4-4 point low approach low extension, contact

  Difficulty: Intermediate   Keywords: Opening, Joseki

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The 4-4 point low approach, small knight extension, attachment is the most common local continuation to the 4-4 low approach since the AI revolution.

Unlike the the traditional slide joseki, Black cannot tenuki from W1, which allows White to quickly settle. The subsequent hane B2 and counter-hane W3 are the only natural moves in this position, which forms a staircase shape.

The most common result(s) are comparable to the traditional slide joseki, except that strong AI programs nearly always play the attachment instead of the slide. This joseki also has several variations where either player can opt to take the corner territory instead of outside influence, variations that end in sente/gote, as well as variations that could potentially involve kos.

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Moves are listed by frequency in professional games[1], which is sensitive to whole-board position. Bolded moves are commonly considered joseki. Strong AI programs tend to evaluate a-e similarly (less than 1 point difference in winning rate)[1], although the atari is often regarded the best in most situations.

[Diagram]
Attachment Joseki  
  • a, Atari Down (~82%) - (joseki) (common) (AI favorite)
  • b, Solid Connection (~14%) - (joseki) (simple) (passive) (beginner)
  • c, Hanging Connection (~5%) - (joseki)
  • d, Double Hane (~2%) - (joseki) (territorial)
  • e, Extend (~1%) - (joseki)
  • f, Atari Sideways (<1%) - (mistake)



Overview of AI Attachment Joseki

A simplified way of distinguishing between the six possible responses to the counter-hane is to examine the amount of influence that either player will end up with. The 5-4 position (marked with a square) is the focal point of many joseki in this position, as the player who ultimately controls it holds a relatively more influential position.

Contrary to the "corners, then sides, then center" go proverb, the 5-4 position is so important that Black is often satisfied with the result even if they lose control of the corner. In fact, in AI's favorite variation (the atari down), Black offers White an opportunity to take the corner. Typically, White is not content with taking the corner, because Black's influence would be too good. Regardless, in most situations Black is happy to play for influence with the popular atari variation.

In certain situations, influence is not as valuable for Black. For instance, if White is strong in the local area, it may be better for Black to play for territory or a solid base. In each of the alternate variations, both players will fight for control of the 5-4 position, in some cases even starting a ko or giving up sente. If you are studying these variations for the first time, pay attention to the 5-4 position as the focal position of these joseki.

Atari Down

When Black chooses to atari down, Black must choose whether to take influence on their original side (default) in sente or switch to the outside in gote. Typically, Black does not want to switch to the outside unless the top side of the board is valuable.

Default Influence Variations

Territory Variation
Territory Variation
(~26%)[1]
Influence Variation
Influence Variation
(~23%)[1]
Counter-Atari Variation
Counter-Atari Variation
(~1%)[1]

The atari down variation is typically good for Black because the influence is great. Black gained control of the focal 5-4 stone with B3, which projects influence, potential, and power over a large quadrant of the board. However, there is one cautionary tale: Black should hesitate to play the atari down when White has a strong position on the top side. If White has a strong position on the top, White can opt to resist with W4 Counter-Atari Variation (Dia 3), negating the value of Black's influence. As a result, professionals tend not to play the atari down variation if White is strong on the top.

  • The Territory Variation is solid and territorial. Black is satisfied with their lead in influence and feels no need to gain more. Many amateurs learn to play this variation first. Strong AI programs will usually encourage White to resist with the push at a and attempt to fight for influence, but many human players fear the complex variations that branch from this position and opt for the safer b.
  • The Influence Variation stresses influence and sente. AI programs often recommend it when White has potential on the top side, since this variation keeps White flat. Notably, White can opt to take the corner in gote later in the game, but it is typically not an urgent move in the opening.
  • The Counter-Atari Variation is not good for White on an empty board since White is sealed in and Black is too thick. However, Black should be aware of this potential variation, since White has the option to take the corner. This variation may not be good for Black if White is strong on the top side, negating the value of Black's influence.

Outside Influence Variations

Outside (Peaceful)
Outside Variation
(<1%)[1]
Outside (Fighting)
Outside Variation (Fighting)
(~14%)[1]

Black can choose to take the opposite side in gote by descending at B3. Typically, this is done when Black has potential towards the top.

  • In the Outside Variation (Peaceful), White allows Black to take influence, but White takes sente in exchange. The peaceful variation is probably too good for Black, as Black effortlessly gains the focal 5-4 position, and professionals almost never play it.
  • Instead, the Outside Variation (Fighting) occurs more commonly among professionals when White resists W4 by cutting first at the 5-4 position. White typically will not run those stones at a immediately, preferring instead to come back them later when White is stronger in the area. As before, white takes sente in this variation.


Solid connection

[Diagram]
Fan Yin (7p) (B) vs. Lee Changho (9p) (W) - 23rd LG Cup 2018  

The solid connection is a simple and solid response. It is a good move for beginners or anyone who wants to avoid the AI joseki, and it is not that much worse (less than 1 point winning rate)[2] than AI's favorite atari joseki. In fact, many professionals play it (~14%), often times on an open board for apparently no reason at all, presumably because they did not want to play an AI joseki.

On an open board, strong AI programs regard the solid connection to be slightly inferior to the atari down variation. The approacher settles (too) easily and has many good options later, with a powerful shape at the unoccupied 5-4 position (marked square), an approach at a, and territory at b.

