Bill Spight wrote:Gérard TAILLE wrote:Bill Spight wrote:
$$B Seki
$$ -----------------
$$ | W W W X X . . |
$$ | C C B O X . . |
$$ | B B B O X . . |
$$ | O O O O X . . |
$$ | . . . . . . . |
$$ | . . . . . . . |
$$ | . . . . . . . |
$$ -----------------
- Click Here To Show Diagram Code
[go]$$B Seki
$$ -----------------
$$ | W W W X X . . |
$$ | C C B O X . . |
$$ | B B B O X . . |
$$ | O O O O X . . |
$$ | . . . . . . . |
$$ | . . . . . . . |
$$ | . . . . . . . |
$$ -----------------[/go]
By area scoring the corner is worth +1 point. But the CGT value is {9|-9||9|-9} = 0, which is also the territory value. Normalizing the area score yields the CGT value.

Now it's quite clear for infinitesimals let's take sekis
You wrote {9|-9||9|-9} = 0
Assume the game G = {13|-5||13|-5}
Neither black nor white want to play in this game. How do you calculate the value of such game for a CGT point of view?
{13|-5||13|-5} = 0
By definition, 0 is a second player win.

$$B Seki
$$ -----------------
$$ | W W W X X C C |
$$ | C C B O X X X |
$$ | B B B O X C C |
$$ | O O O O X X X |
$$ | . . . . . . . |
$$ | . . . . . . . |
$$ | . . . . . . . |
$$ -----------------
- Click Here To Show Diagram Code
[go]$$B Seki
$$ -----------------
$$ | W W W X X C C |
$$ | C C B O X X X |
$$ | B B B O X C C |
$$ | O O O O X X X |
$$ | . . . . . . . |
$$ | . . . . . . . |
$$ | . . . . . . . |
$$ -----------------[/go]
This result {13|-5||13|-5} = 0 proves that describing a game by {13|-5||13|-5} fails to show the referenced score used (normalization?)
Maybe we have to be carreful when transforming a go game into a CGT game.
You hightlighted the
Three Points without Capturing and the
sekis which are zugswang positions and cannot be scored by CGT. My view is the following. When you encounter a zugswang position it cannot help to go further and show a sub game tree because CGT will not be able to put a score on the position. In that case the go player have to describe the zugswang simply by the number that have to be eventually allocated to the position due to go player knowledge.
$$B Seki
$$ -----------------
$$ | W W W X X . . |
$$ | C C B O X . . |
$$ | B B B O X . . |
$$ | O O O O X . . |
$$ | . . . . . . . |
$$ | . . . . . . . |
$$ | . . . . . . . |
$$ -----------------
- Click Here To Show Diagram Code
[go]$$B Seki
$$ -----------------
$$ | W W W X X . . |
$$ | C C B O X . . |
$$ | B B B O X . . |
$$ | O O O O X . . |
$$ | . . . . . . . |
$$ | . . . . . . . |
$$ | . . . . . . . |
$$ -----------------[/go]
Maybe it is a mistake to define this seki by the game {9|-9||9|-9}.
In territory scoring this position is simply the number 0 and in area scoring it is the number +1.
$$B Three Points
$$ -----------------
$$ | C W X X . . . |
$$ | B B O X . . . |
$$ | B B O X . . . |
$$ | O O O . . . . |
$$ | . . . . . . . |
$$ | . . . . . . . |
$$ | . . . . . . . |
$$ -----------------
- Click Here To Show Diagram Code
[go]$$B Three Points
$$ -----------------
$$ | C W X X . . . |
$$ | B B O X . . . |
$$ | B B O X . . . |
$$ | O O O . . . . |
$$ | . . . . . . . |
$$ | . . . . . . . |
$$ | . . . . . . . |
$$ -----------------[/go]
Here it is the same:
In territory scoring this position is simply the number -2 (2 more prisonners for white) and in area scoring it is the number 0.
That way the CGT game corresponding to the go game seems far better.