[computer-go] UCT/MoGo confusion

[Richard Lorentz]

Perhaps I am oversimplifying, but if I understand correctly, MoGo 
primarily gets its strength in 9x9 go by improving upon the random 
simulations by preferring "good" moves over purely random moves during 
the random game. Yet I have two results that seem to indicate that it's 
not really that simple

The first is that we have a purely random UCT version running on CGOS 
(GoJin) and its rating seems to sit around 1640. But in the paper we are 
told that the very first Mogo achieved almost the identical rating, yet 
it already had some improvements, such as preferring large captures. Can 
I conclude that those improvements to the random simulations actually 
have no effect on the performance of the program?

But even more confusing to me is that we've tried some simple 
improvements to the random program that have had no effect. The ones 
that I was certain would improve performance were versions that changed 
random simulations so that moves near existing stones would be preferred 
over stones placed too far away from the action. Many versions have been 
tried, e.g., moves that must be adjacent to some other stone, moves that 
must be no more than 1 space away from existing stones, etc. Surely on 
average these are going to be better moves than purely random moves -- 
or is this, indeed, the flaw in my logic? Shouldn't these versions 
outperform the purely random versions? In almost every case the modified 
version performed identical to the purely random version -- no worse and 
no better -- at least according to the self tests. Does this really 
sound right?

-Richard