With X to move, Many Faces immediately gives about a 1% win rate, and after a few seconds, resigns, showing 23742 playouts with 0.5% win rate. 10 ply principal variation, staring with A7. I don't have any special code to detect superko or give-2, get-1 in playouts, but the playouts don't generate self- atari moves in a seki, so I think it never tries J6 for either side.
David > -----Original Message----- > From: computer-go-boun...@computer-go.org [mailto:computer-go- > boun...@computer-go.org] On Behalf Of Brian Sheppard > Sent: Friday, June 26, 2009 10:37 AM > To: computer-go@computer-go.org > Subject: [computer-go] Complicated seki with Ko > > Here is a position that exposed some bugs in Pebbles. Maybe it will help > you. > > 1 2 3 4 5 6 7 8 9 > A - O - O X - - X - > B - X O - O X - O O > C - O O - O - X O - > D X X X O O O O O O > E - O X X X O X O O > F - - O X O X X X X > G - - X X O O X X - > H - O X O - O O X X > J - O X O O - X - X > X to play. > > X is already doomed in this position. The bottom O group is in a seki > with the X group at right. O cannot play J6 self-atari. X cannot fill > in J8 and then play J6, and after X J6, O captures and X cannot recapture. > So it will be dual life. Because the top of the board is O's, O have > more than half the board, even without komi. > > The playouts have to handle certain issues well in order to find that. > The first point is to filter out plays that make self-atari on large > groups. This will cause the rest of the board to fill up until only > the seki remains. > > The the playout will be in a position like the following: > > 1 2 3 4 5 6 7 8 9 > A - O - O O - O O - > B O - O - O O - O O > C - O O - O - O O - > D X X X O O O O O O > E - X X X X O X O O > F X X - X O X X X X > G X - X X O O X X - > H X X X O - O O X X > J X - X O O - X - X > X to play. > > Pebbles does not detect superko in playouts, so this position will loop > forever with J6/J8/J7/pass. In Pebbles, infinite games were scored as > draws. I changed that to give the win to O on the basis of its > preponderance > of material. (No doubt that will bite me at some point.) > > Even if we detect the superko repetition, it seems to me that we are only > getting the right answer by accident. For instance, if X plays J6 then > after J8/J7 there is no move for X, so X has self-ataried himself. > > Another possibility if to see that X's J6 is atari and also self-atari, so > X can look for the approach move. In this case X would play J8 instead of > J6 > which avoids the ko. Then the seki is obvious. > > How do other programs handle this case? > > _______________________________________________ > computer-go mailing list > computer-go@computer-go.org > http://www.computer-go.org/mailman/listinfo/computer-go/ _______________________________________________ computer-go mailing list computer-go@computer-go.org http://www.computer-go.org/mailman/listinfo/computer-go/
