Additional Joseki notes for games 37-46
(Note: these games were played with group tax, which affects opening strategy somewhat)

4-4 point direct 3-3 invasion

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[go]$$Wc Preferred sequence
$$ --------------------
$$ | . . . . . . . . . .
$$ | . . . . . . . . . .
$$ | . . X 1 . . . . . .
$$ | . . 2 O . . . . . ,
$$ | . . 4 5 . . . . . .
$$ | . 6 3 . . . . . . .
$$ | . 8 7 . . . . . . .
$$ | . . 9 . . . . . . .
$$ | . . . . . . . . . .
$$ | . . . , . . . . . ,
$$ | . . . . . . . . . .
$$ | . . . . . . . . . .
$$ | . . . . . . . . . .
$$ | . . . . . . . . . .
$$ | . . . . . . . . . .
$$ | . . . X . . . . . ,
$$ | . . . . . a . . . .
$$ | . . . . . . . . . .
$$ | . . . . . . . . . .
$$ --------------------[/go]

There are many ways of dealing with a 3-3 invasion, but in a cross-hoshi fuseki with group tax, the knight's move at is favored by about 0.2 points. The sequence through is expected; may either be as shown or at a.

Actually, the direct 3-3 invasion rarely seems to come up in these games, but I think I might see it if I ever play group tax games against opponents more familiar with modern Go, so this seems worth knowing.

4-4 point, keima approach, side hoshi pincer, tenuki

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[go]$$Bc Black a is a high priority
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . 1 . . . . . . . 2 a . . . . |
$$ | . . . O . . . . . 3 . . . c . X . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . b . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . 4 . . . . . . . . . . . . . . . |
$$ | . . . , . . . . . , . . . . . , . . . |[/go]

Kosumi-tsuke is a famous handicap joseki; when the supporting stone at is present, a follow-up at a is considered superior to other responses such as b or c.

In this situation in game 41, I played a move elsewhere on the board. But the priority of a is quite high, almost equivalent to playing in an empty corner. So black should play at a.

4-4 point, keima approach supported by side hoshi, side invasion

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

Black invades at , so naturally white covers at . If black plays elsewhere, what is white's local continuation?

I sort of assumed that making the tiger's mouth at c must be the ideal shape. But b and especially a turned out to be slighly better, at least in the context of my game 42. I will definitely consider these moves in a similar situation, and not just assume that c is the move.

4-4 point, keima approach, attachment

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[go]$$Bc Options for
$$ --------------------
$$ | . . . . . . . . . .
$$ | . . . . . . . . . .
$$ | . . c 5 . 1 . a . .
$$ | . . 6 O . 2 3 . . ,
$$ | . . . . . 4 b . . .
$$ | . . . . . . . . . .
$$ | . . . . . . . . . .
$$ | . . . . . . . . . .
$$ | . . . . . . . . . .
$$ | . . O , . . . . . ,[/go]

Black should continue at a (linking up all stones), or b (possibly sacrificing the corner, but building side influence). Black c was my greedy mistake in game 43.

4-4 point keima approach ōgeima response continuation

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[go]$$Bc A now-familiar sequence
$$ --------------------
$$ | . . . . . . . . . .
$$ | . . . . . . . . . .
$$ | . . . . 8 1 6 . . .
$$ | . . . O . 4 . . . ,
$$ | . . . . . . . . . .
$$ | . . 5 . 3 . . . . .
$$ | . . 2 7 . . . . . .
$$ | . . a . . . . . . .
$$ | . . . . . . . . . .
$$ | . . . , . . . . . ,
$$ | . . . b . . . . . .
$$ | . . . . . . . . . .
$$ | . . . . . . . . . .
$$ | . . . . . . . . . .
$$ | . . . . . . . . . .
$$ | . . . X . . . . . ,
$$ | . . . . . . . . . .
$$ | . . . . . . . . . .
$$ | . . . . . . . . . .
$$ --------------------[/go]

This sequence is becoming quite familiar to me. Usually black will continue at a, or possibly play an extension such as b.

