Opening study with KataGo

hakuseki · **#41**

I played black in this game and lost 27.9 points by move 80.

Game 19, position 1

Click Here To Show Diagram Code: [go]$$Wc elsewhere $$ -------------------- $$ | . . . . . . . . . . $$ | . . 8 . . . . . . . $$ | . . 4 1 7 . . c . . $$ | . . . 6 . a . b . , $$ | . . . 2 . . . . . . $$ | . . . . . . . . . . $$ | . . 9 . . . . . . . $$ | . . . . 5 . . . . . $$ | . . . . . . . . . . $$ | . . . , . . . . . ,[/go]

In this position I pincered at c, but covering at a is about 0.5 points better. Another good option is b.

Click Here To Show Diagram Code: [go]$$Bc Variation $$ -------------------- $$ | . . . . . . . . . . $$ | . . X . . . . . . . $$ | . . X O O . . 1 . . $$ | . . . X . b . . . , $$ | . . . X . a . . . . $$ | . . . . . . . . . . $$ | . . O . . . . . . . $$ | . . . . O . . . . . $$ | . . . . . . . . . . $$ | . . . , . . . . . ,[/go]

If black pincers, white is able to split at either a or b. While a appears less solid, white would be happy to sacrifice the two stones for shape should black try to cut.

Click Here To Show Diagram Code: [go]$$Bc Continuation $$ -------------------- $$ | . . . . . . . . . . $$ | . . X . . . . . . . $$ | . . X O O . . X . . $$ | . . . X . a . . . , $$ | . . . X . . 1 . . . $$ | . . . . . . . . . . $$ | . . O . . . . . . . $$ | . . . . O . . . . . $$ | . . . . . . . . . . $$ | . . . , . . . . . ,[/go]

In the game, white played elsewhere, so black was able to continue locally. Although I played at a in the game, :b1:

is the correct local move, about 0.5 points better.

Game 19, position 2

Click Here To Show Diagram Code: [go]$$Wc Asymmetric double apprach $$ | . . . a . . . . . $$ | . . . b . . . . . $$ | . . d . . . . . . $$ | . . . . . . . . . $$ | . . O e . . . . . $$ | . . . . . . . . . $$ | . c . X . . 1 . . $$ | . . . . . . . . . $$ | . . . . . . . . . $$ | . . . . . . . . . $$ ------------------[/go]

With the stone-scoring AI, I see my 4-4 stones approached in several different ways; consequently, there is a great variety of double approaches.
In the game, I responded with the familiar contact play at e, any of the labeled counter-pincers would be much better; enclosing the corner at c is also superior to e.

Game 19, position 3

Click Here To Show Diagram Code: [go]$$Bc Mistake $$ | . . . , . . . . . $$ | . . . . . . . . . $$ | . . . . . . . . . $$ | . . . O . . . . . $$ | . . O X X . 1 . . $$ | . O O . . . . . . $$ | . X O X . . O . . $$ | . . X . X O . . . $$ | . . . . a . . . . $$ | . . . . . . . . . $$ ------------------[/go]

In this game position, I jumped out at 1, neglecting the weakness at a. If white were to hane here, black would be forced to either leave the corner territory open or allow the two stones to be cut off. I was aware of this, but thought that a defensive move would be too slow.

Click Here To Show Diagram Code: [go]$$Bc Correct defense $$ | . . . , . . . . . $$ | . . . . . . . . . $$ | . . . . . . . . . $$ | . . . O . . . . . $$ | . . O X X . . . . $$ | . O O . . . . . . $$ | . X O X . 1 O . . $$ | . . X . X O . . . $$ | . . . . . . . . . $$ | . . . . . . . . . $$ ------------------[/go]

With

, black is able to fix the connection while simultaneously threatening white's cutting point. This is the correct move.

