Life In 19x19

I keep reading that "a one-point jump cannot be cut", in a variety of situations. After the sequence shown, how does Black connect the marked stones?

Click Here To Show Diagram Code

[go]$$Wc
$$ +-------------------+
$$ | . . . . . . . . . |
$$ | . . . . . . . . . |
$$ | . . , . , . , . . |
$$ | . . . 4 2 5 . . . |
$$ | . . , Z 1 Z , . . |
$$ | . . . . 3 . . . . |
$$ | . . , . . . , . . |
$$ | . . . . . . . . . |
$$ | . . . . . . . . . |
$$ +-------------------+[/go]

Well obviously it can be cut. But most of the time it's not good to cut the one space jump.

PeterPeter wrote:I keep reading that "a one-point jump cannot be cut", in a variety of situations. After the sequence shown, how does Black connect the marked stones?

$$Wc
$$ +-------------------+
$$ | . . . . . . . . . |
$$ | . . . . . . . . . |
$$ | . . , . , . , . . |
$$ | . . . 4 2 5 . . . |
$$ | . . , Z 1 Z , . . |
$$ | . . . . 3 . . . . |
$$ | . . , . . . , . . |
$$ | . . . . . . . . . |
$$ | . . . . . . . . . |
$$ +-------------------+

Click Here To Show Diagram Code

[go]$$Wc
$$ +-------------------+
$$ | . . . . . . . . . |
$$ | . . . . . . . . . |
$$ | . . , . , . , . . |
$$ | . . . 4 2 5 . . . |
$$ | . . , Z 1 Z , . . |
$$ | . . . . 3 . . . . |
$$ | . . , . . . , . . |
$$ | . . . . . . . . . |
$$ | . . . . . . . . . |
$$ +-------------------+[/go]

Black cannot connect locally, but it depends on the surrounding situation. It can be a horrible situation for black if there are many white stones around, but it can also be a very comfortable situation for black if there are many black stones to help. There are no "always" in go everything depends on situation.

PeterPeter wrote:I keep reading that "a one-point jump cannot be cut", in a variety of situations.

Where?

PeterPeter wrote: After the sequence shown, how does Black connect the marked stones?

$$Wc
$$ +-------------------+
$$ | . . . . . . . . . |
$$ | . . . . . . . . . |
$$ | . . , . , . , . . |
$$ | . . . 4 2 5 . . . |
$$ | . . , Z 1 Z a . . |
$$ | . . . . 3 . . . . |
$$ | . . , . . . , . . |
$$ | . . . . . . . . . |
$$ | . . . . . . . . . |
$$ +-------------------+

Click Here To Show Diagram Code

[go]$$Wc
$$ +-------------------+
$$ | . . . . . . . . . |
$$ | . . . . . . . . . |
$$ | . . , . , . , . . |
$$ | . . . 4 2 5 . . . |
$$ | . . , Z 1 Z a . . |
$$ | . . . . 3 . . . . |
$$ | . . , . . . , . . |
$$ | . . . . . . . . . |
$$ | . . . . . . . . . |
$$ +-------------------+[/go]

By extending at a. This makes miai of killing one or other of the white groups, but the sequences are too long for this margin to contain.

To pick one example, in a well-regarded book, this was presented as a successful outcome for Black. a and b look like cutting points to me, and I am trying to understand why they are not.

Click Here To Show Diagram Code

[go]$$Bc
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . O . 2 . 1 . O . . O . X . . . . |
$$ | . . . , . . . a . , . . . . . X . . . |
$$ | . . O . . . . 3 . 4 . . . . . . . . . |
$$ | . . . . . . . b . . . . . . . X . . . |
$$ | . . . . . . . 5 . . . . . . . . . . . |
$$ | . . . O . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . X . . |
$$ | . . . X . . . . . , . . . . . , . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . , . . . . . , . . . . . , . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------[/go]

PeterPeter wrote:"a one-point jump cannot be cut"

Proverbs are only correct 50% of the time. Probably. Maybe more, maybe less.
It all boils down to the specific individual situation.

W(a) is a bad wedge for W.

Click Here To Show Diagram Code

[go]$$W Broken shape for W: :wc: damaged
$$ ----------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . O . W 4 X . O . . O . X . . . . |
$$ | . . . , . . 2 1 3 , . . . . . X . . . |
$$ | . . O . . . . X . O . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . X . . . |
$$ | . . . . . . . X . . . . . . . . . . . |
$$ | . . . O . . . . . . . . . . . . . . . |[/go]

Click Here To Show Diagram Code

[go]$$W Broken shape for W: :wt: damaged
$$ ----------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . O . O . X 4 Q . . O . X . . . . |
$$ | . . . , . . 3 1 2 , . . . . . X . . . |
$$ | . . O . . . . X . O . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . X . . . |
$$ | . . . . . . . X . . . . . . . . . . . |
$$ | . . . O . . . . . . . . . . . . . . . |[/go]

(Globally, B has to choose which side to atari to get the better result for B.)

In other words, just because W can cut (or wedge) does not necessarily mean W can get a good result --
there are good cuts and bad cuts, as there are good wedges and bad wedges.