If black plays elsewhere instead, then white may continue at a. This seems to be more urgent than approaching a 4-4 stone or defending a 4-4 stone, but less urgent than answering a double approach or 3-3 invasion. I tried setting up a position with a 3-4 stone in another corner, and a was considered very slightly less urgent than approaching the 3-4 stone.

Perhaps this seems like a rather fine point to be bringing up, but this sequence really is appearing a lot in my games with group tax, so it is valuable for me to know the priority of this move.

4-4 point, keima approach, ōgeima extension, one-space approach

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[go]$$Bc White to play
$$ --------------------
$$ | . . . . . . . . . .
$$ | . . . . f . . . . .
$$ | . . . . . 1 . . . .
$$ | . . . O . e . . . ,
$$ | . . . . . c . . . .
$$ | . . . . d b . . . .
$$ | . . 2 . a . . . . .
$$ | . . . . . . . . . .
$$ | . . 3 . . . . . . .
$$ | . . . , . . . . . ,[/go]

A move such as a, b, c, or d would be good. I thought these moves seemed slow and played e, but this was suboptimal.

EDIT: Another interesting move is f. This move happens to appear in Josekipedia. Although the policy model rates this move very low, it only loses 0.20 points compared to a (in the context of my game 46). Furthermore, it is actually 0.71 points better than a in the context of a (somewhat different) position in my game 48, although is on the fourth line in that game.

Shape point

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[go]$$Wc White to make shape
$$ | . . . . . . . . . .
$$ | . . . , . . . . . ,
$$ | . . . X 2 b . . . .
$$ | . . . . 1 c a . . .
$$ | . . . . . . d . . .
$$ | . . O O . e f . . .
$$ | . . X . . g . . . .
$$ | . . . X . . X . . ,
$$ | . . . . . . . . . .
$$ | . . . . . . . . . .
$$ | . . . . . . . . . .
$$ --------------------[/go]

White is running towards the center, and would like to run with good shape. My move was g, but this is aji keshi. I thought about a, but it felt to me like an incomplete shape.

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[go]$$Wc Miai
$$ | . . . . . . . . . .
$$ | . . . , . . . . . ,
$$ | . . . X X a . . . .
$$ | . . . . O . 1 . . .
$$ | . . . . . . . . . .
$$ | . . O O . . b . . .
$$ | . . X . . . . . . .
$$ | . . . X . . X . . ,
$$ | . . . . . . . . . .
$$ | . . . . . . . . . .
$$ | . . . . . . . . . .
$$ --------------------[/go]

In fact, is a good move, as either a or b would complete a good shape.

Here's my second attempt at a checklist.

I've played ten more openings, and this time I achieved an average point loss of 8.87 points, which is more than 2 points better than my previous result.

This progress gives me hope that I may gain a stone in strength this year.

I'll post a more detailed analysis soon.

I mentioned my mistakes totaled about 8.87 points per opening in this last set.

Of these, about 1.1 points were lost to joseki mistakes; about 1.5 points to direction of play mistakes, and about 2.2 points to technique mistakes.

"Technique mistakes" is a sort of vague category, but I am referring to questions like: Should I make a solid or hanging connection? Should I push from behind or run ahead with a keima? Should I hane or extend? Generally, these situations did not involve immediate life and death concerns, so the focus is more on judging shape qualities in a particular context.

There were other mistakes, but these seem sufficient to focus on for now. I will make some more detailed posts with diagrams soon.

I also categorized some moves as "dogma mistakes," by which I mean moves that humans would probably consider reasonable but that don't follow the AI style perfectly. These mistakes were very small, but there were a lot of them, so I wanted to see whether they're worth paying attention to. However, they only totaled about 0.4 points per opening, so I will set this concern aside for now.

