About compositions of four ko-shapes
- Click Here To Show Diagram Code
[go]$$B
$$ +-------------------+
$$ | . . . . . . . . . |
$$ | . . . . . . . . . |
$$ | . . . X X X X . . |
$$ | . X X X O O X X . |
$$ | X X O O X O O X X |
$$ | O O O X X X O O O |
$$ | O O X . X . X O O |
$$ | O O O X X X O O O |
$$ | . O . O X O . O . |
$$ +-------------------+[/go]
This is the example with four ko-shapes that Gérard kindly provided to me.
- Click Here To Show Diagram Code
[go]$$B
$$ +-------------------+
$$ | . . . . . . . . . |
$$ | . . . . . . . . . |
$$ | . . . X X X X . . |
$$ | . X X X O O X X . |
$$ | X X O O X O O X X |
$$ | O O O Y X Y O O O |
$$ | O O Y b X c Y O O |
$$ | O O Q Y X Y Q O O |
$$ | e O a Q X Q d O f |
$$ +-------------------+[/go]
The four ko-shapes are a, b, c and d.
All three groups in question have TWO liberties each.
-- White's group at the left has one liberty at e in her eye, and another one in the neighbored double-ko (at a or b).
-- Black's group in the centre has one liberty in the double-ko at left (at a or b), and another one in the double-ko at right (at c or d)
-- White's group at the left has one liberty at f in her eye, and another one in the neighbored double-ko (at c or d).
Thus, we can expect this position being a seki.
##### Honte's magic DOUBLE-KO spell #####
- Click Here To Show Diagram Code
[go]$$B
$$ +-------------------+
$$ | . . . . . . . . . |
$$ | . . . . . . . . . |
$$ | . . . X X X X . . |
$$ | . X X X O O X X . |
$$ | X X O O X O O X X |
$$ | O O O X X X O O O |
$$ | O O T Y X Y T O O |
$$ | O O O X X X O O O |
$$ | . O Q T X T Q O . |
$$ +-------------------+[/go]
After Honte used his magic wand...
- Click Here To Show Diagram Code
[go]$$B
$$ +-------------------+
$$ | . . . . . . . . . |
$$ | . . . . . . . . . |
$$ | . . . B B B B . . |
$$ | . B B B @ @ B B . |
$$ | B B @ @ # @ @ B B |
$$ | @ @ @ # # # @ @ @ |
$$ | @ @ . # # # . @ @ |
$$ | @ @ @ # # # @ @ @ |
$$ | . @ @ . # . @ @ . |
$$ +-------------------+[/go]
... we can easily see that the position is seki.
No wonder that this is the fastest method, as magic was involved.
##### GT territory rules #####Second fastest is using the GENUINE quadruple-ko cycle.

GENUINE quadruple-ko cycle
- Click Here To Show Diagram Code
[go]$$B GENUINE quadruple-ko cycle
$$ +-------------------+
$$ | . . . . . . . . . |
$$ | . . . . . . . . . |
$$ | . . . X X X X . . |
$$ | . X X X O O X X . |
$$ | X X O O X O O X X |
$$ | O O O X X X O O O |
$$ | O O X 2 X 4 X O O |
$$ | O O O X X X O O O |
$$ | . O 1 O X O 3 O . |
$$ +-------------------+[/go]

GENUINE quadruple-ko cycle
- Click Here To Show Diagram Code
[go]$$B GENUINE quadruple-ko cycle
$$ +-------------------+
$$ | . . . . . . . . . |
$$ | . . . . . . . . . |
$$ | . . . X X X X . . |
$$ | . X X X O O X X . |
$$ | X X O O X O O X X |
$$ | O O O X X X O O O |
$$ | O O 5 O X O 7 O O |
$$ | O O O X X X O O O |
$$ | . O X 6 X 8 X O . |
$$ +-------------------+[/go]