W(b) is also a bad wedge for W:

Click Here To Show Diagram Code

[go]$$W Broken shape for W: :ws: damaged (and all 3 W stones under attack!)
$$ -----------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . O . O . X . O . . O . X . . . . |
$$ | . . . , . . . . . , . . . . . X . . . |
$$ | . . O . . . . X 4 @ . . . . . . . . . |
$$ | . . . . . . 3 1 2 . . . . . . X . . . |
$$ | . . . . . . . X . . . . . . . . . . . |
$$ | . . . O . . . . . . . . . . . . . . . |[/go]

OK.

So the white pincer stones on f17 and k17 are more of a liability than an asset?

PeterPeter wrote:So the white pincer stones on f17 and k17 are more of a liability than an asset?

No -- it depends on what W does with them (and how B replies). It's a fight. The outcome depends on what happens in the fight.

PeterPeter wrote:OK.

So the white pincer stones on f17 and k17 are more of a liability than an asset?

K17 was not a pincer stone, it was already there. F17 was the pincer stone and it doesn't look right. My instinct would be to cap at h15.

Alguien wrote:K17 was not a pincer stone, it was already there. F17 was the pincer stone and it doesn't look right. My instinct would be to cap at h15.

That's an entirely different game. If , W hurts his own 2 stones on top (and the fight continues):

Click Here To Show Diagram Code

[go]$$Bc
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . O . . . 1 . O . . O . X . . . . |
$$ | . . . , . . . . 3 5 . . . . . X . . . |
$$ | . . O . . . . 2 . . . . . . . . . . . |
$$ | . . . . . . . . . 4 . . . . . X . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . O . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . X . . |
$$ | . . . X . . . . . , . . . . . , . . . |[/go]

If instead, the fight changes like this:

Click Here To Show Diagram Code

[go]$$Bc
$$ -----------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . O . . . 1 . O . . O . X . . . . |
$$ | . . . , . . . . 3 . . . . . . X . . . |
$$ | . . O . . . . 2 5 . 4 . . . . . . . . |
$$ | . . . . . . . . . . . . . . . X . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . O . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . X . . |
$$ | . . . X . . . . . , . . . . . , . . . |[/go]

EdLee wrote:

PeterPeter wrote:So the white pincer stones on f17 and k17 are more of a liability than an asset?

No -- it depends on what W does with them (and how B replies). It's a fight. The outcome depends on what happens in the fight.

So they are OK unless White tries to cut at a, in which case they are little help and become vulnerable.

PeterPeter wrote:So they are OK unless White tries to cut at a...

I don't know if the original moves were OK or not --
(that's interesting, but not the point of your original question ) --
the point is to study the wedges W(a) and W(b) and look at the results,
and see what happens to the W and B stones: the resulting shapes, which stones are damaged,
which stones got cut off, which got captured, etc.; both the local and global situations.

If the W(a) and W(b) wedges are good for W, then B needs to worry about them
and maybe do something about them; if they are bad for W, then B is happy if W wedges!

Peter, here, at (a) kills something:

Click Here To Show Diagram Code

[go]$$B
$$-------------------
$$. . . . . . . . . .
$$. . . . . . . . . .
$$. . . O . X . O . .
$$. . . O . a . O . .
$$. . . O . 1 . O . .
$$. . . . . . . . . .[/go]

In this case, the one-point jump can be cut AND the local result is good for W.

EdLee wrote:Peter, here, at (a) kills something:

$$B
$$-------------------
$$. . . . . . . . . .
$$. . . . . . . . . .
$$. . . O . X . O . .
$$. . . O . a . O . .
$$. . . O . 1 . O . .
$$. . . . . . . . . .

Click Here To Show Diagram Code

[go]$$B
$$-------------------
$$. . . . . . . . . .
$$. . . . . . . . . .
$$. . . O . X . O . .
$$. . . O . a . O . .
$$. . . O . 1 . O . .
$$. . . . . . . . . .[/go]

In this case, the one-point jump can be cut AND the local result is good for W.

Or, with less stones.

Click Here To Show Diagram Code

[go]$$B
$$-------------------
$$. . . . . . . . . .
$$. . . . . . . . . .
$$. . . . . X . . . .
$$. . . . . a O . . .
$$. . . . . 1 . . . .
$$. . . . . . . . . .[/go]

In this case, the one-point jump can be cut. Which is why most of the times B will want to play a before W does.

PeterPeter wrote: So the white pincer stones on f17 and k17 are more of a liability than an asset?

No, they are an asset with weaknesses, just like black's one point jumps. It is a very common situation in Go that weaknesses in your own positions prevent you from exploiting weaknesses in your opponent's positions. If the weaknesses in your positions are repaired, only then does it become feasible to exploit your opponent's; it's all about balance. The example of adjacent one point jumps is in fact a very common one. The reason the wedge at a is ineffective is that black j16 is basically a sente peep against white's one point jump to k15. (I think black should atari this way, the atari from the left looks like it could get dangerous for black.)