Joseki notes for games 47-56
(Note: these games were played with group tax, which affects opening strategy somewhat)

4-4 point, keima approach, keima extension, contact play

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[go]$$Bc How does this joseki finish?
$$ , . . . . . , . . . |
$$ . . . . . . . . . . |
$$ . . . . . . . . . . |
$$ . . . . . . . . . . |
$$ . . . . . . a 1 . . |
$$ . . . . . . 8 6 9 . |
$$ , . . . . . O 3 7 . |
$$ . . . . 2 . . 4 5 . |
$$ . . . . . . . . . . |
$$ . . . . . . . . . . |
$$ --------------------[/go]

This is very common AI joseki, but sometimes I've forgotten how it ends. White will play a, and then what?

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

I played b but this is too passive. should either be at a or tenuki. Let's look at both:

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[go]$$Bc Hane
$$ --------------------
$$ . . . . . . . . . . |
$$ . . . . . . . . . . |
$$ . . . . . . . . . . |
$$ , . . . . . X . . . |
$$ . . . . . . . . . . |
$$ . . . . . . . . . . |
$$ . . . . . . . . . . |
$$ . . . . . . . . . . |
$$ . . . . . . 9 8 . . |
$$ , . . . . . 7 6 . . |
$$ . . . . . . 5 4 . . |
$$ . . . . . . 1 2 3 . |
$$ . . . . . . O X . . |
$$ . . . . . . O X . . |
$$ . . . . . . O O X . |
$$ , . . . . . O X X . |
$$ . . . . O . . O X . |
$$ . . . . . . . . . . |
$$ . . . . . . . . . . |
$$ --------------------[/go]

White will probably cut at , but this isn't scary for black. Black is happy to just keep pushing like this. There are some other variations, but black's goal will be the same: build a wall.

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

If black tenukis, white may double hane, but black can simply tenuki again. The black stones will are alive via the miai of a and b.

4-4 point, low approach, kosumi-tsuke transposition

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[go]$$Bc tenuki
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . 4 1 . . . . . b c d . . . . . |
$$ | . . . O . 5 . . . 6 . . . . . B . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . 2 . . . . . . . . . . . . . . . |
$$ | . . . . . a . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . , . . . . . , . . . . . , . . . |[/go]

Various move orders; may result in this shape in the upper-left; this particular order is from my game 47.

Where should black play next? I played a, which I have seen in handicap games. This move would have been correct if the marked stone (the upper right star point) were white, but stronger moves are available in this position. Black should pincer the stone, for instance with b, c, or d.

4-4 point, low approach, one-space low pincer

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[go]$$Wc Where should white continue?
$$ | . . . . . . . . . ,
$$ | . . . . . . . . . .
$$ | . . . . . . . . . .
$$ | . . . . . . . . . .
$$ | . . b . . . . . . .
$$ | . . . . . a . . . .
$$ | . . . X . . . . . ,
$$ | . . . . . 1 . 2 . .
$$ | . . . . . . . . . .
$$ | . . . . . . . . . .
$$ --------------------[/go]

Here's what I've noticed about how KataGo responds to pincers when playing with group tax:

Generally, white will not invade at the 3-3 point, in contrast to games without group tax, in which case 3-3 invasions are quite common.

In the case of a near pincer (whether on the third or fourth line), the one-space jump at a is good.

For more distant pincers, a double approach or counter-pincer will usually be preferred.

In any case, answering a pincer does not seem be urgent. Tenuki, e.g. to approach another corner, is often the best move.

In my game 48, I played a, but b would have been about 0.4 points better. I also misplayed the continuation, as shown below:

4-4 point, low approach, one-space low pincer, double approach, continuation

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[go]$$Wc Continuation
$$ | . . . . . . . . . ,
$$ | . . . . . . . . . .
$$ | . . . . . . . . . .
$$ | . . . . . . . . . .
$$ | . . 1 . . . . . . .
$$ | . . . . . . . . . .
$$ | . . 5 X a 2 3 . . ,
$$ | . . 7 . 6 O 4 X . .
$$ | . . . . . . . . . .
$$ | . . . . . . . . . .
$$ --------------------[/go]

Even after , the local situation is not urgent; white would most likely tenuki, then come back and play later, or perhaps directly invade at instead. But I think the sequence shown in the diagram is easy to understand. In my game 48, I played the atari at a instead of , which was a mistake of 2.5 points.

