KataGo @ Igo Hatsuyoron 120

Cassandra · **#41**

lightvector wrote:

The thing is, some of white's gains on the left side costs white some turns or some liberties, but don't actually lose very much in the case that ultimately the semeai variation is chosen. If black spends those extra liberties pushing in the upper right, black improves the capture variation, but those moves *lose* points on the semeai variation.

So given that most of black's ability to balance white's gains comes at the cost of making one variation worse to improve the other, whereas some of white's gains just purely make one variation better without costing in the other, black starts to get squeezed in both variations.

Sorry, but this is not how the problem works!

Click Here To Show Diagram Code: [go]$$B $$ --------------------------------------------------------------------------------- $$ - . . . B O O . . . . O X X X O . O X . - . . . . X X W W . . O X X X O . O X . - $$ - . . . B X O O X O O O X O X O . . O . - . . . . X O O . O O O X O X O . . O . - $$ - . . . X O X O O . . O X O O O O O . . - . . . X . X X O . . O X O O O O O . . - $$ - . X O , . X X X Q O O X . O O X O . . - . X O , X . X O . O O X O O O X O . . - $$ - . . X X X X O O O . O X X . X X O O . - . . X X X X O O O . O X X O X X O O . - $$ - X X X O O O . . . O . O X X X O O O O - X X X O O O . . . O . O X X X O O O O - $$ - O O O O O X O O . . O O X . X O O X O - O O O O X X O O . . O O O O X . O X . - $$ - O X X X X X O O O . O O O X X X X X X - O X X X . X . O O . O . O . X X X X X - $$ - O X X X X X X O . . O O X X X X . . . - O X X X . X . O . . O O X X X X . . . - $$ - O O O X X X O O . O O X X . . , . X X - O O O X . X O O . O O X X . . , . X X - $$ - O O O O X O O O . O O X . . . X X X X - X . O O X . . O . O . X . . . X X X X - $$ - X . O O X O X O . O . X . . X X X . . - . . O O X . . O . O . X . . X X X . . - $$ - . . O O X X X O . O . X . . . X X X . - O O O X X . . O . O . X . . . X X X . - $$ - O O O O O X . O . O X X X . . . X . . - O O O X O X . O . O O X X . . . X . . - $$ - O O X O X X . O . O X O O X X X . . . - O O X . . X . O . O . O O X X X . . . - $$ - O X X X X X . O . O O O O X O X . . X - O X X , X X . O . O O O O X . X . . X - $$ - O X . . O X O O . . . O O O O X X . X - O X . . O X O O . . . O O O O X X . X - $$ - O X X . X O . O O O O O O X X X X . X - O X X . X O . O O O O O O X . X X . X - $$ - X X . . X O O O . . . . O X X X X . . - X X . . X O O O . . . . O X X X X . . - $$ +-------------------------------------------------------------------------------+ $$ - . . . B O O . . . . O . . . O . O X . - . . . . X X W W . . O . . . O . O X . - $$ - . . . B X O O X O O O . O . O . . O . - . . . . X O O . O O O . O . O . . O . - $$ - . . . X O X O O . . O . O O O O O . . - . . . X . X X O . . O . O O O O O . . - $$ - . X O , . X X X Q O O . O O O , O . . - . X O , X . X O . O O . O O O , O . . - $$ - . . X X X X O O O . O . . O . . O O . - . . X X X X O O O . O . . O . . O O . - $$ - X X X O O O X X X O O O . . . O O O O - X X X O O O X X X O . O . . . O . O O - $$ - O O O O O X O O X X O O . O . O O . O - O O O O X X O O X X O O O O . O O . O - $$ - O X X X X X O O O X O O O . . . . . . - O X X X . X . O O X O . O O . . . . . - $$ - O X X X X X X O X X O O . . . . O O O - O X X X . X . O X X O O . . . . O O O - $$ - O O O X X X O O X O O . . O O O O X . - O O O X . X O O X O O . . O O O O X . - $$ - O O O O X O O O X O O . O O O X X X X - X X O O X . . O X O O . O O O . X X X - $$ - X X O O X O X O X O O . O O X X X . . - . O O O X . . O X O O . O O X X X . . - $$ - . O O O X X X O X O O . O O O X X X . - O O O X X . . O X O O . O O O X X X . - $$ - O O O O O X . O X O . . . O O O X . . - O O O X O X . O X O O . . O O O X . . - $$ - O O X O X X . O X O . O O X X X . . . - O O X . . X . O X O . O O X X X . . . - $$ - O X X X X X . O X O O O O X . X . . X - O X X , X X . O X O O O O X . X . . X - $$ - O X . . O X O O X X X X X X O X X . X - O X . . O X O O X X X X X X O X X . X - $$ - O X X . X O . O O O O O O X . X X . X - O X X . X O . O O O O O O X . X X . X - $$ - X X . . X O O O . . . . O X X X X . . - X X . . X O O O . . . . O X X X X . . - $$ --------------------------------------------------------------------------------+[/go]

Only territorial gains and losses that are located OUTSITE the Main Semeai area (i.e. not in the immediate vicinity of White's large group on the left nor of Black's large group in the upper right) have an identical effect on both Main Variations (Capture and Semeai Variation).

White gained an absolute advantage of three points (B + 5 / B + 3 ==> B + 2 / Jigo).

Click Here To Show Diagram Code: [go]$$B $$ --------------------------------------------------------------------------------- $$ - . . . X O O . . . . O X X X O . O X . - . . . . X X O O . . O X X X O . O X . - $$ - . . . X X O O X O O O X O X O . . O . - . . . . X O O . O O O X O X O . . O . - $$ - . . . X O X O O . . O X O O O O O . . - . . . X . X X O . . O X O O O O O . . - $$ - . X O , . X X X O O O X . O O X O . . - . X O , X . X O . O O X O O O X O . . - $$ - . . X X X X O O O . O X X . X X O O . - . . X X X X O O O . O X X O X X O O . - $$ - X X X O O O . . . O . O X X X O O O O - X X X O O O . . . O . O X X X O O O O - $$ - O O O O O X O O . . O O X . X O O X O - O O O O X X O O . . O O O O X . O X . - $$ - O X X X B X O O O . O Q O X X X X X X - O X X X . X . O O . O . O . X X X X X - $$ - O X X X B X X O . . O O X X X X . . . - O X X X . X . O . . O O X X X X . . . - $$ - O O O X B X O O . O O X X . . , . X X - O O O X . X O O . O O X X . . , . X X - $$ - O O O O X O O O . O O X . . . X X X X - X . O O X . . O . O . X . . . X X X X - $$ - X . O O X O X O . O . X . . X X X . . - . . O O X . . O . O . X . . X X X . . - $$ - . . O O X X X O . O . X . . . X X X . - O O O X X . . O . O . X . . . X X X . - $$ - O O O O O X . O . O X X X . . . X . . - O O O X O X . O . O O X X . . . X . . - $$ - O O X O B X . O . O X O O X X X . . . - O O X . . X . O . O . O O X X X . . . - $$ - O X X B B X . O . O O O O X O X . . X - O X X , X X . O . O O O O X . X . . X - $$ - O X . . O X O O . . . O O O O X X . X - O X . . O X O O . . . O O O O X X . X - $$ - O X X . X O . O O O O O O X X X X . X - O X X . X O . O O O O O O X . X X . X - $$ - X X . . X O O O . . . . O X X X X . . - X X . . X O O O . . . . O X X X X . . - $$ +-------------------------------------------------------------------------------+ $$ - . . . X O O . . . . O . . . O . O X . - . . . . X X O O . . O . . . O . O X . - $$ - . . . X X O O X O O O . O . O . . O . - . . . . X O O . O O O . O . O . . O . - $$ - . . . X O X O O . . O . O O O O O . . - . . . X . X X O . . O . O O O O O . . - $$ - . X O , . X X X O O O . O O O , O . . - . X O , X . X O . O O . O O O , O . . - $$ - . . X X X X O O O . O . . O . . O O . - . . X X X X O O O . O . . O . . O O . - $$ - X X X O O O X X X O O O . . . O O O O - X X X O O O X X X O . O . . . O . O O - $$ - O O O O O X O O X X O O . O . O O . O - O O O O X X O O X X O O O O . O O . O - $$ - O X X X B X O O O X O Q O . . . . . . - O X X X . X . O O X O . O O . . . . . - $$ - O X X X B X X O X X O O . . . . O O O - O X X X . X . O X X O O . . . . O O O - $$ - O O O X B X O O X O O . . O O O O X . - O O O X . X O O X O O . . O O O O X . - $$ - O O O O X O O O X O O . O O O X X X X - X X O O X . . O X O O . O O O . X X X - $$ - X X O O X O X O X O O . O O X X X . . - . O O O X . . O X O O . O O X X X . . - $$ - . O O O X X X O X O O . O O O X X X . - O O O X X . . O X O O . O O O X X X . - $$ - O O O O O X . O X O . . . O O O X . . - O O O X O X . O X O O . . O O O X . . - $$ - O O X O B X . O X O . O O X X X . . . - O O X . . X . O X O . O O X X X . . . - $$ - O X X B B X . O X O O O O X . X . . X - O X X , X X . O X O O O O X . X . . X - $$ - O X . . O X O O X X X X X X O X X . X - O X . . O X O O X X X X X X O X X . X - $$ - O X X . X O . O O O O O O X . X X . X - O X X . X O . O O O O O O X . X X . X - $$ - X X . . X O O O . . . . O X X X X . . - X X . . X O O O . . . . O X X X X . . - $$ --------------------------------------------------------------------------------+[/go]

Opponent's territory can be also destroyed in an identical manner in both Main Variations IN the Main Semeai area, but these destructions are costly.
In principle, the destructor has to pay in LIBERTIES in the CAPTURE Variation, but in POINTS of territory in the SEMEAI Variation.

