We've probably all learned about sector lines. They are my primary concept when reducing a territorial framework aka sphere of influence aka moyo (not all pure synonyms, as John F. may object).

Here's an example

Click Here To Show Diagram Code

[go]$$B Moves 33 to 33
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . O O O . O b . . . . . . . . . . . . |
$$ | . O X X X a . . . , . . . . . X . . . |
$$ | . X . . . C . . . . . . . . . . . . . |
$$ | . X O . . C . . . . . . . . . . X . . |
$$ | . . . . . C . . . . . . . . . . . . . |
$$ | . . X . . C . . . . . . . . . . . . . |
$$ | . . . . . C . . . . . . . . . . . . . |
$$ | . . . , . C . . . , . . . . . , . . . |
$$ | . . . . . . C . . . . . . . . . . . . |
$$ | . . . . . . C . . . . . . . . . . . . |
$$ | . . . . . . C . . . . . . . . . . . . |
$$ | . . . O . . C . . . . . . . . . O . . |
$$ | . # X X . . C . . . . . . . . . . . . |
$$ | . X O X . . C . . , . . . . . O . . . |
$$ | . O O O X X X . . . . . . . . . . . . |
$$ | . . O . O O . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------[/go]

Black has just played a premature gote endgame and now White can freely tackle the moyo (or play elsewhere). Factoring in the a-b exchange, the sector line looks something like this.

Click Here To Show Diagram Code

[go]$$W reduce
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . O O O . O . . . . . . . . . . . . . |
$$ | . O X X X . . . . , . . . . . X . . . |
$$ | . X . . . . . . . . . . . . . . . . . |
$$ | . X O . . . . . . . . . . . . . X . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . X . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . , . . . . . , . . . |
$$ | . . . 2 . 1 . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . 5 . |
$$ | . . . . . . . . . . . . . . . 4 . . . |
$$ | . . . W . . 3 . . . . . . . . . O . . |
$$ | . X X X . . . . . . . . . . . . . . . |
$$ | . X O X . . . . . , . . . . . O . . . |
$$ | . O O O X X X . . . . . . . . . . . . |
$$ | . . O . O O . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------[/go]

KataGo endorses that is to say, it features among its candidate moves and doesn't drop too many points with respect to the "blue move". It pictures and then Black plays elsewhere. In this no komi game White is just a little behind. The reduction has happened on the sector line but we need to also note how takes the marked stone into account. That is even true for . If is not played there, a white move on the same spot would create a good relationship for all White's stones in that area.

Click Here To Show Diagram Code

[go]$$W reduce
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . O O O . O . . . . . . . . . . . . . |
$$ | . O X X X . . . . , . . . . . X . . . |
$$ | . X . . . . . . . . . . . . . . . . . |
$$ | . X @ . . . . . . . . . . . . . X . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . X 4 a . . . . . . . . . . . . . . |
$$ | . . . 3 5 . . . . . . . . . . . . . . |
$$ | . . . . . . . . . , . . . . . , . . . |
$$ | . . . 1 . 2 . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . W . . . . . . . . . . . . O . . |
$$ | . X X X . . . . . . . . . . . . . . . |
$$ | . X O X . . . . . , . . . . . O . . . |
$$ | . O O O X X X . . . . . . . . . . . . |
$$ | . . O . O O . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------[/go]

In fact, KataGo's blue move is here. That is because if Black now prevents the good shape and attacks from above, White can follow up with the shoulder hit at . Next 4 and 5 are natural and now a White turn at A would again take advantage of the marked stone on the other side.

So in this case, KataGo wants to go in "deep" at the 4th line, as it appears to make better use of White's existing stones and their aji.

Sector line thinking takes into account the enemy's stones. To complete the analysis, one must take into account friendly stones in that sphere of influence and optimize their relationship.

It's not that I object, Dieter. It's simply that I despair! I think it holds you back. A territorial framework (jimoyo) is about territory. A sphere of influence is about influence. A moyo is just a framework that can go either way. You need to know that in order to decide on your overall strategy, otherwise you end up making Putin's mistake. If you treat men, women and transgenders and just 'people' all the time, without taking account of each category's attributes and needs, you'll end up in hot water eventually.

But a bigger problem, it seems to me, is that you have an imperfect understanding of sector lines, presumably derived from Wilcox, a weak amateur. The concept was known before him among professionals. I first came across it in a work by Miyamoto. I can't remember now what he called it, but I think it was something simple like dividing lines. Still groping in my memory, the important difference is that you don't automatically take the tips of the crab's claws as the end points of a sector. Instead, you view the shape from the point of view of the person making a 'sector' and, if you decide that you want to make that sector your territory, you draw an imaginary line within it, on which you can play a single move and can then assume you have more or less secured that territory. If you can't do that in a single move, you have either mis-drawn the sector line or your sector is still too undefined - it is still just a moyo. If you decide that influence is your main goal, then the tips of the claws acquire more significance, of course, because they extend your reach.