4-4 point, low approach, ōgeima, ōgeima, variation 1

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[go]$$Bc How should black deal with ?
$$ , . . . . . , . . . |
$$ . . . . . . . . . . |
$$ . . . . . . . . . . |
$$ . . . . . . . 6 . . |
$$ . . . . . . 4 1 . . |
$$ . . . . 3 . . e . . |
$$ d c b 7 . . O . . . |
$$ . . 8 2 5 . . . . . |
$$ . . . . . a . . . . |
$$ . . . . . . . . . . |
$$ --------------------[/go]

In my previous games, has been at e, but the move shown here is probably more common. In response, I played at e, which is not terrible, but the other options shown here are about half a point better.

Black may aim for the corner with a, in which case white will turn at b; otherwise, black may aim to press white down with b, c, or d.

4-4 point, low approach, ōgeima, ōgeima, variation 2

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[go]$$Bc How should black deal with ?
$$ , . . . . . , . . . |
$$ . . . . . . . . . . |
$$ . . . . . . . . . . |
$$ . . . . . . 5 . . . |
$$ . . . . . a 4 1 . . |
$$ . . . . 3 . . b . . |
$$ , . . . . . O . . . |
$$ . . . 2 . . . . . . |
$$ . . . . . . . . . . |
$$ . . . . . . . . . . |
$$ --------------------[/go]

Here's another variation. is a mistake of about 0.5 points. should be at a. I played at b, but this was a mistake of about 2 points.

4-4 point, double approach, contact play, hane, extend, push

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[go]$$Bc elsewhere
$$ --------------------
$$ | . . . . . . . . . .
$$ | . . . . . . . . . .
$$ | . . . . . 1 . . . .
$$ | . . . O . . . . . ,
$$ | . . . . . . . . . .
$$ | . . 3 4 6 . . . . .
$$ | . . . 5 7 . . . . .
$$ | . . . . . . . . . .
$$ | . . . . . . . . . .
$$ | . . . , . . . . . ,[/go]

I find this rather characteristic of the group tax opening style. Continuation follows.

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[go]$$Wc Continuation
$$ --------------------
$$ | . . . . . . . . . .
$$ | . . . . . . . . . .
$$ | . . . b . X . . . .
$$ | . 5 . O 8 . . . . ,
$$ | . 2 1 a . . . . . .
$$ | . 3 X O O 6 . . . .
$$ | . 7 4 X X . . . . .
$$ | . . . . . . . . . .
$$ | . . c . . . . . . .
$$ | . . . , . . . . . ,[/go]

is not really sente. In my game, I responded at a. The Josekipedia move is b. Both of these are inferior to c. Tenuki is also a good option.

In the case of tenuki, b and c may be considered miai. If black reduces the corner with b, white moves to the side with c. If black instead plays c, or some other move to secure the side, then white takes the corner with b.

4-4 point, approach, low pincer, one-space jump, two-space jump

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[go]$$Bc elsewhere
$$ --------------------
$$ . . . . . . . . . . |
$$ . . . . . . . . . . |
$$ . . . . . . . . . . |
$$ , . . . . . X . . . |
$$ . . . . . . . . . . |
$$ . . . . . . . . . . |
$$ . . . . . . . . . . |
$$ . . . . . . . . . . |
$$ . . . . . . . . . . |
$$ , . . . . . , 5 . . |
$$ . . . . . . . . . . |
$$ . . . . . 8 . 2 . . |
$$ . . . . . . . . . . |
$$ . . . 9 . 3 . 1 . . |
$$ . . a . . . . . . . |
$$ , . . 4 . . O . . . |
$$ . 7 . . . . . . . . |
$$ . . . . . . . . . . |
$$ . . . . . . . . . . |
$$ --------------------[/go]

