
> 
> Oakfoam uses both, progressive bias and progressive widening. My
> understanding is, this is state of the art in many mc bots, at least the
> theses I read used both.
> 
> Both is working well in oakfoam. Now I turned off progressive widening
> and tuned progressive bias carefully (good scaling of the bias and
> improved decay functions). I got the same playing strength as with both
> (bias and
> widening) before on 9x9 against gnugo, but I can not improve anymore
> with progressive widening turned on again.
> 
> My interpretation is: Progressive bias is the superior concept, but it
> is easier to use progressive widening.
> Progressive widening is not sensitive to the ratio of the pre knowledge
> value of two moves, only the better move must be unpruned first, but
> progressive bias is sensitive to the ratio between the pre knowledge
> values.
> 
> It may be even more difficult to improve the progressive bias on 19x19,
> so there might be a reason to use widening, but at the moment I feel I
> should try without?
> 
> Am I wrong?
> 
> Detlef
> 
> 
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