Life In 19x19 :: 2-4 defense against keima approach to hoshi stone?

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2-4 defense against keima approach to hoshi stone? http://www.lifein19x19.com/viewtopic.php?f=11&t=7231	Page 1 of 1

Author:	hibbs [ Mon Nov 19, 2012 4:56 am ]
Post subject:	2-4 defense against keima approach to hoshi stone?
Hi all, in two of my recent games, my opponent has used the following defense against a keima approach to the hoshi stone: Click Here To Show Diagram Code `[go]$$B $$ --------------------------------------- $$ \| . . . . . . . $$ \| . . . . . . . $$ \| . . . . . . . $$ \| . 3 . 1 . . . $$ \| . . . . . . . $$ \| . . 2 . . . . $$ \| . . . . . . . $$ \| . . . . . . . $$[/go]` This seems not to be a joseki move... Well, I usually do not care too much about learning joseki, but somtime I look them up after a game where I feel something went wrong. Anyways, in the Brugo database, is not seen as joseki move. This should indicate that the move is not good. However, I have not found a good continuation, an extension from is already undercut, no matter how to peep or wedge, always black seems to get the much better result from the exchange. Trying to approach from the open side of the corner still weakens and ends with two split white groups... Am I missing something here?

Author:	EdLee [ Mon Nov 19, 2012 5:02 am ]
Post subject:
hibbs, just my idle thoughts: hibbs wrote: an extension from is already undercut Click Here To Show Diagram Code `[go]$$B $$ --------------------------------------- $$ \| . . . . . . . . $$ \| . . . . . . . . $$ \| . . . . . . a . $$ \| . 3 . 1 . . . . $$ \| . . . . . . . . $$ \| . . 2 . . . . . $$ \| . . . . . . . . $$ \| . . . . . . . . $$ \| . . 4 . . . . . $$ \| . . . . . . . . $$[/go]` If W simply jumps to , then B will eventually want to add 1 more move in the (a) direction. W can also consider to tenuki on . Either way, on an empty board is not very severe on W, and W has sente. hibbs wrote: or wedge, always black seems to get the much better result from the exchange. This is a hint that the wedge is not good for W. hibbs wrote: I have not found a good continuation Another way to think about it: if turns out to be not a very good move (slow, etc.), then W already has a good result locally. A contrived example: if B makes the strange move of , W needs not find a "good continuation" locally -- W can simply tenuki, since (a) and (b) are miai for W: Click Here To Show Diagram Code `[go]$$ $$ ------------------- $$ \| . . . . . . . . . $$ \| . . . . . . . . . $$ \| . . b . 5 3 . . . $$ \| . 4 . 1 . . . . . $$ \| . . . . . . . . . $$ \| . . 2 . . . . . . $$ \| . . . . . . . . . $$ \| . . . . . . . . . $$ \| . . a . . . . . . $$ \| . . . , . . . . .[/go]`

Author:	Phoenix [ Mon Nov 19, 2012 5:29 am ]
Post subject:	Re: 2-4 defense against keima approach to hoshi stone?
Dailyjoseki has the most common continuation as below, and it's the point I play by default against this reply (global position notwithstanding). Click Here To Show Diagram Code `[go]$$W $$ --------------------------------------- $$ \| . . . . . . . $$ \| . . . c . . . $$ \| . . . . . 1 . $$ \| . X . X . b . $$ \| . . . . a . . $$ \| . . O . . . . $$ \| . . . . . . . $$ \| . . . . . . . $$[/go]` The most common continuations are the splitting diagonal at a and attachment at b. One of White's groups comes under attack after a, but White still got to play on both sides (a dreadful thing for Black's 4-4 stone), and Black hasn't made any territory as of yet. Fun fact: I've had opponents play c after this sequence, after which I gleefully took a. This makes for very one-sided games.

Author: SoDesuNe [ Mon Nov 19, 2012 7:38 am ]

Post subject: Re: 2-4 defense against keima approach to hoshi stone?

