Ladder read should be helpful in the open space. But when the surrounding area is not full of space, the ladder play could hurt the eyes.
for example below in the corner. b is better than a. By ladder reading, it would play at a, and the defender answer at b, leaves the attacker no eye in the corner. *|.#.....* *|bOOOO..* *|.##aO..* *-------* On Fri, Aug 1, 2008 at 1:37 PM, Mark Boon <[EMAIL PROTECTED]> wrote: > > On 1-aug-08, at 14:15, Peter Drake wrote: > > On Aug 1, 2008, at 8:08 AM, Mark Boon wrote: > > The neighbours of the last move come in the picture because usually it's > only the last stone played that can be escaping a ladder and it's the > neighbours of the last move that could have been put into atari. Nothing to > do with the additional complexities Don mentioned. > > > Let me give a specific example. Suppose that, during a playout, the tree > leads us to this position, with O to play: > *.........* > *...OO....* > *..O##a...* > *...Ob....* > *....c....* > *.........* > *.........* > *.........* > *.........* > > Having reached the frontier of the tree, we now finish the game using Monte > Carlo with a ladder reader. The last stone played, to the left of a, is > trapped in a ladder, but can escape if not chased. Our ladder reader > therefore suggests O play at a. > > For the next move in the playout, if # only reads ladders from the last > move played, it will see that the O stone at a is not in a ladder, so move > is suggested. The playout now turns completely random, and it's a coin toss > as to whether the group will escape. > > > That's it. That's all there's to it. (Assuming you meant to write "so no > move is suggested".) > > If we also search stones next to the last stone played, things only get > slightly better. # sees that its stones are in a ladder from which they > cannot escape, so it doesn't suggest b. > > > Exactly. This is the neighbour part. In case 'a' was played by accident and > # can escape it will suggest 'b'. > > If we tell it to play a ladder breaker in such situations, it might play c, > which is fine. However, on O's next turn, c is not in a ladder, nor is any > stone next to c, so no move is suggested. Specifically, O does not make the > vital capture at b. > > > I don't bother with ladder-breakers. > > > It seems too expensive to search every point on the board for ladders. What > to do? > > > What you could do is keep track of stones with one or two liberties and > keep them in a list. But I found it's still too expensive for relatively > little gain in strength, although I'd have to admit not yet having exhausted > all possibilities here. > > What was the question again? ;-) > > Mark > > > _______________________________________________ > computer-go mailing list > [email protected] > http://www.computer-go.org/mailman/listinfo/computer-go/ >
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