Mark Boon wrote:
Not an expert on AB-search or UCT search but there's a subtle
difference I think. In AB search, if some processors have been
searching in a branch that is subsequently cut off, the work is 100%
wasted. In UCT there's no such black-and-white cutting. If you do
sampling in what then turns out not to be the optimal branch, further
sampling in the optimal branch may cause the UCT-value to drop to a
point where you'd otherwise start sampling the sub-optimal branch
again. So in that case you gain back part of the 'wasted' work.
I'm also inclined to think that the 'chunks' of work that are wasted
tend to be larger for AB-search than for UCT. But I'm not 100% sure.
The problem is that the optimal settings for UCT appear to be much
stronger on the exploitation side than on the exploration side, making
it much more likely that such work is really wasted.
It is not so obvious to me any more what the differences are between a
state of the art UCT searcher (i.e. with nearly no exploration) and a
state of the art alpha-beta searcher (i.e. with heavy late move reductions).
They both just hammer out the mainline deeper until the score drops a
bit, or an alternative rises strongly.
UCT without exploration is just minimax, no?
--
GCP
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