Shapes to remember (SDK level)

jlt · Post by **jlt** » Thu Mar 25, 2021 4:20 pm

A no-brainer for today. Somehow I had never thought seriously about that topic before.

Position #46, Black to play.

Click Here To Show Diagram Code: [go]$$Bc Black to play $$ --------------------------------------- $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . O . . . . . , . . . . . X . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . , . . . . . , . . . . . , . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . O O X . . . . . . . . . . . . | $$ | . . . O X X X . . . . . . . . . . . . | $$ | . . . O X O . . . . . . . . . . . . . | $$ | . . . O O X . O . O . X . . . , . . . | $$ | . . . . . X . . . . . . . . . X . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ ---------------------------------------[/go]

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

In the game I captured directly following the proverb to capture the laddered stone at the earliest opporunity, but this is less good than the solution. The move above allows White to play a forcing move

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

It's clearly better than playing

directly. Adding moves

and

is good for Black, as

is almost useless while

faces the center and exerts pressure on the white group.

jlt · Post by **jlt** » Tue Mar 30, 2021 11:39 am

Position #47, White to play.

Click Here To Show Diagram Code: [go]$$Wc White to play $$ --------------------------------------- $$ | . . . . . . . . . . . . . . . . . . . | $$ | . O X . O . . . O X X . . X X O O . . | $$ | . O X O . O . . . O . X . O . X O . . | $$ | . O X O . X . . . O . . . X . X O . . | $$ | . X O O X . . . . . . . . . . X X O . | $$ | X . X X O O . . . . . O . O O O O O . | $$ | . X . . X O . . . . . . O X X O X X O | $$ | . . . . X X . . . . . . O . X X X . O | $$ | . . . . . . . . . O . X X X . X X O O | $$ | . . . , . . . . . , O X X O X O X X O | $$ | . . . . . . . . . . . X O O O O X . X | $$ | . . . X . . . . . O . . . . . X O X . | $$ | . . X . O . . . . . . . . . O O O X X | $$ | . X . . . . . . . . . . . . X . . O . | $$ | . . . O . . . . . . X . . . . . O . . | $$ | . . X O . . . O O , . . . . X , . X . | $$ | . . X O . O O X . . X . . . . X . . . | $$ | . . . . . . X . X . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ ---------------------------------------[/go]

Black only has one eye but M7 and T6 are miai so Black can connect to a living group. However White has a good endgame move.

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

Black can't block at "a":

Click Here To Show Diagram Code: [go]$$Wc Blocking at a $$ --------------------------------------- $$ | . . . . . . . . . . . . . . . . . . . | $$ | . O X . O . . . O X X . . X X O O . . | $$ | . O X O . O . . . O . X . O . X O . . | $$ | . O X O . X . . . O . . . X . X O . . | $$ | . X O O X . . . . . . . . . . X X O . | $$ | X . X X O O . . . . . O . O O O O O . | $$ | . X . . X O . . . . . . O X X O X X O | $$ | . . . . X X . . . . . . O . X X X . O | $$ | . . . . . . . . . O . X X X . X X O O | $$ | . . . , . . . . . , O X X O X O X X O | $$ | . . . . . . . . . . . X O O O O X . X | $$ | . . . X . . . . . O . 5 . . . X O X . | $$ | . . X . O . . . . . . . . . O O O X X | $$ | . X . . . . . . . . . . . . X . . O c | $$ | . . . O . . . . . . X . . . . . O e d | $$ | . . X O . . . O O , . . . . X , 1 X . | $$ | . . X O . O O X . . X . . . . X 2 3 . | $$ | . . . . . . X . X . . . . . . . . 4 . | $$ | . . . . . . . . . . . . . . . . . . . | $$ ---------------------------------------[/go]

If Black c White d then Black e would be self-atari so Black is dead. Therefore

was wrong and should have been at "b". Here is a continuation suggested by Katago:

