When I can't be sure of uninterrupted play, I will set up a board with Crazy Stone on Android (the newer version) and always run my games through its analysis tool afterwards looking for large discrepancies. This is one such discrepancy.

White to play.

Click Here To Show Diagram Code

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

This is one of those things I've read about in go books, that if you play at b and black kills the corner, black's move would take away 4-5 points from white and gain about 13 points for himself, but it would also be gote, which would allow w another move. Seems those two moves could easily be worth more than the 18 pts in the corner, so black might be disinclined to take the corner right away, thus white still might get a chance to save it. Nonetheless, I share your trepidation.

_________________
Patience, grasshopper.

"a" is a large yose. It gains 10 points. Compare that with the first moves of the game, which gain about 14-15 points. Is "b" worth at least as much as early plays? IMO, yes. It enlarges White's potential while reducing Black's. It is hard to put a point value on such plays, but it may well be in the 14-17 point range. (Not that a point value means much, but we can certainly give one to "a".) Given the choice, then, "a" is like a DDK move.

Edit: That'll teach me to post at 4:00 a.m. I originally miscalculated "a", assuming that White has a sente follow-up. There is no sente follow-up for White. I overlooked the obvious damezumari.

Click Here To Show Diagram Code

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

After White has to continue with . That means the gains only 10 points. It loses something like 5 points to par, most of the komi in one self-inflicted blow.

_________________
The Adkins Principle:
At some point, doesn't thinking have to go on?
— Winona Adkins

Visualize whirled peas.

Everything with love. Stay safe.

IMO reducing Black's potential on the bottom is worth at least as much as increasing White's potential in the center.

_________________
The Adkins Principle:
At some point, doesn't thinking have to go on?
— Winona Adkins

Visualize whirled peas.

Everything with love. Stay safe.

I'm not a very good player (6k KGS / 11k EGF), but I have difficulties to tell what is better : a or b.

a is worth around 22 points double gote, but it has no potential at all. The corner is closed, "Dead for development". You take the points, then the stones stop working.
It means these 22 points are not "interesting points".

I don't know how much b is worth, but it has a lot of potential because of the weakness of Black in E7. The sequence may be White hane in G8, Black blocks in G7, White sacrifices a stone in F7 atari, Black connects in E7, White can now double hane in H7 atari, Black extends in G6, White makes the double tiger mouth in H9, and has influence both toward the top and the right side.

I don't get it. Why would anybody suggest “a”? Shouldn’t “a” rather be at A2 than B1? B1 looks totally useless to me (being ~10k) because both follow-ups would be self-atari for Black.



(Thx, Marcel!)

_________________
“The only difference between me and a madman is that I’m not mad.” — Salvador Dali ★ Play a slooooow correspondence game with me on OGS?

Without thinking about calculations, 'b' feels much bigger.

D5 is strong with or without capturing the white stones, so capturing is basically irrelevant right now.

Later in the endgame it will be pretty big, but right now, killing or living with that group doesn't matter much.

_________________
be immersed

Objectively speaking, I agree B is almost certainly bigger. But in a game against a human there are added psychological factors. I'm guessing black's last move was C1, thinking it was sente. Maybe he then planned to play in the urgent centre. So if you tenuki and let him capture (and he might make the mistake of playing b1 not a2, a very real possibility for the level of player likely to play c1) you get to thumb your nose at him and gain a psychological victory. This could cause him to get upset and play worse moves later.

This seems like one of those examples that are the bane of all early go students. This move asks you to weigh a sizable, concrete gain in "a" against the future utility of "b" in gaining even more points. It's easy to see the value of "a", but seeing the value of "b" requires the experience to know what one can eventually do with "b". How exactly "b" would be used is much less clear. The stronger players here can probably look at "b" and immediately think of a number of scenarios in which "b" would be a significant value, but for those of us with less experience, playing "b" feels like more of an act of faith.

I looked at your post and immediately answered "b" (and I would have played "b"). However, I came to this conclusion only because I anticipated that this is the kind of move that stronger players typically make. I can see that the hane starts to limit the development of the black framework on the bottom and expands white's upwards influence on the left. However, I can't immediately give you a single example of how play might continue so that white would gain enough from the move to offset the loss in the corner.

