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Nakade
DougSGoBlogJune2003

 

Biggest Known Eye Space for which there is a Nakade
    Keywords: Life & Death

[Diagram]
A problem from Igo Hatsuyoron (Black to play)

The bigger the eye shape gets, the less likely it is that all surrounding stones can be killed. There is no known nakade for an eye shape (resulting from a capture) bigger than 16 points. (Igo Hatsuyoron) Here is [ext] the problem as an applet.


[Diagram]
Failure

Well, the applet doesn't seem to work so... lemme try this. B1 takes WC (any alternative?), W2 threatens the whole group, so B3 has to connect at WC, and W4 finishes it off? Have I missed something here?


[Diagram]
Solution (4 at marked stone)

unkx80: Black sacrifices one more stone and plays atari at B3.


[Diagram]
Solution

B5 and B7 capture four white stones (including W6). Interestingly the eye space of the White group at the top is not enough to make two eyes. If White a then Black b (bulky five), if White c then Black b (farmer's hat eyespace).


[Diagram]
Solution - White?

Jasonred- ah, I stopped thinking once I saw Black's entire structure there die... I was also wondering about the whole title for this page! (why it's about eye spaces) but ... I was wondering about this following sequence? After W8, are a and b miai for life?

unkx80: No. Check out nakade. Also check out some of the Beginner Exercises.

Note: White dies in gote after W8. That is to say, after W8, Black can play tenuki and White is still dead.


[Diagram]
Black kills White?

Jasonred: Let me try this, for Black to kill White... is this the correct sequence? Is B5 in the diagram (Solution) a nakadeafter which White should just play tenuki?

Dieter: The point is, White is dead. In order to prove/disprove that, we have to verify what happens if White goes first, not Black.


[Diagram]
Black kills White? (2)

For instance: W1 then B2 makes miai of a and b: White needs both a and b to live, so Black can always play one of them to kill. Verify there is no eye in the corner.



[Diagram]
From 16 to 17 eye space nakade?

Jasonred- verify this for me, but, ummm... modifying the above, I think I got a nakade for a 17-space eye... is this correct?

jvt: This eye space cannot possibly result from a capture. If such eye spaces are allowed, it is easy to add cutting points and stones in atari.


[Diagram]
Construction

Dieter: The eyespace and ensuing nakade you propose, would have to come from this capture. In your diagram, however there is a stone at a but then Black gets a double capture and is out of trouble already.


[Diagram]
Construction 2

Moreover, to get there, Black would have to play B1 here. That's not a smart thing to do: Black will much rather play at W2 or at one of the ataris.



This is a copy of the living page "Biggest Known Eye Space for which there is a Nakade" at Sensei's Library.
(OC) 2004 the Authors, published under the OpenContent License V1.0.