Click Here To Show Diagram Code: [go]$$Wc Stepping back at b $$ --------------------------------------- $$ | . . . . . . . . . . . . . . . . . . . | $$ | . O X . O . . . O X X . . X X O O . . | $$ | . O X O . O . . . O . X . O . X O . . | $$ | . O X O . X . . . O . . . X . X O . . | $$ | . X O O X . . . . . . . . . . X X O . | $$ | X . X X O O . . . . . O . O O O O O . | $$ | . X . . X O . . . . . . O X X O X X O | $$ | . . . . X X . . . . . . O . X X X . O | $$ | . . . . . . . . . O . X X X . X X O O | $$ | . . . , . . . . . , O X X O X O X X O | $$ | . . . . . . . . . . . X O O O O X . X | $$ | . . . X . . . . . O . . . . . X O X . | $$ | . . X . O . . . . . . . . . O O O X X | $$ | . X . . . . . . . . . . f . X . . O . | $$ | . . . O . . . . . . X . . . 0 . O . . | $$ | . . X O . . . O O , . . . 9 X 8 1 X . | $$ | . . X O . O O X . . X . . . 7 X 3 2 . | $$ | . . . . . . X . X . . . . . . 5 4 6 . | $$ | . . . . . . . . . . . . . . . . . . . | $$ ---------------------------------------[/go]

Next move

is at "f". I can't read the fight but the basic idea is that Black is forced to connect in gote at some point, allowing White to save stones around

or at least to have a good endgame, using the aji of the stones

,

and

. Anyway these three stones are in Black's area so can be sacrificed without damage if necessary.

jlt · Post by **jlt** » Mon Apr 05, 2021 2:48 pm

Position #48, White to play.

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

In the game I was surprised by

but this is actually the "blue move". What I had expected instead of

was

Back to the game. Here is the continuation suggested by Katago, which is apparently not in Josekipedia:

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

Actually Katago suggests to tenuki at "a" for

but I am showing the local continuation.

But what if

jumps, are the three white stones in trouble?

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

Click Here To Show Diagram Code: [go]$$Wcm6 $$ --------------------------------------- $$ | . . . . . . . . . . . . . . . . . . . | $$ | . 4 . . a X 2 . . . . . . . . . . . . | $$ | 6 3 X X . 1 . . . . . . . . . . . . . | $$ | . . O O O . . . . , . . . . . X . . . | $$ | . 5 . . . . . . . . . . . . . . . . . | $$ | . 7 X . X . X . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . O . O . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . O , . . . . . , . . . . . , . . . | $$ | . . . . . . . . . . . . . . . . . . . |[/go]

Black can't play

at

because of the threat at "a".

dhu163 · Post by **dhu163** » Mon Apr 05, 2021 6:34 pm

I'm not sure how useful human comments are post AI, but here's a try for coming up with explanations without checking the AI.

48:
From what I've seen, just in the upper left, hane connect is particularly popular for AI when white's pincer stone is at D11. Otherwise, I think katago prefers hane connect normally for closer pincers anyway. The key is to threaten either B14 (directly) or prepare with E14, trying to induce white to press at F16. But

at F18 has also become played after it was found in alphago teach, released in Dec 2017. It was almost not considered at all (or at least discarded/forgotten) pre alphago. These days it is common enough that I might realise it is better in this position (in a 1hr each game) but still rare.

47:

46:
hmm, my thought process was

45:
thought process (not so linearly this time):

44:
Thought process:

43:

42:

37:

I think

can consider playing at K3 to avoid the white's O2 life making tesuji. My ideal sequence is

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

at L3 is ko for life. But it isn't trivial for black to fight either as white is so thick.
However, looking at this diagram compared to KG's variation, KG's variation seems better both for endgame and life as P2 is a valuable move to prevent S2. The only thing my diagram gains is to reduce white by around 2 points. Furthermore,

is probably better at J1. Although

is a tesuji, black is happy to force white into it because black gains by answer everything. I was too aggressive in my variation.

jlt · Post by **jlt** » Mon Apr 05, 2021 11:54 pm

Thank you for your comments, I will read them in more detail tonight (no time right now), but to answer to

I'm not sure how useful human comments are post AI

Yes, I am very interested in human comments, whether coming from stronger players like you or from weaker players who have been silent so far. An AI can only show the main lines and answer my questions, but cannot think about all the variations that might be played in a game between humans.

jlt · Post by **jlt** » Wed Apr 07, 2021 2:10 pm

Further Katago variations on my third hidden diagram.

