On Wed, Jan 30, 2008 at 03:23:35PM -0500, Don Dailey wrote:
> Having said that, I am interested in this. Is there something that
> totally prevents the program from EVER seeing the best move? I don't
> mean something that takes a long time, I mean something that has the
> theoretical property that it's impossible to every find the best move,
> even given eternity?
Someone, I think it was Gunnar, pointed out that something like this:
5 | # # # # # #
4 | + + + + + #
3 | O O O O + #
2 | # # + O + #
1 | # + # O + #
-------------
a b c d e f
Here black (#) must play at b1 to kill white (O). If white gets to move
first, he can live with c2, and later making two eyes by capturing at b1.
Depending on the definitions, b1 can be seen as an 'eyelike' point, and will
not be considered in any playouts. No amount of UCT-tree bashing will make
the program play it.
In random playouts, it is 50-50 who first egts to c2. But it does not matter,
as white lives in any case (at least as long as he has some outside
liberties, I think).
As I mentioned earlier, it is possible to get around that by allowing even
eye-filling suicide moves in the UCT tree, even if not allowing them in the
playouts. Even then, the UCT tree has to extend to the point where this kind
of situation can occur, before the program can see it.
- Heikki
--
Heikki Levanto "In Murphy We Turst" heikki (at) lsd (dot) dk
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