This sequence may favor black slightly. Perhaps should have been at a. Continuation follows:

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[go]$$Wc Continuation
$$ --------------------
$$ . . . . . . . . . . |
$$ . . . . . . . . . . |
$$ . . . . 1 . . . . . |
$$ , . . . d . X . . . |
$$ . . . . . . . . . . |
$$ . . . . . . . . . . |
$$ . . . . . . e . . . |
$$ . . . . . . . . . . |
$$ . . . . . . . . . . |
$$ , . . . . a , X . . |
$$ . . . . . . . . . . |
$$ . . . . . O . O . . |
$$ . . . . . . . . . . |
$$ . . . X . X . X . . |
$$ . . c . . . . . . . |
$$ , . . O . . O . b . |
$$ . X . . . . . . . . |
$$ . . . . . . . . . . |
$$ . . . . . . . . . . |
$$ --------------------[/go]

Black has several good responses to . I played e, but this lukewarm move is not great. The other labeled moves are good.

I'm especially interested in b. This kind of slide under the 4-4 point has fallen off my radar along with the old "4-4 point, keima approach, keima extension, slide" joseki. However, in the context of this pincer fight, it seems to be effective. I've also seen it in other, similar contexts. I'll try to keep it in mind from now on.

4-4 point, approach, two-space high extension, 3-3 invasion

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[go]$$Wc elsewhere
$$ --------------------
$$ . . . . . . . . . . |
$$ . . . . . . . . . . |
$$ . . . . 1 . 4 3 . . |
$$ , . . . . . X 5 . . |
$$ . . . . . . a b . . |
$$ . . . . . . . . . . |
$$ . . . . . . 2 . . . |
$$ . . . . . . . . . . |
$$ . . . . . . . . . . |
$$ , . . . . . , X . . |[/go]

In this position, at a is favored over b by about 0.2 points. I played b because I thought it limited white's movement more and the presence of the stone would help reinforce black's weakness at a. But this cutting point did end up becoming a problem later in my game 51.

4-4 point, double approach, contact play, hane, extend

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[go]$$Wc elsewhere
$$ --------------------
$$ . . . . . . . . . . |
$$ . . . . . . . . . . |
$$ . . . . 3 . . c . . |
$$ , . . . . . X a . . |
$$ . . . . . . . b e . |
$$ . . . . . 6 4 1 . . |
$$ . . . . . d 5 . . . |
$$ . . . . . . . . . . |
$$ . . . . . . . . . . |
$$ , . . . . . , . . . |[/go]

Here are some of white's various options for , but I'm mainly interested in discussing a and b. When should white choose a and when should white choose b?

I usually play a because I feel it gives me slightly more territory than b. But recently I feel that b damages the stone less than a. So I should decide whether I want to establish a group on the top side; if so, then I should lean more towards playing b.

4-4 point, inside contact play, inside hane, extend, push

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[go]$$Bc elsewhere
$$ --------------------
$$ | . . . . . . . . . .
$$ | . . . . . . . . . .
$$ | . . 2 1 3 b . . . .
$$ | . . . O 4 a . . . ,
$$ | . . . . . . . . . .
$$ | . . . . . . . . . .
$$ | . . . . . . . . . .
$$ | . . . . . . . . . .
$$ | . . . . . . . . . .
$$ | . . . , . . . . . ,[/go]

Here's a sequence from my game 56. I played as white here. In the context of a mostly-empty board, seems a bit premature. For , either the inside or outside hane is fine; I've also seen other whole-board situations where the outside hane was preferred. I played because it felt to me like a move AI would play; this was correct, but I did not really understand the meaning of this move and I made mistakes in the continuation.

In particular, I think if the hane at a were a good move for black, this would suggest that is bad. However, black should not hane because the cut at b would be severe.