Suppose that Black plays

at B17, then Katago thinks the only move for

is B16.

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

Click Here To Show Diagram Code: [go]$$Bcm7 :w14: at a or b $$ --------------------------------------- $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . X . . . . . . . . . . . . . | $$ | . X X X . . 2 . . . . . . . . . . . . | $$ | . O O O O . . . . , . . . . . X . . . | $$ | . . . . . . a . . . . . . . . . . . . | $$ | . . X . X . b . . . . . . . . . . . . | $$ | . . . 1 . . . . . . . . . . . . . . . | $$ | . . O 3 O . . . . . . . . . . . . . . | $$ | . . . 4 5 7 . . . . . . . . . . . . . | $$ | . . O , 6 . . . . , . . . . . , . . . | $$ | . . . . . . . . . . . . . . . . . . . |[/go]

Instead of peeping, Black may want to continue jumping.

Click Here To Show Diagram Code: [go]$$Bcm7 Running fight $$ --------------------------------------- $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . X 5 . . . . . . . . . . . . | $$ | . X X X . . 2 . . . . . . . . . . . . | $$ | . O O O O . . 4 . , . . . . . X . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . a X . X . 1 . . . . . . . . . . . . | $$ | . . . 3 . . . . . . . . . . . . . . . | $$ | . . O . O . . . . . . . . . . . . . . | $$ | . . . . . . 6 . . . . . . . . . . . . | $$ | . . O , . . . . . , . . . . . , . . . | $$ | . . . . . . . . . . . . . . . . . . . |[/go]

In the above diagram, White may want to connect underneath at "a" for

, this is slightly less good.

In any case, Black cannot push and cut

Click Here To Show Diagram Code: [go]$$Bcm7 bad for Black $$ --------------------------------------- $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . X . . . . . . . . . . . . . | $$ | . X X X . 3 2 . . . . . . . . . . . . | $$ | . O O O O 4 5 7 9 , . . . . . X . . . | $$ | . . . . . . 6 8 . . . . . . . . . . . | $$ | . a X . X . 1 . . . . . . . . . . . . | $$ | . . . . . . 0 . . . . . . . . . . . . | $$ | . . O . O . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . O , . . . . . , . . . . . , . . . | $$ | . . . . . . . . . . . . . . . . . . . |[/go]

White can save the 5 stones with "a" at any time.

Edit: last diagram corrected.

jlt · Post by **jlt** » Thu May 13, 2021 2:53 pm

Really a shape problem.

Position #49, White to play. What is White's next move, and what is the continuation?

Click Here To Show Diagram Code: [go]$$Wc $$ --------------------------------------- $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . O X X O | $$ | . . X O . . . . . . X X . X . O X O . | $$ | . . X O . . . . . , . O . X . X O O O | $$ | . . . O . . . . . . O . O X . X X O . | $$ | . X . . . . . . . . O O X X X O O O . | $$ | . . . . . . . . . . . X O O O X X . . | $$ | . . . . . . . . . . . X . . . O X . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . , . . . . . , . . . . . , . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . O . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . O . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . O . . | $$ | . . . O O O . . . , . . . . X , . . . | $$ | . . O X O X X . . . . . . . . X . . . | $$ | . . X X X . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ ---------------------------------------[/go]

Answer:

