Click Here To Show Diagram Code

[go]$$c
$$ | . . . . . . . .
$$ | . . . . . . . .
$$ | . . X a . . . .
$$ | . O O b O . . .
$$ | . X X O . . . .
$$ | . X O X O O . .
$$ | . . . X X . X .
$$ | . . . . . . . .
$$ | . . . . . . . .
$$ +-----------------[/go]

The diagram is the result of a joseki (Edit: Sorry, it is not joseki, white has advantage). It's whites turn now and he will probably tenuki.

My question: is there a reason for black not to play at a? It looks like definitely sente. Does it remove any aji, if yes which one?

I know the black stone above is sort of sacrificed for getting the corner and it's difficult to make something out of it. But it looks like it still has potential for creating some aji later, depending on the fight going on at the left side.

Therefore, in the exchange (Black a-White b), White-b looks more useless than Black-a. If so, (why) is the exchange bad for black?

Sorry if the question is silly but I would like to learn the idea behind avoiding such moves. Thanks for the answers in advance?

_________________
If you say no, Elwood and I will come here for breakfast, lunch, and dinner every day of the week.

At the very least you will want to preserve this move for later as a potential ko threat. So peeping is aji-keshi.

_________________
Human beings cannot stop doing what they really desire to do. ; Amamiya-sensei
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Click Here To Show Diagram Code

[go]$$c
$$ | . . . . . . . .
$$ | . . . . . . . .
$$ | . . X a . . . .
$$ | . O O b O . . .
$$ | . X X O d c . .
$$ | . X O X O O . .
$$ | . . . X X . X .
$$ | . . . . . . . .
$$ | . . . . . . . .
$$ +-----------------[/go]

"c" is the only other logical peep aji, and may have situations where you'd want to play it. The fact it makes "d" into not only cutting the stones off below, but because of the atari doing so in sente, makes it a large peep. If the exchange of "a" and "b" has already happened, White can choose to sacrificing the two White stones quite easily - in which case both "c" and "d" would be gote for Black for a relatively small gain as there's no atari for White to connect after "d". Also "a" just makes Black a bit bigger and heavier. Sure, it may be sente, but it's also a big ko threat (though White I would have thought would opt to play "a" himself before that sort of ko appeared - at least, I would).

That would be my take anyway, take it with a grain of salt

Just to add to what has been said about ko threats, "a", played too early, seems like it would be the definition of heavy play.

Indeed it reduces the aji at "c". I also thought about it but because of the white stone at f4, I felt that there is anyway no aji there. Or at least the aji at "c" is smaller than the aji created by the two black stones. But thinking about it again, probably my feeling was wrong

Ko threat argument is definitely a valid one.

Anyway, thanks a lot for the replies.

_________________
If you say no, Elwood and I will come here for breakfast, lunch, and dinner every day of the week.

Hmm, I get a little bit confused about that. For the following reason:

As far as I know "heavy" means that you can neither make easy life nor sacrifice the group because the stones did not yet accomplish their jobs.

But these two stones can be sacrificed because c7 stone has already accomplished its job (allowing black to take the corner) and d7 stone is also not wasted because it is answered by another useless (maybe not useless because of aji-keshi but let's assume just for a minute it is indeed useless) move of white.
Can you still call these stones heavy, even if they can be sacrificed?

You are probably much stronger than me, my intention is not providing a useless argument just for the sake or arguing. But I am really curious about that interpretation of "heavy".

_________________
If you say no, Elwood and I will come here for breakfast, lunch, and dinner every day of the week.

The situation I see as:

Click Here To Show Diagram Code

[go]$$c
$$ | . . . . . . . .
$$ | . . . . . . . .
$$ | . . X 1 . . . .
$$ | . O O 2 O 4 6 .
$$ | . X X O 7 3 5 8
$$ | . X O X O O 9 .
$$ | . . . X X . X .
$$ | . . . . . . . .
$$ | . . . . . . . .
$$ +-----------------[/go]

White is happy doing this because moves like are more valuable than saving the two stones.

However:

Click Here To Show Diagram Code

[go]$$c
$$ | . . . . . . . .
$$ | . . . . . . . .
$$ | . . X . . . . .
$$ | . O O 9 O 4 6 .
$$ | . X X O 7 3 5 8
$$ | . X O X O O . .
$$ | . . . X X . X .
$$ | . . . . . . . .
$$ | . . . . . . . .
$$ +-----------------[/go]

this is a disaster for White, so White must connect instead at

Click Here To Show Diagram Code

[go]$$c
$$ | . . . . . . . .
$$ | . . . . . . . .
$$ | . . X 5 . . . .
$$ | . O O 6 O 2 . .
$$ | . X X O 4 1 3 .
$$ | . X O X O O 7 .
$$ | . . . X X . X .
$$ | . . . . . . . .
$$ | . . . . . . . .
$$ +-----------------[/go]

I think White is more likely to block there here, and now the exchange looks well timed on the other side.

