The playouts often give the side with fewer liberties the advantage in a semeai. This causes a large fraction of Many Faces' lost games to strong players on KGS.
One problem is approach moves. Say W has a group with 3 liberties, but they must be played in order (perhaps one is an eye, and one needs an approach move). B has a group with 5 liberties, but they are all equivalent and can be filled in any order. W has only one random move that wins the semeai. B has 5 random moves that improve its chance to win the semeai. Most playouts will end with B winning this semeai even though W is one move ahead. The other problem is local patterns. Often a 3x3 pattern will cause one side to fill its own liberty. David > -----Original Message----- > From: computer-go-boun...@computer-go.org [mailto:computer-go- > boun...@computer-go.org] On Behalf Of Stefan Kaitschick > Sent: Monday, September 07, 2009 2:36 AM > To: computer-go > Subject: [computer-go] two won semiais = lost game? > > I have a general question: how good are the current information gathering > mechanisms in the mc tree to insure that advantagous semiais are actually > won? Random playouts will surely give the side with more libs the > advantage, > but to what degree? Lets say the leading side wins the semiai in 2/3 of > all > playouts. This seems comfortable. But except for turnarounds through ko, > the > leading side should allways win the semiai. What if one side has 2 winning > semiais on the board, with winning both needed to win the game? If both > have > a 2/3 chance of winning in playouts they combine to 4/9 - a losing > evaluation for a won game. > > Stefan > > _______________________________________________ > 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/