So, what do we do? First, given that the strongest players who have responded agree with Crazy Stone, I'd accept that Crazy Stone is right and that "b" is the better move. Tuck that into your pocket. When you see similar instances occur in your games, try playing "b" to see what you can do with it. You'll probably misplay it a few times. It may even cost you a few games, but eventually, you'll start to see the value of the move.

More broadly, I resolve this -- somewhat unsatisfactorily I'll admit -- by using a rule of thumb like the one that Kirby mentioned. In general in the fuseki, I consider defending stones if their loss: (1.) threatens the life of a group or (2.) allows my opponent to box the group in (creating a wall for example). Otherwise, I look for what seems to be the biggest move available elsewhere. I see this as a crutch. Without knowing their value ex ante, it gets me to moves like "b" so that I can develop an appreciation for them.

EDIT: Drew, apologies if this seems obvious. I was mislead by your "infant" rank . Looking at your other posts, I'm guessing my comments are not useful. However, I'm leaving them up in the hopes that they might be useful for newer players.

How about this?

Click Here To Show Diagram Code

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

Of course, 'a' is worth less than in the original diagram, but I think it's the same concept.

_________________
be immersed

And as another (harder) example, how about this position from a recent BIBA league game of mine (I was black). I decided to play 1 to kill the upper right corner. This is a pure endgame move as it has no effect on the rest of the board and the surrounding black group is strong*. It is quite a few points (about 35), but is it more than approaching the lower left? I thought it was maybe a mistake but as I thought my opponent liked points I would take the cash and fight it out later. This position differs from the original one in that the cash move is bigger, and there is no single urgent point on the rest of the board, but several very large ones (approach corner, lower side, left side, and maybe something to do with my floating yet light middle stones). I'd be interested in other's opinions!

Click Here To Show Diagram Code

[go]$$B
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . X . 1 . |
$$ | . . . . O . O O . X . . X O . X O . . |
$$ | . . . O . . X . X , . X . . . X O . . |
$$ | . . . . . . X . X O O . . O . X X O . |
$$ | . . . . . . . O O X . O . . . X O O . |
$$ | . . . . . . . . . X . O X . X . X O . |
$$ | . . . . . . . . O O . O . . . X . X . |
$$ | . . . . . . . . . X . . . . . O X . . |
$$ | . . . , . . . . . , . O . . . , . . . |
$$ | . . . . . . . . . X . . . . . . . . . |
$$ | . . . . . . . . . . . O . . . . . . . |
$$ | . . . . . . . . . X . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . , . . . . . , . . . . . , X . . |
$$ | . . . O . . . . . . . . . X . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------[/go]

*Actually that black group later died due to some awful play from me: when white threatened to live as a ko threat I answered the wrong way and then he lived in a ko, I made a not so big ko threat, and then he killed the surrounding double ponnuki group! Oh dear. See below for a chuckle at my expense:

It is quite rare for a Tennozan move in the region of B to be bad. I would expect stronger players to look at such moves first and to look on them favourably. But I don't think this is a simple case.

If White plays B it leaves a cut behind it. That cut should never cause Black any problems here, but it can cause White problems, especially if Black captures the corner, because the cut and the lone Black stone on the left create powerful aji. If White makes a move different from B but in the same area (e.g. the nobi or jump) that looks heavy, and if he adds a stone on the left side somewhere he looks overconcentrated (as well as taking gote).

B only really works if it's followed through locally (but how? - and in sente?), or if Black does not respond in the corner.

The fact that B is a tad unsatisfactory for White, suggests to me (as does Black's overconcentration) that there have been errors by both sides in the play so far, so subsequent moves are likely to be blighted by that. But going with what we have, since B for White is imperfect and capturing the corner for Black has the effect of removing much of his own overconcentration, I think a strong case can be made for A, preventing Black from taking the corner A and White thus facing the risk of Black making use of the aji on the left side. If that happened, White would end up with overconcentration, cancelling out Black's - but Black would have more points in the bag already.

Or the moves may be of roughly equal value and style supervenes.

I'm not sure whether CrazyStone's choice of B has to be given great weight. It may just reflect the programmer's choice, or it may be that the strength of programs mostly lies in not making frequent silly tactical mistakes (as humans do) rather than in big strategic ideas.