GENUINE quadruple-ko cycle
- Click Here To Show Diagram Code
[go]$$B GENUINE quadruple-ko cycle
$$ +-------------------+
$$ | . . . . . . . . . |
$$ | . . . . . . . . . |
$$ | . . . X X X X . . |
$$ | . X X X O O X X . |
$$ | X X O O X O O X X |
$$ | O O O X X X O O O |
$$ | O O X . X . X O O |
$$ | O O O X X X O O O |
$$ | . O . O X O . O . |
$$ +-------------------+[/go]
Same position as eight moves before.
Neither side will ever create a two-eye-formation in the lower part of the board.
==> NO territory.
--------------------------
Using the "permanent prohibited ko" feature will neither shorten nor ease the sequences required.
It seems to me that "permanent prohibited ko" will be most useful in ASYMMETRICAL positions.

Status confirmation for White groups
- Click Here To Show Diagram Code
[go]$$B Status confirmation for White groups
$$ +-------------------+
$$ | . . . . . . . . . |
$$ | . . . . . . . . . |
$$ | . . . X X X X . . |
$$ | . X X X O O X X . |
$$ | X X O O X O O X X |
$$ | O O O X X X O O O |
$$ | O O X . X . X O O |
$$ | O O Q X X X O O O |
$$ | . O 1 Q X O . O . |
$$ +-------------------+[/go]
We will start with trying to find out, whether White will be able to create a two-eye-formation at the bottom.

Status confirmation for White groups
- Click Here To Show Diagram Code
[go]$$B Status confirmation for White groups
$$ +-------------------+
$$ | . . . . . . . . . |
$$ | . . . . . . . . . |
$$ | . . . X X X X . . |
$$ | . X X X O O X X . |
$$ | X X O O X O O X X |
$$ | O O O Y X X O O O |
$$ | O O Y 2 X . X O O |
$$ | O O O Y X X O O O |
$$ | . O X . X O . O . |
$$ +-------------------+[/go]

Status confirmation for White groups;

pass
- Click Here To Show Diagram Code
[go]$$B Status confirmation for White groups;
pass
$$ +-------------------+
$$ | . . . . . . . . . |
$$ | . . . . . . . . . |
$$ | . . . X X X X . . |
$$ | . X X X O O X X . |
$$ | X X O O X O O X X |
$$ | O O O Y X X O O O |
$$ | O O T P X . X O O |
$$ | O O O Y X X O O O |
$$ | . O X . X O . O . |
$$ +-------------------+[/go]
Black also claims "permanently prohibited ko" for

.

Status confirmation for White groups
- Click Here To Show Diagram Code
[go]$$B Status confirmation for White groups
$$ +-------------------+
$$ | . . . . . . . . . |
$$ | . . . . . . . . . |
$$ | . . . X X X X . . |
$$ | . X X X O O X X . |
$$ | X X O O X O O X X |
$$ | O O O X X Y O O O |
$$ | O O . O X 4 Y O O |
$$ | O O O X X Y O O O |
$$ | . O X . X O . O . |
$$ +-------------------+[/go]

Status confirmation for White groups
- Click Here To Show Diagram Code
[go]$$B Status confirmation for White groups
$$ +-------------------+
$$ | . . . . . . . . . |
$$ | . . . . . . . . . |
$$ | . . . X X X X . . |
$$ | . X X X O O X X . |
$$ | X X O O X O O X X |
$$ | O O Q X X X O O O |
$$ | O O 5 Q X O . O O |
$$ | O O Q X X X O O O |
$$ | . O X . X O . O . |
$$ +-------------------+[/go]

Status confirmation for White groups
- Click Here To Show Diagram Code
[go]$$B Status confirmation for White groups
$$ +-------------------+
$$ | . . . . . . . . . |
$$ | . . . . . . . . . |
$$ | . . . X X X X . . |
$$ | . X X X O O X X . |
$$ | X X O O X O O X X |
$$ | O O O X X X O O O |
$$ | O O X . X O . O O |
$$ | O O O Y X X O O O |
$$ | . O Y 6 X O . O . |
$$ +-------------------+[/go]