In the present position, I would suggest that with so many stones invested by Black, territory is his main goal, and so the sector line should be drawn from something like C16 to G4 because the single move that would stake a reasonable claim to all the left side territory would be G4.

Once you know that, you can predict that the correct play for White (in terms of sector lines) is to encroach at G4.

Of course, Black may decide not to go yet for either territory or influence. Instead, he may try to extend his moyo (which would naturally change prospective sector lines), but that is a decision you can only make by considering the rest of the board or the state of the game.

My sense is that the Japanese pros don't normally think of or talk about sector lines because they are too low level. First they decide on their higher strategy (territory or influence or keep the ball rolling). If they then decide on "territory", the next step in their mind is not "where is the sector line" but "how to I play a kakoi" (surrounding move). The concept of sector line then only comes in as a post facto way of explaining the choice of kakoi move.

That, at least, is how I have remembered it all.

The (old) Chinese took a rather different approach. But group tax maybe plays too large a part in that to allow a fair comparison with the Japanese way of thinking.

Thanks for the input. It's a little odd though that, when I'm correcting a superficial concept inherited from Wilcox, you point out I'm inheriting a superficial concept from Wilcox.

The most useful element in your reply, for me that is and my desparately poor understanding of Go, is that one should understand if Black (in this case) can turn his territorial framework into territory with one move. If that is the case, White should probably suffice with reducing around the spot where Black would do so. If Black couldn't, White can be more ambitious in the area. In the past I would have used "invade" for such a deeper entry but since studying with KataGo I have understood that real effective invasions not merely try living in the opponent's sphere of influence but rather dislodge it altogether and aim at the weaknesses of the surrounding positions. Friendly stones can help in that regard, which is the aji they provide.

Other than those insights, my mental framework remains very much the same. A sphere of influence (not just "influence" but an area that is affected by at least two positions of the same color, often walls of some sort) and a territorial framework are more or less synonyms, with the latter probably aiming more explicitly at territory, the former more aiming at taking any kind of profit should enemy stones enter the area. Both concepts - in my mind - can be translations of "moyo".

Then there's Takemiya's kind of moyo, which has influence radiating from many directions, often all 4, and where the invader can only hope to live, not to affect the surrounding position. This means the owner of the moyo (often Black) can think of each local piece of influence as thickness, even if there are defects in it or it's lacking a base, because all the other pieces reinforce it on a larger scale.

In summary, here are the concepts I can use:

- a moyo (territorial framework), which can be turned into territory with 1 move, so that it makes sense to reduce it and the reduction is urgent
- a moyo (sphere of influence) which can't be turned into territory with 1 move, so that it can probably be entered more ambitiously and it is not urgent
- an invasion of a moyo which has the potential of weakening the surrounding positions and where simply living is probably not enough
- an invasion of a moyo which can't do that and so will have to live in order to be successful
- the special case of Takemiya style moyos

I don't know if moyo or other terms describe any of these or whether moyo describes all of these. I'm not expecting such miracles. In the past I have been happy to add concepts like local thickness and global thickness to my portfolio of concepts, borrowing from your atsumi/atsusa reports. Even if I fail to fully get aligned with your teachings, I do learn from it in my idiosynchratic way.

I would never try to convince a Dutch speaker of anything by mere argument, but I'll make some responses for you to mull over at your leisure.

1. Why do the Japanese pros bother to distinguish these terms?

2. (Expanding on what I said above) A jimoyo is literally a territorial framework. A moyo is just a framework. A jimyo is one where "an area territory cannot be said to be established yet, but it is not a mere moyo; the probability of it turning into territory is rather high" (quoting from a Japanese go dictionary; my emphasis).

3.

Agreed he was special, but it's the exception that proves the rule. If you want to keep him in the framework (so to speak) covered by the ordinary rules, you can also consider his styles in other ways. The obvious one is that he made omoyos (big-scale moyos) which have the property that they can fission off and form multiple moyos of (eventually) differing types. You can also turn this around and, based on the fact that Japanese normally doesn't distinguish singular and plural, say that we should talk about Takemiya moyos (plural) that just happen to be adjacent. Matthew Macfadyen's concept of virtual territory is especially useful in that regard.

4. I'm not disputing that one and the same position can, pending the next decisive move, superficially be interpreted as a territorial framework, a framework or a sphere of influence. But they are not synonymous. The choice of term depends on the strategic use to which the position is put. The strategy comes first, then the term.

