Flying below the radar of area scoring
Lightvector highlighted (and simultaneously warned us all?) that KataGo – using area scoring – will be unable to distinguish between W+1
(territory scoring) and W+2
(territory scoring). This posting will show how significant his annotation was.
- Click Here To Show Diagram Code
[go]$$Wcm120
$$ +---------------------------------------+
$$ | . . . X O . . . . . . . X X . . O X . |
$$ | . . . X X O O X O O . X O X O . . O . |
$$ | . . . X O X O O . . . X O O . O O . . |
$$ | . X O , . X X 2 3 O . X . O O X . . . |
$$ | . . X X X X O O O . O X X . X X O O . |
$$ | . X . O O O X X X O . . X . X O O . . |
$$ | O O O O 1 X O O X X O O 6 O X . . X . |
$$ | O X . X . X . O O X O . . . X X X X X |
$$ | O X . X . . . O X X O . X X X X O O O |
$$ | X O O X . X . O X O O X X O O O O X . |
$$ | X X O O X . . O X O . X O O O . X X X |
$$ | X X . O X . . O X O . X O O X X X O O |
$$ | X X O O X . . O X O . X O O O X X X O |
$$ | X O O 5 O X . O X O . X X O O O X O O |
$$ | X O X O 4 X . O X O X . O X X X O O O |
$$ | O X X X X X . O X O O O O X O X O O X |
$$ | O . . . O X O O X X X X X . O X X O X |
$$ | O . X . X O . O O O O O O X O X . O X |
$$ | . X . . X O O O . . . . O X X X . O . |
$$ +---------------------------------------+[/go]
White's bad-shape move at 120 is gote locally, so Black – after inserting some forcing moves – might play tenuki with 125.
- Click Here To Show Diagram Code
[go]$$Wcm126
$$ +---------------------------------------+
$$ | . . . X O . . . . . . . X X . . O X . |
$$ | . . . X X O O X O O . X O X O . . O . |
$$ | . . . X O X O O . . . X O O . O O . . |
$$ | . X O , . X X X O O . X . O O X . . . |
$$ | . . X X X X O O O . O X X . X X O O . |
$$ | . X . O O O X X X O . . X . X O O . . |
$$ | O O O O O X O O X X O O X O X . . X . |
$$ | O X . X . X . O O X O . . . X X X X X |
$$ | O X . X 4 1 2 O X X O . X X X X O O O |
$$ | X O O X . X 3 O X O O X X O O O O X . |
$$ | X X O O X . . O X O . X O O O . X X X |
$$ | X X . O X . . O X O . X O O X X X O O |
$$ | X X O O X . . O X O . X O O O X X X O |
$$ | X O O O O X . O X O . X X O O O X O O |
$$ | X O X O X X . O X O X . O X X X O O O |
$$ | O X X X X X . O X O O O O X O X O O X |
$$ | O . . . O X O O X X X X X . O X X O X |
$$ | O . X . X O . O O O O O O X O X . O X |
$$ | . X . . X O O O . . . . O X X X . O . |
$$ +---------------------------------------+[/go]
If Black plays away, White's wedge at 126 is best.
- Click Here To Show Diagram Code
[go]$$Wcm130
$$ +---------------------------------------+
$$ | . . . X O . . . . . . . X X . . O X . |
$$ | . . . X X O O X O O . X O X O . . O . |
$$ | . . . X O X O O . . . X O O . O O . . |
$$ | . X O , . X X X O O . X . O O X . . . |
$$ | . . X X X X O O O . O X X . X X O O . |
$$ | . X . O O O X X X O . . X . X O O . . |
$$ | O O O O O X O O X X O O X O X . . X . |
$$ | O X . X a X 1 O O X O . . . X X X X X |
$$ | O X . X X 2 X O X X O . X X X X O O O |
$$ | X O O X b X O O X O O X X O O O O X . |
$$ | X X O O X 5 . O X O . X O O O . X X X |
$$ | X X . O X 3 . O X O . X O O X X X O O |
$$ | X X O O X 4 . O X O . X O O O X X X O |
$$ | X O O O O X . O X O . X X O O O X O O |
$$ | X O X O X X . O X O X . O X X X O O O |
$$ | O X X X X X . O X O O O O X O X O O X |
$$ | O . . . O X O O X X X X X . O X X O X |
$$ | O 6 X . X O . O O O O O O X O X . O X |
$$ | . X . . X O O O . . . . O X X X . O . |
$$ +---------------------------------------+[/go]
White did not only destroy all of Black's territory in the left centre.
