Largest capture that still can't live

    Keywords: Life & Death

Table of contents

It is well-known that a group with a large eye space has a better chance of living. In particular, any group with a non-defective eye space of more than seven spaces is known to live independently or in seki; an example is butterfly seven which is guaranteed to live at least with a seki. However, a group with a larger eye space may be killed if its eye space contains defects.

On this page, we study eye spaces created by the capturing a single chain of stones. In particular, we ask: What is the largest capture that still can't live? Igo Hatsuyoron contained a famous life-and-death problem where a 16-stone chain is captured but still can't live, and for about 300 years 16 has been taken as the maximum number. On 2004 May 1, Robert Pauli constructed a problem involving a 17-stone capture. This new record stood until 2009 September 9, when a 18-stone capture is constructed. As of 2009 September 11, the current known record is 18 stones.

18-stone chain capture

Black to play and kill all White stones  

asmobia?: A slightly modified version of Mr. Pauli's construction (below) was [ext] published on a Chinese Weiqi website in 2009/09/09.


Black to play and kill all White stones  

Yee Fan Tan: I composed this problem and listed it here on 2009 September 10. It is discussed at RTG Problem 59.

White dies  

asmobia?: I simplified the first case of 18 stones.

-- 2009/Sep/10

Herman: Yes, but isn't it "White to play and fail to live" now? It seems slightly more interesting to me to have "Black to play and kill" :-)

17-stone chain capture

Black starts and kills  

Robert Pauli: Improved Dosetsu Inseki's great construction (below) by one on 2004-05-01. As far as I see, the record is now at 17.


16-stone chain capture

Black starts and kills  

From Dosetsu Inseki's Igo Hatsuyoron. However, it is not sure whether he himself actually constructed this problem.

Here [ext] as applet.


Is Black making life?  

From Hirose Heijiro's Book of definitions...

Robert Pauli: ...according to JF's post on RGG, 1999-09-15. Initial ko capture added by me.


Other discussion

There has been disagreements whether a move inside such a large eye space with defects is considered a nakade. It appears that Japanese professionals such as Hirose Heijiro and Hayashi Yutaka and historians such as John Fairbairn consider it nakade. For example, John Fairbairn describes Hayashi's definition as follows: The base meaning is a "move inside". Hayashi does not restrict this to any particular shape except to say that the surrounding group is "continuous". From the examples I have seen, it is safe to say that the shape into which the "inside move" is played is always fully enclosed. It may, however, have defects.

On this page, John Fairbairn mentioned that a magazine claimed a nakade covering a 36-point area, but the actual problem was not made known.

hnishy This type of larger than usual inside play is sometimes called 大ナカデ (O-nakade).

See also

Largest capture that still can't live last edited by hnishy on February 1, 2023 - 05:21
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