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Aliases (info)
LosingKoThreat
LossMakingThreat

Paths
Mistake
SecondCourseOnKo
ForcingAndInitiative

Referenced by
LocalKoThreat
SenteGainsNothing
RemoveDoubleThrea...
DoubleKoThreats
ValueOfAKoThreat
BasicKofightExample
KoThreatPlayingOrder
TemporarySeki
Oiotoshi/Discussion
AlmostAlmostFill
TemperatureAndTer...
3354Enclosure
TheAjiMachine
SowDiscordInTheEn...
LosingSente
SimpleOrComplicated

 

Loss-Making Threats
Path: ForcingAndInitiative   · Prev: KoThreat   · Next: KikashiSenteDiscussion
Path: Mistake   · Prev: KyuDisease   · Next: Low
Path: SecondCourseOnKo   · Prev: LocalKoThreat   · Next: ThereAreNoKoThreatsInTheOpening

    Keywords: Ko

Generally playing a threat just because it is sente, and for no other reason, is a typical novice mistake.

When it comes to ko fights, this becomes a more difficult discussion. Ko threats that are loss-making have a special name, sonko, in Japanese; and to become a ko expert one has to pay great attention to the idea. You do need ko threats in a ko fight. Playing loss-making threats is clumsy, and assumes that the ko fight is all that matters. That need not be the case.


[Diagram]
Choice of threat

Should Black prefer a, b or c here? We assume Black is looking for a ko threat in this part of the board.


[Diagram]
Like a failed invasion

Usually playing c is the worst idea. Aftef W2, Black's stone looks like abject failure (mochikomi). Black can probably make further threats here such as d, but after White e Black has lost some further points.


[Diagram]
Best taste

From the point of view of avoiding possible loss, Black's best choice is this threat. When White answers at W2, B1 looks like a kikashi, that is, has some positive effect in addition simply to being sente. Of course B1 has aspects of aji keshi - just about any ko threat does (see the aji machine).


[Diagram]
Not clear

It isn't clear without more information whether B1 is a loss. After W2 Black has the play at d, and one should know before coming to a judgement whether White could play e or f. If White can play f and capture everything that would constitute a big loss for Black, but the fight might be big enough to distract attention from the ko. White might play W2 at e, in which case Black will probably be satisfied.

Summary: Threats that come in deeper risk loss; threats from outside risk little.

Charles Matthews



Some examples of a local ko threat that may make a loss.

Example 1:

[Diagram]
Local threat



Suppose White plays WC as a threat during the ko fight in the corner.

[Diagram]
A change in the position



If Black answers it at BS, and White later wins the fight, it is a bit disappointing for White to have made this exchange.

[Diagram]
Poor exchange for White



That is, in this position the exchange WC/BC looks better for Black.

[Diagram]
Better prospects for White



Here White should want to jump - at least as far as a.

Example 2:

[Diagram]
Local threat 2

If Black wins the ko, White will regret the exchange of W1 for B2, since it loses 2/3 point, on average, by comparison with the position when Black wins the ko without that exchange.


[Diagram]
Black wins ko

(We assume that B1 is sente, threatening to invade White's surrounding territory.)

Therefore, even though White has a local ko threat, she should play it only if it is crucial; for instance, if it is necessary to win the ko or if it forces Black to make a losing ko threat of his own.



Path: ForcingAndInitiative   · Prev: KoThreat   · Next: KikashiSenteDiscussion
Path: Mistake   · Prev: KyuDisease   · Next: Low
Path: SecondCourseOnKo   · Prev: LocalKoThreat   · Next: ThereAreNoKoThreatsInTheOpening

This is a copy of the living page "Loss-Making Threats" at Sensei's Library.
(OC) 2004 the Authors, published under the OpenContent License V1.0.