White gained a temporary advantage of another five points (B + 2 / Jigo ==> W + 3 / W + 5).

Click Here To Show Diagram Code: [go]$$B $$ --------------------------------------------------------------------------------- $$ - . . . X O O . . . . O X X X O . O X . - . . . . X X O O . . O X X X O . O X . - $$ - . . . X X O O X O O O X O X O . . O . - . . . . X O O . O O O X O X O . . O . - $$ - . . . X O X O O . . O X O O O O O . . - . . . X . X X O . . O X O O O O O . . - $$ - . X O , . X X X O O O X . O O X O . . - . X O , X . X O . O O X O O O X O . . - $$ - . . X X X X O O O . O X X . X X O O . - . . X X X X O O O . O X X O X X O O . - $$ - X X X O O O . . . O . O X X X O O O O - X X X O O O . . . O . O X X X O O O O - $$ - O O O O O X O O . . O O X . X O O X O - O O O O X X O O . . O O O @ X . O X . - $$ - O X X X X X O O O . O O O X X X X X X - O X X X . X . O O . O . O . X X X X X - $$ - O X X X X X X O . . O O X X X X . . . - O X X X . X . O . . O O X X X X . . . - $$ - O O O X X X O O . O O X X . . , . X X - O O O X . X O O . O O X X . . , . X X - $$ - O O O O X O O O . O O X . . . X X X X - X . O O X . . O . O . X . . . X X X X - $$ - X . O O X O X O . O . X . . X X X . . - . . O O X . . O . O . X . . X X X . . - $$ - . . O O X X X O . O . X . . . X X X . - O O O X X . . O . O . X . . . X X X . - $$ - O O O O P X . O . O X X X . . . X . . - O O O X O X . O . O O X X . . . X . . - $$ - O O X O X X . O . O # O O X X X . . . - O O X . . X . O . O . O O X X X . . . - $$ - O X X X X X . O . O O O O X O X . . X - O X X , X X . O . O O O O X . X . . X - $$ - O X . . O X O O . . . O O O O X X . X - O X . . O X O O . . . O O O O X X . X - $$ - O X X . X O . O O O O O O X X X X . X - O X X . X O . O O O O O O X . X X . X - $$ - X X . . X O O O . . . . O X X X X . . - X X . . X O O O . . . . O X X X X . . - $$ +-------------------------------------------------------------------------------+ $$ - . . . X O O . . . . O . . . O . O X . - . . . . X X O O . . O . . . O . O X . - $$ - . . . X X O O X O O O . O . O . . O . - . . . . X O O . O O O . O . O . . O . - $$ - . . . X O X O O . . O . O O O O O . . - . . . X . X X O . . O . O O O O O . . - $$ - . X O , . X X X O O O . O O O , O . . - . X O , X . X O . O O . O O O , O . . - $$ - . . X X X X O O O . O . . O . . O O . - . . X X X X O O O . O . . O . . O O . - $$ - X X X O O O X X X O W O . . . O W O O - X X X O O O X X X O . O . . . O . O O - $$ - O O O O @ X O O X X O O . W . O O . O - O O O O X X O O X X O O P O . O O . O - $$ - O X X X X X O O O X O O O . . . . . . - O X X X . X . O O X O . O P . . . . . - $$ - O X X X X X X O X X O O . . . . O O O - O X X X . X . O X X O O . . . . O O O - $$ - O O O X X X O O X O O . . O O O O X . - O O O X . X O O X O O . . O O O O X . - $$ - O O O O X O O O X O O . O O O X X X X - X X O O X . . O X O O . O O O . X X X - $$ - X X O O X O X O X O O . O O X X X . . - . O O O X . . O X O O . O O X X X . . - $$ - . O O @ X X X O X O O . O O O X X X . - O O O X X . . O X O O . O O O X X X . - $$ - O O O @ O X . O X O . . . O O O X . . - O O O X O X . O X O P . . O O O X . . - $$ - O O X @ X X . O X O . O O X X X . . . - O O X . . X . O X O . O O X X X . . . - $$ - O X X X X X . O X O O O O X . X . . X - O X X , X X . O X O O O O X . X . . X - $$ - O X . . O X O O X X X X X X O X X . X - O X . . O X O O X X X X X X O X X . X - $$ - O X X . X O . O O O O O O X . X X . X - O X X . X O . O O O O O O X . X X . X - $$ - X X . . X O O O . . . . O X X X X . . - X X . . X O O O . . . . O X X X X . . - $$ --------------------------------------------------------------------------------+[/go]

In the CAPTURE Variation, White's connection of her single stone at the left gained her two points.
However, she also lost liberties in the process, so Black is able to connect his single stone in the centre, as well as creating an eye (with White prisoner) in the top right, spending this won liberties for his own territorial gain.
In total, White lost two points from her temporary advantage (W + 3 ==> W + 1).

In the SEMEAI Variation, White spent four additional stones for destroying Black territory at the left, but Black added only three stones to his large group in the upper right.
Additionally, due to Black's eye, White has to occupy all cutting points around Black's large group, as well as Black's eye point, so losing another three points in the process.
In total, White lost five points from her temporary advantage (W + 5 ==> Jigo).

dany · **#42**

Cassandra wrote:

A 50 per cent approach-move liberty

Did you ever wonder why the score difference between the Capture Variation and the Semeai Variation with KataGo's new ( & amateurish enhanced) solution is odd (W + 1 vs. Jigo), while this difference was even with Our Solution (B + 5 / B + 3), as well as decades ago?

...
With the Semeai Variation, however, due to Black's eye at O13 (and his connection at L6, and White's vanished eye in the centre at M12), White is able to approach at c AND d, only after connecting at the crossed board point before. This connection costs her one point of territory, but in the Semeai Variation only.

144 White's move should be in M11 instead of M12. its one point better for White in Semeai Variation.
so in both variations the result will be W + 1

Cassandra · **#43**

dany wrote:

144 White's move should be in M11 instead of M12. its one point better for White in Semeai Variation.
so in both variations the result will be W + 1.

Thanks a lot, dany. When thinking about the consequences of Joachim's tesuji of O14 (instead of O12), the Semeai Variation was not yet on our radar ...

Joachim will be very happy now, as he found different scores in both Main Variations a bit disappointing.

alreadydone · **#44**

This is maybe OT, but has anyone tested DNN-based bots (Leela Zero, KataGo, SAI, etc.) on the whole-board endgame problems (attached) in Appendix C of [BW94], including the 9-dan stumping problem [0] and many 9x9 problems? (LZ may be less appropriate due to fixed 7.5 komi.) Additional problems are found in:
http://library.msri.org/books/Book29/files/kim.pdf
http://library.msri.org/books/Book56/fi ... kamura.pdf (4.2. Whole board problems)
https://webdocs.cs.ualberta.ca/~mmuelle ... board.html
https://webdocs.cs.ualberta.ca/~mmuelle ... hesis.html (compressed pdf, A.3, modifications of [BW94] problems; Chapter 7 describes the program Explorer)
https://www.dumbo.ai.kyutech.ac.jp/~tei ... 1slide.pdf (Problems 3 and 4)

I wonder how these problems designed with mathematical theory differ from those from traditional Go practice. I think they likely also require specific training (like what lightvector did for Hatsuyoron 120) to solve. The search would need to be extremely wide and the number of variations/branches may be enormous due to lack of forced moves.
The attachments contain solutions to the [BW94] problems, but only the first moves. It's said in the paper [1] that "Our program Explorer uses this tool to play full board endgames. It plays a nontrivial class of endgame positions perfectly"; Explorer can be downloaded at [2] but only runs in Mac. Also, I can't find SGF files for the "Perfect Play" and "Node Rooms" collections (see [3]) in Mueller's Computer Go Test Collection [4]. Any idea?

[BW94] Berlekamp--Wolfe 1994, Mathematical Go: Chilling Gets the Last Point
[0] https://zhuanlan.zhihu.com/p/33860825 (in Chinese)
[1] https://webdocs.cs.ualberta.ca/~mmuelle ... dgames.pdf (Optimizations as described in 4. Local Move Generation are potentially necessary to solve the problems besides the AlphaZero/KataGo algorithms.)
[2] http://www.computer-go.info/db/oprog.php?a=Explorer or https://www.applefritter.com/node/13972
[3] https://webdocs.cs.ualberta.ca/~mmuelle ... endix.html
[4] https://webdocs.cs.ualberta.ca/~games/go/cgtc/

Cassandra · **#45**

The Variation Tree of our website has been updated:

KataGo's New Move Suggestions

Please let me know if you find any issues ...

