KataGo @ Igo Hatsuyoron 120

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Re: KataGo @ Igo Hatsuyoron 120

Post by Cassandra »

"Classical" way of play => White's weakness in the upper right

We will still examine the "classical" way of play, i.e. the situation without Black's guzumi in the upper right.
Click Here To Show Diagram Code
[go]$$Wcm98
$$ +---------------------------------------+
$$ | . . . . . 6 . 7 . . . . X . . . O X . |
$$ | . . . . 2 1 3 X O O . X O X O . . O . |
$$ | . . . 8 5 X 4 O . . . X O . O O O . . |
$$ | . X O , . . . . . O . X . O O X . . . |
$$ | . . X X X X O O O . O X X X X X O O . |
$$ | . X . O O O X X X O . . X . X O . . . |
$$ | O O O O . X O O X X O O . O X . a O . |
$$ | O X . X . X . O O X O . . . X X X X X |
$$ | O X . X . . . O X X O . X X X X . O O |
$$ | X O O X . X . O X O O X X O O O O . . |
$$ | X X O O X . . O X O . X O O O . X X X |
$$ | X X . O X . . O X O . X O O X X X O O |
$$ | X X O O X . . O X O . X O . O . X X O |
$$ | X 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 . . O X O O O O X O X O O X |
$$ | O . . . O X . O X X X X X . O X X O X |
$$ | O . X . . . X O O O O O O X O X . O X |
$$ | . X . . . . . O . . . . O X X X . O . |
$$ +---------------------------------------+[/go]
In order to set the scene for another finding of the new KataGo net, let us assume that White chooses the original line of Yamada Shinji's tsuke in the upper right corner.

Please note that White has NOT defended with a in the upper right before starting the endgame at the left side.
Click Here To Show Diagram Code
[go]$$Wcm106
$$ +---------------------------------------+
$$ | . . . . . X . O . . . . X . . . O X . |
$$ | . . . . X O O . O O . X O X O . . O . |
$$ | . . . X O X X O . . . X O . O O O . . |
$$ | . X O , 8 . 6 7 . O . X . O O X . . . |
$$ | . . X X X X O O O . O X X X X X O O . |
$$ | . X . O O O X X X O . . X . X O . . . |
$$ | O O O O . X O O X X O O . O X . . O . |
$$ | O X . X . X . O O X O . . . X X X X X |
$$ | O X . X . . . O X X O . X X X X . O O |
$$ | X O O X . X . O X O O X X O O O O . . |
$$ | X X O O X . . O X O . X O O O . X X X |
$$ | X X . O X . . O X O . X O O X X X O O |
$$ | X X O O X . . O X O . X O . O . X X O |
$$ | X 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 0 . O X O O O O X O X O O X |
$$ | O . . . O X 9 O X X X X X . O X X O X |
$$ | O . X . 2 1 X O O O O O O X O X . O X |
$$ | . X . . 4 3 5 O . . . . O X X X . O . |
$$ +---------------------------------------+[/go]
The "early" endgame continues in the lower left corner.

Again, Black plays tenuki with :b11:, in order to play a profitable move at the top.
Click Here To Show Diagram Code
[go]$$Wcm116
$$ +---------------------------------------+
$$ | . . . . . X . O . . . . X . . . O X . |
$$ | . . . . X O O . O O . X O X O . . O . |
$$ | . . . X . X X O . . . X O . O O O . . |
$$ | . X O , X . X O . O . X . O O X . . . |
$$ | . . X X X X O O O . O X X X X X O O . |
$$ | . X . O O O X X X O . . X . X O 3 9 5 |
$$ | O O O O 6 X O O X X O O . O X . 2 O 4 |
$$ | O X . X . X . O O X O . . . X X X X X |
$$ | O X . X . 8 . O X X O . X X X X . O O |
$$ | X O O X . X 7 O X O O X X O O O O . . |
$$ | X X O O X . . O X O . X O O O . X X X |
$$ | X X . O X . . O X O . X O O X X X O O |
$$ | X X O O X . . O X O . X O . O . X X O |
$$ | X O O 1 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]
Black ended in gote at the top, so White will connect her two stones in the lower left with :w16:, gaining two points overall.
However, she lost two tempi in the Main Semeai by this connection.

This makes Black's push :b17: in the guzumi area possible, which will result in a gain of TWO points overall for Black.

Here, White blocks with :w18:, but she could simplify the issue by connecting at :w24: immediately, instead.

Thereafter, Black plays another push into White's potential territory with :b19:.
Black could have changed the order of moves here, and started at the edge.

White blocks again with :w20:.
Again, immediately connecting at :w24: could simplify the matter.

At first sight, it seems that Black lost two tempi in the Main Semeai by his new procedure (White's moves occupied liberties of his large group at the right) -- making him a victim of the Punishment Semeai -- but this is not true.
Sooner or later, White will have to connect at :w24:, also losing one tempo in the Main Semeai.

White lost three points of territory here, Black lost one tempo in the Main Semeai effectively (two minus one for White), so the net effect is a loss of TWO points for White (in the Capture Variation, which will be better for White than the Semeai Variation).

This means that White must be careful to not provide Black with a single additional Main Semeai Liberty, if she had not yet defended her potential territory in the upper right.
Click Here To Show Diagram Code
[go]$$Wcm124
$$ +---------------------------------------+
$$ | . . . . . X . O . . 1 2 X . . . O X . |
$$ | . . . . X O O . O O . X O X O . . O . |
$$ | . . . X . X X O . . . X O . O O O . . |
$$ | . X O , X . X O . O . X . O O X . . . |
$$ | . . X X X X O O O . O X X X X X O O a |
$$ | . X . O O O X X X O . . X . X O O 4 O |
$$ | O O O O X X O O X X O O 3 O X . X O X |
$$ | O X . X . X . O O X O . . . X X X X X |
$$ | O X . X . X . O X X O . X X X X . O O |
$$ | X O O X . X O O X O O X X O O O O . . |
$$ | X X O O X . . O X O . X O O O . X X X |
$$ | X X . O X . . O X O . X O O X X X O O |
$$ | X X O O X . . O X O . X O . O . X X O |
$$ | 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 X O O O O O O X O X . O X |
$$ | . X . . X O O O . . . . O X X X . O . |
$$ +---------------------------------------+[/go]
Let's assume that White does not want to connect the ko shape in the upper right, but continues with the Main Semeai.

Black will capture the ko with :b27:.

White is forced to fight this ko, because simply connecting at a would cost her another point.

However, White does not have any change to "win" this ko fight (i.e. to leave the ko shape open), because Black can use his liberty-occupying moves of the Main Semeai as ko threats (contrary to White, who has to choose "real" threats).

This implies that White has to connect the ko lastest after she had invested her very last "real" ko threat.
It would be much simpler to do so in the very beginning :razz:
Last edited by Cassandra on Mon Jan 11, 2021 6:23 am, edited 2 times in total.
The really most difficult Go problem ever: https://igohatsuyoron120.de/index.htm
Igo Hatsuyōron #120 (really solved by KataGo)
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Re: KataGo @ Igo Hatsuyoron 120

Post by Cassandra »

"Classical" way of play => Black's weakness in the upper left

SEATBELTS FASTENED?
OK, then let's go...

