Discussion of Stone Activation aLegendWai (9k? KGS): Correct me if wrong. -
The no. of stones in the second line is vital to the winning and losing of the capturing race:
4 stones in a row = B loses
5 stones in a row = Seki (Both groups live together)
6 stones in a row = B wins
aLegendWai: Now I show you why it is seki when B only gets 5 stones in the second line.
Charles Hang on - is obviously correct here?
aLegendWai: So do you have any better ideas?
aLegendWai: After my trial (briefly), I think 2 kinds of results are possible - seki or ko. Please anyone finds a way to make B win / make W win. Please amend my materials. Thanks.
Rich: What happens for
at
?
at
.
B forms an eye in the side.
On one hand, W has to fill up its inside liberties (from a to d) before capturing B. However it would be suicide because B will capture W when W filled up "a" and "b". It loses the capture race.
On the other hand, if B wishes to capture W, it has to fill up its inside liberties (from c to a) too. However it would be suicide to B because W will capture B when B filled up "c" and "b", It loses the capture race.
So it is seki.
But B gets a very good ko threat which is never exhausted. When B plays at "b", it threatens to capture W, W has to respond at "c". Then B re-captures the W stone. This will return to the same state as the diagram "Result - Seki in the corner" shown.
However every time B activates this ko threat, B loses by 1 point (because W gets 2 prisoners. B gets 1 during the process).
(PS: I was originally confused by the diagram "When W extends 03" that B won capturing race. Thanks so much for Rich to point that out. It is really helpful if the website itself allows the upload of sgf file. So this silly mistake will hopefully happen less frequently. :D)
What Rich said previously:
B cannot win the capturing race, unfortunately; this is a seki. While he has a strong group on the left, I can't help feeling this is a bad result from a 3-3 invasion.
aLegendWai: I feel W is in great favor however.
Reasons:
1. Seki means both parties gain no point (under Japanese rule). Altho W can't get any; B still can't get any. (W gets compensation due to some other reasons)
2. B's side gets complete destruction. If it happens in B's framework, B feel like dying!
3. W gains excellent wall (and influence too)
4. It is very difficult for B to capture the W's wall
Even if B extends and form 6 stones in a row and so gets the corner, the result is still considered to be favorable to W. So when the W dead stone activates, the best remedy B can do seems to forgo the corner.
Rich: I disagree; Black has a very thick group on the left, the white wall still has no eyes (and presumably black stone/s to the right) and can be chased or sealed in as black sees fit. W's influence is offset by black's, IMO.
at
,
one point left of
Rich: As black, I would be grateful if W tenukis after in "when W extends 02"! ;)
aLegendWai: Definitely. How happy B would be! :P
Rich: However, if white has any support in the centre, instead of in "When W extends 01", he can settle his corner group and black may be unable to capture the cutting stones.
aLegendWai: Possible and good idea :P At that time, B will suffer a lot.
So if there's a B stone at "a", W cannot activate its dead stone. If "b", it is no use for the B stone to stop W.
-
will be observed.
However a much better way is to avoid this variation (ie avoid playing
) in the first place when W notices the presence of
.