Simple question that bugs this beginner - hitting the head

Kirby · Post by **Kirby** » Wed Jun 29, 2011 10:05 am

FWIW, I think I've also heard a proverb, "Beginners atari".

Bill Spight · Post by **Bill Spight** » Wed Jun 29, 2011 10:42 am

Well, as our current discussion has shown, it's not a simple question, and I doubt if strong amateurs will reach a consensus about correct play (assuming an otherwise empty board). Strong pros might, however. It might be worth doing a database search.

Let me share my thinking.

Click Here To Show Diagram Code: [go]$$c After hitting the head, white cross cuts! $$ ......... $$ ......... $$ ......... $$ ..XX2b... $$ .cOO1a... $$ ....o.... $$ ......... $$ ......... $$ .........[/go]

restores equality, but is doubtful. It may give Black a bigger play than normal.

Black "b" is surely bad, as it strengthens White and weakens Black after White extends. The other atari would not be so good, either.

Mr. Yang's heuristic is interesting, and it recommends strengthening one's weaker group. But which group is weaker? Yes, the single stone has only two liberties, but that is not the only indicator of weakness. The two stone group has a weakness by virtue of having more stones. That makes it harder to sacrifice. (Not that we want to sacrifice either group.) Also, the two stone group has only a single play to increase its dame, while the single stone has two plays to do so. (The other plays for the two stone group make bad shape.)

topazg's extension from the single stone is interesting, because it carries an immediate threat of a ladder, and then, if White saves the threatened stone, Black can hane at the base (head?) of the White two stone group, threatening it with a ladder, too. That's very nice, and it may well be the best play.

OTOH, Black's single stone is not particularly weak, and it has two different extensions, while the hane at the base of the White two stone group is the best way to reduce its liberties. And it is the play I want to make, sooner or later, anyway. Why not now?

So the hane is my choice, but topazg's extension may be better.

Kirby · Post by **Kirby** » Wed Jun 29, 2011 11:01 am

Bill Spight wrote:...

Mr. Yang's heuristic is interesting, and it recommends strengthening one's weaker group. But which group is weaker? Yes, the single stone has only two liberties, but that is not the only indicator of weakness. The two stone group has a weakness by virtue of having more stones. That makes it harder to sacrifice. (Not that we want to sacrifice either group.) Also, the two stone group has only a single play to increase its dame, while the single stone has two plays to do so. (The other plays for the two stone group make bad shape.)
...

It could be the case that the two stones are weaker than the single stone. If that is the case, it would add to my distaste toward such algorithms, as misunderstanding a small part can lead to a totally different decision.

I do feel that the single stone is, at least, more flexible.

Bill Spight · Post by **Bill Spight** » Wed Jun 29, 2011 11:14 am

Kirby wrote:
Bill Spight wrote:...

Mr. Yang's heuristic is interesting, and it recommends strengthening one's weaker group. But which group is weaker? Yes, the single stone has only two liberties, but that is not the only indicator of weakness. The two stone group has a weakness by virtue of having more stones. That makes it harder to sacrifice. (Not that we want to sacrifice either group.) Also, the two stone group has only a single play to increase its dame, while the single stone has two plays to do so. (The other plays for the two stone group make bad shape.)
...

It could be the case that the two stones are weaker than the single stone. If that is the case, it would add to my distaste toward such algorithms, as misunderstanding a small part can lead to a totally different decision.

Go is hard.

Kirby · Post by **Kirby** » Wed Jun 29, 2011 11:23 am

Bill Spight wrote:
Kirby wrote:
Bill Spight wrote:...

Mr. Yang's heuristic is interesting, and it recommends strengthening one's weaker group. But which group is weaker? Yes, the single stone has only two liberties, but that is not the only indicator of weakness. The two stone group has a weakness by virtue of having more stones. That makes it harder to sacrifice. (Not that we want to sacrifice either group.) Also, the two stone group has only a single play to increase its dame, while the single stone has two plays to do so. (The other plays for the two stone group make bad shape.)
...

It could be the case that the two stones are weaker than the single stone. If that is the case, it would add to my distaste toward such algorithms, as misunderstanding a small part can lead to a totally different decision.

Go is hard.

Yeah. Algorithms seem to be an attempt to simplify it too much. Though, I suppose you could argue that you at least know what to look for using such an algorithm (in this case, perhaps the "weakest group").

daal · Post by **daal** » Wed Jun 29, 2011 12:08 pm

Joaz Banbeck wrote:I tend to disagree with Kirby's reasoning. is not all that weak, for it has miai to run at 'a' and 'o'. I still like 'c' better.

Kirby's reasoning above closely follows Yilun Yang's advice on how to approach a crosscut fight (See: The Workshop Lectures, Vol. 1). Another thing that Yang says however, is that a stone or group that has lost half its liberties can be considered weak. Although :b1:

can easily gain liberties, atm it's two stones away from oblivion.

Post by **Joaz Banbeck** » Wed Jun 29, 2011 12:11 pm

True. But by that definition, all black groups in the diagram are equally weak.

daal · Post by **daal** » Wed Jun 29, 2011 12:20 pm

Yes, the situation is a bit unusual because no edges are in sight. Yang often points out that the inside group, i.e., the one closer to a wall, usually ought to be helped first.

yoyoma · Post by **yoyoma** » Wed Jun 29, 2011 12:45 pm

Click Here To Show Diagram Code: [go]$$Bc $$ --------------------------------------- $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . , . . . . . , . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . 0 . . . . . . . . | $$ | . . . . . . 9 7 6 4 3 . . . . . . . . | $$ | . . . , . . . 8 5 1 2 . . . . , . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . , . . . . . , . . . . . , . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ ---------------------------------------[/go]

1 - Tengen!
2 - I challenge you to a duel!
3 - Attack!
4 - Counter-attack!
5 - Imma ladder you yo.
6 - Denied.
7 - Double hane sup?
8 - COUNTER double hane yo!
9 - Imma ladder you!
10 - Ponnuki > ladder

Click Here To Show Diagram Code: [go]$$Bcm11 $$ --------------------------------------- $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . , . . . . . , . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . O . . . . . . . . | $$ | . . . . . . X X O O X 1 . . . . . . . | $$ | . . . , . . . O X X O 2 3 . . , . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . , . . . . . , . . . . . , . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ ---------------------------------------[/go]

11 - DOUBLE ladder threat sup!
12 - Break one ladder, make another. Ladder 2 stones > Ladder 1 stone
13 - Double ladder is back yo.

DrEntropy · Post by **DrEntropy** » Wed Jun 29, 2011 6:44 pm

Wow, thanks everyone for the responses! This board is awesome. Kirby's post in particular was very valuable to me. I worried there was some easy answer I was missing. But Bill Spight summarized it best:

Bill Spight wrote:
Go is hard.

But also fun! :tmbup:

Life In 19x19

Simple question that bugs this beginner - hitting the head

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Re: Simple question that bugs this beginner - hitting the he