[Welcome to Sensei's Library!]

StartingPoints
ReferenceSection
About


Referenced by
CapturingRaceExer...

 

Capturing Race Exercise 1 Solution
    Keywords: Problem

[Diagram]
Solution

White 1 reduces the size of Black's big eye. The big eyes are of the same size. White has 13 inside liberties + outside liberties. Black has 8 inside liberties + outside liberties. White is alive.

[The terminology here is confusing. Is that 13 (inside liberties + outside liberties) or (13 inside liberties) + outside liberties? Neither seems correct. The former should be 17, the latter gets inside and outside liberties reversed. PS: hope I did this right, since I've not editted pages before -- Geoff Wedig]

Richard Hunter I'd call the terminology extremely confusing. This is a case of working backwards from the answer and throwing some random words at it. The moves are correct, but the explanation is hard to follow in the forward direction.

Dieter: Thanks for noticing. As the original author I couldn't believe I had stated it as it is now. Page info and history relieved me.

Richard Hunter Yes Dieter, your EL got changed to inside liberties. Completely wrong. But I think EL is confusing as it could mean eye liberties or exclusive liberties. Since this problem is not included in my book, let me offer my description here, just this once. On SL, I'm only going to explain my terminology, not give any more problems. I've given all the examples I want in my book. Please edit this page later.

White 1 is the vital point for both sides. Since it threatens to cut and capture two black stones, Black plays inside his own eye space with B2 to defend. Now the type of fight is determined. It's just a question of counting the liberties. Black and White both have a big eye of the same size. In this type of fight, the side with more exclusive liberties is the favorite and is alive. In this case, that's White. Black either lives in seki or dies, depending on how many liberties he has. In order to kill Black, White must play on all the inside liberties, so they all count for Black and none of them count for White. White has 7 eye liberties plus 6 outside liberties making a total of 13. Black counts 7 eye liberties, 1 outside liberty, and 4 inside liberties, making a total of 12. So the position is settled. Black is dead. White can play W3 elsewhere and still win.

Having arrived at that result, we can now see that Black loses even if he defends at B2. Therefore, Black should actually play elsewhere with B2 and save this point as a ko threat. (Dieter, Is this too complicated for beginner problem #1. Why not reduce the white outside liberties by one?)


[Diagram]
Variation 1

This resistance obviously fails. Black ends up with a small eye. All inside liberties count for White.


[Diagram]
Failure

White 1 here would be a huge mistake. Black has the bigger eye and counts the inside liberties. The count is now 15 against 13. White is dead.



This is a copy of the living page "Capturing Race Exercise 1 Solution" at Sensei's Library.
(OC) 2003 the Authors, published under the OpenContent License V1.0.