We still examine the "classical" way of play, i.e. the situation without Black's guzumi in the upper right.
Please note that I have not checked yet whether the following variations, concerning the upper left corner only, are also valid with the Guzumi Exchange played.
Click Here To Show Diagram Code
[go]$$Wcm108
$$ +---------------------------------------+
$$ | . . . . . B . W . . . . X . . . O X . |
$$ | . . . . B W W . O O . X O X O . . O . |
$$ | . . . B W X B O . . . X O . O O O . . |
$$ | . X O , . . 1 . . O . X . O O X . . . |
$$ | . . X X X X O O O . O X X X X X O O . |
$$ | . X . O O O X X X O . . X . X O . . . |
$$ | O O O O . X O O X X O O . O X . Q O . |
$$ | O X . X . X . O O X O . . . X X X X X |
$$ | O X . X . . . O X X O . X X X X . O O |
$$ | X O O X . X . O X O O X X O O O O . . |
$$ | X X O O X . . O X O . X O O O . X X X |
$$ | X X . O X . . O X O . X O O X X X O O |
$$ | X X O O X . . O X O . X O . O . X X O |
$$ | X O O Y . X . O X O . X X O O O X O O |
$$ | X O X . X X . O X O X . O X X X O O O |
$$ | O X X X X . . O X O O O O X O X O O X |
$$ | O . . . O X . O X X X X X . O X X O X |
$$ | O . X . . a X O O O O O O X O X . O X |
$$ | . X . . . . . O . . . . O X X X . O . |
$$ +---------------------------------------+[/go]
After the classical line of play after Yamada Shinji's tsuke in the upper left ( :wc:, :bc:), White does NOT continue the endgame with a move at a in the lower left corner here, but gives atari :w8: in the upper left immediately.
For the sake of simplicity, let's assume that the exchange of :wt: for :bt: has already been inserted.
Click Here To Show Diagram Code
[go]$$Wcm108
$$ +---------------------------------------+
$$ | . . . . . X . O . . . . X . . . O X . |
$$ | . . . . X O O . O O . X O X O . . O . |
$$ | . . . X O X X O . . . X O . O O O . . |
$$ | . X O , 2 a O . . O . X . O O X . . . |
$$ | . . X X X X O O O . O X X X X X O O . |
$$ | . X . O O O X X X O . . X . X O . . . |
$$ | O O O O . X O O X X O O . O X . O O . |
$$ | O X . X . X . O O X O . . . X X X X X |
$$ | O X . X . . . O X X O . X X X X . O O |
$$ | X O O X . X . O X O O X X O O O O . . |
$$ | X X O O X . . O X O . X O O O . X X X |
$$ | X X . O X . . O X O . X O O X X X O O |
$$ | X X O O X . . O X O . X O . O . X X O |
$$ | X O O X . X . O X O . X X O O O X O O |
$$ | X O X . X X . O X O X . O X X X O O O |
$$ | O X X X X . . O X O O O O X O X O O X |
$$ | O . . . O X . O X X X X X . O X X O X |
$$ | O . X . . . X O O O O O O X O X . O X |
$$ | . X . . . . . O . . . . O X X X . O . |
$$ +---------------------------------------+[/go]
Black has to capture with :b9:.

Intending to maximise his corner territory by connecting at a would be mistaken, see the next posting.
Click Here To Show Diagram Code
[go]$$Wcm110
$$ +---------------------------------------+
$$ | . . . . . X . O . . . . X . . . O X . |
$$ | . . . . X O O . O O . X O X O . . O . |
$$ | . . . X 8 X X O . . . X O . O O O . . |
$$ | . X O , X 7 O . . O . X . O O X . . . |
$$ | . . X X X X O O O . O X X X X X O O . |
$$ | . X . O O O X X X O . . X . X O . . . |
$$ | O O O O . X O O X X O O . O X . O O . |
$$ | O X . X . X . O O X O . . . X X X X X |
$$ | O X . X . . . O X X O . X X X X . O O |
$$ | X O O X . X . O X O O X X O O O O . . |
$$ | X X O O X . . O X O . X O O O . X X X |
$$ | X X . O X . . O X O . X O O X X X O O |
$$ | X X O O X . . O X O . X O . O . X X O |
$$ | X O O X . X . O X O . X X O O O X O O |
$$ | X O X . X X . O X O X . O X X X O O O |
$$ | O X X X X . . O X O O O O X O X O O X |
$$ | O . . . O X 6 O X X X X X . O X X O X |
$$ | O . X . 2 1 X O O O O O O X O X . O X |
$$ | . X . . 4 3 5 O . . . . O X X X . O . |
$$ +---------------------------------------+[/go]
After having gained in the upper left, White continues with the usual endgame sequence in the lower left.

There is no other large endgame point remaining on the board, so Black will connect his single stone with :b15:.

Please note that Black is still par with the Punishment Semeai Liberty Level, so White will give atari :w16: after her decision point; Black will connect at :b17:.
Click Here To Show Diagram Code
[go]$$Wc
$$ +---------------------------------------+
$$ | . . . . . X . O . . . . X . . . O X . |
$$ | . . . . X O O . O O . X O X O . . O . |
$$ | . . . X Z X X O . . . X O . O O O . . |
$$ | . X O , X P O T . O . X . O O X . . . |
$$ | . . X X X X O O O . O X X X X X O O . |
$$ | . X . O O O X X X O . . X . X O . . . |
$$ | O O O O . X O O X X O O . O X . O O . |
$$ | O X . X . X . O O X O . . . X X X X X |
$$ | O X . X . a . O X X O . X X X X . O O |
$$ | X O O X . X . O X O O X X O O O O . . |
$$ | X X O O X . . O X O . X O O O . X X X |
$$ | X X . O X . . O X O . X O O X X X O O |
$$ | X X O O X . . O X O . X O . O . X X O |
$$ | X O O X . X . O X O . X X O O O X O O |
$$ | X O X . X X . O X O X . O X X X O O O |
$$ | O X X X X . . O X O O O O X O X O O X |
$$ | O . . . O X X O X X X X X . O X X O X |
$$ | 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]
Compared with the "classical" line of play ...
-- Black lost two points of territory in the upper left ( :bx:, :wx:).
-- White gained one point of territory there ( :et:).
-- Black connected his single stone in the lower left ( :bs:), so gaining two points.

In total, White gained ONE point.

Please note that she will gain another point by choosing the newly discovered wedge at a in the left centre.

The game will now end with a White win by TWO points, instead of becoming a Jigo.
Last edited by Cassandra on Mon Jan 11, 2021 8:41 am, edited 2 times in total.
The really most difficult Go problem ever: https://igohatsuyoron120.de/index.htm
Igo Hatsuyōron #120 (really solved by KataGo)
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Re: KataGo @ Igo Hatsuyoron 120

Post by Cassandra »