She also keeps her liberty at a, and created an additional approach-move liberty at b.
- Click Here To Show Diagram Code
[go]$$Wcm136
$$ +---------------------------------------+
$$ | . . . X O 1 . . . . . 6 X X 5 . O X . |
$$ | . . . X X O O X O O . X O X O . . O . |
$$ | . . . X O X O O . . . X O O . O O . . |
$$ | . X O , . X X X O O . X . O O X . . . |
$$ | . . X X X X O O O . O X X . X X O O . |
$$ | . X . O O O X X X O . . X . X O O . . |
$$ | O O O O O X O O X X O O X O X . . X . |
$$ | O X . X . X O O O X O . 7 . X X X X X |
$$ | O X . X X X X O X X O . X X X X O O O |
$$ | X O O X . X O O X O O X X O O O O X . |
$$ | X X O O X O 3 O X O . X O O O . X X X |
$$ | X X . O X O 2 O X O . X O O X X X O O |
$$ | X X O O X X 4 O X O . X O O O X X X O |
$$ | X O O O O X . O X O . X X O O O X O O |
$$ | X O X O X X . O X O X . O X X X O O O |
$$ | O X X X X X . O X O O O O X O X O O X |
$$ | O . . . O X O O X X X X X . O X X O X |
$$ | O X X . X O . O O O O O O X O X . O X |
$$ | . X . . X O O O . . . . O X X X . O . |
$$ +---------------------------------------+[/go]
White 136 and Black 137 are miai.
Finally, White answers at the top right, wedging in at 142.
- Click Here To Show Diagram Code
[go]$$Bcm143
$$ +---------------------------------------+
$$ | . . . X O O . . . . . X X X O . O X . |
$$ | . . . X X O O X O O . X O X O . . O . |
$$ | . . . X O X O O . . . X O O . O O . . |
$$ | . X O , . X X X O O . X . O O X . . . |
$$ | . . X X X X O O O . O X X 2 X X O O . |
$$ | . X . O O O X X X O . . X 3 X O O . . |
$$ | O O O O O X O O X X O O X O X . . X . |
$$ | O X . X . X O O O X O . O 1 X X X X X |
$$ | O X . X X X X O X X O . X X X X O O O |
$$ | X O O X . X O O X O O X X O O O O X . |
$$ | X X O O X O O O X O . X O O O . X X X |
$$ | X X . O X O X O X O . X O O X X X O O |
$$ | X X O O X X X O X O . X O O O X X X O |
$$ | X O O O O X . O X O . X X O O O X O O |
$$ | X O X O X X . O X O X . O X X X O O O |
$$ | O X X X X X . O X O O O O X O X O O X |
$$ | O . . . O X O O X X X X X . O X X O X |
$$ | O X X . X O . O O O O O O X O X . O X |
$$ | . X . . X O O O . . . . O X X X . O . |
$$ +---------------------------------------+[/go]
Black 143 might be the reply that comes to mind first, but the subsequent sequence will not change the final score.
- Click Here To Show Diagram Code
[go]$$Wcm146
$$ +---------------------------------------+
$$ | . . . X O O . . . . . X X X O . O X . |
$$ | . . . X X O O X O O . X O X O . . O . |
$$ | . . . X O X O O . . 1 X O O . O O . . |
$$ | . X O , . X X X O O . X . O O X . . . |
$$ | . . X X X X O O O . O X X O X X O O . |
$$ | . X . O O O X X X O . . X X X O O . . |
$$ | O O O O O X O O X X O O X . X . . X . |
$$ | O X . X . X O O O X O 2 O X X X X X X |
$$ | O X . X X X X O X X O . X X X X O O O |
$$ | X O O X . X O O X O O X X O O O O X . |
$$ | X X O O X O O O X O . X O O O . X X X |
$$ | X X . O X O X O X O . X O O X X X O O |
$$ | X X O O X X X O X O . X O O O X X X O |
$$ | X O O O O X . O X O . X X O O O X O O |
$$ | X O X O X X . O X O X . O X X X O O O |
$$ | O X X X X X . O X O O O O X O X O O X |
$$ | O . . . O X O O X X X X X . O X X O X |
$$ | O X X . X O . O O O O O O X O X . O X |
$$ | . X . . X O O O . . . . O X X X . O . |
$$ +---------------------------------------+[/go]
Black 147 is sente, ...
