Life In 19x19

Posted: **Thu Jan 05, 2023 10:03 am**

Click Here To Show Diagram Code: [go]$$B What is the best move ? $$ --------------------------------------- $$ . . . O O X . | $$ . . . O X X X | $$ . . . O X b O | $$ . . . O O X a | $$ . . . . O O X | $$ . . . . . O . | $$ . . . . . O O | $$ . . . . . . . |[/go]

Very often apparently simple position are not that easy.
AGA rule : for a theoritical point of view what is the best move for black? a or b ?

Posted: **Thu Jan 05, 2023 10:56 am**

I forget if the AGA rules allow for suicide, but 'a' should be superior to 'b' in any ruleset that does. For black to play 'b' leaves 'a' as a ko threat.

Posted: **Thu Jan 05, 2023 11:02 am**

pwaldron wrote:I forget if the AGA rules allow for suicide, but 'a' should be superior to 'b' in any ruleset that does. For black to play 'b' leaves 'a' as a ko threat.

For me AGA rules do not allow suicide. BTW, if you prefer you can also consider you use chinese rules (I mean area counting).
I do not understand your point with ko threat : after black "a" white has also a ko threat availbale hasn't she?

Posted: **Thu Jan 05, 2023 11:06 am**

If both players play alternatively then a and b are equivalent:

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

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

But suppose Black plays a. Later if there is a ko fight, White ataris to make a ko threat, Black doesn't respond and White kills.

Click Here To Show Diagram Code: [go]$$B $$ --------------------------------------- $$ . . . O O X . | $$ . . . O X X X | $$ . . . O X 4 O | $$ . . . O O . . | $$ . . . . O O . | $$ . . . . . O 2 | $$ . . . . . O O | $$ . . . . . . . |[/go]

If another ko appears later then Black still has chances to survive by playing twice in a row. Then Black lives with 2 points and there is one dame left.

Click Here To Show Diagram Code: [go]$$B $$ --------------------------------------- $$ . . . O O X . | $$ . . . O X X X | $$ . . . O X . . | $$ . . . O O 7 5 | $$ . . . . O O . | $$ . . . . . O O | $$ . . . . . O O | $$ . . . . . . . |[/go]

On the other hand if Black plays b, after one ignored ko threat by Black and one ignored ko threat by White, Black lives with 3 points.

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

Click Here To Show Diagram Code: [go]$$B $$ --------------------------------------- $$ . . . O O X . | $$ . . . O X X X | $$ . . . O X X . | $$ . . . O O X 7 | $$ . . . . O O 5 | $$ . . . . . O O | $$ . . . . . O O | $$ . . . . . . . |[/go]

The end result depends on the parity of the number of dame at the end of the game, but with the assumption that the sequence of plays is Black-White-White-Black-Black, then b is superior by 1 point on average.

Posted: **Thu Jan 05, 2023 11:23 am**

Click Here To Show Diagram Code: [go]$$B What is the best move ? $$ --------------------------------------- $$ . . . O O X . | $$ . . . O X X X | $$ . . . O X b O | $$ . . . O O X a | $$ . . . . O O X | $$ . . . . . O . | $$ . . . . . O O | $$ . . . . . . . |[/go]

Very nice jlt I agree entirely.
Here is an example where it remains only three small areas for the yose.
Black "b" is the best move in order to avoid the following (wrong) sequence :

Posted: **Thu Jan 05, 2023 11:24 am**

Gérard TAILLE wrote: For me AGA rules do not allow suicide. BTW, if you prefer you can also consider you use chinese rules (I mean area counting).
I do not understand your point with ko threat : after black "a" white has also a ko threat availbale hasn't she?

You're right. I was just thinking of the suicidal ko threat, but the external atari is there with the other move. My mistake.

Posted: **Sat Jan 07, 2023 2:12 pm**

Here is another problem:

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

What is the best choice :

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

or immediatly

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

Posted: **Sat Jan 07, 2023 6:05 pm**

I guess it's the same philosophy as the first example: if white is going to respond to the peep, then the outcome is the same regardless of move order, so the real question is what happens if white ignores the peep?

If white responds: you're going to end up with this position in either case --

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

and the point is to stop white gaining a tempo with

this way --

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

If white is going to ignore, then the

-

exchange below looks like an example of a reverse in CGT terms: black doesn't gain anything, and possibly loses something (one point from

becoming a prisoner)?

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

So I'd say just play

at

directly, an example of the 123 principle.

What have I missed?

Posted: **Sun Jan 08, 2023 3:28 am**

xela wrote:I guess it's the same philosophy as the first example: if white is going to respond to the peep, then the outcome is the same regardless of move order, so the real question is what happens if white ignores the peep?

