[computer-go] How does MC do with ladders?

[Rémi Coulom]

Robert Jasiek wrote:
> Mark Boon wrote:
>> Question: how do MC programs perform with a long ladder on the board?
>
> Mogo makes the 20k mistake to push an intrusion of ladder shape into 
> the own territory like tooth paste. I do not know if this is caused by 
> reading ladder-like, by juding the adjacent life wrongly (in a nakade 
> there are often more death than life sequences even if a simple vital 
> point makes life), or by the short but wrong pattern database. The UCT 
> programmers should tell us.
>
Hi,

I don't understand what you mean by "push an intrusion of ladder shape 
into the own territory like tooth paste".

Crazy Stone handles ladder with progressive widening. Ladder atari is 
usually ranked first or very high in the move list, and ladder extension 
lower. So, the tree-search part usually does not read out the ladder 
completely, but prunes the extension. It seems to work well in practice. 
Because progressive widening will include the ladder extension at some 
point, Crazy Stone may still play ladder extensions if it finds reasons 
to do so.

According to some discussions I had with Sylvain in Amsterdam, MoGo's 
approach is a little more primitive. If I remember correctly, it 
completely prunes ladder extensions. I am not sure if it is done only at 
the root, or inside the tree search too.

Rémi