Game 19, position 4

Click Here To Show Diagram Code: [go]$$Bc Black a, b, or c? $$ -------------------- $$ . . . . . . . . . . | $$ . . . . . . . . . . | $$ . . . . . . . . . . | $$ , . . . . . X . . . | $$ . . . . . . . . . . | $$ . . . . . . . c . . | $$ . . . . . . . . . . | $$ . . . . . . . . . . | $$ . . . . . . . . . . | $$ , . . . . . , . . . | $$ . . . . . . O . . . | $$ . . . . . . . . . . | $$ . . . . . . . 8 a . | $$ . . . . . . . 4 7 . | $$ . . . . . . 6 5 . . | $$ , O . . . . O 3 . . | $$ . . . . . . 2 1 . . | $$ . . . . . . b . . . | $$ . . . . . . . . . . | $$ --------------------[/go]

My tenuki at c seems rather small, losing two points compared to b, which is slightly better than a.

Game 19, position 5

Click Here To Show Diagram Code: [go]$$Wc Defend or approach? $$ --------------------------------------- $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . X . . . . . . . . . . . 1 a . . . | $$ | . . X O O . . X . . . . . c . b . . . | $$ | . . . X . X . . . , . . . . . X . . . | $$ | . . . X . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . X . . | $$ | . . O . . . . . . . . . . . . . . . . | $$ | . . . . O . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . , . . . . . , . . . . . , . . . | $$ | . . . . . . . . . . . . . . . O . . . | $$ | . . . O . . . . . . . . . . . . . . . | $$ | . . . O . O . . . . . . . . . . O . . | $$ | . . O X X . . . . . . . . . . . O X . | $$ | . O O X . . . . . . . . . . . O X . . | $$ | . X O X O . O . O , O . . . . O X . . | $$ | . . X X X O . . . . . . . . . O X . . | $$ | . X . . O . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ ---------------------------------------[/go]

In the game I responded to :w1:

with a. but c is a bit better and b is the best move, considering the whole board situation.
I guess the problem with a is that black has a moyo up top, and white would like to disrupt it. In this case, it is more important to make use of the moyo than to strongly defend the corner territory.
In another recent game of mine, the same local situation came up but the evaluation was different, so if I get a chance I would like to compare the two games.

hakuseki · **#42**

I played black in this game and lost 17.5 points by move 80.

Game 20, position 1

Click Here To Show Diagram Code: [go]$$Bc Should black follow up in the lower right? $$ --------------------------------------- $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . b . . . . . . . . . . . . . . . . | $$ | . . . 4 . . . . . , . . . . . 1 . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . c . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . , . . . . . , . . . . . 6 . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . d . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . 3 . . . . . , . . . . . 2 . . . | $$ | . . . . . . . . . . . . . 5 . . a . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ ---------------------------------------[/go]

was new to me. I thought about playing a local followup, such a 3-3 invasion at a or a double approach at d. I finally decided to tenuki at c, but I think a would have been a slightly better choice.
Afterwards, I reviewed various options for :w6:

and how black should respond to each of them, and came up with this rough guide:

Click Here To Show Diagram Code: [go]$$Bc Keima extension $$ --------------------------------------- $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . 4 . . . . . , . . . . . 1 . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . , . . . . . , . . . . . , . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . 6 . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . 3 . . . . . , . . . . . 2 . . . | $$ | . . . . . . . . . . . . . 5 . 7 8 . . | $$ | . . . . . . . . . . . . . . . . 9 . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ ---------------------------------------[/go]

If white plays the keima extension at :w6:

, then black plays the familiar contact joseki.

Click Here To Show Diagram Code: [go]$$Bc One-space extension $$ --------------------------------------- $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . b . . . . . . . . . . . . . . . . | $$ | . . . 4 . . . . . , . . . . . 1 . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . , . . . . . , . . . . . , . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . 6 . . . | $$ | . . . . . . . . . . . . . . a . . . . | $$ | . . . 3 . . . . . , . . . . . 2 . . . | $$ | . . . . . . . . . . . . . 5 . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ ---------------------------------------[/go]

If white plays the one-space extension, then a black follow-up is not so urgent and a tenuki such at b is fine. However, locally a followup at a is also a good option.

Click Here To Show Diagram Code: [go]$$Bc Loose extension or pincer $$ --------------------------------------- $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . 4 . . . . . , . . . . . 1 . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . , . . . . . , . . . . . 6 6 . . | $$ | . . . . . . . . . . . . . . . 6 6 . . | $$ | . . . . . . . . . . . . . . . 6 6 . . | $$ | . . . . . . . . . . . . . . . 6 6 . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . 3 . . . . . 6 6 6 . . . 2 . . . | $$ | . . . . . . . . . 6 6 . . 5 . . 7 . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ ---------------------------------------[/go]

If white plays any of the loose extensions on the right, or a pincer on the bottom, then the 3-3 invasion is great. Basically a double approach is not good when one of the two approaching stones is already pincered.

