Hane-descend

Path: <= Endgame =>
    Keywords: EndGame, Ko

This is a quite special endgame technique.

[Diagram]
Hane-descend  

Assume the black+circle/white+circle exchange has just been played: so that black+circle is the hane play in the title.



In this case the descent B1 is the best available defence for the black+circle stone. If Black played at a White might at some later point gain by playing at B1.

Since b is a neutral point, White will have no reason to play there except as a ko threat.


Let's look at the ko threats here.

[Diagram]
White's ko threats  

Certainly White should start at W1. Then there are three threats. If W3, Black at W1, White has only one threat.

[Diagram]
Alternative  

This W1 could seemingly improve on W3 of the previous diagram. There is no real difference to White's threats.

But now Black has no threat at a. With the given configuration White has two threats, net, here.

Charles Matthews


[Diagram]
Simple connection  

Fhayashi: For my own clarification, the alternative to the above, playing at B1, allows White a, Black b, which is one point worse than the above, but offers White no ko threat, right?



Charles Correct. Or, being pedantic, White a is likely to be 2/3 point in sente.

By the way, there is no 'exchange rate' in the endgame between points of territory and ko threats. I think this might be added to the assumptions of yose problems page.

In real life there might for example be a large approach ko left on the board, meaning that one would trade-off points against ko threats to some limited extent.


unkx80: May I also mention in passing that hane-descent is also commonly used in life and death, as in the example below.

[Diagram]
Hane-descent.  

B3 is the only possible way to make life.

[Diagram]
Hane-descent.  

The result is a ko.



Charles It's obviously a day for nit-picking:

[Diagram]
Another way to ko  

Starting with W1 is usual in pro games. Still a ko, but in realistic position (white+circle not necessarily present) this might lose fewer points if White loses, and certainly is more solid for White if she wins by capturing B4.



I see this is discussed on the J groups page; but I seem to be disagreeing with the detail of what is said under straight J groups.


Path: <= Endgame =>
Hane-descend last edited by CharlesMatthews on July 25, 2003 - 18:59
RecentChanges · StartingPoints · About
Edit page ·Search · Related · Page info · Latest diff
[Welcome to Sensei's Library!]
RecentChanges
StartingPoints
About
RandomPage
Search position
Page history
Latest page diff
Partner sites:
Go Teaching Ladder
Goproblems.com
Login / Prefs
Tools
Sensei's Library