KataGo starts the endgame on the left side of the board "early", choosing the Tsuke of Yamada Shinji 6p as a precondition for an immediately subsequent further improvement of the classical sequence.

Yamada Shinji discovered his tsuke at a time when we had only identified Joachim's Rediscovered Oki and my Second Throw-in, and when the endgame had not begun until after the hanezeki in the lower right corner had been resolved.

We will determine the effects of the new move compared to the classical solution of Fujisawa Hideyuki 9p and explain some failures in deviations from the continuation proposed by Yamada Shinji.

Referenced by ( 2022MainLine), ( 2038)

Let's go back a few years and enter the world of KataGo ...

: ( 2022MainLine)
This is the position from lightvector's initial KataGo version (2019), when White plays Yamada Shinji's Tsuke, so starting the endgame on the left side of the board.

:
Black has to block.

This immediate crosscut is an invention of KataGo that will be described in detail in the next section.

For further details, please refer to section "KataGo's Immediate Crosscut after Yamada Shinji's Tsuke" ( 2038).

Let's go back in time and enter the world of the amateurs, seeking professional assistance ...

: (A 2037)
At a time when we were still uncertain about the validity of my Second Throw-in, Yamada Shinji was kind enough to look into our findings.
In this context he discovered (still based on the classical solution, enriched by Joachim's Oki) an improvement for White's endgame on the left side of the board for the Capture Variation, his Tsuke - instead of the atari chosen by Fujisawa Hideyuki.

At that time, the endgame was played after White's decision point (i.e. after the capture of the hanezeki's tail here), so that KataGo's Immediate Crosscut could not be identified, as it does not work after Black's borders in the upper left corner have been settled.

For further details, please refer to section "KataGo's Immediate Crosscut after Yamada Shinji's Tsuke" ( 2038).

Please note that Yamada Shinji's Tsuke could not be played in the Semeai Variation here, as Black's resistance (a reply at ) will result in a seki in the upper left corner (as you will see below), but which will collapse, as White's large group at the left can be taken of the board in this alternative Main Variation.

Since Prof. Jeong SooHyun's kind advice, the endgame was started "early" by us, i.e. after the termination of the Nakade Sequence.

For further details, please refer to section "Prof. Jeong SooHyun's Advice to Start the Endgame Early" ( 2043).

Thus Yamada Shiji's Tsuke finally improved White's score also in the Semeai Variation.

: (144 2037a)
Black must block.

He is unable to resist with , intending to save his single stone at the upper edge, and capturing White's intruder(s).

: (146 2037c)
So late in the game, White is forced to draw back.

KataGo's Immediate Crosscut at , instead, does not work any longer.

:
Black immobilises White's cutting stone in the corner.

:
The endgame continues in the lower left corner.

: (156 2037d)
Black plays Cheng's Tenuki.

Jérôme Hubert's Solid Connection with would be one point worse here, and so a mistake.

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White plays Cheng's Bump in the left centre, ...

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... before securing the last available point of territory in the right centre.

Let's utilise the knowledge that existed at the dawn of time ...

: ( 2037)
This atari had been played by Fujisawa Hideyuki.

:
Again, Black has to block.

:
White further reduces Black's territory in the upper left corner, following the suggestions of Jérôme Hubert for a while.

For further details, please refer to section "Jérôme Hubert's Correction of the Mutual Occupation of Opponent's Liberties" ( 2041).

:
Black ends in gote.

:
The endgame continues in the lower left corner.

: (156 2037e)
This is Cheng's Tenuki.

Choosing Jérôme Hubert's Connection at would be a mistake here.

:
Cheng's Bump in the left centre.

:
White ended in gote at the top, so Black is able to take the last valuable point on the board.

Capture Variation (left side of the board):

Fujisawa Hideyuki's Atari (at left):

• Black has seven points of territory.

Yamada Shinji's Tsuke (at right):

• Black has six points of territory.

White gained one point at the left side of the board through Yamanda Shinji's Tsuke.

Capture Variation (right side of the board):

Fujisawa Hideyuki's Atari (at left):

• White does not have territory in the right centre.

Yamada Shinji's Tsuke (at right):

• White has one point of territory in that area.

White gained one point at the right side of the board through Yamanda Shinji's Tsuke.

In total, Yamama Shinji's Tsuke gained White two points.

White + 1 => White + 3

2037

2022MainLine