Status confirmation for White groups
- Click Here To Show Diagram Code
[go]$$B Status confirmation for White groups
$$ +-------------------+
$$ | . . . . . . . . . |
$$ | . . . . . . . . . |
$$ | . . . X X X X . . |
$$ | . X X X O O X X . |
$$ | X X O O X O O X X |
$$ | O O O Y X X Q O O |
$$ | O O Y M X Q 7 O O |
$$ | O O O Y X X Q O O |
$$ | . O . O X O . O . |
$$ +-------------------+[/go]
White must not capture into the ko-shape at left.

Status confirmation for White groups;

pass
- Click Here To Show Diagram Code
[go]$$B Status confirmation for White groups;
pass
$$ +-------------------+
$$ | . . . . . . . . . |
$$ | . . . . . . . . . |
$$ | . . . X X X X . . |
$$ | . X X X O O X X . |
$$ | X X O O X O O X X |
$$ | O O O Y X X Q O O |
$$ | O O Y M X T Z O O |
$$ | O O O Y X X Q O O |
$$ | . O . O X O . O . |
$$ +-------------------+[/go]
White must not capture into the ko-shape at left, instead.
White also claims "permanently prohibited ko" for

.

Status confirmation for White groups
- Click Here To Show Diagram Code
[go]$$B Status confirmation for White groups
$$ +-------------------+
$$ | . . . . . . . . . |
$$ | . . . . . . . . . |
$$ | . . . X X X X . . |
$$ | . X X X O O X X . |
$$ | X X O O X O O X X |
$$ | O O O X X X O O O |
$$ | O O X . X . X O O |
$$ | O O Q X X X O O O |
$$ | . O 9 Q X O . O . |
$$ +-------------------+[/go]

Status confirmation for White groups
- Click Here To Show Diagram Code
[go]$$Wm10 Status confirmation for White groups
$$ +-------------------+
$$ | . . . . . . . . . |
$$ | . . . . . . . . . |
$$ | . . . X X X X . . |
$$ | . X X X O O X X . |
$$ | X X O O X O O X X |
$$ | O O O Y X Y O O O |
$$ | O O Y M X 1 Y O O |
$$ | O O O Y X Y O O O |
$$ | 2 O X . X O . O . |
$$ +-------------------+[/go]

must not capture into the ko-shape at left, instead.
==> NO White territory.
------------------------

Status confirmation for Black groups
- Click Here To Show Diagram Code
[go]$$W Status confirmation for Black groups
$$ +-------------------+
$$ | . . . . . . . . . |
$$ | . . . . . . . . . |
$$ | . . . X X X X . . |
$$ | . X X X O O X X . |
$$ | X X O O X O O X X |
$$ | O O O X X Y O O O |
$$ | O O X . X 1 Y O O |
$$ | O O O X X Y O O O |
$$ | . O . O X O . O . |
$$ +-------------------+[/go]
Will Black be able to create a two-eye-formation at the bottom?

Status confirmation for Black groups
- Click Here To Show Diagram Code
[go]$$W Status confirmation for Black groups
$$ +-------------------+
$$ | . . . . . . . . . |
$$ | . . . . . . . . . |
$$ | . . . X X X X . . |
$$ | . X X X O O X X . |
$$ | X X O O X O O X X |
$$ | O O O X X X O O O |
$$ | O O X . X O . O O |
$$ | O O O X X X Q O O |
$$ | . O . O X Q 2 O . |
$$ +-------------------+[/go]

Status confirmation for Black groups;

pass
- Click Here To Show Diagram Code
[go]$$W Status confirmation for Black groups;
pass
$$ +-------------------+
$$ | . . . . . . . . . |
$$ | . . . . . . . . . |
$$ | . . . X X X X . . |
$$ | . X X X O O X X . |
$$ | X X O O X O O X X |
$$ | O O O X X X O O O |
$$ | O O X . X O . O O |
$$ | O O O X X X Q O O |
$$ | . O . O X T Z O . |
$$ +-------------------+[/go]
White also claims "permanently prohibited ko" for

.

