Almost-fill without taking vital point? [#2732]

118.11.190.1: Almost-fill without taking vital point? (2012-01-03 09:03) [#9199]

Is it possible to almost fill an eyespace without taking the vital point (ie. after your opponent has already taken the vital point)?

"If you manage to almost fill the eye shape of an enemy group with a killing shape, and there is no escape for that group, it is dead."

I'm still a bit confused about the concept of almost-filling. Well, at least I sense that there's something going on that I'm not fully grasping. In the example given (below), it appears that the White group was already dead before Black started almost-filling it. (I'm assuming that and are the vital points, both of which Black has taken before proceeding to almost-fill the eyespace.) Is this correct?

Kill

Can a situation occur in which one is able to almost-fill one's opponent's group, even though the vital point has been taken by the opponent? In other words, almost-filling as a method of KILLING a group rather than as a method of removing the (dead) pieces from the board?

Perhaps, in the diagram on the left, almost-filling was used to be 100% certain that the group was dead, without sealing the outside liberties-- even though the group was, for all practical purposes, already functionally dead. That would explain this "KILL," but I'm still curious as to whether or not almost-filling can be used to kill a group that is, prior to successful almost-filling, very much alive.

RobertJasiek: ((no subject)) (2012-01-03 09:10) [#9200]

As you can learn from Capturing Races 1, p. 44, the only strong eye shape with a defender's stone is:

White to move can almost-fill despite Black's stone on the most vital eye intersection.

118.11.190.1: I see. Thanks! (2012-01-03 12:21) [#9201]

Thanks, Robert, that's very clear.

I guess this would be another example of an almost-fill kill after the main vital point has been taken:

Square nine
RobertJasiek: ((no subject)) (2012-01-03 13:45) [#9202]

In the position before 1, in the position after 1, in the position after 2, or in the position after 4, the semeai eye's condition "[...] the [black] player moving second cannot necessarily permanently partition [the surrounded region] into at least two region" is violated because Black moving second can necessarily permanently partition.

In the position after 6, the semeai eye's condition "does not contain any stone of an essential string" is violated because the three white stones are essential because a white play at 8 threatens to create a non-nakade shape.

Here, if Black attacks White's internal shape, then White can avoid the nakade creation but wins by means of a white semeai eye within what was supposed to be a greater black semeai eye.