"Classical" way of play => Black's weakness in the upper left (contd.)
Click Here To Show Diagram Code
[go]$$Wcm108
$$ +---------------------------------------+
$$ | . . . . . X . O . . . . X . . . O X . |
$$ | . . . . X O O . O O . X O X O . . O . |
$$ | . . . X O X X O . . . X O . O O O . . |
$$ | . X O , . 2 O . . O . X . O O X . . . |
$$ | . . X X X X O O O . O X X X X X O O . |
$$ | . X . O O O X X X O . . X . X O . . . |
$$ | O O O O . X O O X X O O . O X . O O . |
$$ | O X . X . X . O O X O . . . X X X X X |
$$ | O X . X . . . O X X O . X X X X . O O |
$$ | X O O X . X . O X O O X X O O O O . . |
$$ | X X O O X . . O X O . X O O O . X X X |
$$ | X X . O X . . O X O . X O O X X X O O |
$$ | X X O O X . . O X O . X O . O . X X O |
$$ | X O O X . X . O X O . X X O O O X O O |
$$ | X O X . X X . O X O X . O X X X O O O |
$$ | O X X X X . . O X O O O O X O X O O X |
$$ | O . . . O X . O X X X X X . O X X O X |
$$ | O . X . . . X O O O O O O X O X . O X |
$$ | . X . . . . . O . . . . O X X X . O . |
$$ +---------------------------------------+[/go]
Black is too greedy, when he closes the right-hand hole in his corner's encirclement.
Click Here To Show Diagram Code
[go]$$Wcm108
$$ +---------------------------------------+
$$ | . . . . . X . O . . . . X . . . O X . |
$$ | . . . . X O O . O O . X O X O . . O . |
$$ | . . . X O X X O . . . X O . O O O . . |
$$ | 3 X O , . X O . . O . X . O O X . . . |
$$ | . . X X X X O O O . O X X X X X O O . |
$$ | . X . O O O X X X O . . X . X O . . . |
$$ | O O O O . X O O X X O O . O X . O O . |
$$ | O X . X . X . O O X O . . . X X X X X |
$$ | O X . X . . . O X X O . X X X X . O O |
$$ | X O O X . X . O X O O X X O O O O . . |
$$ | X X O O X . . O X O . X O O O . X X X |
$$ | X X . O X . . O X O . X O O X X X O O |
$$ | X X O O X . . O X O . X O . O . X X O |
$$ | X O O X . X . O X O . X X O O O X O O |
$$ | X O X . X X . O X O X . O X X X O O O |
$$ | O X X X X . . O X O O O O X O X O O X |
$$ | O . . . O X . O X X X X X . O X X O X |
$$ | O . X . . . X O O O O O O X O X . O X |
$$ | . X . . . . . O . . . . O X X X . O . |
$$ +---------------------------------------+[/go]
It made "boooooooom".

White's torpedo hit Black's vessel below the waterline.
How does Black intend to stop the impending water ingress?
The really most difficult Go problem ever: https://igohatsuyoron120.de/index.htm
Igo Hatsuyōron #120 (really solved by KataGo)
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Re: KataGo @ Igo Hatsuyoron 120

Post by Cassandra »

"Classical" way of play => Black's weakness in the upper left (contd.)

Black has to passively back away.
Click Here To Show Diagram Code
[go]$$Wcm108
$$ +---------------------------------------+
$$ | . . . . . X . O . . . . X . . . O X . |
$$ | . . . . X O O . O O . X O X O . . O . |
$$ | b 4 . X O X X O . . . X O . O O O . . |
$$ | O X O , . X O . . O . X . O O X . . . |
$$ | c a X X X X O O O . O X X X X X O O . |
$$ | d X . O O O X X X O . . X . X O . . . |
$$ | O O O O . X O O X X O O . O X . O O . |
$$ | O X . X . X . O O X O . . . X X X X X |
$$ | O X . X . . . O X X O . X X X X . O O |
$$ | X O O X . X . O X O O X X O O O O . . |
$$ | X X O O X . . O X O . X O O O . X X X |
$$ | X X . O X . . O X O . X O O X X X O O |
$$ | X X O O X . . O X O . X O . O . X X O |
$$ | X O O X . X . O X O . X X O O O X O O |
$$ | X O X . X X . O X O X . O X X X O O O |
$$ | O X X X X . . O X O O O O X O X O O X |
$$ | O . . . O X . O X X X X X . O X X O X |
$$ | O . X . . . X O O O O O O X O X . O X |
$$ | . X . . . . . O . . . . O X X X . O . |
$$ +---------------------------------------+[/go]
Black's best option here to answer White's submarine attack is to passively back away with :b11:.

Alternatively, he might consider connecting at a, instead, achieving the same final score.
Any other move in the corner would be even worse for him, the more aggressive the worse.
Click Here To Show Diagram Code
[go]$$Wcm112
$$ +---------------------------------------+
$$ | . . . . . X . O . . . . X . . . O X . |
$$ | . . . . X O O . O O . X O X O . . O . |
$$ | 2 X . X O X X O . . . X O . O O O . . |
$$ | O X O , . X O . . O . X . O O X . . . |
$$ | 1 4 X X X X O O O . O X X X X X O O . |
$$ | 3 X . O O O X X X O . . X . X O . . . |
$$ | O O O O . X O O X X O O . O X . O O . |
$$ | O X . X . X . O O X O . . . X X X X X |
$$ | O X . X . . . O X X O . X X X X . O O |
$$ | X O O X . X . O X O O X X O O O O . . |
$$ | X X O O X . . O X O . X O O O . X X X |
$$ | X X . O X . . O X O . X O O X X X O O |
$$ | X X O O X . . O X O . X O . O . X X O |
$$ | X O O X . X . O X O . X X O O O X O O |
$$ | X O X . X X . O X O X . O X X X O O O |
$$ | O X X X X . . O X O O O O X O X O O X |
$$ | O . . . O X . O X X X X X . O X X O X |
$$ | O . X . . . X O O O O O O X O X . O X |
$$ | . X . . . . . O . . . . O X X X . O . |
$$ +---------------------------------------+[/go]
White connects to the outside, at the cost of one tempo in the Main Semeai.
Click Here To Show Diagram Code
[go]$$Wcm116
$$ +---------------------------------------+
$$ | . . . . . X . O . . . . X . . . O X . |
$$ | . . . . X O O . O O . X O X O . . O . |
$$ | X X . X O X X O . . . X O . O O O . . |
$$ | O X O , . X O . . O . X . O O X b c . |
$$ | O X X X X X O O O . O X X X X X O O . |
$$ | O X . O O O X X X O . . X . X O . . . |
$$ | O O O O . X O O X X O O . O X . O O . |
$$ | O X . X . X . O O X O . . . X X X X X |
$$ | O X . X . a . O X X O . X X X X . O O |
$$ | X O O X . X . O X O O X X O O O O . . |
$$ | X X O O X . . O X O . X O O O . X X X |
$$ | X X . O X . . O X O . X O O X X X O O |
$$ | X X O O X . . O X O . X O . O . X X O |
$$ | X O O X . X . O X O . X X O O O X O O |
$$ | X O X . X X . O X O X . O X X X O O O |
$$ | O X X X X . . O X O O O O X O X O O X |
$$ | O . . . O X 6 O X X X X X . O X X O X |
$$ | O . X . 2 1 X O O O O O O X O X . O X |
$$ | . X . . 4 3 5 O . . . . O X X X . O . |
$$ +---------------------------------------+[/go]
The endgame in the lower left corner follows.

:b21: connects, as there is nothing move valuable left on the board.

White will continue in the left centre with her wedge at a.
Black will use his surplus Main Semeai Liberty for reducing White's territory in the upper right by one point, e.g. with B b, W c.

