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Big bulge
  Difficulty: Intermediate   Keywords: Joseki, Tesuji, Shape

Alex Weldon: This is a term coined in Charles Matthews' book [ext] Shape Up! and introduced to Sensei's on the Shape Problem 4 Discussion page. I don't know much about it, except that it's a good shape, but I'm hoping that creating a page about it will serve as an inducing move to get those more knowledgeable than me to write about it. :)

[Diagram]
Big bulge

Abstractly, the Big bulge is the shape formed by three stones with a keima-keima-ogeima relationship, as shown here. It's a good shape because it's flexible, but also very well connected.


[Diagram]
One big bulge joseki

I know of two common joseki that involve this shape. One arises from a 4-4 point one space low pincer invasion block, and looks like this.


[Diagram]
And another

The other joseki I know that involves this shape comes from the 4-5 point 4-3 approach keima joseki. It looks like this.



Charles If I can comment on the feeling behind the name: it came from examples like this one.

[Diagram]
Move 115

Here B1 plays steadily for influence in the centre, to counter-act White's power there. (The game is Takagi Shoichi-Kobayashi Koichi (B) 1988-01-07.)



Alex Weldon: I forgot to mention that it also works as a tesuji for connecting groups. There's a good example in Tesuji and Anti-suji of Go, but I'm flipping through the book and can't find it, so I'll try to recreate something similar from memory:

[Diagram]
Big Bulge as connection tesuji

B1 connects unfailingly (if White a, Black b and vice versa), although here the shape looks more like a "big dip" than a bulge.


HolIgor: Please, indicate a and b. There is no connection here. See the diagram below. One has to make black's stones at the top less vulnerable.

Alex Weldon: Ah, yes, sorry. Two mistakes. I forgot to put a and b, and you're right that I gave Black's top stones too few liberties. Fixed now.

[Diagram]
White cuts succesfully (old, flawed diagram)


John F. I imagine it was you who deleted my comment, but your original diagram was fine and the connection is secure. Black answers a one point above, not at b. It is that move that is the point of the tesuji. But if you are going to insist on the less interesting version, you need to change the second diagram as well.

[Diagram]
Old diagram, John F.'s point

Alex Weldon: Sorry about that. Somehow, I misinterpreted what you were saying. Now I see your point, and think you're correct that the original was fine. I guess I should restore the original, remove all these comments, and fully explain the variations that preserve the connection. However, being weaker than both you and HolIgor, I'm not confident in saying you're right and he's wrong, so I'll hold off on doing that until a third, stronger player confirms one way or another, or the two of you agree.

unkx80: I think the original problem could be Kyu Exercise 19.



Charles See keima side connection. There is an obvious point about how many stones of the other colour one allows, while still using the same name for the shape. All I can say on that is that one should stop using the name when it stops being useful to think of the shape in the same 'cluster' of ideas.

Alex Weldon: Well... the keima side connection and big bulge aren't just related by the relationship of the stones, exactly. Both seem to have the purpose of establishing a firmer connection between two existing stones with an ogeima relationship. But you're right that it's being used in a completely different context. Maybe we should remove this whole section and just leave a note "See keima side connection for the same shape applied in a different context."?

[Diagram]
Strengthen thin connection

Charles I wouldn't see any need to remove anything. Is this diagram a case of 'big bulge' or not? It's really the wrong question. Thinking of three stones as a unit is probably an advance, and demarcating when names apply can come later, if at all.



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