5. There's a similar issue implied in your response:



To which I want to say, "Precisely." Western amateurs love to invade. They think of the tasty word and then are led by the nose by it. Somewhat stronger amateurs have learned to keep two words in mind: "invade" and "reduce." So, sometimes they invade, and sometimes they reduce. But in each case the word is still leading them by the nose. But take the word used in old Chinese: 侵 (qin). It can be used of an invasion, a reduction, a peep or an incursion along the edge, and other things. But (I postulate) in no case did Huang Longshi or the like ever think of any of these words specifically. At best he would thing of an overarching term: namely qin, which encompasses all these possibilities. The way I render it to use the word 'encroach'. Apart from the fact that it covers all the above possibilities, it is a rarish word in English and so does not have too many distracting associations.

Now if you look at the starting position above and, instead of saying yo yourself, "how do I invade" or "how do I reduce" or even "how do I play on the sector line", you say "how do I encroach," I think you will evolve a very different and richer mindset. The implication of your quote is that you have already done that to an extent. It's just that, instead of saying "how do I encroach", you are saying "what does katago do here". One of the things you've observed is that friendly stones can be a big help in these situations. Ideas stemming from encroaching will show exactly the same sort of thing. The beauty of using encroach as your high-level starter word, is that you don't even need to worry about whether an area id a framework or a sphere or a gefurtel. (Similarly, incidentally, if Black above thinks in higher-level terms of how do I stop the opponent encroaching, as distinct from how do I stop him from invading or reducing, he will end up with a richer palette of ideas.)

You can go further along the same route. You can ask yourself, how does katago's choice help my other groups in the other, remote areas of the board (and you will find that it does indeed so that). Alternatively, you can use the same concept dressed up in human terms: zhaoying (call & response). Either way, the idea is to think first at a higher strategic level. Strategy first, term second. Otherwise you end up with a 'special operation.'

What strikes me about the original position is not that black is about to play the last move that will make a large territory, it is that black has an outside that would dominate the game if it were perfect. Maybe it would also be one move away from being a large territory. However it is not perfect.

Example of what would be a perfect outside, adding purely reinforcing stones for black

Click Here To Show Diagram Code

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

The move shown as the blue move worried me at first (takes to long to settle when black attacks), my KataGo setup prefers a move that I liked more (see next diagram). It leaves more ways to escape which means it is harder to contain and that feels more powerful, but it is kind of the same thing and can get complicated. Anyway, it feels good to attack wall like Hayashi Kozo was teaching before AlphaGo.

Click Here To Show Diagram Code

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

I won't say it has nothing to do with "sector lines". When you attack a strong group you need to encroach on it and anticipate that it will not be weak (but maybe you get to push it around). In this case the easy connection to the closest group is interfered with and how would black have preferred to connect? Simple, playing on what would be the border of a developing territory, that is also know as the "sector line".

Thanks both.

I'll add "encroach" to my vocabulary. I knew the word's existence but it's one that I've probably never used in those domains of my life where I tend to speak or write English (work, Go, the Internet altogether ...). It does help getting beyond the (false?) dichotomy of invade or reduce.

Kvasir's convenient perfection of Black's position made me think of another concept I took from John: Go Seigen groups. I say "convenient" because Black got 2 free moves. Having Go Seigen groups is a specific kind of local and global thickness. The encroachment becomes almost irrelevant. I noticed this in some of the variations of this position: in exchange for letting his "territorial framework being reduced" Black (KataGo) was happy to turn both Black groups into efficient looking invulnerable groups and turn elsewhere. So if we (I) think of the result of a territorial fraemweork to be profitable for Black IF he kills the invader OR turns it into territory OR allows for small life inside in exchange for a thick outside wall that serves as a new prospect, there are clearly other, more subtle types of profit.

I'm using KataGo to improve because 1) it is strong 2) it is always there for me when I need it. Not because it is almighty or explanatory. I don't have immediate access to Japanese or other pros. Michael Redmond has been offering insights at amateur level with his YT channel. (There are not many pros who do this: female pro YeongWoo is another one. Then there's Baduk Doctor who seems to have realized streaming games is more popular than actually teaching - which shows the lazy side of the Go audience.)

For active understanding, the discussion we're having here is currently irreplacable. If the preponderance of KataGo arguments may irritate the more traditional, human knowledge oriented, or vice versa, I like to think of the debate as trying to get the best of both worlds.

I created https://senseis.xmp.net/?ShallowInvasion to cover the ideas brought up here. I will still work on it to do a better job at that - currently it mostly reflects the way I went into this discussion.

Those who like to study with AI may find the following tidbit of interest.

The background was that I noticed in the latest Go World that there seemed to be no mention of AI, despite pretty dense coverage of a hectic title-match scene recently. Out of curiosity, I decided to do a check of the whole magazine (273 pages). It was not rigorous and I may have may something, but my quick skim did seem to confirm that AI was noticeable by its absence - with one exception.