Click Here To Show Diagram Code: [go]$$Bc Double approach $$ --------------------------------------- $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . c . . . . . . . . . . . . . | $$ | . . . 4 . . . . . , . . . . . 1 . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . b . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . , . . . . . , . . . . . , . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . a . . . . . . . . . . . . . 7 . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . 3 . . . . . , . . . . . 2 . . . | $$ | . . . . . . . . . . . 6 . 5 . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ ---------------------------------------[/go]

The one exceptional pincer is the low pincer. :w6:

is especially helpful for containing a 3-3 invasion, so in this case the double approach is preferred. It is also good when white tenukis, e.g. at a, b, or c.

Game 20, position 2

Click Here To Show Diagram Code: [go]$$Wc Double approach joseki $$ -------------------- $$ | . . . . . . . . . . $$ | . . . . . . . . . . $$ | . . 5 c . X d . . . $$ | . . 4 O . 7 b . . , $$ | . . 6 a . . . . . . $$ | . . X 1 3 . . . . . $$ | . . . 2 . . . . . . $$ | . . . . . . . . . . $$ | . . . . . . . . . . $$ | . . . , . . . . . ,[/go]

I think this is a pretty normal double-approach joseki, but I'm still not super familiar with :w7:

(which is also a slightly mistake in the game position).
At this point I was thinking about how to make use of my upper-side stone and considered moves like b, c, and d, but actually the push at a is considered the best move.

Click Here To Show Diagram Code: [go]$$Bc Continuation $$ -------------------- $$ | . . . . . . . . . . $$ | . 7 5 4 . . . . . . $$ | . 3 O 6 . X . c b . $$ | . . X O 2 O . . a , $$ | . . X 1 . . . . . . $$ | . . X O O . . . . . $$ | . . . X . . . . . . $$ | . . . . . . . . . . $$ | . . . . . . . . . . $$ | . . . , . . . . . ,[/go]

After

, white will enclose the top with a move like a, b, or c, but black can continue to reduce white's top anyway (the exact technique depending on white's move). Or, if white tries to tenuki instead, then black may play something like c to help the isolated black stone.

Game 20, position 3

Click Here To Show Diagram Code: [go]$$Bc Double approach joseki $$ | . . . , . . . . . $$ | . . . . . . . . . $$ | . . . . . . . . . $$ | . . . . . . . . . $$ | . . O . . . . . . $$ | . . . . . 3 4 . . $$ | . . . X . 1 2 . . $$ | . . . . 5 O . . . $$ | . . . . 6 . . . . $$ | . . . . . . . . . $$ ------------------[/go]

My own corner was double-approached, leading to this sequence. :w4:

seems like a group tax-style move.

Click Here To Show Diagram Code: [go]$$Bc Continuation from the game $$ | . . . , . . . . . $$ | . . . . . . . . . $$ | . . . . . . . . . $$ | . . . . . . . . . $$ | . . O . . 3 . . . $$ | . . . . . X O . . $$ | . . . X . X O . . $$ | . . a . X O . . . $$ | . . . 1 O 2 . . . $$ | . . . . . . . . . $$ ------------------[/go]

I played this sequence, thinking to keep white separated and be able to attack the stone on the left side. However, black will be unable to make a severe attack given the aji in the corner e.g. at a. Therefore this is not a good plan.

Click Here To Show Diagram Code: [go]$$Bc Better idea $$ | . . . , . . . . . $$ | . . . . . . . . . $$ | . . . . . . . . . $$ | . . . . . . . . . $$ | . . O . . 4 . . . $$ | . . . . . X O . . $$ | . . . X . X O . . $$ | . . . . X O 2 . . $$ | . . . 3 O 1 . . . $$ | . . . . . . . . . $$ ------------------[/go]

Instead, black should capture one stone and allow white to enclose with :w4:

. Now black is completely safe and can take sente to play elsewhere.

hakuseki · **#43**

I played white in this game and lost 17.5 points by move 80.