Hane at 'b' does not seem unsatisfactory at all to me. I get a little excited just thinking about playing it.

Yeah, there is a cut, but white is strong everywhere (the stone at C8 is as good as captured).

I'd go so far as to say that 'b' is the only move, in my book.

_________________
be immersed

This appears to be a 2 stone game, and Black does appear to be overconcentrated. Without going into Black's aji if he takes the corner, let's see how that might affect Black's overconcentration.

First, let's look at the situation if White takes the corner.

Click Here To Show Diagram Code

[go]$$Wc White takes the corner
$$ +---------------------------------------+
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . X . . . . . , . . . . . X . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . O . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . , . . . . . , . . . . . , . . . |
$$ | . . . O O O 4 . . . . . . . . . . . . |
$$ | . . X O X X . . . . . . . . . . . . . |
$$ | . O O X . . . . . . . . . . . . . . . |
$$ | O . O X . . . . . . . . . . . . . . . |
$$ | . O X X . . . . . . . . . . . . . . . |
$$ | 3 X O X . . . . . , . . . . . O . . . |
$$ | . X O X X O . X . . . . . . . . . . . |
$$ | . O O O X . . . . . . . . . . . . . . |
$$ | . 1 X X 2 . . . . . . . . . . . . . . |
$$ +---------------------------------------+[/go]

I expect that White will reply to , but let's leave that discussion for later and do some tewari in the corner.

Click Here To Show Diagram Code

[go]$$Wc Tewari
$$ +---------------------------------------+
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . X . . . . . , . . . . . X . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . O . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . , . . . . . , . . . . . , . . . |
$$ | . . . O O O X . . . . . . . . . . . . |
$$ | . . X O X X . . . . . . . . . . . . . |
$$ | . O O X . . . . . . . . . . . . . . . |
$$ | w b O X . . . . . . . . . . . . . . . |
$$ | . O X X . . . . . . . . . . . . . . . |
$$ | w b O X . . . . . , . . . . . O . . . |
$$ | . B O X X O . X . . . . . . . . . . . |
$$ | . O O O X . . . . . . . . . . . . . . |
$$ | . O X X X . . . . . . . . . . . . . . |
$$ +---------------------------------------+[/go]

The w's and b's represent Black and White stones that are paired. Black has made a wasted play in the corner, represented by the stone. The Black C-08 stone is pretty much a goner, but the White F-03 stone is in bad health, as well.

Now let's look at the case where Black takes the corner.

Click Here To Show Diagram Code

[go]$$Wc Black takes the corner
$$ +---------------------------------------+
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . X . . . . . , . . . . . X . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . O . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . , . . . . . , . . . . . , . . . |
$$ | . . . O O O . . . . . . . . . . . . . |
$$ | . . X O X X 1 . . . . . . . . . . . . |
$$ | . O O X . . . . . . . . . . . . . . . |
$$ | O . O X . . . . . . . . . . . . . . . |
$$ | b O X X . . . . . . . . . . . . . . . |
$$ | 3 X O X . . . . . , . . . . . O . . . |
$$ | a X O X X O . X . . . . . . . . . . . |
$$ | 2 O O O X . . . . . . . . . . . . . . |
$$ | . 4 X X . . . . . . . . . . . . . . . |
$$ +---------------------------------------+[/go]

Perhaps Black will reply to before taking the corner, but we leave that discussion until later. Before scoring we assume that Black will play at "a" and White will play at "b". Let's do some tewari in this corner.

Click Here To Show Diagram Code

[go]$$Wc Black takes the corner
$$ +---------------------------------------+
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . X . . . . . , . . . . . X . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . O . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . , . . . . . , . . . . . , . . . |
$$ | . . . O O O . . . . . . . . . . . . . |
$$ | . . B O # # O . . . . . . . . . . . . |
$$ | . O O X . . . . . . . . . . . . . . . |
$$ | W b O X . . . . . . . . . . . . . . . |
$$ | O O X X . . . . . . . . . . . . . . . |
$$ | O X w # . . . . . , . . . . . O . . . |
$$ | X X w # X W . B . . . . . . . . . . . |
$$ | b w w w B . . . . . . . . . . . . . . |
$$ | . b b b . . . . . . . . . . . . . . . |
$$ +---------------------------------------+[/go]