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[go]$$Bc Continuation; is incorrect
$$ --------------------
$$ | . . . . . . . . . .
$$ | . . a . . . . . . .
$$ | . . O X X 1 . . . .
$$ | . . b O O 2 3 . . ,
$$ | . . . . . . . . . .
$$ | . . . . . . . . . .
$$ | . . . . . . . . . .
$$ | . . . . . . . . . .
$$ | . . . . . . . . . .
$$ | . . . , . . . . . ,[/go]

Since black cannot hane, black extends with . My push at was a mistake, because this time black can hane at and the cut is less severe. Instead of continuing to push, white should have defended the corner with a move such at a or b.

The mistakes discussed above accounted for an average of 1 lost point per game within this set of ten openings.

I tried playing an opening (up to move 46) against the AI from the Play Go Against a DCNN page.

My mistakes totaled 17.3 points (and the AI's mistakes totaled 17.4 points). Actually, it was mostly the same mistake, as we both kept ignoring the most urgent point on the board.

I am not sure if I will bother to post a review, but I think it is worth noting that just because I have reduced my point loss against one AI does not mean I have improved by a similar amount in general.

At some point I'd like to practice more openings against the linked AI or something similar, i.e. a policy model trained to emulate human players. I'd be interested in alternatives to the site I linked, because it doesn't provide a way to download an SGF, so I'm left to transcribe it by hand.

Also, this reminds me that I wanted to talk about metrics a bit. I've been judging my performance purely in terms of point loss, but I think this may have drawbacks. For instance, it may lead me to avoid difficult variations, even if they would be equally difficult for my opponent.

I am considering a new metric where I would subtract half my opponent's score loss from my score loss, so e.g. if my point loss is 20 points and my opponent's is 6, then my adjusted point loss would be 17 points. This would help encourage me to play variations that are difficult for my opponent, and also penalize me less when both players repeatedly fail to notice something.

I won't be adopting this immediately, however, as I still need to finish my current kifu study project, and changing metrics mid-way through would just be confusing.

I'm about halfway through writing up these notes, but I feel like it is taking too long and I'd like to move on to playing more games, so I may not finish.

Anyway, while playing my next set of openings I'd like to focus on the following questions:
Am I moving in the right direction? / Am I approaching from the right direction?
Am I using the right technique?

Here are my incomplete technique notes:

Technique notes for games 47-56
(Note: these games were played with group tax, which affects opening strategy somewhat)

Surrounding is better than approaching

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[go]$$B should be at a
$$ --------------------
$$ | . . . . . . . . . .
$$ | . . . . . . . . . .
$$ | . . . . O B . . . .
$$ | . . . W . X . . . O
$$ | . . . . . . . . . .
$$ | . . . W . . . . . .
$$ | . . . . . X . . . .
$$ | . . 1 a . . . . . .
$$ | . . . . . . . . . .
$$ | . . . , . . . . . ,[/go]

In this position I played . My reasoning was as follows: Black approached, and white played a fourth-line extension (see marked stones). A double approach is good in that situation. The extra stones don't matter. In fact, the extra stones do matter, because black has a chance to surround instead of merely approaching. Black should have played at a instead. As it is, invites white to answer at a, keeping black separated.

Hane a contacting stone

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[go]$$Wc should be at a
$$ --------------------
$$ | . . . . . . . . . .
$$ | . . . . . . . . . .
$$ | . . . . O X . . . .
$$ | . . . O . X . . . O
$$ | . . . b 2 . . . . .
$$ | . . . O c 1 a . . .
$$ | . . . . . X . . . .
$$ | . . X . . . . . . .
$$ | . . . . . . . . . .
$$ | . . . , . . . . . ,[/go]

I kind of think I should have addressed this in my joseki review, but I'm including it here anyway. I played but I should have played at a. Perhaps a hane against a contacting stone is intuitive, and is weak for black as well as white.