White gained three points in the upper left corner, so she will win this game with FOUR points.
The really most difficult Go problem ever: https://igohatsuyoron120.de/index.htm
Igo Hatsuyōron #120 (really solved by KataGo)
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Re: KataGo @ Igo Hatsuyoron 120

Post by Bill Spight »

Cassandra wrote:"Classical" way of play => White's weakness in the upper right

We will still examine the "classical" way of play, i.e. the situation without Black's guzumi in the upper right.
Click Here To Show Diagram Code
[go]$$Wcm98
$$ +---------------------------------------+
$$ | . . . . . 6 . 7 . . . . X . . . O X . |
$$ | . . . . 2 1 3 X O O . X O X O . . O . |
$$ | . . . 8 5 X 4 O . . . X O . O O O . . |
$$ | . X O , . . . . . O . X . O O X . . . |
$$ | . . X X X X O O O . O X X X X X O O . |
$$ | . X . O O O X X X O . . X . X O . . . |
$$ | O O O O . X O O X X O O . O X . a O . |
$$ | O X . X . X . O O X O . . . X X X X X |
$$ | O X . X . . . O X X O . X X X X . O O |
$$ | X O O X . X . O X O O X X O O O O . . |
$$ | X X O O X . . O X O . X O O O . X X X |
$$ | X X . O X . . O X O . X O O X X X O O |
$$ | X X O O X . . O X O . X O . O . X X O |
$$ | X 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 . . O X O O O O X O X O O X |
$$ | O . . . O X . O X X X X X . O X X O X |
$$ | O . X . . . X O O O O O O X O X . O X |
$$ | . X . . . . . O . . . . O X X X . O . |
$$ +---------------------------------------+[/go]
In order to set the scene for another finding of the new KataGo net, let us assume that White chooses the original line of Yamada Shinji's tsuke in the upper right corner.

Please note that White has NOT defended with a in the upper right before starting the endgame at the left side.
Click Here To Show Diagram Code
[go]$$Wcm106
$$ +---------------------------------------+
$$ | . . . . . X . O . . . . X . . . O X . |
$$ | . . . . X O O . O O . X O X O . . O . |
$$ | . . . X O X X O . . . X O . O O O . . |
$$ | . X O , 8 . 6 7 . O . X . O O X . . . |
$$ | . . X X X X O O O . O X X X X X O O . |
$$ | . X . O O O X X X O . . X . X O . . . |
$$ | O O O O . X O O X X O O . O X . . O . |
$$ | O X . X . X . O O X O . . . X X X X X |
$$ | O X . X . . . O X X O . X X X X . O O |
$$ | X O O X . X . O X O O X X O O O O . . |
$$ | X X O O X . . O X O . X O O O . X X X |
$$ | X X . O X . . O X O . X O O X X X O O |
$$ | X X O O X . . O X O . X O . O . X X O |
$$ | X 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 0 . O X O O O O X O X O O X |
$$ | O . . . O X 9 O X X X X X . O X X O X |
$$ | O . X . 2 1 X O O O O O O X O X . O X |
$$ | . X . . 4 3 5 O . . . . O X X X . O . |
$$ +---------------------------------------+[/go]
The "early" endgame continues in the lower left corner.

Again, Black plays tenuki with :b11:, in order to play a profitable move at the top.
Please note that :b11: - :b13: gains 3 pts. on average. Normally we think of such a small play as part of the late endgame. If that is indeed best play, the rest of the endgame should be solvable by humans. :)

Edited for correctness.
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Re: KataGo @ Igo Hatsuyoron 120

Post by Cassandra »

"Classical" way of play => Black's weakness in the upper left (contd.)

Black has to passively back away (II).
Click Here To Show Diagram Code
[go]$$Wcm108
$$ +---------------------------------------+
$$ | . . . . . X . O . . . . X . . . O X . |
$$ | . . . . X O O . O O . X O X O . . O . |
$$ | . . . X O X X O . . . X O . O O O . . |
$$ | O X O , . X O . . O . X . O O X . . . |
$$ | . 4 X X X X O O O . O X X X X X O O . |
$$ | . X . O O O X X X O . . X . X O . . . |
$$ | O O O O . X O O X X O O . O X . O O . |
$$ | O X . X . X . O O X O . . . X X X X X |
$$ | O X . X . . . O X X O . X X X X . O O |
$$ | X O O X . X . O X O O X X O O O O . . |
$$ | X X O O X . . O X O . X O O O . X X X |
$$ | X X . O X . . O X O . X O O X X X O O |
$$ | X X O O X . . O X O . X O . O . X X O |
$$ | X O O X . X . O X O . X X O O O X O O |
$$ | X O X . X X . O X O X . O X X X O O O |
$$ | O X X X X . . O X O O O O X O X O O X |
$$ | O . . . O X . O X X X X X . O X X O X |
$$ | O . X . . . X O O O O O O X O X . O X |
$$ | . X . . . . . O . . . . O X X X . O . |
$$ +---------------------------------------+[/go]
:b11: connects immediately, seeling the lock at the left side.
Click Here To Show Diagram Code
[go]$$Wcm112
$$ +---------------------------------------+
$$ | . . . . a X . O . . . . X . . . O X . |
$$ | . . . 1 X O O . O O . X O X O . . O . |
$$ | . . . X O X X O . . . X O . O O O . . |
$$ | O X O , 2 X O . . O . X . O O X . . . |
$$ | . X X X X X O O O . O X X X X X O O . |
$$ | . X . O O O X X X O . . X . X O . . . |
$$ | O O O O . X O O X X O O . O X . O O . |
$$ | O X . X . X . O O X O . . . X X X X X |
$$ | O X . X . . . O X X O . X X X X . O O |
$$ | X O O X . X . O X O O X X O O O O . . |
$$ | X X O O X . . O X O . X O O O . X X X |
$$ | X X . O X . . O X O . X O O X X X O O |
$$ | X X O O X . . O X O . X O . O . X X O |
$$ | X O O X . X . O X O . X X O O O X O O |
$$ | X O X . X X . O X O X . O X X X O O O |
$$ | O X X X X . . O X O O O O X O X O O X |
$$ | O . . . O X . O X X X X X . O X X O X |
$$ | O . X . . . X O O O O O O X O X . O X |
$$ | . X . . . . . O . . . . O X X X . O . |
$$ +---------------------------------------+[/go]
But White remembers the dud at the right, and gives atari with :w12:.

It is best for Black to capture with :b13:.
Connecting at a, instead, might turn the entire corner into a seki.
Click Here To Show Diagram Code
[go]$$Wcm112
$$ +---------------------------------------+
$$ | . 6 5 . 7 X 9 O . . . . X . . . O X . |
$$ | . 4 3 O X O O . O O . X O X O . . O . |
$$ | . . . X 8 X X O . . . X O . O O O . . |
$$ | O X O , X X O . . O . X . O O X . . . |
$$ | . X X X X X O O O . O X X X X X O O . |
$$ | . X . O O O X X X O . . X . X O . . . |
$$ | O O O O . X O O X X O O . O X . O O . |
$$ | O X . X . X . O O X O . . . X X X X X |
$$ | O X . X . . . O X X O . X X X X . O O |
$$ | X O O X . X . O X O O X X O O O O . . |
$$ | X X O O X . . O X O . X O O O . X X X |
$$ | X X . O X . . O X O . X O O X X X O O |
$$ | X X O O X . . O X O . X O . O . X X O |
$$ | X O O X . X . O X O . X X O O O X O O |
$$ | X O X . X X . O X O X . O X X X O O O |
$$ | O X X X X . . O X O O O O X O X O O X |
$$ | O . . . O X . O X X X X X . O X X O X |
$$ | O . X . . . X O O O O O O X O X . O X |
$$ | . X . . . . . O . . . . O X X X . O . |
$$ +---------------------------------------+[/go]
:w14: extends into the corner.