Click Here To Show Diagram Code: [go]$$Wc Katago's answer $$ --------------------------------------- $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . O X X O | $$ | . . X O . . . . . . X X . X . O X O . | $$ | . . X O . . . . . , . O . X . X O O O | $$ | . . . O . . . . . . O . O X . X X O . | $$ | . X . . . . . . . . O O X X X O O O . | $$ | . . . . . . . . . . . X O O O X X . . | $$ | . . . . . . . . . . b X . . . O X . . | $$ | . . . . . . . . . . . 3 . 1 . 2 . . . | $$ | . . . , . . . . . , . . . . . , . . . | $$ | . . . . . . . . . . . . . . a . . . . | $$ | . . . . . . . . . . . . . . . . O . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . O . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . O . . | $$ | . . . O O O . . . , . . . . X , . . . | $$ | . . O X O X X . . . . . . . . X . . . | $$ | . . X X X . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ ---------------------------------------[/go]

White cannot kill the three stones, at least not immediately.

strengthens the three white stones so that White can aim at attacking one of the black groups later. For instance if Black doesn't defend the group on the right, then "a" will be a good point for White. If Black doesn't defend the two stones then "b" will be a good point for White.

Bill Spight · Post by **Bill Spight** » Fri May 14, 2021 6:48 am

Edit: Nevermind.

I assume that the following is the correct diagram for the last one in #81..

jlt · Post by **jlt** » Fri May 14, 2021 7:33 am

Yes indeed, there were two

in the diagram, I forgot to erase one. I edited my post according to your comment.

jlt · Post by **jlt** » Fri Jun 11, 2021 3:40 am

Position #50, White to play. Shouldn't be hard but I missed it.

Click Here To Show Diagram Code: [go]$$Wc White to play $$ --------------------------------------- $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . O . X X X X X . O . . . . | $$ | . . . O X . O X X O O O . X O . . . . | $$ | . . O , O . . O O , . . . X . O . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . X . . . . . . . . . . . . . O . . | $$ | . . . . . . . . . . . . . . . . . O . | $$ | . . X . . . . . . . . . . . . . O X . | $$ | . . . . . . . . . . . . . . . . O X . | $$ | . X . O . . . . . , . . . . . , O X . | $$ | . X O . . . . . . . . . . . . . . X . | $$ | X . X O . . . . . . . . . . . O O O X | $$ | . X . . . . . . . X X . X O . O X X . | $$ | X O O O . O . . O X O X . X O X X . . | $$ | . X X . . . O O X O O O X . O O X . . | $$ | . . . X X X O X X X . . X X O X . . . | $$ | . . O X O O X . X . O O . . X X . . . | $$ | . O . O O O X . . . . . . . . . . . . | $$ | . . . . . X . . . . . . . . . . . . . | $$ ---------------------------------------[/go]

Answer:

jlt · Post by **jlt** » Fri Jun 11, 2021 10:56 pm

Yet another simple move.

Position #51, White to play. There are several possible good moves, the question is how to attack/put pressure on the group K16.

Click Here To Show Diagram Code: [go]$$Wc White to play $$ --------------------------------------- $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . O . | $$ | . . . . . . . . . . . X . . . . . . O | $$ | . . . O . . O . . X . . . O . O O O X | $$ | . . . . . . . . . . . . . . . . X X X | $$ | . . . . . . O . . X . . . . . X . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . , . . . . . , . . . . . X . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . O . O O . . | $$ | . O . . . . . . . . . . . . . . X X . | $$ | O . O . . . . . . . . . . . . X . . . | $$ | . O X X . . . . . . . . . . . . . . . | $$ | . X O X . . . . . , O . . . . X . . . | $$ | . X O X . . . . . . . O O O . . . . . | $$ | . X O . . . . . . . . . X X X . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ ---------------------------------------[/go]

Answer:

In fact, many good moves are available on the board:

Click Here To Show Diagram Code: [go]$$Wc Possible moves $$ --------------------------------------- $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . O . | $$ | . . . . . . . b a . . X . . . . . . O | $$ | . . . O . . O . . X . . . O . O O O X | $$ | . . d . . . . . . . . . . . . . X X X | $$ | . . e . . . O . . X . . . . . X . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . c . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . , . . . . . , . . . . . X . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . O . O O . . | $$ | . O . . . . . . . . . . . . . . X X . | $$ | O . O f . . . . . . . . . . . X . . . | $$ | . O X X . . . . . . . . . . . . . . . | $$ | . X O X . . . . . , O . . . . X . . . | $$ | . X O X . . . . . . . O O O . . . . . | $$ | . X O . . . . . . . . . X X X . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ ---------------------------------------[/go]

I am mostly interested in move "a" which attacks Black's shape. Katago expects Black to just answer and then White takes a big point elsewhere.