Status confirmation for Black groups
- Click Here To Show Diagram Code
[go]$$W Status confirmation for Black groups
$$ +-------------------+
$$ | . . . . . . . . . |
$$ | . . . . . . . . . |
$$ | . . . X X X X . . |
$$ | . X X X O O X X . |
$$ | X X O O X O O X X |
$$ | O O O X X X Q O O |
$$ | O O X . X Q 4 O O |
$$ | O O O X X X Q O O |
$$ | . O . O X . X O . |
$$ +-------------------+[/go]

Status confirmation for Black groups
- Click Here To Show Diagram Code
[go]$$W Status confirmation for Black groups
$$ +-------------------+
$$ | . . . . . . . . . |
$$ | . . . . . . . . . |
$$ | . . . X X X X . . |
$$ | . X X X O O X X . |
$$ | X X O O X O O X X |
$$ | O O O X X X O O O |
$$ | O O X . X . X O O |
$$ | O O O X X Y O O O |
$$ | . O . O X 5 Y O . |
$$ +-------------------+[/go]

Status confirmation for Black groups;

pass
- Click Here To Show Diagram Code
[go]$$W Status confirmation for Black groups;
pass
$$ +-------------------+
$$ | . . . . . . . . . |
$$ | . . . . . . . . . |
$$ | . . . X X X X . . |
$$ | . X X X O O X X . |
$$ | X X O O X O O X X |
$$ | O O O X X X O O O |
$$ | O O X . X . X O O |
$$ | O O O X X Y O O O |
$$ | . O . O X P T O . |
$$ +-------------------+[/go]
Black also claims "permanently prohibited ko" for

.
This does not have any effect, as Black must not re-capture into that ko-shape anyway.

Status confirmation for Black groups
- Click Here To Show Diagram Code
[go]$$W Status confirmation for Black groups
$$ +-------------------+
$$ | . . . . . . . . . |
$$ | . . . . . . . . . |
$$ | . . . X X X X . . |
$$ | . X X X O O X X . |
$$ | X X O O X O O X X |
$$ | O O O X X Y O O O |
$$ | O O X . X 7 Y O O |
$$ | O O O X X Y O O O |
$$ | . O . O X O . O . |
$$ +-------------------+[/go]

Status confirmation for Black groups
- Click Here To Show Diagram Code
[go]$$W Status confirmation for Black groups
$$ +-------------------+
$$ | . . . . . . . . . |
$$ | . . . . . . . . . |
$$ | . . . X X X X . . |
$$ | . X X X O O X X . |
$$ | X X O O X O O X X |
$$ | O O O X X X O O O |
$$ | O O X . X O . O O |
$$ | O O Q X X X Q O O |
$$ | . O 8 Q X Q M O . |
$$ +-------------------+[/go]
Black must not re-capture at right, instead.

Status confirmation for Black groups
- Click Here To Show Diagram Code
[go]$$W Status confirmation for Black groups
$$ +-------------------+
$$ | . . . . . . . . . |
$$ | . . . . . . . . . |
$$ | . . . X X X X . . |
$$ | . X X X O O X X . |
$$ | X X O O X O O X X |
$$ | O O O Y X X O O O |
$$ | O O Y 9 X O . O O |
$$ | O O O Y X X O O O |
$$ | . O X . X O . O . |
$$ +-------------------+[/go]

Status confirmation for Black groups
- Click Here To Show Diagram Code
[go]$$Bm10 Status confirmation for Black groups
$$ +-------------------+
$$ | . . . . . . . . . |
$$ | . . . . . . . . . |
$$ | . . . X X X X . . |
$$ | . X X X O O X X . |
$$ | X X O O X O O X X |
$$ | O O O X X X Q O O |
$$ | O O . O X Q 1 O O |
$$ | O O O X X X Q O O |
$$ | . O X . X Q M O . |
$$ +-------------------+[/go]
Black must not re-capture into the lower ko-shape.

