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Kikashi And Influence
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Kikashi and influence

This is a spin-off of the discussion about thickness

AlainWettach: There is a close relation between thickness/thinness and kikashi plays. This brings us to the complex question of good and bad forcing moves (usually only the good forcing moves are called kikashis). A real kikashi shouldn't make the opponent's thin group thicker. Kikashis are usually played against strong groups. Just an example:

[Diagram]
Diag.: A good kikashi

This is a common takamoku (5-4 point) joseki and the marked stone is a good kikashi. Black should answer it at the marked point.

It doesn't make the black group thicker, since White couldn't cut anyway and it has some influence for white (it might break a ladder for instance) even if the marked stone cannot be considered as "thick". So this shows that even "weak stones" or, in this case "light stones", have influence. Here White wins 1 in terms of influence and loses 0 in terms of potential.



[Diagram]
Diag.: A bad forcing move

In this position, Black 1 would be a bad forcing move (a thank-you move). Of course, the stone is not completely wasted since it exerts some influence (it could be a ladder breaker for instance), but Black could and should have cut. This means that the peep makes White thicker since she won't have to worry about being cut whatever Black plays in the area. One could say that Black 1 wins 1 in influence and loses a lot in terms of potential.



MortenPahle asks:

A group which is alive if you answer kikashis by the opponent is not as thick as a group which does not have to answer kikashis, and A real kikashi shouldn't make the opponent's thin group thicker.

I agree with both these statements, but there is an inconsistency between them, no? If the group which has a kikashi played against is thick enough to ignore the kikashi, we agree that the kikashi was just a wasted move. But, if the group is so thin that it needs to answer the kikashi, the group will, per definition, become thicker afterwards. So I think that a kikashi will always make the 'kikashi'ed group thicker. Of course, a good kikashi should gain more than it loses, but I think that this assessment is very difficult to make sometimes (and very rarely 'black and white'). -- MortenPahle


AlainWettach answers Morten, you are right, it might seem contradictory. In a way, even good kikashis make the opponent "thicker". What I wanted to point out is that forcing moves which kill potential on "really thin" groups (those you might want to attack later) should not be played. Another concept which should also be taken into consideration is light/heaviness.

It is often a good idea to refrain from playing forcing moves if you think that, by doing so, you lose potential you might use later in the game. A good example for this is the peep against an ikken tobi.

[Diagram]
Diag.: Two forcing moves possible

In this example, Black might peep at a or b, but it is impossible at this stage to say which one is better. So, it is better not to play either of a or b and to await the right moment.



[Diagram]
Diag.: Thicker, but also heavier

White 2 is a classical example of a forcing move against a more or less "thin" group in order to make it heavier (but also thicker).

In some cases, the border between thick and heavy is very difficult to see, even for the pros!

AlainWettach



Charles Matthews --

  • The point of playing kikashi against a weak group is to make it heavy, that is, harder to sacrifice; the weak group will probably become a little stronger, but less flexible.
  • The point of playing kikashi against a strong group is as a type of probe; later in the fighting you might get a different answer.

If one considers weak groups as possessing some type of negative influence, this discussion might be clarified.

  • Negative influence means the 'need to defend' (negated form of 'possibility to attack' given by influence).
  • QARTS analysis means counting lack of eye shape as negative territory.
  • Flexibility in defence means ability to sacrifice some or all of a weak group.

So a kikashi against a weak group that makes it heavier, reduces its eye shape, and forces a rigid shape on it is probably good.

[Diagram]
Diag.: Answers to Black's peep

In this case, if White has to answer Black 1 at a it seems that all three purposes are fulfilled. But if is possible for White to play at b, taking account of the overall position and perhaps sacrificing some stones, that isn't so clear.



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This is a copy of the living page "Kikashi And Influence" at Sensei's Library.
(OC) 2003 the Authors, published under the OpenContent License V1.0.