Actually I don't think this is so clear-cut, which is why I now hesitate to discuss this as a "technique" mistake. If white responds at b, as happened in the game, then white has been tricked and the sequence is not bad for black. Instead, white should block at c, but I think this requires deep reading to verify.

Two-space extension to create a base

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[go]$$Wc should be at a
$$ --------------------
$$ | . . . . . . . . . .
$$ | . . . . . . . . . .
$$ | . . . . O X . . . .
$$ | . . . O . X . . . O
$$ | . . . O X . . . . .
$$ | . . . O X O . . . .
$$ | . . . 1 . X . . . .
$$ | . . X . . . . . . .
$$ | . . . . . . . . . .
$$ | . . 2 , . . . . . ,
$$ | . . a . . . . . . .
$$ | . . . . . . . . . .
$$ | . . . . . . . . . .
$$ | . . W . . . . . . .
$$ | . . . . . . . . . .
$$ | . . . X . . . . . ,
$$ | . . . . . . X . . .
$$ | . . . . . . . . . .
$$ | . . . . . . . . . .
$$ --------------------[/go]

I am not sure why I played only a one-space extension here, but it should clearly be a two-space extension, both for stability and to pincer white's marked stone.

Capture or connect?

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[go]$$Wc Should black respond at a or b?
$$ --------------------
$$ | . . . . . . . . . .
$$ | . . . . . . . . . .
$$ | . . . . O X . . . .
$$ | . . . O . X . . . O
$$ | . . . O X b . . . .
$$ | . . . O X O X . . .
$$ | . . . O O X a . . .
$$ | . . X . . 1 . . . .
$$ | . . . . . . . . . .
$$ | . . X , . . . . . ,[/go]

White plays the atari at . In this case black should connect at a. In this case I think a does more to develop the center; although white's stone is not captured immediately, the remaining aji doesn't seem very useful for white. Still, I played the wrong move of b here, losing 2.4 points.

I think this kind of capture vs. connect situation is interesting, however, because this decision can go either way depending on the surrounding context. I'd like to collect a set of example positions like this to compare these moves. Once I have several such examples I may create a new post.

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[go]$$Bc Should white extend or jump?
$$ --------------------
$$ . . . . . . . . . . |
$$ . . . . . . . . . . |
$$ . . . . O . . . . . |
$$ , . . . . . X . . . |
$$ . . . . . . . . . . |
$$ . . . . . . . . . . |
$$ . . . . . . . . . . |
$$ . . . . . . . . . . |
$$ . . . . . . a . . . |
$$ , . . . . . b . . . |
$$ . . . . . 1 O . . . |
$$ . . . . . X O . . . |
$$ . . . . . X X O . . |
$$ . . . . . . . O . . |
$$ . . . . . . . . . . |
$$ , . . . . . O . . . |
$$ . . . . X . . . . . |
$$ . . . . . . . . . . |
$$ . . . . . . . . . . |
$$ --------------------[/go]

Black is pushing from behind. How should white respond?

The answer is the one-space jump at a. This move is faster than a nobi, but it's important to check that the weakness of the one-space jump is not exploitable:

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[go]$$B If black extends
$$ . . . . . . . . . . |
$$ . . . . . . . 2 . . |
$$ . . . . . . O . . . |
$$ , . . . . 1 , . . . |
$$ . . . . . X O . . . |
$$ . . . . . X O . . . |
$$ . . . . . X X O . . |
$$ . . . . . . . O . . |
$$ . . . . . . . . . . |
$$ , . . . . . O . . . |[/go]

Click Here To Show Diagram Code

[go]$$B If black wedges
$$ . . . . . . . . . . |
$$ . . . . . . . 4 . . |
$$ . . . . . . O . . . |
$$ , . . . . 3 1 2 . . |
$$ . . . . . X O . . . |
$$ . . . . . X O . . . |
$$ . . . . . X X O . . |
$$ . . . . . . . O . . |
$$ . . . . . . . . . . |
$$ , . . . . . O . . . |[/go]

Running technique

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[go]$$Bc How should white mobilize the marked stone?
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . X . . . . X . . W . . . . . |
$$ | . O . O X . . . . , . . . . . X . . . |
$$ | . X O O . . . . . . . . . . . . . . . |
$$ | . O X O O X . . . . . . . . . X O . . |
$$ | . O X X X . X . . . . . . . . . O . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . , . . . . . , . . . . . O . . . |[/go]

Solution follows:

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

I've previously discussed how this is a nice shape. The 3-3 invasion at a is also a good option. My move was the one-space jump at b, but this is inferior by about 0.4 points.