Blocking at :b15: is Black's only choice to prevent a seki in the corner.

:w16: prepares creating a ko shape at the upper edge.

It is best for Black to connect with :b19:, as he will be unable to win a ko fight in this corner.
Click Here To Show Diagram Code
[go]$$Wcm120
$$ +---------------------------------------+
$$ | . X O 4 O 3 O O . . . . X . . . O X . |
$$ | . X O O X O O . O O . X O X O . . O . |
$$ | . . 2 X X X X O . . . X O . O O O . . |
$$ | O X O , X X O . . O . X . O O X . . . |
$$ | . X X X X X O O O . O X X X X X O O . |
$$ | . X . O O O X X X O . . X . X O . . . |
$$ | O O O O . X O O X X O O . O X . O O . |
$$ | O X . X . X . O O X O . . . X X X X X |
$$ | O X . X . . . O X X O . X X X X . O O |
$$ | X O O X . X . O X O O X X O O O O . . |
$$ | X X O O X . . O X O . X O O O . X X X |
$$ | X X . O X . . O X O . X O O X X X O O |
$$ | X X O O X . . O X O . X O . O . X X O |
$$ | X O O X . X . O X O . X X O O O X O O |
$$ | X O X . X X . O X O X . O X X X O O O |
$$ | O X X X X . . O X O O O O X O X O O X |
$$ | O . . . O X . O X X X X X . O X X O X |
$$ | O . X . . a X O O O O O O X O X . O X |
$$ | . X . . . . . O . . . . O X X X . O . |
$$ +---------------------------------------+[/go]
After :b23:, the upper left corner is settled.
White will continue with a in the lower left corner.

Compared to the superordinate variation above, Black gained one point in the upper left corner, but White did not lose a tempo in the Main Semeai there.
The net effect is zero, so White will win this variation by FOUR points, too.
The really most difficult Go problem ever: https://igohatsuyoron120.de/index.htm
Igo Hatsuyōron #120 (really solved by KataGo)
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Re: KataGo @ Igo Hatsuyoron 120

Post by Cassandra »

"Classical" way of play => Black's weakness in the upper left (contd.)

Black gives atari at the left edge.
Click Here To Show Diagram Code
[go]$$Wcm108
$$ +---------------------------------------+
$$ | . . . . . X . O . . . . X . . . O X . |
$$ | . . . . X O O . O O . X O X O . . O . |
$$ | a . . X O X X O . . . X O . O O O . . |
$$ | O X O , . X O . . O . X . O O X . . . |
$$ | 4 . X X X X O O O . O X X X X X O O . |
$$ | . X . O O O X X X O . . X . X O . . . |
$$ | O O O O . X O O X X O O . O X . O O . |
$$ | O X . X . X . O O X O . . . X X X X X |
$$ | O X . X . . . O X X O . X X X X . O O |
$$ | X O O X . X . O X O O X X O O O O . . |
$$ | X X O O X . . O X O . X O O O . X X X |
$$ | X X . O X . . O X O . X O O X X X O O |
$$ | X X O O X . . O X O . X O . O . X X O |
$$ | X O O X . X . O X O . X X O O O X O O |
$$ | X O X . X X . O X O X . O X X X O O O |
$$ | O X X X X . . O X O O O O X O X O O X |
$$ | O . . . O X . O X X X X X . O X X O X |
$$ | O . X . . . X O O O O O O X O X . O X |
$$ | . X . . . . . O . . . . O X X X . O . |
$$ +---------------------------------------+[/go]
:b11: gives atari from the outside.

You will easily realise that starting with the inside atari at a results in a change in the order of moves with the sequence shown below.
Click Here To Show Diagram Code
[go]$$Wcm108
$$ +---------------------------------------+
$$ | . . . . . X . O . . . . X . . . O X . |
$$ | . . . . X O O . O O . X O X O . . O . |
$$ | 6 5 . X O X X O . . . X O . O O O . . |
$$ | O X O , . X O . . O . X . O O X . . . |
$$ | X . X X X X O O O . O X X X X X O O . |
$$ | . X . O O O X X X O . . X . X O . . . |
$$ | O O O O . X O O X X O O . O X . O O . |
$$ | O X . X . X . O O X O . . . X X X X X |
$$ | O X . X . . . O X X O . X X X X . O O |
$$ | X O O X . X . O X O O X X O O O O . . |
$$ | X X O O X . . O X O . X O O O . X X X |
$$ | X X . O X . . O X O . X O O X X X O O |
$$ | X X O O X . . O X O . X O . O . X X O |
$$ | X O O X . X . O X O . X X O O O X O O |
$$ | X O X . X X . O X O X . O X X X O O O |
$$ | O X X X X . . O X O O O O X O X O O X |
$$ | O . . . O X . O X X X X X . O X X O X |
$$ | O . X . . . X O O O O O O X O X . O X |
$$ | . X . . . . . O . . . . O X X X . O . |
$$ +---------------------------------------+[/go]
:w12: gives counter-atari in the corner.

Black has to capture with :b13:.
Click Here To Show Diagram Code
[go]$$Wcm108
$$ +---------------------------------------+
$$ | . . . . . X . O . . . . X . . . O X . |
$$ | 7 . 8 a X O O . O O . X O X O . . O . |
$$ | X O . X O X X O . . . X O . O O O . . |
$$ | 9 X O , . X O . . O . X . O O X . . . |
$$ | X 0 X X X X O O O . O X X X X X O O . |
$$ | . X . O O O X X X O . . X . X O . . . |
$$ | O O O O . X O O X X O O . O X . O O . |
$$ | O X . X . X . O O X O . . . X X X X X |
$$ | O X . X . . . O X X O . X X X X . O O |
$$ | X O O X . X . O X O O X X O O O O . . |
$$ | X X O O X . . O X O . X O O O . X X X |
$$ | X X . O X . . O X O . X O O X X X O O |
$$ | X X O O X . . O X O . X O . O . X X O |
$$ | X O O X . X . O X O . X X O O O X O O |
$$ | X O X . X X . O X O X . O X X X O O O |
$$ | O X X X X . . O X O O O O X O X O O X |
$$ | O . . . O X . O X X X X X . O X X O X |
$$ | O . X . . . X O O O O O O X O X . O X |
$$ | . X . . . . . O . . . . O X X X . O . |
$$ +---------------------------------------+[/go]
:w14: gives another atari in the corner.

Black has to defend his cutting point at a with :b15:.

:w16: captures the first ko.

:b17: connects the second one, as Black cannot afford to fight any ko in this corner, due to White's unbeatable ko threats in the hanezeki.
Click Here To Show Diagram Code
[go]$$Wcm118
$$ +---------------------------------------+
$$ | . . . . . X . O . . . . X . c . O X . |
$$ | O . X . X O O . O O 1 X O X O . . O . |
$$ | . O . X O X X O . . . X O b O O O . . |
$$ | O X O , a X O . . O . X . O O X . . . |
$$ | X X X X X X O O O . O X X X X X O O . |
$$ | . X . O O O X X X O . . X . X O . . . |
$$ | O O O O . X O O X X O O . O X . O O . |
$$ | O X . X . X . O O X O . . . X X X X X |
$$ | O X . X . . . O X X O . X X X X . O O |
$$ | X O O X . X . O X O O X X O O O O . . |
$$ | X X O O X . . O X O . X O O O . X X X |
$$ | X X . O X . . O X O . X O O X X X O O |
$$ | X X O O X . . O X O . X O . O . X X O |
$$ | X O O X . X . O X O . X X O O O X O O |
$$ | X O X . X X . O X O X . O X X X O O O |
$$ | O X X X X . . O X O O O O X O X O O X |
$$ | O . . . O X . O X X X X X . O X X O X |
$$ | O . X . . . X O O O O O O X O X . O X |
$$ | . X . . . . . O . . . . O X X X . O . |
$$ +---------------------------------------+[/go]
White continues with the Main Semeai.