- Click Here To Show Diagram Code
[go]$$Wcm148
$$ +---------------------------------------+
$$ | . . . X O O . . . . . X X X O . O X . |
$$ | . . . X X O O X O O . X O X O . . O . |
$$ | . . . X O X O O . . O X O O . O O . . |
$$ | . X O , . X X X O O . X . O O X . . . |
$$ | . . X X X X O O O . O X X O X X O O . |
$$ | 2 X . O O O X X X O . . X X X O O . . |
$$ | O O O O O X O O X X O O X . X . . X . |
$$ | O X . X . X O O O X O X . X X X X X X |
$$ | O X . X X X X O X X O 1 X X X X O O O |
$$ | X O O X . X O O X O O X X O O O O X . |
$$ | X X O O X O O O X O . X O O O . X X X |
$$ | X X . O X O X O X O . X O O X X X O O |
$$ | X X O O X X X O X O . X O O O X X X O |
$$ | X O O O O X . O X O . X X O O O X O O |
$$ | X O X O X X . O X O X . O X X X O O O |
$$ | O X X X X X . O X O O O O X O X O O X |
$$ | O . . . O X O O X X X X X . O X X O X |
$$ | O X X . X O . O O O O O O X O X . O X |
$$ | . X . . X O O O . . . . O X X X . O . |
$$ +---------------------------------------+[/go]
...but White will capture this stone (and connect) in the very end.
Black 149 continues with the Main Semeai.
The game will still end with W + 2.
+ + + + + + + + + + + + + + + + + + + + + + + + + + + + + +
- Click Here To Show Diagram Code
[go]$$Bcm143
$$ +---------------------------------------+
$$ | . . . X O O . . . . . X X X O . O X . |
$$ | . . . X X O O X O O . X O X O . . O . |
$$ | . . . X O X O O . . . X O O . O O . . |
$$ | . X O , . X X X O O . X . O O X . . . |
$$ | . . X X X X O O O . O X X a X X O O . |
$$ | . X . O O O X X X O . . X 1 X O O . . |
$$ | O O O O O X O O X X O O X O X . . X . |
$$ | O X . X . X O O O X O b Q c X X X X X |
$$ | O X . X X X X O X X O . X X X X O O O |
$$ | X O O X . X O O X O O X X O O O O X . |
$$ | X X O O X O O O X O . X O O O . X X X |
$$ | X X . O X O X O X O . X O O X X X O O |
$$ | X X O O X X X O X O . X O O O X X X O |
$$ | X O O O O X . O X O . X X O O O X O O |
$$ | X O X O X X . O X O X . O X X X O O O |
$$ | O X X X X X . O X O O O O X O X O O X |
$$ | O . . . O X O O X X X X X . O X X O X |
$$ | O X X . X O . O O O O O O X O X . O X |
$$ | . X . . X O O O . . . . O X X X . O . |
$$ +---------------------------------------+[/go]
However, Joachim suggested answering White's wedge (triangled) by giving atari from above, with the move at 143 here.
In principle, this move is a kind of Michael Redmond's kikashi, just played on the other side of the bamboo joint. Black gains an additional liberty at a, being worth one destroyed point of White territory.
(Funnily enough I had to convince Joachim from the validity of the above mentioned effect in this case. Usually, it is Joachim, who has to remind ME of findings that we had a decade ago.)Black will capture at c, only after White connected at b.