Click Here To Show Diagram Code: [go]$$Wc continuation of move a $$ --------------------------------------- $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . O . | $$ | . . . . . . . . 1 2 . X . . . . . . O | $$ | . . . O . . O . . X . . . O . O O O X | $$ | . . . . . . . . . . . . . . . . X X X | $$ | . . 3 . . . O . . X . . . . . X . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . , . . . . . , . . . . . X . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . O . O O . . | $$ | . O . . . . . . . . . . . . . . X X . | $$ | O . O . . . . . . . . . . . . X . . . | $$ | . O X X . . . . . . . . . . . . . . . | $$ | . X O X . . . . . , O . . . . X . . . | $$ | . X O X . . . . . . . O O O . . . . . | $$ | . X O . . . . . . . . . X X X . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ ---------------------------------------[/go]

For move

, White shouldn't make a move around N17: the upper right corner doesn't need to be protected since it is completely alive (for instance, a black move at O18 wouldn't be sente), and since Black has strenghthened his group with

, a white move around N17 won't put a lot of pressure so Black won't respond.

Black can't play

at O18, otherwise we get the following sequence:

Click Here To Show Diagram Code: [go]$$Wc continuation of move a (2) $$ --------------------------------------- $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . 7 8 6 2 . . . O . | $$ | . . . . . . . . 1 . 9 X 3 5 . . . . O | $$ | . . . O . . O . . X 0 b 4 O . O O O X | $$ | . . . . . . . . . . . . a . . . X X X | $$ | . . . . . . O . . X . . . . . X . . . | $$ | . . . . . . . . . . . . . . c . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . , . . . . . , . . . . . X . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . O . O O . . | $$ | . O . . . . . . . . . . . . . . X X . | $$ | O . O . . . . . . . . . . . . X . . . | $$ | . O X X . . . . . . . . . . . . . . . | $$ | . X O X . . . . . , O . . . . X . . . | $$ | . X O X . . . . . . . O O O . . . . . | $$ | . X O . . . . . . . . . X X X . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ ---------------------------------------[/go]

and then White a, Black b, White c follow.

jlt · Post by **jlt** » Fri Jul 23, 2021 12:59 am

Position #52, from an OGS 1k vs. 2k game. Black to play an endgame move.

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

Katago's answer:

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

White is not alive yet so

is sente. After

, Black aims at a.

If Black doesn't play at

then a sequence like this can happen:

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

jlt · Post by **jlt** » Sat Jul 24, 2021 1:52 am

Position #53, White to play.

Click Here To Show Diagram Code: [go]$$Wc $$ --------------------------------------- $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . X X . X . . . . . . . . . . . . | $$ | . . . , O O . . . , . . . . . X . . . | $$ | . . O . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . X . . . . . . . . . . . . . . . . | $$ | . . . X . . . . . , . . . . . , . . . | $$ | . . O X . . . . . . . . . . . . . . . | $$ | . . . O . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . X . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . O . . . . . , . . . . . O . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ ---------------------------------------[/go]

Two moves are possible:

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

The cut isn't a problem:

Click Here To Show Diagram Code: [go]$$Wc Very good for White $$ --------------------------------------- $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . X X . X . . . . . . . . . . . . | $$ | . . . , O O . . . , . . . . . X . . . | $$ | . . O . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . X . . . . . . . . . . . . . . . . | $$ | . . . X . . . . . , . . . . . , . . . | $$ | . 6 O X . . . . . . . . . . . . . . . | $$ | . 4 2 O 1 . . . . . . . . . . . . . . | $$ | . 5 3 . . . . . . . . . . . . . . . . | $$ | . . X 7 . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . O . . . . . , . . . . . O . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ ---------------------------------------[/go]

So Black would rather play from the other group:

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

However if Black decides to jump then White can protect the cut:

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

jlt · Post by **jlt** » Wed Aug 04, 2021 12:26 am

Position #54, Black to play. Several good moves are possible, find a good move in the bottom part of the board.