This was a new series by Shibano with his latest thoughts on AI. The way he approached this was to plot the absorption by pros of AI techniques.

He began with a "pre-absorption" game from April 2017. AlphaGo had already rocked the boat by then, but access to its games was still hard, so this seems a reasonable choice of starting date by Shibano. He chose a game of his with Sin Chin-seo to illustrate the old thinking.

The next phase he identifies is "the transition period to introduction of AI techniques." His example there shows a case of attacking a wall (i.e. not treating the wall as thickness, he says) as part of the new thinking), something that has been attributed here to Hayashi Kozo (to my amusement: he is an arch-traditionalist when it comes to music; he plays the shamisen). Shibano's example in this case is dated November 2017. He himself points out that this change was apparent within 6 months.

His third example is dated April 2018 and is described as "complete absorption" of AI techniques by pros. He seems to mean other pros, because he again states his claim that he himself doesn't really study AI (as he said in The First Teenage Meijin). But he is regularly exposed to it, especially in his many games online. He has reached the stage where, "Even in my own games the influence of AI has become clearly apparent." In the example given, one of his own games, he gives five examples where people more AI-savvy than him would even then have played in a new way.

He adds that this "speed of absorption of AI techniques has been remarkable" and he comments that it seems as if pros are taking new stuff on board at a rate that can measured in "units of days". That is the bit that really caught my eye: amateurs here are talking about absorbing AI in units of never or years or months.

Exactly what he feels has been completely absorbed is not made clear yet, but the first hints seem to include (to my delight) the old Chinese idea of call & response, and also the bemusing idea of using a solid connection on the side to inhibit the opponent from playing the Direct 3-3. I stress the "seem." The following episodes may be Shibano's best stuff yet.

Thanks for the story, John. As a side note, if I had Shibano whispering stuff in my head all the time, I would probably not use much of KataGo either.

I don’t have much to add to this discussion at the moment, but I want to offer a word of encouragement: I really appreciate this sort of conversation, and I think it adds a lot to the site.

It might sound negative but I don't think concepts such as "shallow invasion" are that useful.

When you make a new group it is useful to have an idea of what will happen next: are you going to live locally, run away or are you pressuring the opponent's group and fighting on an equal footing. Often it is not the first move that determines which of these is preferable or possible. It is more important how quickly you can do these things. If you reduce from above there is no guarantee that it won't be attacked, if you didn't consider this it can catch you unprepared. If you invade there is also no guarantee that it won't be chased into the center and if you didn't consider this it can catch you unprepared as well. Basically, concepts of "invasion" of "reduction" don't clearly separate two modes of thinking. A lot more flexibility is needed in most situations, I view this specific situation being more about how to take care of the new group (once you decide you need to do something on the left side) then how far you go in.

These two concepts, invasion and reduction, are useful. They express different contingencies that are often clearly separate. I don't think "shallow invasion" expresses anything about what happens with the new group, instead it appears to attempt to identify a halfway point between the two concepts which anyway refer more to the outcome (do you try to live locally?) than where you started and it is something of a backward approach to me. Of course we need to be flexible about language as with Go but I have doubts about this concept.

Hi Kvasir

I understand your apprehension but I do take some value out of this concept:

A deep invasion is heavy: it can and will be attacked and if it dies then potential territory has turned into firm territory, so it can't be easily sacrificed. A reduction is light: it's very hard to attack it and when responded to by defending the territory, it has served its purpose and can be treated as a forcing move, or one can continue pressing so as to overconcentrate the opponent and get stronger influence out of it.

A shallow invasion is somewhat heavy. It will be harder to live with it than a deep invasion and it will be easier to attack it than a reduction. Therefore, something else needs to be there to make it a valuable choice. That extra is the presence of extra stones in the area to which the shallow placement of the invading stone relates well. It invites an attack from above and next will likely try moving towards those friendly stones while threatening to move out.

Still I agree (if you do) that the real differentiator for an invasion is the strength of the surrounding structure. If a (deep) invasion weakens those structures, then it is more called for than a reduction, since a defensive response to the reduction will not only make territory but also link up the weakish structures. If an invasion doesn't have that effect, it can only aim for (total) erasure. On the other hand, if it succeeds at that, the stronger structures have not really taken their strength to full advantage.

With the actual position I view it as a situation of creating a new group that separates the opponent's groups, interfering before they become very strong and make a large territory. Ideally, white will create the new group without offering a target. It's more obvious to myself after looking at it with the computer but still it seems like this is a better way to look this position than to distinguish between different styles of reductions.

There is a different kind of positions, one where the "surrounding structures" are strong and only minimally affected by changes in the power balance. I can get behind that when erasing territory (or potential) in such positions it's a useful concept to realize that you don't necessarily have more effect by going in deeper with your invasions and reductions. Still, isn't this simply the old concept of keeping away from strong groups?