Click Here To Show Diagram Code

[go]$$Wc
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . O . O . X 4 O . . O . X . . . . |
$$ | . . . , . . 3 1 2 , . . . . . X . . . |
$$ | . . O . . . . X . O . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . X . . . |
$$ | . . . . . . . X . . . . . . . . . . . |
$$ | . . . O . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . X . . |
$$ | . . . X . . . . . , . . . . . , . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . , . . . . . , . . . . . , . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------[/go]

If white now realises the k16 weakness and connects there, then black connects and white's wedge achieved worse than nothing: it made black stronger and with more eyeshape and gave white two stones with few liberties.

Click Here To Show Diagram Code

[go]$$Wc Abort -> fail
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . O . O . X X O . . O . X . . . . |
$$ | . . . , . . W W X 5 . . . . . X . . . |
$$ | . . O . . . . X 6 O . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . X . . . |
$$ | . . . . . . . X . . . . . . . . . . . |
$$ | . . . O . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . X . . |
$$ | . . . X . . . . . , . . . . . , . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . , . . . . . , . . . . . , . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------[/go]

If white cuts, which is the only consistent thing to do after the wedge, then at a minimum black can capture k17 to live at the top. However white has got some outside so this isn't necessarily good for black.

Click Here To Show Diagram Code

[go]$$Wc Capture k17
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . 0 . . . . . . . . . |
$$ | . . . O . O . X X O 8 . O . X . . . . |
$$ | . . . , . . W W X 6 7 9 . . . X . . . |
$$ | . . O . . . . X 5 O . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . X . . . |
$$ | . . . . . . . X . . . . . . . . . . . |
$$ | . . . O . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . X . . |
$$ | . . . X . . . . . , . . . . . , . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . , . . . . . , . . . . . , . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------[/go]

However, black may be able to be more ambitious and cut at L15. This leads to a more complicated fight that I haven't read out yet. The sort of outcome I plan for as black is to sacrifice h15 and h13 in exchange for killing the white stones at k17 and n17: this would be a good trade for black. (Notice that thanks to h15 and h13 white can't connect at l17 or k14 captures the cutting stones in a ladder).

Click Here To Show Diagram Code

[go]$$Wc Fight hard.
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . O . O . X X O . . O . X . . . . |
$$ | . . . , . . W W X 6 7 . . . . X . . . |
$$ | . . O . . . . X 5 O 8 . . . . . . . . |
$$ | . . . . . . . . . . . . . . . X . . . |
$$ | . . . . . . . X . . . . . . . . . . . |
$$ | . . . O . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . X . . |
$$ | . . . X . . . . . , . . . . . , . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . , . . . . . , . . . . . , . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------[/go]

So now what did I mean by if the weaknesses in white's shape are repaired? That he gets a stone at k16 due to black peeping the other side. So say the following sequence occurs:

Click Here To Show Diagram Code

[go]$$Bc
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . 3 9 . . . . . . |
$$ | . . . O . O . X . O 4 5 O . X . . . . |
$$ | . . . , . . . . . 2 1 6 7 a . X . . . |
$$ | . . O . . . . X . O . 8 0 . . . . . . |
$$ | . . . . . . . . . . . . . . . X . . . |
$$ | . . . . . . . X . . . . . . . . . . . |
$$ | . . . O . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . X . . |
$$ | . . . X . . . . . , . . . . . , . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . , . . . . . , . . . . . , . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------[/go]

Now if white wedges and black ataris from the right, he dies thanks to white already having k16.

Click Here To Show Diagram Code

[go]$$Wc
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . X X . . . . . . |
$$ | . . . O . O . X 4 O O X O . X . . . . |
$$ | . . . , . . 3 1 2 O X O X X . X . . . |
$$ | . . O . . . . X 5 O . O O . . . . . . |
$$ | . . . . . . . . . . . . . . . X . . . |
$$ | . . . . . . . X . . . . . . . . . . . |
$$ | . . . O . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . X . . |
$$ | . . . X . . . . . , . . . . . , . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . , . . . . . , . . . . . , . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------[/go]

But that doesn't mean the wedge works, as black can now decide (noticing that white already has k16) to atari the other side. Notice how when white connects he makes an ugly double empty triangle. Before I said this way is dangerous for black, but probably he won't die, and he already got a lot of profit from capturing n17.

Click Here To Show Diagram Code

[go]$$Wc
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . X X . . . . . . |
$$ | . . . O . O 4 X . O O X O . X . . . . |
$$ | . . . , . . 2 1 3 O X O X X . X . . . |
$$ | . . O . . . 5 X . O . O O . . . . . . |
$$ | . . . . . . . . . . . . . . . X . . . |
$$ | . . . . . . . X . . . . . . . . . . . |
$$ | . . . O . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . X . . |
$$ | . . . X . . . . . , . . . . . , . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . , . . . . . , . . . . . , . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------[/go]

Wanting to wedge one-point jumps is an extremely common beginner trait, and one that you will unlearn as you get stronger. However, you can go too far the other direction and never consider the wedge when occasionally it is a good move. I remember one pro game, I think it was Lee Changho vs Cho Chikun, with a devastating wedge of a one-point jump which I think Cho must have overlooked, I'll see if I can find it when I get home.