Opening problems for AI: Problem 46

Bill Spight · #1

White to play.

As always, assume komi.

Click Here To Show Diagram Code: [go]$$Bc White to play. $$ --------------------------------------- $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . 4 . . . . . . . . . . . . . . . | $$ | . . . , . . . . . , . . . . . , 1 . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . , . . . . . , . . . . . , . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . a . . . . . . . . . . . . . . . . | $$ | . . 6 9 3 . . . . , . . . . . , 2 . . | $$ | . . 7 . . . 8 . . . . b . . 5 . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ ---------------------------------------[/go]

Which is better, the extension to a or the pincer at b?

Enjoy!

Joaz Banbeck · #2

IMHO, 'a' is the better move

Click Here To Show Diagram Code: [go]$$Bc White to play. $$ --------------------------------------- $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . 4 . . . . . . . . . . . . . . . | $$ | . . . , . . . . . , . . . . . , 1 . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . , . . . . . , . . . . . , . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . a . . . . . . . . . . . . . . . . | $$ | . . 6 9 3 . . . . , . . . . . , 2 . . | $$ | . . 7 . . . 8 . . . . b . . 5 . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ ---------------------------------------[/go]

The position of :w8:

makes the difference.

Id :w6:

is captured, then :w8:

is merely a nusiance. It can mostly be ignored by black, and very possibly be swallowed on a large scale without touching it.
If :w6:

lives, then :w8:

is the stepping stone for a white attack.

With a white stone at G3, white's play at C5 is sente, threatening B3.

Click Here To Show Diagram Code: [go]$$Wc The expansive defense, allowing white 3 to undercut in sente $$ | . . . . . . . . . . . . . . . , . . . | $$ | . . . , . . . . . , . . . . . , . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . 1 . . . . . . . . . . . . . . . . | $$ | . . O X X . . . . , . . . . . , O . . | $$ | . 2 X . . . W . . . . b . . X . . . . | $$ | . . . . 3 . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ ---------------------------------------[/go]

Click Here To Show Diagram Code: [go]$$Wc The tight defense, white extends. Black is small and ugly. $$ | . . . . . . . . . . . . . . . , . . . | $$ | . . . , . . . . . , . . . . . , . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . 3 . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . 1 . . . . . . . . . . . . . . . . | $$ | . . O X X . . . . , . . . . . , O . . | $$ | . . X . . . W . . . . b . . X . . . . | $$ | . . . 2 . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ ---------------------------------------[/go]

jlt · #3

Shaddy · #4

Joaz Banbeck wrote:

Click Here To Show Diagram Code: [go]$$Wc The tight defense, white extends. Black is small and ugly. $$ | . . . . . . . . . . . . . . . , . . . | $$ | . . . , . . . . . , . . . . . , . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . 1 . . . . . . . . . . . . . . . . | $$ | . . O X X . . . . , . . . . . , O . . | $$ | . . X . . . W . . . . 3 . . X . . . . | $$ | . . . 2 . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ ---------------------------------------[/go]

I agree, but think 2 is gote.

Joaz Banbeck · #5

Shaddy wrote:

...

Click Here To Show Diagram Code: [go]$$Wc The tight defense, white extends. Black is small and ugly. $$ | . . . . . . . . . . . . . . . , . . . | $$ | . . . , . . . . . , . . . . . , . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . 1 . . . . . . . . . . . . . . . . | $$ | . . O X X . . . . , . . . . . , O . . | $$ | . . X . . . W . . . . 3 . . X . . . . | $$ | . . . 2 . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ ---------------------------------------[/go]

I agree, but think 2 is gote.

I extended to C8 because I didn't like this:

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

As fights unfurl in each of the lower corners, black's groups will become stronger. White's middle group will look relatively weak.
White has three groups that will need stones, black has two.

Gomoto · #6

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

Joaz Banbeck · #7

[admin]
Sorry, folks, we had a leak from an alternate dimension - one in which white had played at C3. TTBOOK, only one post got through.
Quick work by your admins has sealed the tear, and we expect no further problems from it.
[/admin]

jlt · #8

Gomoto lives in dimension (3,3).

Knotwilg · #9

Shaddy · **#10**

Joaz Banbeck wrote:

Shaddy wrote:

...

Click Here To Show Diagram Code: [go]$$Wc The tight defense, white extends. Black is small and ugly. $$ | . . . . . . . . . . . . . . . , . . . | $$ | . . . , . . . . . , . . . . . , . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . 1 . . . . . . . . . . . . . . . . | $$ | . . O X X . . . . , . . . . . , O . . | $$ | . . X . . . W . . . . 3 . . X . . . . | $$ | . . . 2 . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ ---------------------------------------[/go]

I agree, but think 2 is gote.

I extended to C8 because I didn't like this:

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

As fights unfurl in each of the lower corners, black's groups will become stronger. White's middle group will look relatively weak.
White has three groups that will need stones, black has two.

ok, i don't like this, but i think the problem is 3 not 1. maybe let's play 3 as kosumi from 3-4?

Knotwilg · **#11**

@Joaz

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

Surely Black will play :b8:

at A instead?

And so, :w7:

is a mistake

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

White should simply play :w7:

and then Black has to decide how to deal with the bottom. :b8:

attacks the pincer but is already pincered back by the marked stone, which is disposable due to the :w1:

-

having been forcing upon Black.

