Alex Weldon: For some reason, the chapter on creating two weak groups still has me tearing my hair when it comes to finding examples (since most players who make the mistake make it so frequently that their games are too ridiculous to talk about correct play). Here's another one I'm thinking of using now, but I have a few questions and would like to poll the audience again.
dia. : So here's the initial position. Black plays , so now it's White's turn. I'd say the game looks better for Black, mainly because is bad shape, but it isn't hopeless yet, in my opinion. Here are the moves that followed in the actual game.
dia. : My stance, in the book, is that is fine as a peep (maybe the timing is wrong, but that's the kind of thing I need to teach myself, not others... way too advanced for the players I'm aiming at). is questionable, since Black has ways of counterattacking, but makes it into an effective probe, since Black now owes a move here. and are the kind of mistake I'm cautioning against, however. Although they do divide Black into two weak groups (three, counting the one on the left), they also create a new weak White group, while also leaving the corner weak. Both players now have three groups that are not clearly alive, but Black's are, overall, stronger than White's, so White will probably get a bad result from this fight.
Instead, I suggest that White should reinforce either the corner, or his weak group to the left, while threatening to run out with . If Black then plays at a to fix the problem, White can reinforce the other side as well.
However, there's a question of move order. I had three ideas, and I'll present them in chronological order.
dnerra: In my view, is the mistake, creating a second weak group. is a questionable move, but after that I think and are just following through with the original plan of . Of course it is a difficult fight, but not one without chances for white; changing horses in mid of the fight and abandoning is inconsequent, and admits that was a bad move. It is really a matter of style, but I always recommend players to follow through with their plans, instead of accepting a bad result.
dia. : Originally, I was going to suggest playing , inducing Black to defend at so that White could then move out at . I suggested instead of a low extension because it has more influence on the central fighting, and instead of a faster way of moving out because of the aji of Black a.
However, it's too optimistic, I think, to imagine that Black will simply play . The White group is weak enough that Black can attack first and go back to defend later if necessary.
dia. [4: I thought about simply reversing the move order. If would be enough to induce , then White could go back to without risking a counterattack. Furthermore, now that Black's top side group is secure, could be played low, so as not to leave an open skirt if Black gets to play first on the right side.
However, might be a little too far away to force . Black might instead make a double kakari in the top right and try to deal with that way.
dia. : here would be much more likely to get in response. It isn't as good as the diagonal move, since it ends up closer to the strong Black group and further from the weak Black group, but getting in response to still gains more than is lost by the / exchange. Here, you'd probably want to play high again, to help a little more and prevent a leaning attack. If Black would counter-attack with a double kakari in the previous diagram instead of playing , maybe this is better.
So, this is kind of a vague, open-ended question. I just want to hear what some other people think. Corner first, or the middle group? If the middle group is more urgent (I'm pretty sure it is), is the diagonal threatening enough, or does White have to settle for the jump in order to force a defense? Is forcing Black to defend immediately even necessary? Maybe I'm wrong and it's aji keshi.
Rich (~5k): I think the middle group is urgent; I don't think white can permit a black play around , can she? It seems to me the connection around the marked stones is so weak that the top white group is either dead or will have to run so hard that black will all but win by chasing it. Personally, I like the third option, possibly with a kikashi around 'a' before playing .
dia. : tderz: (3d) I support Rich's view that an early attack at is globally so enjoayable. For the same reason White defended (around) there in diagrams 3, 4 and 5. Going back one step in the argumentational chain, it makes in dia.  so unreasonable (there you have your good example for creating 2 groups). After , black does not seem to be able to attack with in this dia. (6), so he should defend, but why with the kosumitsuke (in dia. )? This only strengthens White (White could also tachi at a in dia.  = b here; locally this is a very bad exchange for Black). I would think of only playing in dia , leaving out the - exchange.
dia. : tderz: If White defends now with a, Black can play b (hope no aji left) or c equalling the second idea in dia. .
dia. : tderz: Could one start more efficiently and reply to first with ? Let White chose now between e, Bf, Wg, therewith inducing Bk - and White h, whereby she must watch her weakness i.
Black would make it to complicated for himself, creating own weaknesses. If Black played -Bf, he should be able to play n as well - or leave it all together.
