Hi, I am a newbie to this list and hope the following comments help.
Considering the opening and midgame, with MC evaluation the winrates using either maximization method are similar because there are a lot of unsettle variations thus the winrates in both cases should not have the cutoff issue (term explained in the following). Cutoff issue occurs in endgame when the many moves have winrate around 0 or 1 so that the engine cannot distinguish good yose moves from those with less yose values with the winrate maximization method. In this case, human feels that the engine plays badly and continues to play in the case that the person should actually resign due to the large point difference. This is concerning the user experience and the overall strength of engine. This affects the strength of the engine due to the following reason. Consider we have a winning game in the endgame but the engine keeps playing bad moves (with winrate ~ 1) and losing points. Finally the opponents find the optimal sequence that can turn loss to win (recall that MCTS sometimes finds only suboptimal moves). The engine cannot distinguish good moves from MANY bad moves since all these moves have winrate ~ 1. This is bad and lowers the strength of MCTS at endgame. We should avoid this problem by applying the point difference maximization scheme in this case, and ONLY in this case. For other cases, like having only a few (<= 3) moves with winrate ~ 1 or losing (winrate < 0.5), MCTS can do its job well that we do not need modification. One other thing concerning user experience is that in the VERY LATE endgame (say yose values of all moves < 5), when the engine is facing an experienced (human dan) player and it is losing with a small point difference (e.g. < 4). In this case, since the opponent is not a dum so it is useless to play crazy moves like latest MCTS engines do. In the eyes of experienced human players the winrate is exactly zero for the engine, though the bot gives a non-zero value. In this case, in order to enhance the user experience of these experience human players, we may apply the point difference scheme as well, just to finish the yose "nicely" instead of abrupt resignation. Of course, this lowers the winrate of the game, especially to weak opponents like GNUGo, but I think the dan players are happy to have this feature. Regards, C Chan _______________________________________________ Computer-go mailing list [email protected] http://dvandva.org/cgi-bin/mailman/listinfo/computer-go