Click Here To Show Diagram Code

[go]$$c
$$ | . . . . . . . .
$$ | . . . . . . . .
$$ | . . X . . . . .
$$ | . O O . O . . .
$$ | . X X O . . . .
$$ | . X O X O O . .
$$ | . . . X X a X .
$$ | . . . . . . . .
$$ | . . . . . . . .
$$ +-----------------[/go]

I also have a question- how is this joseki? Black has a small corner and the cut at a seems to work.. even after black put one more move into the corner than white.

I took it from eidogo.com. Maybe it is not joseki, I don't know I was just playing around with the suggested moves from kogo dictionary.
Here is the sequence:

Click Here To Show Diagram Code

[go]$$c
$$ | . . . . . . . .
$$ | . . . . . . . .
$$ | . . 3 . . . . .
$$ | . 0 8 . 4 . . .
$$ | . 9 5 2 . . . .
$$ | . . 6 7 . . . .
$$ | . . . 1 . . . .
$$ | . . . . . . . .
$$ | . . . . . . . .
$$ +-----------------[/go]

It says that is considered joseki for long time but now it is considered inferior for white. So if is the reason why it is not joseki, the result should be favorable for black. I have no idea why that is the case.

But anyway my question was not related to whether it is joseki or not. Just take the position as it is given.

_________________
If you say no, Elwood and I will come here for breakfast, lunch, and dinner every day of the week.

ah, thank you entropi. I'm going to go somewhat offtopic for a moment, please forgive me. For anyone who's interested about this position, it's the reason why black can't connect underneath after white plays 4 (and it is inferior for black). After black adds a move in the corner to swallow 6 up, I believe the right move for w is actually this a. So I'd say that if white does not play there, black should do so immediately- but this doesn't take into acct the e4-e3 and f4-e5 exchanges.

Click Here To Show Diagram Code

[go]$$c
$$ | . . . . . . . .
$$ | . . . . . . . .
$$ | . . 3 a . . . .
$$ | . 0 8 . 4 . . .
$$ | . 9 5 2 . . . .
$$ | . . 6 7 . . . .
$$ | . . . 1 . . . .
$$ | . . . . . . . .
$$ | . . . . . . . .
$$ +-----------------[/go]

edit: I also disagree that peeping at a here reduces the aji of the other peep. I agree with entropi, and don't believe there's much aji there anyway because of the f4 stone. However black may wish to save the peep as a ko threat - that's certainly true. I'd play it immediately but I tend to do aji keshi things like that..

Checking it again, I see that eidogo says for "Black 5 attempts to connect underneath, to no avail", which probably means that it is indeed not suggested as joseki. But why is it then suggested at all, and with the continuation which seems to be even more wrong

Anyway, thanks for the reply. Such positions occur frequently in real games where I tend to play moves like "a" but cannot be sure whether it reduces more aji than it creates.

_________________
If you say no, Elwood and I will come here for breakfast, lunch, and dinner every day of the week.

I think this is a good time to not listen to eidogo. Maybe it is right that this variation is now considered inferior, but if so it's by a small amount only relevant to professionals - and will certainly still have times where it is the most appropriate move.

In this case, regardless of white 4, black has made a mistake here - the sequence seems like no joseki! If you can't connect, don't try, you'll only hurt one of your stones unnecessarily. Black has forgotten this, and settled for a small gote corner.

I feel it's sente, w must play d7. Otherwise black will play there and white's shape will be pretty heavy

Well, okay, gote or with massive followup, as white can still press black down for free later.

Pros play something similar: http://dailyjoseki.com/browse/bxkwvubuf ... mbuewuzbxg

In the analogous position, they played the peep right away both times. (incidentally, the display of that position seems a little buggy on my site... )

They don't leave behind the cut Shaddy mentions, I don't know why kogo's would show that.

_________________
That which can be destroyed by the truth should be.
--
My (sadly neglected, but not forgotten) project: http://dailyjoseki.com

In fact it's not kogo but eidogo which shows it.

eidogo shows sometimes also bad variations but the explanations are not always clear. In this case, it says "Black 5 attempts to connect underneath, to no avail". Probably for the guy who wrote this, it is so obvious that Black 5 cannot be joseki, that he just mentions it with "..., to no avail". Of course would be a surprising move because it obviously cannot connect after , but eidogo does not explicitly say that it is not joseki. I mean without any prejudice, for someone who hasn't seen it before, it could also be an option for black to give up the pincer stone like that.

But the further mistakes in the sequence (e.g. at the final position leaving a cutting point at a) are really inexplicable.

Anyway, moral of the story: be very careful when using eidogo.

_________________
If you say no, Elwood and I will come here for breakfast, lunch, and dinner every day of the week.