RobertJasiek · **#46**

alreadydone,

1) thank you for your links in your message body.

2) Your two attachments contain photo/scan copies of several pages of a book. IMO, the copies have more pages than can be expected to be fair use when spread publicly. Judging from experience here, I'd say, one or two pages of photo/scan copies would be ok. Note that citations (that is not: photo/scan copies) with proper credit would allow more pages if occurring in new printed media (that is not: wiki web pages).

hyperpape · **#47**

Did you by any chance test the version trained on Igo Hatsuyoron against any other versions of Kata? I don't know that it's an important question, but it piqued my curiosity whether it learned anything generalizable, forgot something other versions knew, or was essentially unaffected by spending so much time on such an obscure scenario.

dany · **#48**

new move

W+1

Click Here To Show Diagram Code: [go]$$Wc $$ +---------------------------------------+ $$ | . . . X O . . . . . . . X X . . O X . | $$ | . . . X X O O X O O . X O X O . . O . | $$ | . . . X O X O O . . . X O O . O O . . | $$ | . X O , . X X X O O . X . O O X . . . | $$ | . . X X X X O O O . O X X . X X O O . | $$ | . X . O O O X X X O . . X . X O . O . | $$ | O O O O O X O O X X O O X O X . . X . | $$ | O X . X . X O O O X O . . . X X X X X | $$ | O X . X X X X O X X O . X X X X O O O | $$ | O O O X . X O O X O O X X O O O O X . | $$ | X . O O X 1 . O X O . X O O O . X X X | $$ | . X O O X 2 3 O X O . X O O X X X O O | $$ | X . O O X . . O X O . X O . O . X X O | $$ | . O O O O X . O X O . X X O O O X O O | $$ | O O X O X X . O X O X . O X X X O O O | $$ | 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]

Cassandra · **#49**

Dear dany,

Thank you very much indeed for your very interesting suggestion.

To be honest, I have not checked your ko variations, because usually Black is unable to win any ko in this problem.
In my opinion (not yet crosschecked by Joachim), Black can (should) do without your ko, and still reaches a jigo (with your choice of setting the komi to zero).

To ease the evaluation of "your" position (and the variations thereafter), I have played all the other "unaffected" moves of the Main Semeai first, and reached the following state on the board:

Click Here To Show Diagram Code: [go]$$Bc $$ +---------------------------------------+ $$ | . . . X O a . . . . O X X X O . O X . | $$ | . . . X X O O X O O O X O X O . . O . | $$ | . . . X O X O O . . w X O O O O O . . | $$ | . X O , . X X X O O O X . O O X w . . | $$ | . . X X X X O O O . O X X O X X O O . | $$ | X X X O O O X X X O . O X X X O O O O | $$ | O O O O O X O O X X O O X O X . . X . | $$ | O X X X X X O O O X O . O . X X X X X | $$ | O X X X X X X O X X O O X X X X O O O | $$ | O O O X b X O O X O O X X O O O O X . | $$ | O O O O X O . O X O O X O O O . X X X | $$ | X . O O X . . O X O . X O O X X X O O | $$ | . . O O X b . O X O . X O O O X X X O | $$ | O O O O O X . O X O w X X O O O X O O | $$ | O O X O X X . O X O X w O X X X O O O | $$ | O X X X X X . O X O O O O X O X O O X | $$ | O X . k O X O O X X X X X . O X X O X | $$ | O c 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]

Please be aware:

White will never capture with moves at any of the b-points at the left.
However, Black will have to connect at these points, if necessary, before White's main decision point (i.e. just before she captures the hanezeki's tail, or chooses the Semeai Variation).
Black will never play at any of the w-points at the right, after White's decision between the Capture and the Semeai Variation.
White will capture the hanezeki's tail, or choose to continue with the Semeai Variation, at the moment when Black's large group at the top right has only seven liberties left -- after a Black move.

Please find my variations in the attached SGF.

Main points of interest are:

Will White connect at a at the upper edge, or will Black capture White's single stone there?
Will White play the kikashi of W k & W c in the lower left corner, or will Black be able to defend at c?

Cassandra · **#50**

Dany kindly made me aware that I missed an important detail ...

Click Here To Show Diagram Code: [go]$$Wc $$ +---------------------------------------+ $$ | . . . X O . . . . . . . X X . . O X . | $$ | . . . X X O O X O O . X O X O . . O . | $$ | . . . X O X O O . . . X O O . O O . . | $$ | . X O , . X X X O O . X . O O X . . . | $$ | . . X X X X O O O . O X X . X X O O . | $$ | . X . O O O X X X O . . X . X O . O . | $$ | O O O O O X O O X X O O X O X . . X . | $$ | O X 6 X 7 X O O O X O . . . X X X X X | $$ | O X 5 X X X X O X X O . X X X X O O O | $$ | O O O X . X O O X O O X X O O O O X . | $$ | X . O O X W 8 O X O . X O O O . X X X | $$ | . X O O X B W O X O . X O O X X X O O | $$ | X . O O X . . O X O . X O . O . X X O | $$ | . O O O O X . O X O . X X O O O X O O | $$ | O O X O X X . O X O X . O X X X O O O | $$ | 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 4 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]

After dany's creation of the ko shape in the centre, Black is unable to strive for a jigo (komi = 0) by definding his lower left corner with the move at 4.

Due to the shortage of liberties of Black's two stones at the left, Black is forced to start a ko fight with 8 that he cannot win.

With what we know now, the variation with Black's tenuki after KataGo's bad-shape move really ends with W + 1 (komi = 0) respectively W + 2 (komi = 1).

Cassandra · **#51**

Three weeks ago, my laptop said "Good bye!" to me. A sustainable repair was no longer possible, but luckily it could be restored at least to the extent that I could read out the data on the hard disk and save it. Otherwise, about six weeks of analytic and preparatory work for our website since the last backup would have been lost.
I had a lot of time to think during these three weeks, and now could be a good time to share our findings and results so far.

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Click Here To Show Diagram Code: [go]$$Wc Dany's Ko $$ +---------------------------------------+ $$ | . . . X O . . . . . . . X X . . O X . | $$ | . . . X X O O X O O . X O X O . . O . | $$ | . . . X O X O O . . . X O O . O O . . | $$ | . X O , . X X X O O . X . O O X . . . | $$ | . . X X X X O O O . O X X . X X O O . | $$ | . X . O O O X X X O . . X . X O . O . | $$ | O O O O O X O O X X O O X O X . . X . | $$ | O X . X . X O O O X O . . . X X X X X | $$ | O X . X X X X O X X O . X X X X O O O | $$ | X O O X . X O O X O O X X O O O O X . | $$ | X X O O X 1 . O X O . X O O O . X X X | $$ | X X . O X 2 3 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 . O O O O O O X O X . O X | $$ | . X . . X O O O . . . . O X X X . O . | $$ +---------------------------------------+[/go]

In January, dany kindly introduced his atekomi W 1, resulting in a ko fight in the left centre after B 2 amd W 3.
This ko fight will end with White winning both Main Variations (Capture & Semeai) by two points (= W+2 / W+2 @ komi=1).

Click Here To Show Diagram Code: [go]$$Wc Dany's Ko without Black's kikashi played before $$ +---------------------------------------+ $$ | . . . X O . . . . . . . X X . . O X . | $$ | . . . X X O O X O O . X O X O . . O . | $$ | . . . X O X O O . . . X O O . O O . . | $$ | . X O , . X X ? ? O . X . O O X . . . | $$ | . . X X X X O O O . O X X . X X O O . | $$ | . X . O O O X X X O . . X . X O . O . | $$ | O O O O O X O O X X O O X O X . . X . | $$ | O X . X . X O O O X O . . . X X X X X | $$ | O X . X X X X O X X O . X X X X ? O O | $$ | X O O X . X O O X O O X X O O O O ? . | $$ | X X O O X 1 . O X O . X O O O . X X X | $$ | X X . O X 2 3 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 | $$ | X O X O ? X . O X O X . O X X X O O O | $$ | 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]

Since then, we were busy with investigating the question whether Black might be better in the ko fight, if he had not played his kikashi (shadowed board points) beforehand, and could use these as ko threats.

Click Here To Show Diagram Code: [go]$$Wc Position after W 116 -- no kikashi played $$ +---------------------------------------+ $$ | . . . X O . . . . . . . X X . . O X . | $$ | . . . X X O O X O O . X O X O . . O . | $$ | . . . X O X O O . . . X O O . O O . . | $$ | . X O , . X X . . O . X . O O X . . . | $$ | . . X X X X O O O . O X X . X X O O . | $$ | . X . O O O X X X O . . X . X O . O . | $$ | O O O O O X O O X X O O . O X . . X . | $$ | 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 | $$ | X O X O . X . O X O X . O X X X O O O | $$ | 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]

We used this position as a general starting point for our "no kikashi" variation tree.