Click Here To Show Diagram Code

[go]$$Wc Game continuation
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . X . . . . X . . O . . . . . |
$$ | . O . O X . . . . , a d 4 . . X c . . |
$$ | . X O O . . . . . . 3 . . 1 5 . 2 b . |
$$ | . O X O O X . . . . . . . . . X O . . |
$$ | . O X X X . X . . . . . . . . . O . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . , . . . . . , . . . . . O . . . |[/go]

Actually every white move here is a mistake. should perhaps be at a. But I will especially remember that is aji keshi. Black will connect against the peep, which removes the possibility of a later atari by white stones at b and c. Instead, the kosumi-tsuke at d is a tesuji to make shape.

I've played another ten openings. This time my average loss was about 12.88 points. This is 4.01 points worse than my result in my previous set of 10 games. I might attribute this apparent step backwards to such causes as:

Too much time spent reviewing instead of playing.
Focusing less on defense. In my previous set of games, I made few mistakes on defense, which led me to think I didn't need to focus on it as much. But after changing my focus, I am making more defense mistakes.
Frequently ignoring approaches to approach a different corner. This is not wrong but may lead to a more complex opening with more mistakes.
Playing while tired.
Too small sample size.

Anyway, I would like to try to replicate my previous result of 8.87 points lost, on average, in the opening. That's already a big improvement compared to a month or two ago, so I would be happy if I could consistently achieve it. I will try following the same checklist I used in that set, and play more games, perhaps 30.

I haven't posted recently, but my studies continue. I've played a new set of 64 openings, moves 1-46. Here are my results:

As mentioned, I was in a bit of a slump previously, but I seem to have recovered and maybe even improved a bit. Some observations:

I'm not spending as much time reviewing now. Reviewing is still important, but I think I should spend more time playing the game than reviewing it.
I am trying to play to my strengths rather than strictly following the AI style, especially in the very early moves. I think this leads to positions that I understand a bit better and results in me losing fewer points in the late opening.
I am paying attention to the "Adjusted Point Loss" which is calculated as my point loss minus 1/2 of my opponent's point loss. Essentially, I am taking credit for causing half of my opponent's mistakes. This lets me play a bit more adventurously when I feel so inspired. For now I have reported my point loss as well, for comparison to earlier results, but I will stop tracking this in the future.
I am still studying group tax-style play, but I have stopped forcing the traditional cross-hoshi setup. I do play cross-hoshi at every opportunity, but my opponent has the option to decline now.
I'm setting up 8 different types of games: me playing as black or white; either the full KataGo engine or just the policy model for my opponent; either stone scoring or area scoring for the rules. I am always reviewing with stone scoring even if the game was played under area scoring; these variations are just to induce a variety of play styles from my opponent.

I've been practicing life and death using the BadukPop app. I upgraded to a Pro account so I can study problems with no time limit.

On September 1st of this year, I measured my time to complete a set of 5 problems at each difficulty level 1 through 5. There's also a level 6, but I did not attempt those problems as they felt very hard to me.



Since then, I have been drilling the level 4 problems every day. Today I achieved a time of 10.3 seconds per problem, measured over 15 problems. This is less than my original time for level 3 problems, so one might say that I have improved by one level, which was my goal.

To prove that I have advanced by one level, I will next need to achieve 25.3 seconds on level 5 problems and 58.5 seconds on level 6 problems. I will post later on how that goes.