She has created a shortage of liberties for Black's upper left corner, and so will keep Black down at par with the Punishment Semeai Liberty Level.

Please note that Black is unable to remove his shortage of liberties by capturing at a, because this move would lose him a very decisive tempo in the Main Semeai.
Quite similar, White must not mistakenly play at b or c at the right (which usually would be answered by Black to avoid losing points), because Black would tenuki here to a in the upper left corner, making the game countable.
Click Here To Show Diagram Code
[go]$$Bcm151
$$ +---------------------------------------+
$$ | . . . . . X . O . . . . X . . . O X . |
$$ | O . X . X O O . O O O X O X O . . O . |
$$ | 5 O . X O X X O . . . X O . O O O . . |
$$ | O X O 4 . X O . . O . X 2 O O X . . . |
$$ | X X X X X X O O O . O X X X X X O O . |
$$ | 1 X 3 O O O X X X O . . X . X O . . . |
$$ | O O O O . X O O X X O O . O X . O O . |
$$ | O X . X . X . O O X O . . . X X X X X |
$$ | O X . X . . . O X X O . X X X X . O O |
$$ | X O O X . X . O X O O X X O O O O . . |
$$ | X X O O X . . O X O . X O O O . X X X |
$$ | X X . O X . . O X O . X O O X X X O O |
$$ | X X O O X . . O X O . X O . O . X X O |
$$ | X O O X . X . O X O . X X O O O X O O |
$$ | X O X . X X . O X O X . O X X X O O O |
$$ | O X X X X . . O X O O O O X O X O O X |
$$ | O . . . O X . O X X X X X 6 O X X O X |
$$ | O . X . . . X O O O O O O X O X . O X |
$$ | . X . . . . . O . . . . O X X X . O . |
$$ +---------------------------------------+[/go]
Black will occupy White's liberties in the upper left last.
Please note that I did not adjust the diagram, just assume that this sequence is played earlier.

:w54: is atari, also threatening a snap-back, so Black has to capture the ko at the left edge with :b55:.
White uses the capture of the hanezeki's tail as a ko threat.
Click Here To Show Diagram Code
[go]$$Bcm157
$$ +---------------------------------------+
$$ | . . . . . X . O . . . . X . . . O X . |
$$ | O . X . X O O . O O O X O X O . . O . |
$$ | X O . X O X X O . . . X O . O O O . . |
$$ | 2 X O O a X O . . O . X O O O X . . . |
$$ | X X X X X X O O O . O X X X X X O O . |
$$ | X X X O O O . . . O . . X . X O . . . |
$$ | O O O O . X O O . . O O . O X . O O . |
$$ | O X . X . X . O O . O . . . X X X X X |
$$ | O X . X . . . O . . O . X X X X . O O |
$$ | X O O X . X . O . O O X X O O O O . . |
$$ | X X O O X . . O . O . X O O O . X X X |
$$ | X X . O X . . O . O . X O O X X X O O |
$$ | X X O O X . . O . O . X O . O . X X O |
$$ | X O O X . X . O . O . X X O O O X O O |
$$ | X O X . X X . O . O X . O X X X O O O |
$$ | O X X X X . . O . O O O O X O X O O X |
$$ | O . . . O X . O . . . . 1 O O X X O X |
$$ | O . X . . . X O O O O O O X O X . O X |
$$ | . X . . . . . O . . . . O X X X . O . |
$$ +---------------------------------------+[/go]
Black has to recapture with :b57:, if he wants that his right side survives.

:w58: recaptures the ko in the upper left, and there is nothing Black can do to stop White from killing his upper left corner by capturing at a with her next move.
White will win the game by a large margin.
The really most difficult Go problem ever: https://igohatsuyoron120.de/index.htm
Igo Hatsuyōron #120 (really solved by KataGo)
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Re: KataGo @ Igo Hatsuyoron 120

Post by Cassandra »

"Classical" way of play => Black's weakness in the upper left (contd.)

Black descends to the left edge.
Click Here To Show Diagram Code
[go]$$Wcm108
$$ +---------------------------------------+
$$ | . . . . . X . O . . . . X . . . O X . |
$$ | . . . . X O O . O O . X O X O . . O . |
$$ | . . . X O X X O . . . X O . O O O . . |
$$ | O X O , . X O . . O . X . O O X . . . |
$$ | . . X X X X O O O . O X X X X X O O . |
$$ | 4 X . O O O X X X O . . X . X O . . . |
$$ | O O O O . X O O X X O O . O X . O O . |
$$ | O X . X . X . O O X O . . . X X X X X |
$$ | O X . X . . . O X X O . X X X X . O O |
$$ | X O O X . X . O X O O X X O O O O . . |
$$ | X X O O X . . O X O . X O O O . X X X |
$$ | X X . O X . . O X O . X O O X X X O O |
$$ | X X O O X . . O X O . X O . O . X X O |
$$ | X O O X . X . O X O . X X O O O X O O |
$$ | X O X . X X . O X O X . O X X X O O O |
$$ | O X X X X . . O X O O O O X O X O O X |
$$ | O . . . O X . O X X X X X . O X X O X |
$$ | O . X . . . X O O O O O O X O X . O X |
$$ | . X . . . . . O . . . . O X X X . O . |
$$ +---------------------------------------+[/go]
:b11: descends to the left edge, also intending to maximise the corner territory.
Click Here To Show Diagram Code
[go]$$Wcm112
$$ +---------------------------------------+
$$ | . . . . 5 X . O . . . . X . . . O X . |
$$ | . . 4 3 X O O . O O . X O X O . . O . |
$$ | . 1 . X O X X O . . . X O . O O O . . |
$$ | O X O , a X O . . O . X . O O X . . . |
$$ | . 2 X X X X O O O . O X X X X X O O . |
$$ | X X . O O O X X X O . . X . X O . . . |
$$ | O O O O . X O O X X O O . O X . O O . |
$$ | O X . X . X . O O X O . . . X X X X X |
$$ | O X . X . . . O X X O . X X X X . O O |
$$ | X O O X . X . O X O O X X O O O O . . |
$$ | X X O O X . . O X O . X O O O . X X X |
$$ | X X . O X . . O X O . X O O X X X O O |
$$ | X X O O X . . O X O . X O . O . X X O |
$$ | X O O X . X . O X O . X X O O O X O O |
$$ | X O X . X X . O X O X . O X X X O O O |
$$ | O X X X X . . O X O O O O X O X O O X |
$$ | O . . . O X . O X X X X X . O X X O X |
$$ | O . X . . . X O O O O O O X O X . O X |
$$ | . X . . . . . O . . . . O X X X . O . |
$$ +---------------------------------------+[/go]
First, White gives atari with :w12:, forcing Black to connect at :b13:.

Thereafter, White :w14: cuts at the top, also giving atari.

Black has to give counter-atari with :b15:.
Capturing with a, or connecting at 116, instead, would result in a real desaster in the corner.