BTW, why did Black reply to in dia.  the way he did?
dia. : a and b are miai - who is interested in connecting underneath on the 1st line with d? (Be)
White has effectively weakened herself (-- is stronger than in dia  vs. the white stones in the direction c). White must run away with c now.
Tewari: Any white invasion at f = in dia.  seems now even more obviously premature (no aji around left, B attacks at c).
Andy: Difficult for white. Whatever white was trying to achieve in the upper left has gone wrong and white needs to act quickly to stabilize her group, since white can't get sufficient compensation by sacrificing it. I would start with to undermine black's weak group on the left, then try for some immediate central expansion, treating either or as light when black exploits white's bad shape (). This looks like a bad shape/blown joseki lesson rather than a two-weak-groups lesson to me.
Alex Weldon: Thank you everyone for your comments. Some responses, in no particular order:
- To those who think that (in diag. 1) in response to is bad, I agree. I also say so above, and in the draft of my book.
- To tderz, who suggests simply using (in diag. 1) as my example of two weak groups, I would argue that it is the running out with and that creates weak groups. , although bad in this case because Black can counterattack more strongly than just playing the kosumi-tsuke or contact on top, is the sort of move that's often used as a sacrifice. If that was White's plan, would still be a mistake, but a different level of mistake than I'm talking about.
- To those who think (in diag. 1) should be answered differently. Good point. I'll make mention of it, but that doesn't make useless. It's still a kind of probe, creating endgame aji if Black answers the way you suggest. I agree that it's a bad move, though, since answering on top does remove a potential forcing move for White.( in Andy's diagram).
- To everyone who suggests the peep of in Andy's diagram. I thought about it, but it seemed dangerous to me.
I thought Black could resist like this, but upon looking at it more carefully, it seems to me that it's likely to result in a capturing race in the corner that White can win, so Black can't play this way.
Bill: I think is not so good. White can reply at a, and I think Black has nothing better than B b - W c
Alex Weldon: You are correct, of course. This is typical of me: getting so absorbed in examining more complicated lines of play that I overlook the obvious.
JoelR: More generally, what is the problem with the shape? I don't see a way in which it can be cut, e.g., at . I'll grant it's slow for moving out, but it's faster than a bamboo shape here, and I don't see anything faster and as solid.
Bill: This diagram illustrates White's shape problem. After - , White needs to make an empty triangle with .
- In general, all of these comments illustrate the problem I've been having with this book, namely that it's rare for kyu players to make one mistake in a sequence of good moves. Usually, every move is wrong, so I end up saying " is bad, because blah blah, but is also bad, and makes reasonable. is another mistake, but still not the one we're talking about. is questionable. Ah, now , this is the type of mistake I'm trying to illustrate." I don't want to cut out all the moves except the one in question, because seeing the flow of play helps to understand the mentality that led to the mistake. To talk about why all the other moves are wrong is kind of distracting for the reader and confuses the issue, but I also don't want to imply that the other moves are okay, when they aren't. I already spend at least five times as much time searching for good examples as I do analysing and writing, so I'm beginning to wonder whether this book is as good an idea as it seemed when I first came up with it.
Andrew Grant: Is it really necessary to find examples from real weak players' games? I'd be tempted to "cheat" here and take a position from a professional game where the pro played correctly but a weak amateur would most likely make the sort of mistake you want to illustrate. Then you could simply replace the pro move with the instructive blunder without having to worry about the moves leading up to it being wrong.
Alex Weldon: Not a bad idea... although it loses a bit of its legitimacy that way. It's one thing for me to say "oh yeah, this is the kind of mistake 5 kyus make," but unless I back it up with real life example, people will surely protest "bah! I would never play that!"
Maybe I could do something in between. Host a series of pro game reviews on KGS, and have the kyu players attempt to predict the moves.
Gronk: I've seen the following type of thing written in go books: "While there are some questionable moves in the earlier part of this game, Black "a" illustrates the theme of this chapter." That is, simply acknowledge that play has not been perfect without going into details and leading the reader to the move that illustrates your point is good enough. Anyway, why is it important to show moves preceding what you want to discuss? You're not going to show the whole game are you? Just rule it out of bounds to criticize moves prior to the point of discussion.