+ + + + +
Let's compare the final board positions:
- Click Here To Show Diagram Code
[go]$$B
$$ --------------------------------------------------------------------------------+
$$ - . . . X O O a . . . O X X X O . O X . - . . . X O O P . . . O X X X O . O X . -
$$ - . . . X X O O X O O O X O X O . . O . - . . . X X O O X O O O X O X O . . O . -
$$ - . . . X O X O O . b O X O O O O O . . - . . . X O X O O . P X X O O O O O . . -
$$ - . X O , . X X X O O O X . O O X O . . - . X O , . X X X O O . X . O O X O . . -
$$ - . . X X X X O O O . O X X . X X O O . - . . X X X X O O O . O X X O X X O O . -
$$ - X X X O O O . . . O . O X X X O O O O - X X X O O O . . . O . O X X X O O O O -
$$ - O O O O O X O O . . O O X c X O O X O - O O O O O X O O . . O O O Q X . . X O -
$$ - O X X X X X O O O . O P O X X X X X X - O X X X O X . O O . O e O . X X X X X -
$$ - O X X X X B X O . . O O X X X X . . . - O X X X X Y . O . . O O X X X X . . . -
$$ - O O O X Z X O O . O O X X . . , . X X - O O O X f X . O . O O X X . . , . X X -
$$ - . O O O X O O O . O O X . . . X X X X - X X O O X . O O . O . X . . . X X X X -
$$ - X X O O X O X O . O . X . . X X X . . - X X O O X X . O . O O X . . X X X . . -
$$ - X X O O X X X O . O . X . . . X X X . - . O O O X X . O . O O X . . . X X X . -
$$ - O O O O O X . O . O X X X . . . X . . - O O O O O X . O . O X X X . . . X . . -
$$ - O O X O X X . O . O X O O X X X . . . - O O X O X X . O . O X O O X X X . . . -
$$ - O X X X X X . O . O O O O X O X . . X - O X X X X X . O . O O O O X . X . . X -
$$ - O X . . O X O O . . . O O O O X X . X - O X . . O X O O . . . O O O O X X . X -
$$ - O X X . X O . O O O O O O X . X X . X - O X X . X O . O O O O O O X . X X . X -
$$ - X X . . X O O O . . . . O X X X X . . - X X . . X O O O . . . . O X X X X . . -
$$ --------------------------------------------------------------------------------+[/go]
In Joachim's variation (at the left), White has two points of territory at the top, at a and at b.
In Joachim's variation, Black has captured two White stones, at c and at o.
The net effect is zero.
In KataGo's variation (at the right), White has one point of territory at e, which is compensated for by Black's point of territory at f.
Eventually, Black's additional point of territory inside his eye at c makes the difference.
The game – following Joachim's tesuji – now ends with
W + 1!
+ + + + + + + + + + + + + + + + + + + + + + + + + + + + + +
There can only be one
- Click Here To Show Diagram Code
[go]$$Bc
$$ +---------------------------------------+
$$ | . . . X O . . . . . . . X X . . O X . |
$$ | . . . X X O O X O O . X O X O . . O . |
$$ | . . . X O X O O . . . X O O . O O . . |
$$ | . X O , . X X . . O . X . O O X . . . |
$$ | . . X X X X O O O . O X X . X X O O . |
$$ | . X . O O O X X X O . . X . X O O . . |
$$ | O O O O a X O O X X O O b O X . . Y . |
$$ | O X . X . X . O O X O . . . X X X X X |
$$ | O X . X . . . O X X O . X X X X O O O |
$$ | X O O X . X . O X O O X X O O O O X . |
$$ | X X O O X . . O X O . X O O O . X X X |
$$ | X X . O X . . O X O . X O O X X X O O |
$$ | X X O O X . . O X O . X O O O X X X O |
$$ | X O O . O X . O X O . X X O O O X O O |
$$ | X O X O . X . O X O X . O X X X O O O |
$$ | O X X X X X . O X O O O O X O X O O X |
$$ | O . . . O X O O X X X X X . O X X O X |
$$ | O . X . X O . O O O O O O X O X . O X |
$$ | . X . . X O O O . . . . O X X X . O . |
$$ +---------------------------------------+[/go]
Above we found that White's bad-shape move at a is no longer effective, as it is miai with the point of b.
My guzumi (triangled) remains the only effective bad-shape move in this problem
+ + + + + + + + + + + + + + + + + + + + + + + + + + + + + +
For your convenience follow the SGFs of both lines:
_________________
The really most difficult Go problem ever:
https://igohatsuyoron120.de/index.htmIgo Hatsuyōron #120 (really solved by KataGo)