To keep a long story short:
Black cannot benefit from keeping his kikashi in reserve, but he will give White chances, and increase the complexity of the variation tree dramatically.

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You are probably familiar with the wording of the Pareto Principle, according to which the last 20 percent of the work takes 80 percent of the time.
I have experienced several of these 80/20-moments, when I thought that the end would be near, but when emails from dany, or Joachim, arrived that questioned much of the work so far.
Additionally, you won't get dumber while painting, and commenting, diagrams, so the number of errors found increased, as did the number of variations.
In retrospect, many of our (mainly mine) initial mistakes might look a bit silly, but this cannot be helped.

Cassandra · **#52**

My biggest mistake was to take the kikashi for granted.
Probably my work on the many variations was too mechanical in the very beginning.

Click Here To Show Diagram Code: [go]$$Wc $$ +---------------------------------------+ $$ | . . . X O . . . . . . . X X . . O X . | $$ | . . . X X O O X O O . X O X O . . O . | $$ | . . . X O X O O . . . X O O . O O . . | $$ | . X O , . X X ? ? O . X . O O X . . . | $$ | . . X X X X O O O . O X X . X X O O . | $$ | . X . O O O X X X O . . X . X O . O . | $$ | O O O O O X O O X X O O X O X . . X . | $$ | O X . X . X O O O X O . . . X X X X X | $$ | O X . X X X X O X X O . X X X X ? O O | $$ | X O O X . X O O X O O X X O O O O ? . | $$ | X X O O X . B O X O . X O O O . X X X | $$ | X X . O X B W 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 | $$ | X O X O ? X . O X O X . O X X X O O O | $$ | O X X X X X . O X O O O O X O X O O X | $$ | O . . 2 O X O O X X X X X . O X X O X | $$ | O W X 1 X O . O O O O O O X O X . O X | $$ | . X B . X O O O . . . . O X X X . O . | $$ +---------------------------------------+[/go]

Even with Black's shadowed kikashi unplayed, White will win the ko in the left centre.
However, in the very end, she will have to play the disadvatageous ko threat of W 1 in the lower left corner that costs her one point overall. The final scores will be W+1 / W+1 (@ komi=1).

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Click Here To Show Diagram Code: [go]$$Bc $$ +---------------------------------------+ $$ | . . . X O . . . . . . . X X . . O X . | $$ | . . . X X O O X O O . X O X O . . O . | $$ | . . . X O X O O . . . X O O . O O . . | $$ | . X O , . X X . . O . X . O O X . . . | $$ | . . X X X X O O O . O X X . X X O O . | $$ | . X . O O O X X X O . . X . X O . O . | $$ | O O O O O X O O X X O O 1 O X . . X . | $$ | O X . X . X . O O X O . . . X X X X X | $$ | O X . X 5 2 3 O X X O . X X X X . O O | $$ | X O O X . X 4 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 | $$ | X O X O . X . O X O X . O X X X O O O | $$ | 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]

Dany's first suggestion was ...

Click Here To Show Diagram Code: [go]$$Bc $$ +---------------------------------------+ $$ | . . . X O . . . . . . . X X . . O X . | $$ | . . . X X O O X O O . X O X O . . O . | $$ | . . . X O X O O . . . X O O . O O . . | $$ | . X O , . X X . . O . X . O O X . . . | $$ | . . X X X X O O O . O X X . X X O O . | $$ | . X . O O O X X X O . . X . X O . O . | $$ | O O O O O X O O X X O O X O X . . X . | $$ | O X . X . X a O O X O . . . X X X X X | $$ | O X . X X b X O X X O . X X X X . O O | $$ | X O O X . X O O X O O X X O O O O . . | $$ | X X O O X 6 . O X O . X O O O . X X X | $$ | X X . O X 7 8 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 | $$ | X O X O . X . O X O X . O X X X O O O | $$ | 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]

... to keep White's atari during the creation of the ko shape in the left centre (W a, B b) in reserve for the later use as an additional ko threat.

Click Here To Show Diagram Code: [go]$$Wc $$ +---------------------------------------+ $$ | . . . X O . . . . . . . X X . . O X . | $$ | . . . X X O O X O O . X O X O . . O . | $$ | . . . X O X O O . . . X O O . O O . . | $$ | . X O , . X X . . O . X . O O X . . . | $$ | . . X X X X O O O . O X X . X X O O . | $$ | . X . O O O X X X O . . X . X O . O . | $$ | O O O O O X O O X X O O X O X . . X . | $$ | O X . X . X W O O X O . . . X X X X X | $$ | O X . X X B X O X X O . X X X X . O O | $$ | X O O X . X O O X O O X X O O O O . . | $$ | X X O O X O W O X O . X O O O . X X X | $$ | X X . O X X O 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 | $$ | X O X O . X . O X O X . O X X X O O O | $$ | O X X X X X . O X O O O O X O X O O X | $$ | O . a 1 O X O O X X X X X . O X X O X | $$ | O W X 2 X O . O O O O O O X O X . O X | $$ | . X B . X O O O . . . . O X X X . O . | $$ +---------------------------------------+[/go]

Now, after White won the ko in the left centre, White is able to play the forcing move W 1 in the lower left corner later, threatening to reduce Black's large group at the left to only one eye. Black is forced to answer below.
Black does not have any eyes in the left centre, and so will have to capture White's two stones in the lower left corner with B a before the game ends.
The final scores will become W+2 / W+2 (@ komi=1) again.

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Click Here To Show Diagram Code: [go]$$Wc $$ +---------------------------------------+ $$ | . . . X O . . . . . . . X X . . O X . | $$ | . . . X X O O X O O . X O X O . . O . | $$ | . . . X O X O O . . . X O O . O O . . | $$ | . X O , . X X . . O . X . O O X . . . | $$ | . . X X X X O O O . O X X . X X O O . | $$ | . X . O O O X X X O . . X . X O . O . | $$ | O O O O O X O O X X O O B O X . . X . | $$ | 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 1 . | $$ | X X O O X . . O X O . X O O O . X X X | $$ | 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 | $$ | X O X O . X . O X O X . O X X X O O O | $$ | 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]

Dany's second suggestion was related to a White's gote move at 1 in the hanezeki, stopping Black from playing his kikashi there.

Click Here To Show Diagram Code: [go]$$Wc W 5 is played elsewhere on the board ... $$ +---------------------------------------+ $$ | . . . X O . . . . . . . X X . . O X . | $$ | . . . X X O O X O O . X O X O . . O . | $$ | . . . X O X O O . . . X O O . O O . . | $$ | . X O , . X X . . O . X . O O X . . . | $$ | . . X X X X O O O . O X X . X X O O . | $$ | . X . O O O X X X O . . X . X O . O . | $$ | O O O O O X O O X X O O X O X . . X . | $$ | O X . X . X . O O X O . . . X X X X X | $$ | O X . X . . . O X X O . X X X X 4 O O | $$ | X O O X . X . O X O O X X O O O O O . | $$ | X X O O X . . O X O . X O O O 3 X X X | $$ | X X . O X . . O X O . X O O X X X O O | $$ | X X O O X . . O X O . X O a O . X X O | $$ | X O O 6 P X . O X O . X X O O O X O O | $$ | X O X P 2 X . O X O X . O X X X O O O | $$ | 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]

After Black's atari 2 in the lower left corner, White might be able to sacrifice her two stones there.

White's kikashi 3 in the hanezeki gains her an additional three points in the Semeai Variation. B 4 will become an additional prisoner, while the point of a will remain White territory.
(White will lose one point in the Capture Variation by this action, but she prioritises the Semeai Variation.)
Capturing two White stones with B 6 gains two points in the Capture Variation only, but which might not help if White finally chooses the other Main Variation.
Additionally, Black does not gain two additional liberties in the Main Semeai, as with a White connection at 6. This might restrict his actions in other parts of the board.

Cassandra · **#53**

Click Here To Show Diagram Code: [go]$$Bc $$ +---------------------------------------+ $$ | . . . X O . . . . . . . X X . . O X . | $$ | . . . X X O O X O O . X O X O . . O . | $$ | . . . X O X O O . . . X O O . O O . . | $$ | . X O , . X X . . O . X . O O X . . . | $$ | . . X X X X O O O . O X X . X X O O . | $$ | . X . O O O X X X O . . X . X O . O . | $$ | O O O O O X O O X X O O X O X . . X . | $$ | O X . X . X . O O X O . . . X X X X X | $$ | O X . X X . X O X X O . X X X X . O O | $$ | X O O X . X O O X O O X X O O O O . . | $$ | X X O O X O 9 O X O . X O O O . X X X | $$ | X X 0 O X X O 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 | $$ | X O X O . X . O X O X . O X X X O O O | $$ | 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]

Dany's third suggestion concerned a split of the Nakade Sequence (that is used as first White ko threat).