I think EdLee's diagramme of just making a basic extension is good for White. If Black does not defend his corner now with another move ('a'), White can approach at 'b' and :b3:

loses a lot of its meaning, in my opinion. Either surrounding a very small corner with no prospects for further development ('c') or being completely useless when Black tries to split or pincer White ('d'), so that the corner is easily invadable.

Click Here To Show Diagram Code: [go]$$Bc $$ --------------------------------------- $$ | . . . . . . . . . . . . . $$ | . . . c . . . . . . . . . $$ | . . . . . b a . d d . . . $$ | . 3 . 1 . . . . . , . . . $$ | . . . . d . . . . . . . . $$ | . . 2 . . . . . . . . . . $$ | . . . . . . . . . . . . . $$ | . . . . . . . . . . . . . $$ | . . 4 . . . . . . . . . . $$ | . . . , . . . . . . . . . $$[/go]

Even if Black plays 'a' directly, it only secures around 15 points. With two moves! Losing Sente. In the opening! Locally this is plain bad for Black, in my opinion.

I'm not a big fan of double-approaching, though (unless it's a handicap game or White has support). Black can split White almost without worries and now White has to defend two weak-ish groups. I think White profits enough when he plays plain and simple. No need to put it all on a fight, which could end badly.

post scriptum:

Maybe another way to think of it:

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

Why is

here a good move in a lot of situations? A lot of beginners and - back in the times myself included - think this is a weak response. Giving up the corner so easily (and the corner is worth the most points, isn't it?). It's only later when they understand or get explained that :b3:

is a very flexible move. Black does not want to fixate on something on e.g. move 3.

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

fixates on the corner. If Black does not get the corner or can attack :w2:

, then what does this move achieve? If White plays :w4:

, neglecting a Black attack, Black is somehow pressed to play :b5:

, in my opinion. And that result is not good in the opening (see above).

Click Here To Show Diagram Code: [go]$$Bc $$ --------------------------------------- $$ | . . . . . . . . . . . . . $$ | . . . . . . . . . . . . . $$ | . . a . . 3 . . b . . . . $$ | . 4 . 1 . . . . . , . . . $$ | . . . . . . . . . . . . . $$ | . . 2 . . . . . . . . . . $$ | . . . . . . . . . . . . . $$ | . . . . . . . . . . . . . $$ | . . . . . . . . . . . . . $$ | . . . , . . . . . . . . . $$[/go]

So why is

better or flexible? For one you don't have to answer :w4:

, 'a' and 'b' are Miai for Black, means equal in local value (making a base). The reason why this is good (flexible), isn't solely because Black can take Sente to play elsewhere.

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

Playing

is Sente, too, for Black. White has to make a base with :w6:

to not come under attack.

Click Here To Show Diagram Code: [go]$$Bc $$ --------------------------------------- $$ | . . . . . . . . . . . . . $$ | . . . . . . . . . . . . . $$ | . . c . . 3 . . d . . . . $$ | . 4 . 1 . . . . . , . . . $$ | . . . . . . . . . . . . . $$ | . . 2 . . . . . . . . . . $$ | . . b . . . . . . . . . . $$ | . . a . . . . . . . . . . $$ | . . . . . . . . . . . . . $$ | . . . , . . . . . . . . . $$ | . . . . . . . . . . . . . $$[/go]

One of the main reasons is, that Black has 'a' to 'c' at his disposal. All lead to different games and depending on the whole board 'a' might be better later on than having played 'c'. Black can chose how to carry on with this corner after :b3:

, he has many different possibilities and White may deny him this when he plays 'c' himself at the right time but this is no attack on Black since he can easily take the other side to extend ('d').

