We will present Joachim Meinhardt's alternative move suggestions, which basically lead to the creation of a ko-shape in the Guzumi Area within a semeai between Black's large group in the upper right and White's centre group.

Unlike our historical attempts, which resulted in the initial variation of Joachim's Ko-Semeai, KataGo invades the top left corner, but then falls for its tragic love of triple-ko, presumably a holdover from its early days under area scoring.

First, to set the record straight, we present some simple ideas with which KataGo could easily circumnavigate the aforementioned cliff.

We then shed light on Joachim's ideas at the time.

KataGo - as usual - has some sharper moves on offer, but in principle fully confirms the validity of Joachim's considerations, which, despite all their efforts, ultimately end in Black's defeat.

Referenced by ( 2035), ( 2044)

Let's go back in time and enter the world of amateurs ...

: ( 2022MainLine)
Black plays the hiki at the upper edge, a large endgame move, following a suggestion of Joachim Meinhardt.

Black did not occupy White's Main Semeai Liberty at , instead, and so has to sacrifice both hasami-tsuke stones to survive the Punishment Semeai.

Joachim's Ko-Semeai is a variation of the "classical" solution, i.e. the Guzumi has not been played before.

Please also note that at the time of its creation, my Second Throw-in, but none of the kikashi in the hanezeki, had been played by us.

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White makes sure that her large group at the left edge cannot be captured easily.

With komi = -1, KataGo also favours this move.

With larger reverse komi, KataGo prefers to insert the atari in the upper left as a kikashi beforehand, which Black will have to answer by connecting at .

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Black captures White's single stone in the centre, setting his hopes on a semeai with White's centre group.
This move loses one tempo in the Main Semeai, but which is irrelevant here, as Joachim favoured the Central Semeai anyway.

Inserting Michael Redmond's Kikashi in the Bamboo Joint , before will not make a difference.

Black is unable to return to the Main Semeai with a move at , instead, as White would capture his nakade stones at the left edge with , for example.

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White occupies the Guzumi Point, stopping Black from creating a second eye in this area.

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Black cuts at , intending to create a ko-shape at the right edge.

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He can do so in sente, as White must connect her two stones below with .

Vital points for Black's forthcoming attack on White's centre group are , and .

Let's find out what KataGo thinks about this matter ...

: (A 2034e)
With komi = -1, KataGo favours White's move in the Nakade Area, as we did.

With larger reverse komi, White's push into Black's upper left corner becomes a bit more attractive for KataGo.
Black would have to answer by connecting with .

: (A 2034f)
Thereafter, KataGo lives out its AI-typical preference for kikashi played early on. It favours inserting the exchange of for at the left edge ...

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... before playing Michael Redmond's Kikashi in the bamboo joint.

We also considered this kikashi, but found out that playing it "early" is irrelevant here (contrary to the classical professional solution), as the outcome of the semeai is not affected.

Capturing White's single stone in the upper right with (as we did) is the runner-up in KataGo's list.

: (92 2034g)
KataGo continues with the Nakade Sequence, allowing White to attack his upper left corner.

Joachim thought that immediately defending with would erase several of White's option in this area.
Please note that the marked exchange (, ) at the left edge was not played at that time.

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Black ends in gote.

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White starts her attack on the upper left corner.

For further details of our earlier analysis, please refer to the history of our investigations ...
270

: ( A 2034h)
White's diagonal move is one of KataGo's surprising moves in the upper left corner.

However, this move also opens up the possibility for KataGo to trip itself up, as we will see below.

It would have been far easier to play the second push on instead, as we usually did.
However, we saw this second push as an enabler for additional White ko-threats in the upper left corner for Joachim's Ko-Semeai, while KataGo will come up with an even much simpler solution, as can be seen from the subvariation.

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Black closes his corner.

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White strives for an eye in the corner.

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Black has to connect his forces.

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White blocks immediately.

Could also be played at ; it would result a change in the order of moves (, , , ).

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Black connects along the left edge, in sente.

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White's throw-in at the left edge creates even more cutting points in Black's formation.

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White establishes an eye at the upper edge, in sente.

She threatens to continue with the double-atari of , starting a ko-fight in the corner.

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Black defends against White's threat by connecting at the left edge.

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Another throw-in for spoiling Black's shape.

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White's hane prevents a Black descent at the same point.

: (112 2034a)
Black gives atari at the upper edge immediately.

Playing at , instead, would it make too easy and uncomplicated for White.

: ( 115 2034b)
White's connection aims at strengthening the shape of her encloses group.

However, she should have better chosen the connection at , instead, which would result in an approach-move ko.

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Black connects for another time at the left edge.

If he played at , instead, it would be White, who would get the point of at the upper edge, after the previous exchange of for in the corner.

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White occupies one of Black's liberties at the left edge.

Again, or would result in an approach-move ko.

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Black wants to avoid the approach-move ko explained in the subvariation above.

: ( 117 2034c)
White occupies one of Black's liberties at the top.

However, a move at would have been preferable, resulting in the already so often mentioned approach-move ko.

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Black's hane establishes a third ko-shape at the upper edge, also creating difficulties for White approaching his corner group.

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Black fills one of his false eyes.

: ( A 2034d)
Capturing into one of the ko-shapes at the upper edge seems to be a mistake.

I found that White should continue with the Main Semeai, instead, and occupy the Guzumi Point with . She will win the game by about ten points thereafter.
There is nothing that Black could do in the upper left corner.

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Black continues with a half triple-ko cycle.

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KataGo interrupts the mutual capture into the ko-shapes by occupying one of Black's outside liberties.

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Black captures into the double-ko in the corner.

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After any Black move on the board ...

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... KataGo will continue capturing into the ko-shapes at the top.

...

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KataGo will continue forever with letting both sides capture in the triple-ko at the top.

White should continue with the Main Semeai, instead, and occupy the Guzumi Point with , as already shown in the corresponding subvariation above.

The game will end with no result.

2022MainLine