Click Here To Show Diagram Code: [go]$$Bc $$ +---------------------------------------+ $$ | . . . X O . . . . . . . X X . . O X . | $$ | . . . X X O O X O O . X O X O . . O . | $$ | . . . X O X O O . . . X O O . O O . . | $$ | . X O , . X X . . O . X . O O X . . . | $$ | . . X X X X O O O . O X X . X X O O . | $$ | . X . O O O X X X O . . X . X O . O . | $$ | O O O O O X O O X X O O X O X . . X . | $$ | O X . X . X . O O X O . . . X X X X X | $$ | O X . X X . X O X X O . X X X X . O O | $$ | 2 O O X . X O O X O O X X O O O O . . | $$ | 1 . O O X 4 X O X O . X O O O . X X X | $$ | . 3 O O X X O O X O . X O O X X X O O | $$ | b . O O X . . O X O . X O . O . X X O | $$ | . O O . O X . O X O . X X O O O X O O | $$ | a O X O . X . O X O X . O X X X O O O | $$ | 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]

Dany idea was to keep the final exchange of W a, B b in reserve (e.g. for the later usage as an additional ko threat), and to recapture the ko as early as with W 4.

Click Here To Show Diagram Code: [go]$$Bc W 10 recaptures the ko in the left centre $$ +---------------------------------------+ $$ | . . . X O . . . . . . . X X . . O X . | $$ | . . . X X O O X O O . X O X O . . O . | $$ | . . . X O X O O . . . X O O . O O . . | $$ | . X O , . X X . . O . X . O O X . . . | $$ | . . X X X X O O O . O X X . X X O O . | $$ | . X . O O O X X X O . . X . X O . O . | $$ | O O O O O X O O X X O O X O X . . X . | $$ | O X . X . X . O O X O . . . X X X X X | $$ | O X . X X . X O X X O . X X X X 6 O O | $$ | O O O X . X O O X O O X X O O O O 5 . | $$ | X . O O X O 7 O X O . X O O O . X X X | $$ | . X O O X X O O X O . X O O X X X O O | $$ | 9 . O O X . . O X O . X O . O . X X O | $$ | . O O . O X . O X O . X X O O O X O O | $$ | 8 O X O . X . O X O X . O X X X O O O | $$ | 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]

Indeed, if Black continued with fighting the ko -- using his kikashi in the hanezeki as a ko threat -- White would achieve her aim by also using the continuation of the Nakade Seqeunce as a ko threat. Black has fallen into a trap, as he unnecessarily wasted his ko threat at B 5 -- compared with the continuesly played Nakade Sequence (i.e. W 4 at 8).

Eventually, it was Joachim, who found the correct continuation for Black.

Cassandra · **#54**

Click Here To Show Diagram Code: [go]$$Wc Black has NINE Main Semeai Liberties $$ +---------------------------------------+ $$ | . . . X O W . . . . W X X X W . O X . | $$ | . . . X X O O X O O W X O X O . . O . | $$ | . . . X O X O O . . W X O O . O O . . | $$ | . X O , . X X B W O W X . O O X W . . | $$ | . . X X X X O O O . O X X W X X O O . | $$ | B X B O O O X X X O . W X B X O W O W | $$ | O O O O O X O O X X O O X O X . . X . | $$ | O X B X B X ? O O X O . W . X X X X X | $$ | O X B X ? ? ? O X X O W X X X X W O O | $$ | O O O X ? X ? O X O O X X O O O O B . | $$ | X . O O X ? ? O X O . X O O O . X X X | $$ | . . O O X ? ? O X O . X O O X X X O O | $$ | O O O O X ? ? O X O . X O W O B X X O | $$ | O O O W O X ? O X O W X X O O O X O O | $$ | O O X O B X ? O X O X Y O X X X O O O | $$ | O X X X X X ? O X O O O O X O X O O X | $$ | O B ? ? O X O O X X X X X . O X X O X | $$ | O B X ? X O . O O O O O O X O X . O X | $$ | B X ? ? X O O O . . . . O X X X . O . | $$ +---------------------------------------+[/go]

Please assume that Black was able to connect his single stone in the lower right with the triangled stone AND that Black's large group in the upper right has NINE Main Semeai Liberties at White's decision point.
If Black had TEN Main Semeai Liberties, White would be unable to capture this Black group in the Semeai Variation.

Click Here To Show Diagram Code: [go]$$Wc $$$ +---------------------------------------+ $$ | . . . X O O . . . . O X X X O . O X . | $$ | . . . X X O O X O O O X O X O . . O . | $$ | . . . X O X O O . . O X O O 1 O O . . | $$ | . X O , . X X X O O O X . O O X O . . | $$ | . . X X X X O O O . O X X O X X O O . | $$ | X X X O O O X X X O . O X X X O O O O | $$ | O O O O O X O O X X O O X O X . . X . | $$ | O X X X X X ? O O X O . O . X X X X X | $$ | O X X X ? ? ? O X X O O X X X X O O O | $$ | O O O X ? X ? O X O O X X O O O O X . | $$ | X . O O X ? ? O X O . X O O O . X X X | $$ | . . O O X ? ? O X O . X O O X X X O O | $$ | O O O O X ? ? O X O . X O O O X X X O | $$ | O O O O O X ? O X O O X X O O O X O O | $$ | O O X O X X ? O X O X X O X X X O O O | $$ | O X X X X X ? O X O O O O X O X O O X | $$ | O X ? ? O X O O X X X X X 2 O X X O X | $$ | O X X ? X O . O O O O O O X O X . O X | $$ | X X ? ? X O O O . . . . O X X X . O . | $$ +---------------------------------------+[/go]

White chooses the Semeai Variation.

Click Here To Show Diagram Code: [go]$$Wc $$$ +---------------------------------------+ $$ | . . . X O O . . . . O X X X O . O X . | $$ | . . . X X O O X O O O X O X O . . O . | $$ | . . . X O X O O . . O X O O O O O . . | $$ | . X O , . X X X O O O X 5 O O X O . . | $$ | . . X X X X O O O . O X X O X X O O . | $$ | X X X O O O X X X O . O X X X O O O O | $$ | O O O O O X O O X X O O X O X . . X . | $$ | O X X X X X ? O O X O . O . X X X X X | $$ | O X X X ? ? ? O X X O O X X X X O O O | $$ | O O O X ? X ? O X O O X X O O O O X . | $$ | X 4 O O X ? ? O X O . X O O O . X X X | $$ | 7 6 O O X ? ? O X O . X O O X X X O O | $$ | O O O O X ? ? O X O . X O O O X X X O | $$ | O O O O O X ? O X O O X X O O O X O O | $$ | O O X O X X ? O X O X X O X X X O O O | $$ | O X X X X X ? O X O O O O X . X O O X | $$ | O X ? ? O X O O X X X X X X 3 X X O X | $$ | O X X ? X O . O O O O O O X . X . O X | $$ | X X ? ? X O O O . . . . O X X X . O . | $$ +---------------------------------------+[/go]

Click Here To Show Diagram Code: [go]$$Bcm8 $$$ +---------------------------------------+ $$ | . . . X O O . . . . O X X X O . O X . | $$ | . . . X X O O X O O O X O X O . . O . | $$ | . . . X O X O O . . O X O O O O O . . | $$ | . X O , . X X X O O O X O O O X O . . | $$ | . . X X X X O O O . O X X O X X O O . | $$ | X X X O O O X X X O . O X X X O O O O | $$ | O O O O O X O O X X O O X O X 2 4 X 6 | $$ | O X X X X X ? O O X O . O . X X X X X | $$ | O X X X ? ? ? O X X O O X X X X O O O | $$ | O O O X ? X ? O X O O X X O O O O X . | $$ | . 1 O O X ? ? O X O . X O O O . X X X | $$ | O 3 O O X ? ? O X O . X O O X X X O O | $$ | O O O O X ? ? O X O . X O O O X X X O | $$ | O O O O O X ? O X O O X X O O O X O O | $$ | O O X O X X ? O X O X X O X X X O O O | $$ | O X X X X X ? O X O O O O X . X O O X | $$ | O X ? ? O X O O X X X X X X O X X O X | $$ | O X X ? X O . O O O O O O X . X 5 O X | $$ | X X ? ? X O O O . . . . O X X X 7 O 8 | $$ +---------------------------------------+[/go]

Click Here To Show Diagram Code: [go]$$Bcm16 $$$ +---------------------------------------+ $$ | . . . X O O . . . . O X X X O . O X . | $$ | . . . X X O O X O O O X O X O . . O . | $$ | . . . X O X O O . . O X O O O O O . . | $$ | . X O , . X X X O O O X O O O X O . . | $$ | . . X X X X O O O . O X X O X X O O . | $$ | X X X O O O X X X O . O X X X O O O O | $$ | O O O O O X O O X X O O X O X O O X O | $$ | O X X X X X ? O O X O . O 5 X X X X X | $$ | O X X X ? ? ? O X X O O X X X X O O O | $$ | O O O X ? X ? O X O O X X O O O O X . | $$ | . X O O X ? ? O X O 2 X O O O . X X X | $$ | O X O O X ? ? O X O 4 X O O X X X O O | $$ | O O O O X ? ? O X O . X O O O X X X O | $$ | O O O O O X ? O X O O X X O O O X O O | $$ | O O X O X X ? O X O X X O X X X O O O | $$ | O X X X X X ? O X O O O O X . X O O 3 | $$ | O X ? ? O X O O X X X X X X O X X O 1 | $$ | O X X ? X O . O O O O O O X . X X O . | $$ | X X ? ? X O O O . . . . O X X X X O O | $$ +---------------------------------------+[/go]

At the last possible moment, Black captures in the upper right.