To sum it up: :b3:

in the last diagrammes is flexible because Black does not need to chose his strategy directly. He can wait and see how the whole board develops to play the proper move in this corner. And even if White plays first, Black has a resilient shape. No milk spilled.
Of course White has many other possibilities instead of playing :w4:

, but that's not the point and of course Go is a two player game =)

Author:	hibbs [ Mon Nov 19, 2012 11:35 am ]
Post subject:	Re: 2-4 defense against keima approach to hoshi stone?
Thanks a lot for all your comments, that was very helpful for me.

Author:	Joaz Banbeck [ Mon Nov 19, 2012 12:02 pm ]
Post subject:	Re: 2-4 defense against keima approach to hoshi stone?
Keep in mind that the 4-4 stone is a high stone. ( If you are not familiar with the concepts of 'high' and 'low', see http://senseis.xmp.net/?HighAndLowMoves, and its associated links. ) If you can get him holed up in a small corner territory, his stone is inefficient.

Author:

Uberdude [ Mon Nov 19, 2012 6:13 pm ]

Post subject:

Re: 2-4 defense against keima approach to hoshi stone?

The 2-4 response is an unusual move on an empty board, but it is a valid move suitable for certain situations. It is focused on defence and securing some corner territory with later aims of attacking the white approach stone rather than developing the side or centre. It prevents white from sliding there to easily settle her stone. It is a bit slow so tenuki is a common response, but it is not unconditionally a good exchange for white who has lost the option of an easy 3-3 invasion. Also beware of thinking a strange move must be bad. Here's an example of Takemiya, that master of 4-4s and influence, playing this on move 45. It's not the first move that springs into my mind in such a position, but I can understand it as securing the corner and stopping r6 making an easy base. Extension to o3 doesn't look good given white's strength on the lower side and leaving the corner open. Given q10 one might think of the traditional r5 kick, but as q10 is not so strong with q12 above maybe that's not such a good idea, and black won't develop the lower side by chasing white out. Maybe someone with Go World 76 can relay its commentary.

Attachments:

1996-04-10a.sgf [1.5 KiB]
Downloaded 653 times

Author:	Bill Spight [ Tue Nov 20, 2012 12:56 am ]
Post subject:	Re: 2-4 defense against keima approach to hoshi stone?
It is an old joseki move which, as Uberdude points out, is still playable in some situations. AFAICT, it went out of favor in the early 19th century. These days you are more likely to see the footsweep (2-5) as a situational play.

Author: snorri [ Tue Nov 20, 2012 12:05 pm ]

Post subject: Re: 2-4 defense against keima approach to hoshi stone?

SoDesuNe wrote:

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

I am not sure :b5:

should be there. If it goes as above, I think white should be satisfied, as black is a bit thinner than the usual formations which might be used as tewari comparisons:

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

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

The 2-4 jump in the OP I like to think of as a variant of the iron pillar immediately above, which is joseki ( :b3:

could be at :b5:

). As is often the case, looking for a severe punishment is probably asking too much.

Author:	ez4u [ Sat Nov 24, 2012 6:35 am ]
Post subject:	Re: 2-4 defense against keima approach to hoshi stone?
Just to put this move in perspective. The current GoGoD (summer 2012) has 56,086 examples of the position below with no other stones in a 10X10 quadrant. There are exactly 9 cases of Black playing at "a" next. Compare this to 22,138 plays at "b", 10,560 at "c", and 8,339 at "d". I think we can safely consign "a" to the bin for 'special circumstances'. Fundamentally the left edge is smaller than the top side unless White (or Black) has already played something around there. Click Here To Show Diagram Code `[go]$$Bc Search Pattern $$+ - - - - - - - - - - $$\| . . . . . . . . . . $$\| . . . . . . . . . . $$\| . . . . . b . . . . $$\| . a . X . c . . . , $$\| . . . . . . . . . . $$\| . . O . . . . . . . $$\| . . . . . . . . . . $$\| . . d . . . . . . . $$\| . . . . . . . . . . $$\| . . . , . . . . . , $$[/go]`

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