[computer-go] Efficiently selecting a point to play in a random playout

[Peter Drake]

I struggled with unto a lot, too. In the current version of Orego,  
there is no undo, just a way to copy a board relatively quickly. This  
falls under "keep the common case fast" again: you only "undo" once  
per playout, so it's faster to make a copy.

(For the "real" board, where actual games moves are played, maintain  
a stack of board state copies for undoing.)

Peter Drake
http://www.lclark.edu/~drake/



On May 27, 2007, at 5:28 PM, Jason House wrote:

> Don Dailey wrote:
>> Lukasz Lew does something far more sophisticated and very fast  
>> using the
>> concept of pseudo liberties which you might want to look into.
>>
>
> Both pseudo liberties as well as disjoint set chain tracking.   
> Curiously enough, they're both things I independently came up with  
> when I was designing HouseBot the first time around, but included  
> neither in the open source version.  Pseudo liberties had a very  
> negative response on the computer go mailing list at the time, so I  
> chose something closer to real liberty tracking.  When I  
> implementing undo's I figured the disjoint set stuff was too  
> complex and might scare away developers on an open source project  
> (simple, easy to read code is a big plus).  I still wonder if I was  
> the original creator of either concept...
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