Game 21, position 1

Click Here To Show Diagram Code: [go]$$Bc How should white respond to ? $$ --------------------------------------- $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . X . . . . . , . . . . . O . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . X . . . . . . . . . . . . . . . | $$ | . . . , . . . . . , . . . . . , . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . a . . . . . . . . . . . . . O . . | $$ | . . . . . . . . . . . . . b . X . . . | $$ | . . . O . d . . . , X . . . . X O . . | $$ | . . . . . 1 . . . . . . . O X X O . . | $$ | . . . . . . . . . . . . . c X O O . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ ---------------------------------------[/go]

I didn't want my stone on the lower-left to lose access to the center, so I played d. I think this was my first real mistake of the game, about 1 point worse than a. Of course, a is the most typical response to an approach, and this situation should not have been an exception.
A move like b or c would also be big. I've seen this kind of follow-up in lectures and reviews a few times, but still haven't gotten into the habit of actually playing it. Hopefully next time.

Game 21, position 2

Click Here To Show Diagram Code: [go]$$Wc Joseki continuation $$ | . . . X . . . . . . $$ | . . . , . . . . . , $$ | . . . . . . . . . . $$ | . . . d . . . . . . $$ | . . a c . . . . . . $$ | . . . . . b . . . . $$ | . . . . . 3 8 . . . $$ | . . . O . 1 2 . . , $$ | . . 5 4 . X . . . . $$ | . . 7 . 6 . . . . . $$ | . . . . . . . . . . $$ --------------------[/go]

I thought about playing a, as this looked to me like a pretty big extension for either player. However, I finally chose b in keeping with my original aim of maintaining access to the center. In fact, now would be a great time to tenuki, but locally it seems like c is the best and b is the worst (a difference of about half a point).

Game 21, position 3

Click Here To Show Diagram Code: [go]$$Wc Approaching black's corner $$ --------------------------------------- $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . b . . 1 . . . . . . . . . . . . . | $$ | . . . X . a . . . , . . . . . O . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . X . . . . . . . . . . . . . . . | $$ | . . . , . . . . . , . . . . . , . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . X . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . O O . . . . . . . . . O . . | $$ | . . . . . O X . X . . . . . . X . . . | $$ | . . . O . O X . . , X . . . . X O . . | $$ | . . O X . X . . . . . . . O X X O . . | $$ | . . O . X . . . . . . . . . X O O . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ ---------------------------------------[/go]

In the game I played :w1:

. However, it seems in this case a is a particularly good local response, perhaps because it helps enlarge black's left side. I think this is the reason why :w1:

is considered a mistake -- white should invade directly at b.

Game 21, position 4

Click Here To Show Diagram Code: [go]$$Bc Upper-right joseki choice $$ --------------------------------------- $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . 7 5 3 . . | $$ | . O O O . O . . . . . . . X 4 1 2 a . | $$ | . . X X X O . . . , . . . b 6 O . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . O . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . X . . . . . . . . . . . . . . . | $$ | . . . , . . . . . , . . . . . , . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . X . . . . . . . . . . . . . . . . | $$ | . . . . . . . . X . . . . . X . . . . | $$ | . . . . . O O . . . . . . . . . O . . | $$ | . X X . . O X . X . . . . . . X . . . | $$ | . O O O . O X . . , X . . . . X O . . | $$ | . . O X . X O X . . . . . O X X O . . | $$ | . . O . X . O X . . . . . . X O O . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ ---------------------------------------[/go]

Without considering the whole board context, b is my usual instinct in the upper-right corner situation. However, given that white has very little potential on the right side, I (correctly) guessed that a might be a bit better here. But then I decided: why not both?