As before, the b's and w's represent paired Black and White stones. Note that we cannot pair the stone on A-06 with the captured Black stone at B-06 because of the presence of the stone on C-08. Black could roll up the White stones there, starting with an atari at A-06. That might change later, but we don't know. So we have paired that Black stone with one of the captured White stones. If anything, Black's corner is less efficient in this diagram, with one or two wasted stones, represented by the stones on D-03 and D-04. In addition, because of the hane in the center, the stones on E-08 and F-08 are poorly placed. Whatever we may say about the aji on both sides, taking the corner has not alleviated Black's overconcentration.

Edit: Widening our scope a little beyond the corner, if we pair on F-03 with on E-02, Black's pincer (I assume), on H-03, is much too close to the Black strength in the corner. Taking the corner has made Black's overconcentration even worse.

_________________
The Adkins Principle:
At some point, doesn't thinking have to go on?
— Winona Adkins

Visualize whirled peas.

Everything with love. Stay safe.

There's always a danger that tewari can be too local. If Black takes the corner he doesn't necessarily have to answer White G7 or moves around K3. If White takes the corner, I think White would have to think very hard before not answering these moves, as they would create fantastic ijime for White and it is that that would make Black's overconcentration truly horrible - i.e. Black alleviates the overconcentrating ijime by prophylaxis as he can then ignore it.

And the more I look at the aji of C11 after Black's corner capture (and knowing how pros always seem to wrest more from aji than I ever dream of) the more I think White cannot afford to be complacent about a future cut at G9. At the very least, I suspect, White is going to have to contrive to play an extra move on the left side.

Indeed. But it can give us a local evaluation. If you can do a tewari on the left side as a whole, be my guest.



To be sure, if Black takes the corner he may be able to gain something from sacrificing the Black stone on C-08. (Not that this Black is capable of such a sacrifice, however. ) But it would have to be enough to overcome the extra stone or two that he has wasted by taking the corner. That is unlikely, even with very good play. (Not counting on Black to play better than White, OC. ) Besides, since White has the move, White might play something like the one space jump to E-14, if the left side is a concern.

_________________
The Adkins Principle:
At some point, doesn't thinking have to go on?
— Winona Adkins

Visualize whirled peas.

Everything with love. Stay safe.

The discussion on the aji(?) around C8 reminds me a little bit of the discussion on what is considered "thick" from another thread.

It is a good point that professionals, compared to amateurs, may very well be better at exploiting aji, and also in showing that positions that are seen to be thick are not actually thick.

For this reason, yes, we must question our judgment as amateurs when we think something is thick. We should question our judgment when we think that there is little aji to exploit in a position. After all, we could be wrong- we are only amateurs.

That being said, this does not mean that our judgment is always wrong. Just because pros are good at exploiting aji, it does not mean that we always underestimate the aji that's present.

We cannot base decisions off of this.

Take another example - pros can sometimes kill a group that I think is alive. So I should be careful and avoid being killed. I should be skeptical of my judgement when I believe something is alive.

But it doesn't mean I'm always dead. Sometimes, a shape is just alive.

Similarly, sometimes the aji in a position is not a big deal.

I feel that this is the case in the current discussion about the stone on the left.

Sure, maybe black has a sente move around the area. But that's nothing compared to the value of the hane in the original post. White is essentially alive, and has very little to fear.

Maybe a pro can make use of something I'm not seeing on the left. Maybe not.

But I can't cower in fear just because there's a chance a pro has a different assessment than me.

I'd just play the hane. It really seems huge.

_________________
be immersed

While we're at it, how strong is Crazy Stone on Android?

_________________
The Adkins Principle:
At some point, doesn't thinking have to go on?
— Winona Adkins

Visualize whirled peas.

Everything with love. Stay safe.

Something like KGS 5d, I think. Might depend on your phone's hardware.

_________________
be immersed

Oh, I'd play it, too. But this is a discussion, not a bull ring. It seems more interesting to try to tease out whether we have blind spots, to learn how other people (including pros) think, to open up new horizons, to take the scenic route. Even if you end up with the same decision, you might pick up some useful insights for future positions.