Click Here To Show Diagram Code: [go]$$Wcm21 $$$ +---------------------------------------+ $$ | . . . X O O . . . . O X X X O . O X . | $$ | . . . X X O O X O O O X O X O . . O . | $$ | . . . X O X O O . . O X O O O O O . . | $$ | . X O , . X X X O O O X O O O X O . . | $$ | . . X X X X O O O . O X X O X X O O . | $$ | X X X O O O X X X O a O X X X O O O O | $$ | O O O O O X O O X X O O X . X O O X O | $$ | O X X X X X ? O O X O 2 O X X X X X X | $$ | O X X X ? ? ? O X X O O X X X X O O O | $$ | O O O X ? X ? O X O O X X O O O O X . | $$ | . X O O X ? ? O X O O X O O O . X X X | $$ | O X O O X ? ? O X O O X O O X X X O O | $$ | O O O O X ? ? O X O 1 X O O O X X X O | $$ | O O O O O X ? O X O O X X O O O X O O | $$ | O O X O X X ? O X O X X O X X X O O O | $$ | O X X X X X ? O X O O O O X . X O O X | $$ | O X ? ? O X O O X X X X X X O X X O X | $$ | O X X ? X O . O O O O O O X . X X O b | $$ | X X ? ? X O O O . . . . O X X X X O O | $$ +---------------------------------------+[/go]

It will not benefit White to connect at a (Black will capture at b thereafter), instead of occupying a Black liberty with 21, just because White does not have any relevant ko threats available.

Click Here To Show Diagram Code: [go]$$Wcm23 $$$ +---------------------------------------+ $$ | . . . X O O . . . . O X X X O . O X . | $$ | . . . X X O O X O O O X O X O . . O . | $$ | . . . X O X O O . . O X O O O O O . . | $$ | . X O , . X X X O O O X O O O X O . . | $$ | . . X X X X O O O . O X X O X X O O . | $$ | X X X O O O X X X O 1 O X X X O O O O | $$ | O O O O O X O O X X O O X . X O O X O | $$ | O X X X X X ? O O X O X . X X X X X X | $$ | O X X X ? ? ? O X X O O X X X X O O O | $$ | O O O X ? X ? O X O O X X O O O O X . | $$ | . X O O X ? ? O X O O X O O O . X X X | $$ | O X O O X ? ? O X O O X O O X X X O O | $$ | O O O O X ? ? O X O O X O O O X X X O | $$ | O O O O O X ? O X O O X X O O O X O O | $$ | O O X O X X ? O X O X X O X X X O O O | $$ | O X X X X X ? O X O O O O X . X O O X | $$ | O X ? ? O X O O X X X X X X O X X O X | $$ | O X X ? X O . O O O O O O X . X X O 2 | $$ | X X ? ? X O O O . . . . O X X X X O O | $$ +---------------------------------------+[/go]

Click Here To Show Diagram Code: [go]$$Wcm25 $$$ +---------------------------------------+ $$ | . . . X O O 4 . . . O X X X O . O X . | $$ | . . . X X O O X O O O X O X O . . O . | $$ | . . . X O X O O 2 . O X O O O O O . . | $$ | . X O , . X X X O O O X O O O X O . . | $$ | . . X X X X O O O . O X X O X X O O . | $$ | X X X O O O X X X O O O X X X O O O O | $$ | O O O O O X O O X X O O X 3 X O O X O | $$ | O X X X X X ? O O X O X 1 X X X X X X | $$ | O X X X ? ? ? O X X O O X X X X O O O | $$ | O O O X ? X ? O X O O X X O O O O X . | $$ | . X O O X ? ? O X O O X O O O a X X X | $$ | O X O O X ? ? O X O O X O O X X X . . | $$ | O O O O X ? ? O X O O X O O O X X X . | $$ | O O O O O X ? O X O O X X O O O X . . | $$ | O O X O X X ? O X O X X O X X X . . . | $$ | O X X X X X ? O X O O O O X . X . . X | $$ | O X ? ? O X O O X X X X X X O X X . X | $$ | O X X ? X O . O O O O O O X . X X . X | $$ | X X ? ? X O O O . . . . O X X X X . . | $$ +---------------------------------------+[/go]

White is unable to answer Black's ko threat at the upper edge, because Black would give atari at a, saving his large group in question.

Black captures with 28 at the upper edge, winning the game by about 15 points.

+ + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + +
+ + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + +

Click Here To Show Diagram Code: [go]$$Wc Black has NINE Main Semeai Liberties $$ +---------------------------------------+ $$ | . . . X O P . . . . W X X X W . O X . | $$ | . . . X X O O X O O W X O X O . . O . | $$ | . . . X O X O O . . W X O O . O O . . | $$ | . X O , . X X B W O W X . O O X W . . | $$ | . . X X X X O O O . O X X W X X O O . | $$ | B X B O O O X X X O . W X B X O W O W | $$ | O O O O O X O O X X O O X O X . . X . | $$ | O X B X B X ? O O X O . W . X X X X X | $$ | O X B X ? ? ? O X X O W X X X X W O O | $$ | O O O X ? X ? O X O O X X O O O O B . | $$ | X . O O X ? ? O X O . X O O O . X X X | $$ | . . O O X ? ? O X O . X O O X X X O O | $$ | O O O O X ? ? O X O . X O W O B X X O | $$ | O O O W O X ? O X O W X X O O O X O O | $$ | O O X O B X ? O X O X Y O X X X O O O | $$ | O X X X X X ? O X O O O O X O X O O X | $$ | O B ? ? O X O O X X X X X . O X X O X | $$ | O B X ? X O . O O O O O O X O X . O X | $$ | B X ? ? X O O O . . . . O X X X . O . | $$ +---------------------------------------+[/go]

This result implies that White must not play her last gote move, e.g. X.

Click Here To Show Diagram Code: [go]$$Wc Black has EIGHT Main Semeai Liberties $$ +---------------------------------------+ $$ | . . . X O 2 . . . . W X X X W . O X . | $$ | . . . X X O O X O O W X O X O . . O . | $$ | . . . X O X O O . . W X O O . O O . . | $$ | . X O , . X X B W O W X . O O X W . . | $$ | . . X X X X O O O . O X X W X X O O . | $$ | B X B O O O X X X O . W X B X O W O W | $$ | O O O O O X O O X X O O X O X . . X 1 | $$ | O X B X B X ? O O X O . W . X X X X X | $$ | O X B X ? ? ? O X X O W X X X X W O O | $$ | O O O X ? X ? O X O O X X O O O O B . | $$ | X . O O X ? ? O X O . X O O O . X X X | $$ | . . O O X ? ? O X O . X O O X X X O O | $$ | O O O O X ? ? O X O . X O W O B X X O | $$ | O O O W O X ? O X O W X X O O O X O O | $$ | O O X O B X ? O X O X X O X X X O O O | $$ | O X X X X X ? O X O O O O X O X O O X | $$ | O B ? ? O X O O X X X X X . O X X O X | $$ | O B X ? X O . O O O O O O X O X . O X | $$ | B X ? ? X O O O . . . . O X X X . O . | $$ +---------------------------------------+[/go]

White's move 1 occupied one of Black's liberties in the upper right, instead.
But then Black could capture at the upper edge ...

Click Here To Show Diagram Code: [go]$$Wc $$ +---------------------------------------+ $$ | . . . X 4 X 3 . . . O X X X O . O X . | $$ | . . . X X O O X O O O X O X O . . O . | $$ | . . . X O X O O . . O X O O 5 O O . . | $$ | . X O , . X X X O O O X . O O X O . . | $$ | . . X X X X O O O . O X X O X X O O . | $$ | X X X O O O X X X O . O X X X O O O O | $$ | O O O O O X O O X X O O X O X . . X O | $$ | O X X X X X ? O O X O . O . X X X X X | $$ | O X X X ? ? ? O X X O O X X X X O O O | $$ | O O O X ? X ? O X O O X X O O O O X . | $$ | X . O O X ? ? O X O . X O O O . X X X | $$ | . . O O X ? ? O X O . X O O X X X O O | $$ | O O O O X ? ? O X O . X O O O X X X O | $$ | O O O O O X ? O X O O X X O O O X O O | $$ | O O X O X X ? O X O X X O X X X O O O | $$ | O X X X X X ? O X O O O O X O X O O X | $$ | O X ? ? O X O O X X X X X 6 O X X O X | $$ | O X X ? X O . O O O O O O X O X . O X | $$ | X X ? ? X O O O . . . . O X X X . O . | $$ +---------------------------------------+[/go]

... and connect thereafter. Black gained two points overall.

