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Monkey Jump
Path: Endgame   · Prev: BasicEndgameTheory   · Next: EndgameClamp
  Difficulty: Beginner   Keywords: EndGame

[Diagram]
Monkey jump is a big yose move

A monkey jump (Japanese: saru-suberi) is a large-knight jump from the second line to the first line into the opponent's would-be territory, reducing it by a considerable amount. The stone on the diagram cannot be cut off. If White has a large territory to the right, the move can't be ignored and has to be replied to.

A monkey jump is proverbially worth 9 points in sente, although the exact amount depends on the position, and it may very well be gote.

In some cases a small jump to a is reasonable as well. This is sometimes known as a small monkey jump.



Sente or Gote?

In the diagram above, B1 is usually not sente, simply because White does not need to answer at all. It also seems that White can answer it in sente:

[Diagram]
Monkey jump ending in gote.

But Black can play better than this, as shown in the next diagram:


[Diagram]
Monkey jump ending in sente.

[Diagram]
Monkey jump ending in sente (follow up).

Later, White will probably get this exchange in sente. But this is still a gain for Black. See Value of a monkey jump for a detailed discussion.


[Diagram]
Monkey jump ending in sente

If the marked stone is one line higher, as in this diagram, Black can keep sente with this simpler (and better) line, as White needs to defend the cutting point at a.



Monkey Jump Failure

The stone on the second line has to be strong. e.g. monkey jump (Black a) doesn't work here because of the weakness at b.

[Diagram]
Monkey jump fails here.

[Diagram]
Monkey jump fails here (continuation)

White can play at W2. If Black responds at B3, then the atari at W4 and the throw-in at W6 will capture all the black stones. Thus in response to W2, Black can only connect at B4, then White plays at W3, and you can see the difference yourself!

See also Endgame Tesuji 4 for a more subtle case where the monkey jump is not an outright failure, but clearly suboptimal.


[Diagram]
Another Monkey Jump failure

Malweth I also saw a Monkey Jump failure in one of my current DGS games:

Here I cannot respond at 'a' because white can connect via 2. If I play Ba,W2,Bb white can connect out with two liberties. Black playing at c after b gives white three liberties to my two.


[Diagram]
(continuation)


The Monkey Jump into a High Position

[Diagram]
How to stop the monkey jump?

What's White's proper defense here?


[Diagram]
Failure

W2 was wrong, as Black can push further into White's territory at B3. The marked squares are miai for Black, and White cannot cut B1 off. Try it out!

Chris Hayashida: What about W2 at B3? Seems to me that Black can't live by taking the inside. Actually, I found my answer. If Black extends upward (down in the diagram) to B2, and White extends to a, then the black hane is hard to deal with. It would work if the ceiling were one line lower, though.


[Diagram]
Correct response:

It looks suprising, but W4 works:


[Diagram]
3 is crucial

W3 putting the two marked stones into atari is correct. If Black continues with B4, W5 cuts it off.

Therefore, Black should play as follows:


[Diagram]
Correct sequence

In an actual game Black should be satisfied by the exchange of the marked stones and keep the plays 1 through 10 in reserve. There is no need to play them out immediately.



WTD: I believe Black's play in 'Correct sequence' above, is not optimal. If B3 is played 1 space to the left (at 6 above), the result is 2 points worse for White.

[Diagram]
Better Black reply

The full sequence is shown in 'Better Black reply'. W4 at 5 gives the same result. Black can still tenuki after W2, but if Black plays next locally, it should be at B3, rather than 7.


[Diagram]
Better White defence

However, if White plays kosumi in response to the monkey jump as here, Black must play B3 to avoid being cut off, then W4 is required. Apart from tenuki, black has three alternatives for B5 (at 6, 7, or 9), each giving the same result. This is equal in value to the 'Correct sequence' above, but without the drawback described in 'Better Black reply'.

Relevant sequences are shown (and tested) for a narrower, but very similar position, at goproblems.com in problems [ext] 3762 and [ext] 4105, the creation of which led to this analysis.



Alternative to the monkey jump

[Diagram]
Better than the monkey jump?

[Diagram]
One Possibility

If White has far superior ko threats, then this sequence can be expected. So the monkey jump is better by 2 points. (The two points marked with a Square).


[Diagram]

If Black can win the ko, White can reply like this, essentially reverting to the original monkey jump diagram. So the one-space jump is never better. (This may, of course, be different in other circumstances.) (White 11 connects at c.)


[Diagram]

Harpreet: If I'm not mistaken, black would play like this if there are enough ko threats for him. 5 at 6 is not possible.



How to stop the Monkey Jump

[Diagram]
Defense summary

The correct White response to B1 depends on whether there is a white stone at a or not. If not, c (or sometimes d) is usually the correct response, and if there is, b is the first move you should think of. If there is no white stone at a, the monkey jump is about 10 points in sente, while if there is a stone at a, it is the regular 8 points in sente.[1]


WTD: In 'Monkey Jump Workshop' by Richard Hunter, c is generally dismissed as a reply to the jump, because it loses points unnecessarily. I don't think it should be considered unless special circumstances apply, such as the invader exploiting a gap in the defenders formation, or forming a separate live group.


You should try to read out the answer precisely, as you should neither give up two points, nor lose the game by producing one of the catastrophic failures we have seen above.

Try out your reading in the Monkey Jump Problem Series.


Examples illustrating the rule of thumb above follow below:

[Diagram]
10 point monkey jump

[Diagram]
Alternative defense

WTD: If W6 is played at e, in '10 point monkey jump' (above), the result is 2 points better for White. This can also be achieved if White replies to the monkey jump at W2 here (d in 'Defense summary').


[Diagram]
Wrong defense

[Diagram]
8 point monkey jump

[Diagram]
Dead monkey - why W2 works

It comes down to whether Black can capture W4 or not. With the squared white stone, W4 is safe.



[1] dnerra: These values assume that White's hane, after preventing the monkey jump by a block on the second line, would be sente.


Contributors: fhayashi, AlexanderYoshi, Jonathan Cano, unkx80, ArnoHollosi, IaGo

WikiMasterEdit by dnerra, 2003-12-01.



Path: Endgame   · Prev: BasicEndgameTheory   · Next: EndgameClamp
This is a copy of the living page "Monkey Jump" at Sensei's Library.
(OC) 2004 the Authors, published under the OpenContent License V1.0.