Click Here To Show Diagram Code: [go]$$Bc Black to play $$ --------------------------------------- $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . O . . . . . . . . . . . . . | $$ | . . . X . . . . . , . . . . . X . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . X . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . , . . . . . , . . . . X , O . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . O O . . . . . . . . . . X . O . . | $$ | . . X O . . . . . . X . . X O O . . . | $$ | . . X O . . . . . O X . X . X . . . . | $$ | . . X O . O . . O X O O . X X , O O . | $$ | . X . X O . . . O X . . . . . X X O . | $$ | . . . X O . . . O X . O . . . . . X . | $$ | . . . . . . . . . . . . . . . . . . . | $$ ---------------------------------------[/go]

Click Here To Show Diagram Code: [go]$$Bc Black to play $$ --------------------------------------- $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . b O . . . . . . . . . . . . . | $$ | . . . X . . . . . , . . . . . X . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . X . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . , . . . . . , . . . . X , O . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . O O . . . . a . . . . . X . O . . | $$ | . . X O . . . . . c X . . X O O . . . | $$ | . . X O . . . . . O X . X . X . . . . | $$ | . . X O . O . . O B O O . X X , O O . | $$ | . X . X O . . . O B . . . . . X X O . | $$ | . . . X O . . . O B . O . . . . . X . | $$ | . . . . . . . . . . . . . . . . . . . | $$ ---------------------------------------[/go]

Black needs to find a good way to use the dead marked stones. In the game I played "b", which loses 2.5 points according to Katago. The move "a" is better since it expands further towards the center. The move "b" is about as good as "a".

jlt · Post by **jlt** » Sun Aug 15, 2021 2:55 am

Position #55:

Click Here To Show Diagram Code: [go]$$Wc White to play $$ --------------------------------------- $$ | . . . . . . . . . . . . . . . . O O X | $$ | . . . X . . . . . . . . . O O O O X . | $$ | . . O . . X . . X . . . . O . O X X X | $$ | . . . O . . . . . , O O O . . , O X . | $$ | . . . . . . . . . . O . . . . O X X X | $$ | . . O . . . . . . X X O O . . O O O X | $$ | . . . . . . . . . X O O O O . . . O O | $$ | . . . . . . . . . . X O O . . O O O . | $$ | . . . . . . . . . . X . O O O O O O X | $$ | . . . , . . . . . , . X X O O X X O X | $$ | . . O . . . . . X . . . O O X . X X . | $$ | . . . . . . X . O X . . X X . X . . . | $$ | . . . . . X . . O . X . . . . . . . . | $$ | . O . O . . . . . . . X . . . . . . . | $$ | . O X O . X . O O . O . . X . X . . . | $$ | . X O O . . X X . , O X X O X , . . . | $$ | X . X O . O . . X . O X O O O X . . . | $$ | . X X X O . . O X X O O O O X . X . . | $$ | . . . . . . . . . . . . . X . X . . . | $$ ---------------------------------------[/go]

Life In 19x19

Shapes to remember (SDK level)

Re: Shapes to remember (SDK level)

Re: Shapes to remember (SDK level)

Re: Shapes to remember (SDK level)

Re: Shapes to remember (SDK level)

Re: Shapes to remember (SDK level)

Re: Shapes to remember (SDK level)

Re: Shapes to remember (SDK level)

Re: Shapes to remember (SDK level)

Re: Shapes to remember (SDK level)

Re: Shapes to remember (SDK level)

Re: Shapes to remember (SDK level)

Re: Shapes to remember (SDK level)

Re: Shapes to remember (SDK level)

Re: Shapes to remember (SDK level)

Re: Shapes to remember (SDK level)