Cassandra · **#55**

There is a similar effect on Black's side, which is likely to be known already.

Click Here To Show Diagram Code: [go]$$Bc Black has SEVEN Main Semeai Liberties $$ +---------------------------------------+ $$ | . . . X O 1 . . . . W X X X W . O X . | $$ | . . . X X O O X O O W X O X O . . O . | $$ | . . . X O X O O . . W X O O . O O . . | $$ | . X O , . X X B W O W X . O O X W . . | $$ | . . X X X X O O O . O X X W X X O O . | $$ | B X B O O O X X X O . W X B X O W O W | $$ | O O O O O X O O X X O O X O X . W X W | $$ | O X B X B X ? O O X O . W . X X X X X | $$ | O X B X ? ? ? O X X O W X X X X W O O | $$ | O O O X ? X ? O X O O X X O O O O B . | $$ | C . O O X ? ? O X O . X O O O . X X X | $$ | . . O O X ? ? O X O . X O O X X X O O | $$ | O O O O X ? ? O X O . X O W O B X X O | $$ | O O O W O X ? O X O W X X O O O X O O | $$ | O O X O B X ? O X O X X O X X X O O O | $$ | O X X X X X ? O X O O O O X O X O O X | $$ | O B ? ? O X O O X X X X X . O X X O X | $$ | O B X ? X O . O O O O O O X O X . O X | $$ | B X ? ? X O O O . . . . O X X X . O . | $$ +---------------------------------------+[/go]

If -- at White's decision point -- Black has only SEVEN Main Semeai Liberties, the "natural" looking move of B 1, capturing White's single stone at the upper edge, is a grave mistake.
By this move, Black has fallen below the Punishment Semeai Liberty Level. He should have played oki at the left edge.

Click Here To Show Diagram Code: [go]$$Bc Black has SIX Main Semeai Liberties $$ +---------------------------------------+ $$ | . . . X . X 2 . . . W X X X W . O X . | $$ | . . . X X O O X O O W X O X O . . O . | $$ | . . . X O X O O . . W X O O . O O . . | $$ | . X O , . X X B W O W X . O O X W . . | $$ | . . X X X X O O O . O X X W X X O O . | $$ | B X B O O O X X X O . W X B X O W O W | $$ | O O O O O X O O X X O O X O X . W X W | $$ | O X B X B X ? O O X O . W . X X X X X | $$ | O X B X ? ? ? O X X O W X X X X W O O | $$ | O O O X ? X ? O X O O X X O O O O B . | $$ | C . O O X ? ? O X O . X O O O . X X X | $$ | . . O O X ? ? O X O . X O O X X X O O | $$ | O O O O X ? ? O X O . X O W O B X X O | $$ | O O O W O X ? O X O W X X O O O X O O | $$ | O O X O B X ? O X O X X O X X X O O O | $$ | O X X X X X ? O X O O O O X O X O O X | $$ | O B ? ? O X O O X X X X X . O X X O X | $$ | O B X ? X O . O O O O O O X O X . O X | $$ | B X ? ? X O O O . . . . O X X X . O . | $$ +---------------------------------------+[/go]

White's blocking move at 2 -- also looking "natural" -- is also a grave mistake, giving the favour back to Black.

White must continue with the Main Semeai, instead, occupying one of Black's liberties in the top right.

+ + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + +
+ + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + +

Click Here To Show Diagram Code: [go]$$Bc How many Main Semeai Liberties does Black have? $$ +---------------------------------------+ $$ | . . . X O 1 . . . . ? ? X X ? . O X . | $$ | . . . X X O O X O O ? X O X O . . O . | $$ | . . . X O X O O . . ? X O O ? O O . . | $$ | . X O , . X X ? ? O ? X ? O O X ? . . | $$ | . . X X X X O O O . O X X ? X X O O . | $$ | ? X ? O O O X X X O . ? X ? X O ? O ? | $$ | O O O O O X O O X X O O ? O X ? ? X ? | $$ | 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 | $$ | X O X O ? X . O X O X ? O X X X O O O | $$ | 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]

Everything is clearly visible at White's decision point.

But what about the period before, back until Black's move 117?
Who can immediately say with certainty whether Black's move at 1 is possible or not?

yoyoma · **#56**

You credited some people with pointing out ideas. What about Katago, is it helping to analyze some of these ideas?

Cassandra · **#57**

yoyoma wrote:

You credited some people with pointing out ideas. What about Katago, is it helping to analyze some of these ideas?

Thank you very much for your interest, and especially for your question about KataGo.

Indeed, most of our work was done manually. I used KataGo sometimes for confirming a new line, when I was very unsure about it. Dany once mentioned that KataGo has confirmed his usage of ko threats during his ko. Joachim did not have a suitable machine for running KataGo. But let me explain in more detail ...

The usage of KataGo was severly affected by the following aspects:

Neither Joachim nor me own that powerful type of machine, which would be necessary to achieve an adequate amount of playouts in justifiable time. Please note that it would be necessary in most cases to analyse the same positition with different komi, in order to get the "optimal" suggestion by KataGo, also with a certain relationship to the (expected) final score. Our machines were simply much too slow / unsuitable for that purpose.
KataGo 1.2, which was used to create the special IgoHatsuyoron120-network, calculates with Area Scoring only. This implies that KataGo 1.2 is unable to distinguish between (e.g.) "W+1" and "W+2" under Territory Scoring. But which would be necessary for a "really" reliable analysis of a problem that originated in Japan.
As far as I know, KataGo does not use the (estimated) final score of a variation for prioritisation. Which is our parameter for ranking subvariations.
Additionally, (I suppose that) KataGo does not use the final score of BOTH Main Variations as parameters for ranking moves / subvariations. ONE "sure" way to (e.g.) a win for White by two points will be enough. However, we would like to prioritise "W+2 / B+4" over "W+2 / W+2" at a branching point for Black's next move.

If one wanted to have an assistant for creating these "Why not play there?" moments (which I encountered during painting the diagrams, and which seems to be one of Joachim's talent when refuting lines of play in question), I think that the following requirements were needed:

A technical environment that enables the creation of a reliable selection of candidate moves by KataGo in seconds, not in minutes.
A (new?) special IgoHatsuyoron120-network that would be compatible with the newer versions of KataGo, which are able to also calculate using Territory Scoring.

dany · **#58**

yoyoma wrote:

What about Katago, is it helping to analyze some of these ideas?

KataGo is a very useful tool and greatly helps in analysis. I usually find the moves manually and then check them with KataGo. This is a good way to find blunders. But KataGo's understanding of the problem is imperfect. Sometimes, for some simple positions, KataGo needs hundreds of thousands of playouts to find the right move. And there are positions where so many playouts are not enough for KataGo. Usually the best move in position is among the top 5 KataGo moves, but often it is not the top move.

Bill Spight · **#59**

Cassandra wrote:

yoyoma wrote:

You credited some people with pointing out ideas. What about Katago, is it helping to analyze some of these ideas?

Thank you very much for your interest, and especially for your question about KataGo.

Indeed, most of our work was done manually. I used KataGo sometimes for confirming a new line, when I was very unsure about it. Dany once mentioned that KataGo has confirmed his usage of ko threats during his ko. Joachim did not have a suitable machine for running KataGo. But let me explain in more detail ...

The usage of KataGo was severly affected by the following aspects:

Neither Joachim nor me own that powerful type of machine, which would be necessary to achieve an adequate amount of playouts in justifiable time. Please note that it would be necessary in most cases to analyse the same positition with different komi, in order to get the "optimal" suggestion by KataGo, also with a certain relationship to the (expected) final score. Our machines were simply much too slow / unsuitable for that purpose.
KataGo 1.2, which was used to create the special IgoHatsuyoron120-network, calculates with Area Scoring only. This implies that KataGo 1.2 is unable to distinguish between (e.g.) "W+1" and "W+2" under Territory Scoring. But which would be necessary for a "really" reliable analysis of a problem that originated in Japan.
As far as I know, KataGo does not use the (estimated) final score of a variation for prioritisation. Which is our parameter for ranking subvariations.
Additionally, (I suppose that) KataGo does not use the final score of BOTH Main Variations as parameters for ranking moves / subvariations. ONE "sure" way to (e.g.) a win for White by two points will be enough. However, we would like to prioritise "W+2 / B+4" over "W+2 / W+2" at a branching point for Black's next move.

If one wanted to have an assistant for creating these "Why not play there?" moments (which I encountered during painting the diagrams, and which seems to be one of Joachim's talent when refuting lines of play in question), I think that the following requirements were needed:

A technical environment that enables the creation of a reliable selection of candidate moves by KataGo in seconds, not in minutes.
A (new?) special IgoHatsuyoron120-network that would be compatible with the newer versions of KataGo, which are able to also calculate using Territory Scoring.

I look forward to lightvector's response.

However, my 2¢, FWIW.

Today's, top bots are not trained as analysts. Instead, they are trained to win games. The neural networks learn generally good plays and evaluations, but require tree search to learn more about specific positions. It would be good, therefore, to have a bot that has been trained on this particular position. Fortunately, lightvector supplied one.

