>-----Original Message-----
>From: [EMAIL PROTECTED]
>To: computer-go@computer-go.org
>Sent: Sun, 14 Jan 2007 11:08 PM
>Subject: Re: [computer-go] Fast Board implementation
>

>What should the mercy threshold be for other board sizes than 9 by 9, 
>particularly 19 by 19? 
>- George Dahl 

 
     I don't know. 
 
     For 9x9, I ran many random playout games and whenever the rule triggered I 
would look at the board. With a little trial and error I picked a threshold 
where, with just a quick glance, it was always obvious which side would win. I 
use this threshold for external nodes and a higher one for internal nodes which 
are more likely to have alot of dead stones. 
 
     Picking it this way is "the 80% solution." I got a nice speedup without 
having to fuss with it and I don't need to constantly revisit the issue, 
wondering if I'm running into some subtle bug.
 
- Dave Hillis
 

> > 
> > Here are a few speedup tricks that have helped me. 
> > 
> > 1. The mercy rule. Since I'm incrementally keeping track of a list of empty 
> > points, it's no real extra pain to keep track of the number of black and 
> > white stones on the board. If the difference between them exceeds a 
> > threshold, the game is over. Ending early has an added bonus that I know 
> > the 
> > outcome without needing to score the board. (You can shoot yourself in the 
> > foot here. Best to pick a more conservative threshold the closer you are to 
> > interior nodes of the tree.) For exterior nodes far from any interior 
> > nodes, 
> > I use a threshold of 25 stones. 
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