:w16: captures Black's stone in the corner, so gaining a massive profit from reducing Black's top left corner.
Click Here To Show Diagram Code
[go]$$Wcm112
$$ +---------------------------------------+
$$ | . . . . O X . O . . . . X . . . O X . |
$$ | . 6 X O . O O . O O . X O X O . . O . |
$$ | . O . X O X X O . . . X O . O O O . . |
$$ | O X O , . X O . . O . X . O O X . . . |
$$ | . X X X X X O O O . O X X X X X O O . |
$$ | X X . O O O X X X O . . X . X O . . . |
$$ | O O O O . X O O X X O O . O X . O O . |
$$ | O X . X . X . O O X O . . . X X X X X |
$$ | O X . X . . . O X X O . X X X X . O O |
$$ | X O O X . X . O X O O X X O O O O . . |
$$ | X X O O X . . O X O . X O O O . X X X |
$$ | X X . O X . . O X O . X O O X X X O O |
$$ | X X O O X . . O X O . X O . O . X X O |
$$ | X O O X . X . O X O . X X O O O X O O |
$$ | X O X . X X . O X O X . O X X X O O O |
$$ | O X X X X . . O X O O O O X O X O O X |
$$ | O . . . O X . O X X X X X . O X X O X |
$$ | O . X . . a X O O O O O O X O X . O X |
$$ | . X . . . . . O . . . . O X X X . O . |
$$ +---------------------------------------+[/go]
:b17: is necessary to bring Black's corner to life.

White will continue with the usual endgame in the lower left, starting with a.

White will win the game by about 12 points.
The really most difficult Go problem ever: https://igohatsuyoron120.de/index.htm
Igo Hatsuyōron #120 (really solved by KataGo)
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Re: KataGo @ Igo Hatsuyoron 120

Post by Cassandra »

"Classical" way of play => Black's weakness in the upper left (contd.)

KataGo does not want to follow Yamada's original sequence any longer!

When painting the diagrams for my postings for LifeIn19x19, I suddenly had the strange feeling that something was wrong.
Finally, I found out: In my draft for the update of our website, I had used another order of moves than had been originally shown by Yamada Shinji to us.
And now, with KataGo's new net, it does not want at all to follow that line of play...
Click Here To Show Diagram Code
[go]$$Wcm98
$$ +---------------------------------------+
$$ | . . . . c b . . . . . . X . . . O X . |
$$ | . . . . 4 3 5 X O O . X O X O . . O . |
$$ | . . . . . X a O . . . X O . O O O . . |
$$ | . X O , . . . . . O . X . O O X . . . |
$$ | . . X X X X O O O . O X X X X X O O . |
$$ | . X . O O O X X X O . . X . X O . . . |
$$ | O O O O . X O O X X O O . O X . 1 O . |
$$ | O X . X . X . O O X O . . . X X X X X |
$$ | O X . X . . . O X X O . X X X X . O O |
$$ | X O O X . X . O X O O X X O O O O . . |
$$ | X X O O X . . O X O . X O O O . X X X |
$$ | X X . O X . . O X O . X O O X X X O O |
$$ | X X O O X . . O X O . X O . O . X X O |
$$ | X O O 2 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 . . O X O O O O X O X O O X |
$$ | O . . . O X . O X X X X X . O X X O X |
$$ | O . X . . . X O O O O O O X O X . O X |
$$ | . X . . . . . O . . . . O X X X . O . |
$$ +---------------------------------------+[/go]
(Again, :w98: for :b99: is inserted for simplicity.)

After White's draw-back to :w2:, KataGo's new net does not seem to consider Yamada's move at a any longer for Black.
Instead, KataGo favours the immediate hane at b, and the descent to c, with the latter getting the upper hand over time.
Click Here To Show Diagram Code
[go]$$Wcm98
$$ +---------------------------------------+
$$ | . . . . . 8 . a . . . . X . . . O X . |
$$ | . . . . X O O X O O . X O X O . . O . |
$$ | . . . 9 7 X 6 O . . . X O . O O O . . |
$$ | . X O , . . . . . O . X . O O X . . . |
$$ | . . X X X X O O O . O X X X X X O O . |
$$ | . X . O O O X X X O . . X . X O . . . |
$$ | O O O O . X O O X X O O . O X . O O . |
$$ | O X . X . X . O O X O . . . X X X X X |
$$ | O X . X . . . O X X O . X X X X . O O |
$$ | X O O X . X . O X O O X X O O O O . . |
$$ | X X O O X . . O X O . X O O O . X X X |
$$ | X X . O X . . O X O . X O O X X X O O |
$$ | X X O O X . . O X O . X O . O . X X O |
$$ | X O O X . X . O X O . X X O O O X O O |
$$ | X O X . X X . O X O X . O X X X O O O |
$$ | O X X X X . . O X O O O O X O X O O X |
$$ | O . . . O X . O X X X X X . O X X O X |
$$ | O . X . . . X O O O O O O X O X . O X |
$$ | . X . . . . . O . . . . O X X X . O . |
$$ +---------------------------------------+[/go]
If we let Black play the "original" :b3:, White will still cut at :w4:, but after Black's atari with :b5:, she does NOT capture at a!
KataGo's new net draws back to :w6:, instead. sacrificing White's two stones at the upper edge.
Click Here To Show Diagram Code
[go]$$Wcm106
$$ +---------------------------------------+
$$ | . . . . . X 2 . . . . . X . . . O X . |
$$ | . . 4 6 X O O X O O . X O X O . . O . |
$$ | . 3 5 O O X X O . . . X O . O O O . . |
$$ | . X O , . . . . . O . X . O O X . . . |
$$ | . . X X X X O O O . O X X X X X O O . |
$$ | . X . O O O X X X O . . X . X O . . . |
$$ | O O O O . X O O X X O O . O X . O O . |
$$ | O X . X . X . O O X O . . . X X X X X |
$$ | O X . X . . . O X X O . X X X X . O O |
$$ | X O O X . X . O X O O X X O O O O . . |
$$ | X X O O X . . O X O . X O O O . X X X |
$$ | X X . O X . . O X O . X O O X X X O O |
$$ | X X O O X . . O X O . X O . O . X X O |
$$ | X O O X . X . O X O . X X O O O X O O |
$$ | X O X . X X . O X O X . O X X X O O O |
$$ | O X X X X . . O X O O O O X O X O O X |
$$ | O . . . O X . O X X X X X . O X X O X |
$$ | O . X . . . X O O O O O O X O X . O X |
$$ | . X . . . . . O . . . . O X X X . O . |
$$ +---------------------------------------+[/go]
Black :b7: takes White's two stones off the board. I suppose that this has to be done anyway -- sooner or later.

:w8: blocks in the corner, whereafter Black attacks White's shape from above.
Click Here To Show Diagram Code
[go]$$Wcm112
$$ +---------------------------------------+
$$ | . . . . . X X . . . . . X . . . O X . |
$$ | 7 6 X X X . . X O O . X O X O . . O . |
$$ | . O O O O X X O . . . X O . O O O . . |
$$ | 1 X O , 5 3 4 . . O . X . O O X . . . |
$$ | . 2 X X X X O O O . O X X X X X O O . |
$$ | . X . O O O X X X O . . X . X O . . . |
$$ | O O O O . X O O X X O O . O X . O O . |
$$ | O X . X . X . O O X O . . . X X X X X |
$$ | O X . X . . . O X X O . X X X X . O O |
$$ | X O O X . X . O X O O X X O O O O . . |
$$ | X X O O X . . O X O . X O O O . X X X |
$$ | X X . O X . . O X O . X O O X X X O O |
$$ | X X O O X . . O X O . X O . O . X X O |
$$ | X O O X . X . O X O . X X O O O X O O |
$$ | X O X . X X . O X O X . O X X X O O O |
$$ | O X X X X . . O X O O O O X O X O O X |
$$ | O . . . O X . O X X X X X . O X X O X |
$$ | O . X . . . X O O O O O O X O X . O X |
$$ | . X . . . . . O . . . . O X X X . O . |
$$ +---------------------------------------+[/go]
White's atari at :w12: has to be answered by the connection of :b13:.

