Good Empty Triangle
Efficiency is one aspect of shape. Late in the game, especially, it can be obviously correct to make an empty triangle and making an empty triangle can also be the vital point. A good empty triangle is an instance of what the Japanese call guzumi.
Example 1 - Joseki (a)
makes "good shape" but becomes overconcentrated.
unkx80: I don't think it's so much about overconcentration. I believe that it's got more to do with destroying White's eye shape.
Bill: Well, it is a question of emphasis, isn't it? Anyway, let's take away the stone.
brindis: Just a question, why not 2 at 'a'?
Serpent: Because doing so would open the black stone above 1 to atari.
(Sebastian:) I don't see that. That black stone has three liberties, reduces 's liberties to two, and it can easily be connected if need be.
This is fine for both players, no? Black does not need an extra stone.
Eagle : Tewari analysis may show that the black shape is overconcentrated, but i think in practice the second diagram is nothing worse than the first one (i think it's better , may be just because i missed something ) .It's worse than the third diagram,not the first diagram . Am i wrong ?
corwin: To my eyes, the biggest difference in the two diagrams is that black ends in sente in the first, and gote in the second.
Example - Joseki (b)
tderz: After the unreasonable cut , the continuation to
gives Black the miai of either a or b,
hence is a 'good empty triangle'. (source: Ishida a.o.)
Similar is this 5-4 Joseki, where white's empty triangle would be a good tesuji to punish Black's overplay-cut:
is an overplay, which empty triangle
helps exploiting.
After 4 moves, the cutting stones
are capured.
[source: D.Ormerot, http://gogameguru.com/5-4-openings]
Example - Joseki (c)
(empty triangle) is often a good way to respond to White's 3-3 invasion in this shape.
(Sebastian:) Indeed, this is not uncommon, with 26 pro games played this way (according to SmartGo's library) only second to 'a', which occurs 49 times. And it occurs more frequently in games that led to a win. But why? What are its advantages over 'a'? (Later:) I found this discussed here, so I see some difference to 'a' now, but I'm still not convinced that it's superior.
Example 2 - Tesuji
This problem comes from the Tesuji Dictionary, by Segoe Kensaku and Go Seigen. They say that if you get this one right, you are 5 dan. (Of course, you have a big hint. ;-))
Example 3 - Middle Game Joseki: "guzumi"
The sequence of to
is one of the best ways of escaping with the lone white stone at the top.
makes the empty triangle and then White has a rather clear exit, while aiming for the cutting point at a (at the correct time).
here would be a mistake.
plays at the vital point, destroying White's eye shape, and forcing
to connect with a bad empty triangle.
Bob McGuigan: Here's an example from one of my own games (I was Black) where Black responds to a White empty triangle move by making one too. White's empty triangle looks good but after Black's response ...
in response to
is good defense.
creates a cutting point in Black's shape.
takes a liberty from White and leaves a lot of aji against White's group.
tderz: Interesting position. (yet I think black's empty triangle is not necessary)
is tempting too - a & b seem miai now.
It is the same technique as in above joseki.
The white cut c seems far fetched with the created white weakness e.
If White wants to solidate first at at f, cutting through with black d would be possible
(resp. Bg, after white q, she cannot cut at r),
however, if replying with white d one has forced white to be very submissive (which is the intention of
) and could hane oneself with f.
Can White survive?
Yes, Wd - Be - Wg - Bf - then k (or l, smaller).
tderz: other ways for White to avoid an empty triangöle?
Perhaps not, after (protecting against the cut y) to
, there is still no connection to the left
, due to Black x (if Black a to white j have been exchanged),
but white cut capture at k and had no problems.
Theoretically, the black could become a target after
ot
, if Black tries too hard with black a to i?
Example 4 - forcing down
Example 5 - historic master games
Game Dosaku - Chitetsu, move 63
tderz: is a good empty triangle.
This a game with many local "tenukis" - ,
,
,
even in succession ! -
for keeping the initiative.
Acceptable empty triangle? - Hamete
tderz: from a Korean book, p.229 (ISBN 89-333-0346-4)
All black moves look completely natural, don't they? (except of course!)
Still he voluntarily created an empty triangle.
Should he have exchanged a for b first?
It's not so easy to decide on white's next move, hence the empty triangle can't be that bad and rather renamed fighting empty triangle.
Fighting empty triangle
Move 81 of the Blood Vomiting Game, diagram 6, move 7 on Senseis' page.
is the third ghost move. It is an example of a "bad shape/good move", and eventually allows Jowa to launch a difficult splitting attack that results in Black's resignation.
Normal Life & Death
Numerous problems are based on the empty triangle move which kills with a nakade shape.
(Therefore it is dangerous to tell beginners that an 'empty triangle is bad'.
One can tell them, that an empty triangle is 'usually inefficient' - but only in the open field.
surprisingly good empty triangle in Life & Death
making an eye
- killing shape - san-moku-nakade?
- [ | ]
below from http://senseis.xmp.net/?KillableEyeShapes:
Number of internal points: 7
Required number of internal White stones to kill: 3
Remaining internal moves to capture: 14
Total internal liberties: 17
Other names: Butterfly Seven
Number of internal points: 7
Required number of internal White stones to kill: 3
Remaining internal moves to capture: 14
Total internal liberties: 17
Number of internal points: 7
Required number of internal White stones to kill: 4
Remaining internal moves to capture: 13
Total internal liberties: 17
miaoshou, brilliant, excellent moves
![[Diagram]](../../diagrams/50/ab9f8f253b4b293a91d56f048ac739ea.png)
is the correct local endgame, afaik
More pro play
Example
This first example, from professional play, offers a surprisingly large number of empty triangles.
brindis: some of these are not good examples; an eye is not counted as an empty triangle. In fact, there is only one thing worst than an empty triangle: filling it with a stone of the same color :-) But if you are forced to convert the inner point of an empty triangle in an eye, just thank your opponent.
The capture of leaves an empty triangle -- in fact, two empty triangles,-- around the vacated point. Since it is a capture and threatens another capture, it may be a good play, but it does form empty triangles.
Next, plays atari, catching the
stones in a connect and die. This illustrates the liberty problem with the empty triangle (too few liberties per stone played).
takes
, forming another empty triangle, and
takes the
stones, incidentally forming one more empty triangle.
A little later cuts, but forms another empty triangle.
forces
, which forms another empty triangle.
is atari, but forms yet another empty triangle.
connects, but forms another empty triangle. Now
forces
, taking advantage of the liberty problem.
forces
, which forms yet another empty triangle. After
secures the corner,
ensures the capture of the
stones, taking advantage of the liberty problem. Finally,
makes an important connection, but forms an empty triangle in the process.
This comedy of empty triangles (11 in 24 moves!) illustrates some of the problems with empty triangles, as well as the professionals' willingness to put up with those problems if the circumstances warrant.
Bob McGuigan: Here's an interesting example from professional play, Ushinohama Satsuo 9p(W) vs. Takemiya Masaki 9p(B), Meijin League, 25 January 1979. The diagram shows the lower half of the board after 86 moves, in the diagram is move 87.
Ushinohama responded with and Takemiya played
, a sort of standard good shape move, but in a commentary he criticized
as being really bad technique. Ushinohama played
and Takemiya played tenuki with a large territorial move in the upper right corner(not shown in this diagram). This allowed Ushinohama to initiate the sequence White b, Black c, White d, which cost Black a lot on the lower side. Takemiya commented that
should have been the empty triangle play at a, which would have been good shape in this situation and would not have allowed White to cross under with d.