Shortage of liberties question

sigger · #1

Hi, I have a question about a diagram showing how to utilize a shortage of liberties (Diagram 33-3 in An Encyclopedia of Go Principles by Richard Bozulich)

The first diagram shows how if white tries to link its stones, black can use 3 to prevent it.

Click Here To Show Diagram Code: [go]$$Bc $$ +---------------------------------------+ $$ . . . . . 6 . . . . | $$ . . . 5 2 3 4 O . . | $$ . . O 7 X O O X X . | $$ , . . . . X X . . . | $$ . . O . . . . X . . | $$ . . . . . . . . . . | $$ . . . . . . . . . . | $$ . . . . . . . . . . |[/go]

What I'm wondering is why white can't atari with six instead of capturing, as in the second diagram. It seems to me that if black plays on the red circle, white could capture black 3. Or if black captures white 2, white could play on the black circle. I can't find a sequence where black can prevent white from linking up. I'm still pretty new to the game, so I imagine it is fairly obvious, but I've gone over it many times and I still can't see it. Thanks.

Click Here To Show Diagram Code: [go]$$Bc $$ +---------------------------------------+ $$ . . . . . . . . . . | $$ . . . 5 2 3 4 O . . | $$ . . O 6 X O O X X . | $$ , . . . C X X . . . | $$ . . O . . . . X . . | $$ . . . . . . . . . . | $$ . . . . . . . . . . | $$ . . . . . . . . . . |[/go]

Kirby · #2

Click Here To Show Diagram Code: [go]$$Bc $$ +---------------------------------------+ $$ . . . . 7 . . . . . | $$ . . . 5 9 3 4 O . . | $$ . . O 6 X O O X X . | $$ , . . . 8 X X . . . | $$ . . O . . . . X . . | $$ . . . . . . . . . . | $$ . . . . . . . . . . | $$ . . . . . . . . . . |[/go]

And then?

EdLee · #3

Hi sigger,

schawipp · #4

EdLee · #5

schawipp wrote:

white will finally die in the corner.

Hi schawipp, if it works out for black, good.

It seems about 15 moves of reading from the original diagram -- how would you approach this when explaining to a beginner ?
Quite a few variations; I don't have the source book --
I don't know what's shown and which variations are omitted.
And how do you feel about having an extra black stone at S18 in the original set-up ? Good, neutral, bad -- concerning the intent and clarity of this problem ?

Bill Spight · #6

EdLee wrote:

And how do you feel about having an extra black stone at S18 in the original set-up ? Good, neutral, bad -- concerning the intent and clarity of this problem ?

Bad, because it makes Black's play sente to kill. You want to show that the Black sequence is good, even if it is gote.

It is not easy to construct good examples.

Edit: Maybe better?

Click Here To Show Diagram Code: [go]$$Wc $$ ----------------------- $$ . . . . . 5 . . . . . . $$ . . . 4 1 2 3 O . . . . $$ . . O 6 X O O X X . X . $$ . . . . . X X . . . . . $$ . . O . . . . X . . . . $$ . . . . . . . . . . . . $$ . . . . . . . . . . . . $$ . . . . . . . . . . . .[/go]

EdLee · #7

Bill Spight wrote:

It is not easy to construct good examples.

Hi Bill, yep; thanks.

Uberdude · #8

sigger wrote:

What I'm wondering is why white can't atari with six instead of capturing, as in the second diagram.

Well done for considering a white resistance. It's important when reading to not be self-indulgent and only look at the moves you want your opponent to play, but the tricky other choices they may have. Even if that tactic doesn't work in this example (was the edge of the board exactly as shown in your diagram?), in some shapes that white counter atari is indeed a clever tactic that works to stop black from cutting successfully, so it's good to be aware of it and you should read to make sure it doesn't work before embarking on this sequence. So I suppose a possible exercise is: can you construct a position in which that white counter atari does work to thwart black's plan?

schawipp · #9

Hi EdLee,

EdLee wrote:

how would you approach this when explaining to a beginner?

Yep, that is probably not the most beginner-friendly example.

Click Here To Show Diagram Code: [go]$$W $$ --------------------- $$ . . . . X . . . . . | $$ . . . X X X O O . . | $$ . . O O X O O X X . | $$ , . . . O X X . . . | $$ . . O . . . . X . . | $$ . . . . . . . . . . |[/go]

First I would try to guide a beginner to the above given position and show that the black stones have 4 effective liberties (i.e. it takes 4 moves to capture them without black answering) while the white stones have only 3. This should already ring the alarm bell for white. It can be easily demonstrated that white cannot just start capturing black:

Click Here To Show Diagram Code: [go]$$Wcm1 $$ --------------------- $$ . . 3 . X . . 4 . . | $$ . . 1 X X X O O 2 . | $$ . . O O X O O X X . | $$ , . . . O X X . . . | $$ . . O . . . . X . . | $$ . . . . . . . . . . |[/go]

For a very first beginner I would stop here try to say that - when in doubt - it is at least helpful to count effective liberties. This may still fail due to special tactical issues in 10% of the cases but it's better than nothing.

So white should rather increase his own liberties first, but black can do the same and has more room for this. The following explanation is probably beyond beginner level:

Click Here To Show Diagram Code: [go]$$W $$ --------------------- $$ . 6 4 . X . 5 . . . | $$ a 2 3 X X X O O 1 . | $$ . b O O X O O X X . | $$ , . . . O X X . . . | $$ . . O . . . . X . . | $$ . . . . . . . . . . |[/go]

Now, regardless whether w plays (a) or (b) black gets into some kind of ladder where black has one liberty too much (very bad idea for w) or black increases his liberties by walking along the 2nd line (in very bad shape, and white gets a strong 3rd line wall, but well...). Nevertheless, even without the additional "double threat" tactical issue, white cannot win this semeai.

Of course this may change if there are more white stones nearby at left side, but since the diagram stops here I assume that it's empty there ;-)

.

Kirby · **#10**

EdLee wrote:

Hi sigger,

Uberdude · **#11**

Uberdude wrote:

So I suppose a possible exercise is: can you construct a position in which that white counter atari does work to thwart black's plan?

With impeccable timing John Fairbairn has posted an old pro game with this shape, look at the game in this post, move 44: viewtopic.php?p=201207#p201207.

Bill Spight · **#12**

Uberdude wrote:

sigger wrote:

What I'm wondering is why white can't atari with six instead of capturing, as in the second diagram.

Well done for considering a white resistance.

Hear, hear! :salute:

sigger · **#13**

Thank you everyone for your help. I can see now specifically that I did not consider 4 in this position shown in schawipp's diagram:

Click Here To Show Diagram Code: [go]$$W $$ --------------------- $$ . . . . X . . . . . | $$ T 3 2 X X X O O 1 . | $$ . 4 O O X O O X X . | $$ , . . T O X X . . . | $$ . . O . . . . X . . | $$ . . . . . . . . . . |[/go]

In fact I think it would have been a loooong time before I considered it. So thank you again.

Shortage of liberties question

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