| Consider this position: ...wBw... .w.wBwwww ...wBBBBB wwwwB.... BBBBBBBBB wwwwBwwww w..wBw... w..wBw.w. w.wwBw... This is black to play, no komi. As I read it (correct me if I'm wrong!), the white groups at upper left and lower right can't be killed (assuming white defends them). Black can kill either of the other groups, and white can respond by saving the remaining one. Since killing the upper right white group is not big enough, black's only winning move is to kill the lower left group by playing at b2. Orego (now using UCT) quickly finds the correct answer, but the estimates of the probability of winning are strange. Here's a graph:  The probability of winning by starting at b2 is greater than the probability starting elsewhere, but shouldn't it approach 1.0, since b2 is a winning move? Do others get this same behavior? Does anyone have an explanation? For what it's worth, here are the probabilities and <black wins> / <total runs> through each move: B1 (0.262654 = 1510/5749): G1 (0.269305 = 2504/9298): H1 (0.276537 = 5200/18804): J1 (0.263229 = 1567/5953): *B2 (0.290454 = 134822/464177): C2 (0.288902 = 69762/241473): G2 (0.274577 = 4156/15136): J2 (0.276275 = 5034/18221): B3 (0.261835 = 1427/5450): C3 (0.269523 = 2554/9476): G3 (0.269982 = 2655/9834): H3 (0.27404 = 3927/14330): J3 (0.273359 = 3660/13389): F6 (0.25266 = 831/3289): G6 (0.268461 = 2334/8694): H6 (0.273485 = 3706/13551): J6 (0.247165 = 632/2557): A7 (0.269866 = 2632/9753): B7 (0.274571 = 4157/15140): C7 (0.268814 = 2404/8943): A8 (0.275441 = 4577/16617): C8 (0.277177 = 5617/20265): A9 (0.259601 = 1237/4765): B9 (0.27903 = 7180/25732): C9 (0.268422 = 2324/8658): G9 (0.257561 = 1090/4232): H9 (0.277021 = 5513/19901): J9 (0.262094 = 1452/5540): PASS (0.221808 = 238/1073): Peter Drake Assistant Professor of Computer Science Lewis & Clark College |
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