Now, the time is ripe to cut Black apart with :w14: at the right.

Black continues in the corner with :b17:
Jumping to 118, instead, would not lead to a better result for him.
Click Here To Show Diagram Code
[go]$$Wcm118
$$ +---------------------------------------+
$$ | . . . . . X X . . . . . X . . . O X . |
$$ | O X X X X . . X O O . X O X O . . O . |
$$ | 5 O O O O X X O . 8 . X O . O O O . . |
$$ | O X O a O O X 2 6 O . X . O O X . . . |
$$ | 4 X X X X X O O O 7 O X X X X X O O . |
$$ | 3 X 9 O O O X X X O . . X . X O . . . |
$$ | O O O O . X O O X X O O . O X . O O . |
$$ | O X . X . X . O O X O . . . X X X X X |
$$ | O X . X . . . O X X O . X X X X . O O |
$$ | X O O X . X . O X O O X X O O O O . . |
$$ | X X O O X . . O X O . X O O O . X X X |
$$ | X X . O X . . O X O . X O O X X X O O |
$$ | X X O O X . . O X O . X O . O . X X O |
$$ | X O O X . X . O X O . X X O O O X O O |
$$ | X O X . X X . O X O X . O X X X O O O |
$$ | O X X X X . . O X O O O O X O X O O X |
$$ | O . . . O X . O X X X X X . O X X O X |
$$ | O . X . . . X O O O O O O X O X . O X |
$$ | . X . . . . . O . . . . O X X X . O . |
$$ +---------------------------------------+[/go]
It is best for Black now to push with :b19: at the top.

As a matter of course, he could capture White's stones in the upper left corner with B a, W 122, B 121.
However, he would be forced to really take White's group at the left off the board, enabling White to win the Punishment Semeai at the right.

:w20: captures Black's partial group in the upper left, while Black starts capturing White's top with :b25:.

This exchange favours White, who will win the game by about 15 points.
Please note that the hanezeki will remain untouched here, as both large groups live independently.
Last edited by Cassandra on Thu Jan 14, 2021 9:46 am, edited 1 time in total.
The really most difficult Go problem ever: https://igohatsuyoron120.de/index.htm
Igo Hatsuyōron #120 (really solved by KataGo)
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Re: KataGo @ Igo Hatsuyoron 120

Post by hakuseki »

Is there any hint of when this network will be available for download? I'd very much like to play with it.
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Re: KataGo @ Igo Hatsuyoron 120

Post by Cassandra »

hakuseki wrote:Is there any hint of when this network will be available for download? I'd very much like to play with it.
According to Friday9i's current schedule, he intends to train his new network for additional three months, at least, before a potential publication.

I have the feeling that he is currently extremely concerned about (probably somewhat unusual) "white spots" in the variation tree of the problem, which KataGo has not yet sufficiently explored / analysed during training. If I understood that issue correct, he is still on the way do develop some kind of tool, which should help a lot to overcome that problem.

To give you a recent example:
As far as I remember (disclaimer: my memory can be deceptive; probably there had been no need to go there any deeper), Lightvector's net did not have any problems with the original line of play after Yamada's tsuke in the upper left.
Probably, Friday9i's new net dislikes this order of moves now, because it had (additionally) analysed subvariations after Joachim's (yet unpubished; this is part of the draft I mentioned above) trial to "punish" KataGo's immediate crosscut (no Black guzumi played before) during training. In my understanding, the resulting positions have significant similarities, especially with regard to the hidden weaknesses in Black's corner.
The really most difficult Go problem ever: https://igohatsuyoron120.de/index.htm
Igo Hatsuyōron #120 (really solved by KataGo)
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Re: KataGo @ Igo Hatsuyoron 120

Post by Cassandra »

"Classical" way of play => Black's weakness in the upper left (contd.)

KataGo does not want to follow Yamada's original sequence any longer!

I feel that I have to add this posting to make clear that Yamada Shinji 6p must not be blamed for the abovementioned impact of KataGo's analysis.

When he, together with his study group, worked out his improvement over the "classical" atari, he had been asked only, if he could be so very kind to validate the correctness of the guzumi.

At that time, the endgame at the left side of the board was still played "late", i.e. after the dissolving of the hanezeki, i.e. after the occupation of White's liberties in the upper left.
Once that border of Black's upper left corner is settled, KataGo's new finding is NOT applicable any longer!

It was Prof. Jeong, who told us later that it would be technically correct to start that endgame early.
Therefore, it were some poor amateurs, who overlooked the hidden weaknesses of Black's upper left corner, when transposing Yamada's sequence to an earlier moment in the game.
The really most difficult Go problem ever: https://igohatsuyoron120.de/index.htm
Igo Hatsuyōron #120 (really solved by KataGo)
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Re: KataGo @ Igo Hatsuyoron 120

Post by Friday9i »

hakuseki wrote:Is there any hint of when this network will be available for download? I'd very much like to play with it.
Hi
As said by Cassandra, I effectively intend to release the new net once the training is finished, in a few months. It already is very significantly stronger than g146 : -): it beats it from starting position even if 50x less visits, as it improved its understanding and knows how to squeeze a bit more profit. From a panel of thousands of random Igo Hatsuyoron positions, with only 25 visits, it manages to beat g146 with 100 visits, with an about 40 Elo performance (from about same Elo 2 months ago), so it still improves quite healthily. I'm also developing a small python tool to automate exploration of board positions (using KataGo's analysis engine), which will hopefully help wide exploration of the problem, and possibly help it to discover unexpected moves : -). We'll see in the coming weeks if we get some interesting results from this additional exploration.
Thanks to Cassandra for its panel of Igo positions (very precious for training), and big thank you to lightvector for precious advice to launch the run with adequate training parameters : -)
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Re: KataGo @ Igo Hatsuyoron 120

Post by Cassandra »

Harry drew my attention to the following Chinese video about KataGo's solution to Igo Hatsuyôron 120:

https://www.bilibili.com/video/BV1JC4y1x7Uv/

The comments are in Chinese AND ENGLISH.
The really most difficult Go problem ever: https://igohatsuyoron120.de/index.htm
Igo Hatsuyōron #120 (really solved by KataGo)
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Re: KataGo @ Igo Hatsuyoron 120

Post by Cassandra »

2021 update of Igo Hatsuyôron 120 website uploaded!

The variation trees for the new sections can be accessed via ...

http://igohatsuyoron120.de/2015/0058.htm and
http://igohatsuyoron120.de/2015/0513b.htm

You will find a short description of the update's topics at the top of these pages.

----------

Please let me know if you find any issues.
The really most difficult Go problem ever: https://igohatsuyoron120.de/index.htm
Igo Hatsuyōron #120 (really solved by KataGo)
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