[computer-go] How to improve Orego

[Chrilly]

In the Orego paper the problem of selecting a move when the board is filled 
with stones is mentioned. Orego uses a sort of double-hashing scheme.
But isn't it trivial to keep a list of empty intersections?
Before the MC-run is started, one builds up this list. If a stone is placed 
now on the board, the entry is removed from the list and the last entry is 
copied into this slot. In this way the list is always dense. One can of 
course not run linearly trough the list to find the entry which should be 
removed. Instead one builds at the beginning another array which is indexed 
by the board-point and which contains the index of the point in the 
empy-point-list. This second array has to be changed too when the last entry 
is copied into the removed slot. With a few operations one gets the big 
advantage to sample all the time only the empty points.
I think this solution is much simpler and more efficient than the 
double-hashing scheme of Orego.

Chrilly