How to use it? Given the difficulty of this problem, and the possibility, given sekis and kos, that correct play may differ between Japanese and area scoring, it does not appear that you can just let the specialized bot run for a day or two. Weeks or months may be required and then the variations would have to be checked by hand. It seems that interactive use is required, with an emphasis, to accomodate human understanding, for mostly depth first search. Also, I would try to find a optimal play by territory scoring first. That will normally be optimal by area scoring. And if not, you will know where to look for differences. Going back and forth between the two before finding optimal play by either one just makes for confusion, IMO.

As I said, I look forward to lightvector's thoughts.

Cassandra · **#60**

Knowing the current status of Black's Main Semeai Liberties at every moment of the game is mandatory to identify "natural looking" moves as mistakes.
I thought that this knowledge would be helpful, at least at amateur (Kyu) level. Therefore I decided to add this "current status" to every diagram of the "no kikashi" variation tree, and to divide diagrams when this status changes. I used the following classification (measured at the start of the diagram):

SIX ==> Black is below the Punishment Semeai Liberty Level, White should continue with the Main Semeai.
SEVEN ==> Black must not play any move outside the Main Semeai area, unless White did so immediately before.
EIGHT ==> Both sides may play with ease.
NINE ==> White must be careful to not play any gote move in special circumstances that would allow Joachim's final ko in the Semeai Variation, if White intends to choose the Semeai Variation.
at least TEN ==> White will lose the Semeai Variation, because she is unable to capture Black's large group in the upper right.

As I mentioned already before, several of our initial mistakes (mainly "natural looking" moves) while creating the variation tree now might look quite silly -- in the light of the explicite marking of the diagrams.

+ + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + +
+ + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + +

Let us accompany this marking on the way to Dany's ko.

Click Here To Show Diagram Code: [go]$$Bc After W 116: EIGHT $$ +---------------------------------------+ $$ | . . . X O . . . . . . . X X . . O X . | $$ | . . . X X O O X O O . X O X O . . O . | $$ | . . . X O X O O . . . X O O . O O . . | $$ | . X O , . X X . . O . X . O O X . . . | $$ | . . X X X X O O O . O X X . X X O O . | $$ | . X . O O O X X X O . . X . X O . O . | $$ | O O O O O X O O X X O O . O X . . X . | $$ | 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 | $$ | X O X O . X . O X O X . O X X X O O O | $$ | 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]

In the starting position of our "no kikashi" analysis, Black has EIGHT Main Semeai Liberties.
This means that Black's large group in the upper right would have EIGHT liberties left at White's decision point, if -- from now on -- both sides played only moves that belong to the Main Semeai.

Click Here To Show Diagram Code: [go]$$Bcm117 EIGHT $$ +---------------------------------------+ $$ | . . . X O . . . . . . . X X . . O X . | $$ | . . . X X O O X O O . X O X O . . O . | $$ | . . . X O X O O . . . X O O M O O . . | $$ | . X O , . X X . . O . X . O O X . . . | $$ | . . X X X X O O O . O X X . X X O O . | $$ | . X . O O O X X X O . . X . X O . O . | $$ | O O O O O X O O X X O O 1 O X . . X . | $$ | 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 | $$ | X O X O . X . O X O X . O X X X O O O | $$ | 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]

B 117 loses TWO Main Semeai Liberties, in priciple.
However, the marked point will become an approach-move liberty of Black's group (Black got an eye), so the effective loss in only ONE liberty.

Click Here To Show Diagram Code: [go]$$Bcm117 SEVEN $$ +---------------------------------------+ $$ | . . . X O . . . . . . . X X . . O X . | $$ | . . . X X O O X O O . X O X O . . O . | $$ | . . . X O X O O . . . X O O . O O . . | $$ | . X O , . X X . . O . X . O O X . . . | $$ | . . X X X X O O O . O X X . X X O O . | $$ | . X . O O O X X X O . . X . X O . O . | $$ | O O O O O X O O X X O O X O X . . X . | $$ | O X . X . X . O O X O . . . X X X X X | $$ | O X . X 5 2 3 O X X O . X X X X . O O | $$ | X O O X . X 4 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 | $$ | X O X O . X . O X O X . O X X X O O O | $$ | 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]

W 118 and 120 are played outside the Main Semeai area, so Black can do also with B 119 and 121.

Click Here To Show Diagram Code: [go]$$Bcm117 SEVEN $$ +---------------------------------------+ $$ | . . . X O . . . . . . . X X . . O X . | $$ | . . . X X O O X O O . X O X O . . O . | $$ | . . . X O X O O . . . X O O . O O . . | $$ | . X O , . X X . . O . X . O O X . . . | $$ | . . X X X X O O O . O X X . X X O O . | $$ | . X . O O O X X X O . . X . X O . O . | $$ | O O O O O X O O X X O O X O X . . X . | $$ | O X . X . X 6 O O X O . . . X X X X X | $$ | O X . X X 7 X O X X O . X X X X . O O | $$ | X O O X M X O O X O O X X O O O O . . | $$ | X X O O X 8 . O X O . X O O O . X X X | $$ | 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 | $$ | X O X O . X . O X O X . O X X X O O O | $$ | 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]

White's forcing exchange of W 122 for B 123 outside the Main Semeai area has been inserted to simplify the presentation.

W 124 is played outside the Main Semeai area, in principle. However, this move creates an approach-move liberty at the marked point for her group at the left side, and so does not lose any tempo in the Main Semeai.

Click Here To Show Diagram Code: [go]$$Bcm117 SEVEN $$ +---------------------------------------+ $$ | . . . X O . . . . . . . X X . . O X . | $$ | . . . X X O O X O O . X O X O . . O . | $$ | . . . X O X O O . . . X O O . O O . . | $$ | . X O , . X X . . O . X . O O X . . . | $$ | . . X X X X O O O . O X X . X X O O . | $$ | . X . O O O X X X O . . X . X O . O . | $$ | O O O O O X O O X X O O X O X . . X . | $$ | O X . X . X O O O X O . . . X X X X X | $$ | O X . X X X X O X X O . X X X X . O O | $$ | X O O X . X O O X O O X X O O O O . . | $$ | X X O O X O . O X O . X O O O . X X X | $$ | X X . O X a . O X O . X O O X X X O O | $$ | X X O O X b . O X O . X O . O . X X O | $$ | X O O . O X . O X O . X X O O O X O O | $$ | X O X O 9 X . O X O X . O X X X O O O | $$ | 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]

And now, at this special moment -- what a surprise -- there will be NO ko in the left centre.

Black is unable to immediately give atari at a. This move is located outside the Main Semeai area, and would push Black below the Punishment Semeai Liberty Level.
Black is bound to choose among his moves in the Main Semeai, and giving atari at White's two stones in the lower left with B 125 is best, because White threatens to cut at b.

Click Here To Show Diagram Code: [go]$$Bcm117 SEVEN $$ +---------------------------------------+ $$ | . . . X O . . . . . . . X X . . O X . | $$ | . . . X X O O X O O . X O X O . . O . | $$ | . . . X O X O O . . . X O O . O O . . | $$ | . X O , . X X . . O . X . O O X . . . | $$ | . . X X X X O O O . O X X . X X O O . | $$ | . X . O O O X X X O . . X . X O . O . | $$ | O O O O O X O O X X O O X O X . . X . | $$ | O X . X . X O O O X O . . . X X X X X | $$ | O X . X X X X O X X O . X X X X . O O | $$ | X O O X . X O O X O O X X O O O O . . | $$ | X X O O X O . O X O . X O O O . X X X | $$ | 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 0 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]

White's connection gives TWO Main Semeai Liberties back to Black.

Click Here To Show Diagram Code: [go]$$Bcm127 NINE $$ +---------------------------------------+ $$ | . . . X O . . . . . . . X X . . O X . | $$ | . . . X X O O X O O . X O X O . . O . | $$ | . . . X O X O O . . . X O O . O O . . | $$ | . X O , . X X . . O . X . O O X . . . | $$ | . . X X X X O O O . O X X . X X O O . | $$ | . X . O O O X X X O . . X . X O . O . | $$ | O O O O O X O O X X O O X O X . . X . | $$ | O X . X . X W O O X O . . . X X X X X | $$ | O X . X X B X O X X O . X X X X . O O | $$ | X O O X . X O O X O O X X O O O O . . | $$ | X X O O X O 3 O X O . X O O O . X X X | $$ | X X 4 O X 1 2 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 . O O O O O O X O X . O X | $$ | . X . . X O O O . . . . O X X X . O . | $$ +---------------------------------------+[/go]

Thereafter, Black has sufficient Main Semeai Liberties to start Dany's ko with B 127 and 129.

However, Black has lost one of his potential ko threats before the start of the ko fight, and so his chances to win this ko (with the marked exchange assumed to be played later).
The final scores of the game will become W+2 / W+2 (@ komi=1) again.

KataGo @ Igo Hatsuyoron 120

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