Still this is playable for for both players, and it can be suitable depending on the context. One example where professionals play the solid connection is depicted in Fan Yin (7p) (B) vs. Lee Changho (9p) (W) (LG Cup 2018). Here, Fan Yin (Black) had an existing wall on the upper side. Lee Changho opted for the solid connection at W4, presumably because the Counter-Atari Variation (discussed above) would have been good for Black.

The solid connection is a good defensive move when White wants to cool down a complicated and potentially dangerous local situation. Neither players have occupied the focal 5-4 point, the influence is balanced, and white has sente.



Hanging Connection

Hanging Connections Variations

Correct Variation
Correct Variation
(~4%)[1]
Incorrect Variation
Incorrect Variation
(n/a)[1]
Ko Variation
Ko Variation
(<1%)[1]

Another variation regularly played by professionals is the hanging connection (~5%)[1]. Since it ends in gote for Black, it is normally a situational move, except that there are many situations in fuseki during the opening where it may be a good move, and it is quite popular among professionals.

As with many joseki on this page, the 5-4 position is the focal point. In an ideal world, White would like to bulge at the 5-4 position, but the atari and connect is bad for White (Incorrect Variation). Instead, White must play the double tiger's mouth (Correct Variation). Next, Black must occupy the critical 5-4 position, which Black will take in gote. The 5-4 position is so important for mutual shape that in rare occasions, White is even willing to fight a ko for the 5-4 position. However, this is not common since "There are No Ko Threats in the Opening".

[Diagram]
Fan Tingyu (9p) (B) vs. Lian Xiao (9p) (W) - 2019  

Why would professionals be so eager to play a gote joseki? The hanging connection repeatedly occurs in the opening of professional games, and a representative example is illustrated by Fan Tingyu (9p) (B) vs. Lian Xiao (9p) (W) (2019).

In this game, the top side of the board is especially valuable because Black's three-stone wall does not have an extension. Both players would like to play a move or establish a position on the top side. The atari down variation may not be the best choice because it gives Black a strong position on the top, and it helps Black develop that potential. Later, it will be difficult for White to invade or attack Black's wall if White is strong on the upper left.

Instead, Lian Xiao (White) plays the hanging connection and dares Fan Tingyu (Black) to tenuki. If Black responds locally at a, the top side is still very open and White can comfortably invade or reduce. If Black chooses to tenuki and plays away, White has a follow up at b, which pressures Black's corner (not fully alive) and helps establish a position on the top.

In summary, the hanging connection is played when White believes that the top side is important and wishes to get a move on the top, even at the cost of giving away sente. White W6 is a critical move that occupies the 5-4 position, which is essential for local shape and projecting influence in this quadrant of the board.



Double Hane

Double Hane Variations

Hanging Connection
Double Hanging Connection
(<1%)[1]
Solid Connection
Solid Connection
(<1%)[1]

The double hane variation is territorial, and Black should anticipate that it might end in gote. It is typically played when neither the top nor bottom sides are interesting for Black, so gaining influence would not be as valuable. White gains control of the focal 5-4 position and has an option to take sente. It is not as common (~2%)[1] in professional play.

  • White can play for sente by making a hanging connection (double tiger mouth).
  • The solid connection is better for points but ends in gote.



Extend

Extend Variations

Correct Variation
Correct Variation
(~1%)[1]
Incorrect Variation
Incorrect Variation
(n/a)[1]
Ko Variation
Ko Variation
(n/a)[1]

The extend variation is rarely seen in professional play (~1%)[1]. It encourages White to play at the focal 5-4 position, which White is more than happy to take.

Although Black has sente, White's influence is quite good with aji at a and b.

It is a mistake for White to play the hanging connection and cede the focal 5-4 position (Incorrect Variation). A ko is possible (Ko Variation), but "There are No Ko Threats in the Opening".

[Diagram]
Gu Zihao (9p) (B) vs. Chen Yaoye (9p) (W) - 2018  

One situation where professionals may play the extend variation is illustrated by Gu Zihao (9p) (B) vs. Chen Yaoye (9p) (W) (2018). In this game, Chen Yaoye (White) already has a stone near the hoshi (marked with a circle), which blocks Black's natural extension.

In this situation, it makes sense to play the extend variation because Black is unable to get an effective extension, and the marked stone neutralizes the value of White's influence.



Atari Sideways

[Diagram]
Other atari  

The sideways atari at B1 is a common kyu mistake. The White marked stone (circle) is not valuable and White gains very powerful influence. Black even took gote.

However, this atari can sometimes be recommended by AI when there is a fight in the area. The sideways atari can sometimes be the most severe response, but Black must have other stones in the area to support it.



Discussion

On an open board, any of the six variations listed on this page (except the sideways atari) is considered playable in the opening, and the difference in AI winning rate is less than one point.

Professionals regularly play whichever variation that suits their style, whether it is the solid connection, hanging connection, or double hane. While searching Waltheri [1], it is common to find professionals playing these less common variations on an open board for no apparent reason at all.

In some situations, certain variations are ideal, but the difference between these joseki can sometimes be so subtle that ultimately it is up to the player's intuition to decide whatever they feel like playing.

References


4-4 point low approach low extension, contact last edited by yuzukitea on August 29, 2021 - 00:26
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