If white responds: you're going to end up with this position in either case --

$$B
$$ -------------------
$$ . . . X . X X O . |
$$ . . . X X X O O . |
$$ . . . . X O O X . |
$$ . . . . O . O . . |
$$ . . . . O O . O O |
$$ . . . . . O O O X |
$$ . . . . . . . X X |
$$ . . . . . . . X . |
$$ . . . . . . . X X |
$$ . . . . . . . . . |
$$ . . . . . . . . . |
Click Here To Show Diagram Code
[go]$$B $$ ------------------- $$ . . . X . X X O . | $$ . . . X X X O O . | $$ . . . . X O O X . | $$ . . . . O . O . . | $$ . . . . O O . O O | $$ . . . . . O O O X | $$ . . . . . . . X X | $$ . . . . . . . X . | $$ . . . . . . . X X | $$ . . . . . . . . . | $$ . . . . . . . . . |[/go]
and the point is to stop white gaining a tempo with this way --

$$B
$$ -------------------
$$ . . . X . X X O . |
$$ . . . X X X O . . |
$$ . . . . X O . W . |
$$ . . . . O . O . . |
$$ . . . . O O . . O |
$$ . . . . . O O O X |
$$ . . . . . . . X X |
$$ . . . . . . . X . |
$$ . . . . . . . X X |
$$ . . . . . . . . . |
$$ . . . . . . . . . |
Click Here To Show Diagram Code
[go]$$B $$ ------------------- $$ . . . X . X X O . | $$ . . . X X X O . . | $$ . . . . X O . W . | $$ . . . . O . O . . | $$ . . . . O O . . O | $$ . . . . . O O O X | $$ . . . . . . . X X | $$ . . . . . . . X . | $$ . . . . . . . X X | $$ . . . . . . . . . | $$ . . . . . . . . . |[/go]
If white is going to ignore, then the - exchange below looks like an example of a reverse in CGT terms: black doesn't gain anything, and possibly loses something (one point from becoming a prisoner)?

$$B
$$ -------------------
$$ . . . X . . . . . |
$$ . . . X X X O . . |
$$ . . . . X O . 3 . |
$$ . . . . O . O . . |
$$ . . . . O O . . 2 |
$$ . . . . . O O O 1 |
$$ . . . . . . . X . |
$$ . . . . . . . X . |
$$ . . . . . . . X X |
$$ . . . . . . . . . |
$$ . . . . . . . . . |
Click Here To Show Diagram Code
[go]$$B $$ ------------------- $$ . . . X . . . . . | $$ . . . X X X O . . | $$ . . . . X O . 3 . | $$ . . . . O . O . . | $$ . . . . O O . . 2 | $$ . . . . . O O O 1 | $$ . . . . . . . X . | $$ . . . . . . . X . | $$ . . . . . . . X X | $$ . . . . . . . . . | $$ . . . . . . . . . |[/go]
So I'd say just play at directly, an example of the 123 principle.

What have I missed?

I understand your point. If white doesn't answer the peep then peeping immediately is better and I agree with you.
However what happens if you suppose all remaining yose points of the board are quite small ? In other word suppose black timing is good and white has to answer the peep in the two considered sequences ? Witch one is the best?

Posted: **Tue Jan 10, 2023 2:15 pm**

Here is a hint:

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

AGA rules. By just adding a ko threat and a dame in the upper right corner do you see which of the two moves "a" and "b" is the best?

Posted: **Mon Jan 16, 2023 5:44 am**

xela wrote:
$$B
$$ -------------------
$$ . . . X . . . . . |
$$ . . . X X X O . . |
$$ . . . . X O . 3 . |
$$ . . . . O . O . . |
$$ . . . . O O . . 2 |
$$ . . . . . O O O 1 |
$$ . . . . . . . X . |
$$ . . . . . . . X . |
$$ . . . . . . . X X |
$$ . . . . . . . . . |
$$ . . . . . . . . . |
Click Here To Show Diagram Code
[go]$$B $$ ------------------- $$ . . . X . . . . . | $$ . . . X X X O . . | $$ . . . . X O . 3 . | $$ . . . . O . O . . | $$ . . . . O O . . 2 | $$ . . . . . O O O 1 | $$ . . . . . . . X . | $$ . . . . . . . X . | $$ . . . . . . . X X | $$ . . . . . . . . . | $$ . . . . . . . . . |[/go]
So I'd say just play at directly, an example of the 123 principle.

I agree entirely with you xela, the exchange

followed by the peep at

is generally inferior to the immediat peep. I like very much the 123 principle and its application is good sense.
A proof of the 123 principle efficiency is that is is quite difficult to change a little the position in order to make the

better.
Maybe here is an exemple after a lot of tries:

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

If I am not wrong, due to the white ko threat existing in the top right corner, the exchnage

followed by the standart

move is better than the immediat

move.
Here again it is only an exception. The 123 principle is a very good principle isn't it?

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