Status confirmation for Black groups;

pass
- Click Here To Show Diagram Code
[go]$$Bm10 Status confirmation for Black groups;
pass
$$ +-------------------+
$$ | . . . . . . . . . |
$$ | . . . . . . . . . |
$$ | . . . X X X X . . |
$$ | . X X X O O X X . |
$$ | X X O O X O O X X |
$$ | O O O X X X Q O O |
$$ | O O . O X T Z O O |
$$ | O O O X X X Q O O |
$$ | . O X . X O . O . |
$$ +-------------------+[/go]
White also claims "permanently prohibited ko" for

.

Status confirmation for Black groups
- Click Here To Show Diagram Code
[go]$$Bm10 Status confirmation for Black groups
$$ +-------------------+
$$ | . . . . . . . . . |
$$ | . . . . . . . . . |
$$ | . . . X X X X . . |
$$ | . X X X O O X X . |
$$ | X X O O X O O X X |
$$ | O O Q X X X O O O |
$$ | O O 3 Q X . X O O |
$$ | O O Q X X X O O O |
$$ | . O X . X O . O . |
$$ +-------------------+[/go]

Status confirmation for Black groups
- Click Here To Show Diagram Code
[go]$$Bm10 Status confirmation for Black groups
$$ +-------------------+
$$ | . . . . . . . . . |
$$ | . . . . . . . . . |
$$ | . . . X X X X . . |
$$ | . X X X O O X X . |
$$ | X X O O X O O X X |
$$ | O O O X X X O O O |
$$ | O O X . X . X O O |
$$ | O O O Y X X O O O |
$$ | . O Y 4 X O . O . |
$$ +-------------------+[/go]

Status confirmation for Black groups;

pass
- Click Here To Show Diagram Code
[go]$$Bm10 Status confirmation for Black groups;
pass
$$ +-------------------+
$$ | . . . . . . . . . |
$$ | . . . . . . . . . |
$$ | . . . X X X X . . |
$$ | . X X X O O X X . |
$$ | X X O O X O O X X |
$$ | O O O X X X O O O |
$$ | O O X . X . X O O |
$$ | O O O Y X X Q O O |
$$ | . O T P X Q M O . |
$$ +-------------------+[/go]
Black must not re-capture into the lower ko-shape at right, instead.
Black also claims "permanently prohibited ko" for

.

Status confirmation for Black groups
- Click Here To Show Diagram Code
[go]$$Bm10 Status confirmation for Black groups
$$ +-------------------+
$$ | . . . . . . . . . |
$$ | . . . . . . . . . |
$$ | . . . X X X X . . |
$$ | . X X X O O X X . |
$$ | X X O O X O O X X |
$$ | O O O Y X X O O O |
$$ | O O Y 6 X . X O O |
$$ | O O O Y X X O O O |
$$ | . O . O X O . O . |
$$ +-------------------+[/go]

Status confirmation for Black groups;

pass
- Click Here To Show Diagram Code
[go]$$Bm10 Status confirmation for Black groups;
pass
$$ +-------------------+
$$ | . . . . . . . . . |
$$ | . . . . . . . . . |
$$ | . . . X X X X . . |
$$ | . X X X O O X X . |
$$ | X X O O X O O X X |
$$ | O O O Y X X O O O |
$$ | O O . O X 8 X O O |
$$ | O O O Y X X Q O O |
$$ | . O . O X Q M O . |
$$ +-------------------+[/go]
Black must not re-capture into the lower ko-shape at right.
==> NO Black territory.