Hello, I am very new to UCT, just implemented basic UCT for go yesterday. But with no success so far for GO,I think mostly because it searches not very deep (depth = 3 on a 5 sec search with those values). I am using the following values as UCT parameters
UCTK = sqrt(1/5) = 0.44 UCTN = 10 (visits afte which best move is expanded) Even if I lower UCTK down to 7 I get a maximum depth of d=7 at the start position for a 5 sec search. For how deep a search should I tune these parameter for ? Before UCT, I have an alpha-beta searcher which sometimes plays on CGOS. It reached a level of ~1500, and this engine seems to be too strong for the UCT version. It just gets outsearched in some tactical positions and also in evaluation I think. For example, I have an evaluation term which gives big bonuses for connected strings which seems to give an edge in a lot of games.. How do you introduce such eval terms in UCT ? But for my checkers program , to my big surprise , UCT made a significant impact. The regular alpha-beta searcher averages a depth=25 but the UCT version I think is equally strong from the games I saw. That was a kind of surprise for me because I thought UCT would work better for bushy trees and when the eval has a lot of strategy. It also reached good depths averaging 16 plies . My checkers eval had only material in it, so I don't know if UCT is bringing strategy (distant information) to the game which the other one don't have.The games are not really played out to the end rather to a MAX_PLY = 96 afte which the material is counted and a WDL score is assigned (I call it partial playout). Also the fact that captures are forced seem to help a lot because it doesn't make too many mistakes. I also found out some positions where it encounters similar problems as ladders in go. But in the checkers case, this problems are still solved correctly. Only problem is that it doesn't report correct looking winning rates. For example, in a position with two kings where one of the kings is chasing the other to the sides to mate it, but the loosing king can draw by making a serious of correct moves to get itself to one of the safe corners; The program displays winning rates of 0.01 (when it should have been more like 0.5) but it still manages the draw ! thanks and apologies for the verbose email Daniel
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