[Computer-go] Progressive Bias, progressive widening

Brian Sheppard sheppardco at aol.com
Sun Jan 20 08:45:07 PST 2013


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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