Bill Spight · **#12**

This seems to have been a better problem than I anticipated. It has sparked some very interesting discussion.

I am including the GoGoD SGF file for the whole game, because this is the game where Dochi plays a famous endgame tesuji. See B225.

Tryss · **#13**

What's interesting is an alternative move by Katago :

Click Here To Show Diagram Code: [go]$$Bc Alternative play by Katago $$ --------------------------------------- $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . 4 . . . . . . . . . . . . . . . | $$ | . . . , . . . . . , . . . . . , 1 . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . , . . . . . , . . . . . , . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . a . . . . . . . . . . . . . . . . | $$ | . . 6 9 3 . . . . , . . . . . , 2 . . | $$ | . . 7 . . . 8 . . W . b . . 5 . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ ---------------------------------------[/go]

It has lower policy than a, but about the same winrate/score, and become the "blue move" with enough playouts ( over 100k in my case)

Bill Spight · **#14**

Tryss wrote:

What's interesting is an alternative move by Katago :

Click Here To Show Diagram Code: [go]$$Bc Alternative play by Katago $$ --------------------------------------- $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . 4 . . . . . . . . . . . . . . . | $$ | . . . , . . . . . , . . . . . , 1 . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . , . . . . . , . . . . . , . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . a . . . . . . . . . . . . . . . . | $$ | . . 6 9 3 . . . . , . . . . . , 2 . . | $$ | . . 7 . . . 8 . . W . b . . 5 . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ ---------------------------------------[/go]

It has lower policy than a, but about the same winrate/score, and become the "blue move" with enough playouts ( over 100k in my case)

Very interesting!

Unlike the pincer, :wc:

will not become a liability.

After White plays :wc:

, what is KataGo's top choice for :b11:

? a?

Tryss · **#15**

Black play at a, then white tenuki in the top right corner with P17. The game could look like this :

Click Here To Show Diagram Code: [go]$$Wc10 $$ --------------------------------------- $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . O . . . . . . . . . . 3 . . . . | $$ | . . . , . . . . . , . . . . . , X . . | $$ | . . c 4 . . . . . . . . . . . 5 6 . . | $$ | . . . . . . . . . . . . . . . 7 . . . | $$ | . . b . . . . . . . . . . . . . 8 . . | $$ | . . a . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . , . . . . . , . . . . . , . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . 2 . . . . . . . . . . . . . . . . | $$ | . . O X X . . . . , . . . . . , O . . | $$ | . . X . . . O . . 1 . . . . X . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ ---------------------------------------[/go]

And the position after :w8:

is interesting : Katago* consider the three moves a, b and c as very close. After 41389 playouts, the results are :
- a has 16k visits, 57.5%wr and +0.9pts
- b has 10k visits, 57.3%wr and +0.9pts
- c has 12k visits, 57.2%wr and +0.9pts

*) with the 20b network from the end of april, 7.5 komi and japanese rules

lightvector · **#16**

Tryss wrote:

What's interesting is an alternative move by Katago :

Click Here To Show Diagram Code: [go]$$Bc Alternative play by Katago $$ --------------------------------------- $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . 4 . . . . . . . . . . . . . . . | $$ | . . . , . . . . . , . . . . . , 1 . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . , . . . . . , . . . . . , . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . a . . . . . . . . . . . . . . . . | $$ | . . 6 9 3 . . . . , . . . . . , 2 . . | $$ | . . 7 . . . 8 . . W . b . . 5 . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ ---------------------------------------[/go]

It has lower policy than a, but about the same winrate/score, and become the "blue move" with enough playouts ( over 100k in my case)

Interestingly, the 40-block network seems to differ here a little, and prefer's ELF's move more.

KataGo seems to have different preferences than ELF in a number of other places in one of Bill's presented lines. It's hard to say whether for sure whether they are better or worse in some cases.

Prefers this slightly over "a":

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

Prefers this slightly over "a". Deeper search suggests this doesn't necessarily lead to a better result, but is also interesting and tricky for white to deal with:

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

Some variations for the diagonal:

One possible way. This way is a little favorable for black. Black has a bit of ugly shape on the left, but white is pretty busy everywhere.

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

This way white pulls some tesujis out of a hat and fights back well, but black will still end up fine ends up fine anyways. The wedge is a sacrifice to let white break out, otherwise white would probably be in trouble here, but black will poke out too and continues to attack afterward.

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

This result is slightly favorable for black. The 8-9 exchange is locally ugly, but stops white from wedging at "a", and black is splitting both white groups while still poking ahead of white on the left side and making profit there.

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

Unlike the above two cases which one might classify as just a difference in preference, in this case, KataGo thinks ELF's "a" for black is a noticeable mistake, and prefers 1-2-3 to take a sente exchange and not let white have the chance to run in the first place. White's lone stone isn't entirely dead, but black has control:

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

White's cut doesn't work, which means that at the expense of strengthening white with a not-great exchange for the outside, black has managed to kill white's two stones in sente, instead of gote. Note that if black were to exchange "a"-"b" below, then white's "c" would work here due to a squeeze and ladder, this is the reason for not playing the peep and why sente is possible if the peep is omitted.

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

Bill Spight · **#17**

Wow! You gotta love those 18th century games.

dhu163 · **#18**

Opening problems for AI: Problem 46

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