Click Here To Show Diagram Code: [go]$$Wc Mistake $$ --------------------------------------- $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . X X X . . | $$ | . O O O . O . . . . . . 2 X O X O 3 . | $$ | . . X X X O . . . , . . . 1 O O . . . | $$ | . . . . . 4 . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . O . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . X . . . . . . . . . . . . . . . | $$ | . . . , . . . . . , . . . . . , . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . X . . . . . . . . . . . . . . . . | $$ | . . . . . . . . X . . . . . X . . . . | $$ | . . . . . O O . . . . . . . . . O . . | $$ | . X X . . O X . X . . . . . . X . . . | $$ | . O O O . O X . . , X . . . . X O . . | $$ | . . O X . X O X . . . . . O X X O . . | $$ | . . O . X . O X . . . . . . X O O . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ ---------------------------------------[/go]

This isn't so good because :w3:

is gote, so black is able to play :b4:

.

Game 21, position 5

Click Here To Show Diagram Code: [go]$$Wc and are mistakes $$ --------------------------------------- $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . X X X . . | $$ | . O O O . O . . . . b . X X O X O O . | $$ | . . X X X O 5 3 . , . . . O O O . . . | $$ | . . . . . X 1 4 . . . . . . . . . . . | $$ | . . . . . 6 2 . . . . . . . . . O . . | $$ | . . a . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . X . . . . . . . . . . . . . . . | $$ | . . . , . . . . . , . . . . . , . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . X . . . . . . . . . . . . . . . . | $$ | . . . . . . . . X . . . . . X . . . . | $$ | . . . . . O O . . . . . . . . . O . . | $$ | . X X . . O X . X . . . . . . X . . . | $$ | . O O O . O X . . , X . . . . X O . . | $$ | . . O X . X O X . . . . . O X X O . . | $$ | . . O . X . O X . . . . . . X O O . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ ---------------------------------------[/go]

is losing about 0.8 points; it seems responding here isn't the biggest point on the board. Invading at a is the best; b is also good.
The more serious mistake is :w3:

. White should not play a hanging connection here. :w3:

at

would be a better move, which threatens to ladder the :b2:

stone.

hakuseki · **#44**

I played white in this game and lost 59.3 points by move 80. However, I'm only covering the early mistakes here:

Game 22, position 1

Click Here To Show Diagram Code: [go]$$Wc Biggest move for white? $$ --------------------------------------- $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . a . . X . . . . . | $$ | . . . X . X . . . , . . . . . O . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . O . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . b . . . . . . . . . . . . . . . . | $$ | . . . , . . . . . , . . . . . , . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . d . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . X . X . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . e . O . . . . . , . . . . X X X . . | $$ | . . . . . O . . . . . . c . . O O . . | $$ | . . . . . . . . . . . . . O . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ ---------------------------------------[/go]

On move 16, white has a lot of options for big moves. The move I chose, e, is the smallest move depicted here -- about 0.7 points smaller than b, which is likely the biggest.
c is somewhat big, and I think it may threaten a follow-up like d later. The value of c will be reduced if black extends first, so now is a good time to play it.
b is a classic splitting move, with enough room for a two-space extension in either direction. Recently I've been playing this kind of move less, because I had gotten the impression that AIs do not like it. However, it is KataGo's recommendation here. I'm guessing it's good in this case because the available space is just wide enough that black's checking extension will be overconcentrated.

Game 22, position 2

Click Here To Show Diagram Code: [go]$$Wc How should white help the upper-left stones? $$ --------------------------------------- $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . X . . . . . | $$ | . . . X . X . . . , . . . . . O . . . | $$ | . . . 6 5 . . . . . . . . . . . . . . | $$ | . . 3 7 8 . . . . . . . . . . . O . . | $$ | . . . . b . . . . . . . . . . . . . . | $$ | . . 4 a . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . 2 . . | $$ | . . . , . . . . . , . . . . . , . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . X . X . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . 1 . O . . . . . , . . . . X X X . . | $$ | . . . . . O . . . . . . . . . O O . . | $$ | . . . . . . . . . . . . . O . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ ---------------------------------------[/go]

,

, and

are all relatively small mistakes. At this point I was considering a and b. Well, often in this kind of situation a is recommended, but I never really though about why (so I played b -- oops).
The problem with b is that it sacrifices the :w5:

stone for little gain. :w5:

is a cutting stone which may become useful.
Also, a isn't weak as I feared; black needs to somehow protect both the :b4:

and the

stone in order to cut, each of which requires an extra move.
Overall, a is about 3.7 points better than b.

Opening study with KataGo

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