The most difficult problem ever. Igo Hatsuyoron 120

Bonobo · Post by **Bonobo** » Tue May 12, 2015 4:20 pm

Cassandra wrote:[..]

@ admin:
I earn nothing with the books, so hopefully this post is not contrary to the forum rules.

Just the opinion of a user: This is a Go forum, and I suppose we all are interested in Go literature, so, IMHO, it should be OK even if you’d earn something :-)

Also, I’d actually wish that people who write good Go literature earn good money by selling their books!

Cordially, Tom

RobertJasiek · Post by **RobertJasiek** » Tue May 12, 2015 11:10 pm

Books may be announced in the Go Books forum. What are the differences to the previous print version?

Cassandra · Post by **Cassandra** » Tue May 12, 2015 11:38 pm

RobertJasiek wrote:Books may be announced in the Go Books forum.

These can be understood as a supplement to the website. It's not the other way round.

RobertJasiek wrote:What are the differences to the previous print version?

Which edition of our books do you mean ?

There is only a publicly available printed edition, from Brett-und-Stein-Verlag, as of 2011.

RobertJasiek · Post by **RobertJasiek** » Tue May 12, 2015 11:56 pm

Yes, this is the latest printed edition I have.

http://senseis.xmp.net/?TheMostDifficultProblemEver

Cassandra · Post by **Cassandra** » Wed May 13, 2015 12:21 am

RobertJasiek wrote:Yes, this is the latest printed edition I have.
http://senseis.xmp.net/?TheMostDifficultProblemEver

Reply in detail will last a bit ...

However, if you are in a hurry:

-- Please refer to the table of contents, especially to the year numbers (and the page count of the chapters):
http://igohatsuyoron120.de/2015/0005.htm

-- Please refer to the introductory chapter "Igo Hatsuyōron 120 - Re-Evaluation by Amateurs", wherein you can find the timeline of the development of our work:
http://igohatsuyoron120.de/2015/0011.htm

Cassandra · Post by **Cassandra** » Wed May 13, 2015 2:58 am

Dear Robert,

Thank you very much for your interest. I will answer step by step, in several single posts, in order to ease citation.

+ + + + + + + + + + +

Some more general remarks first.

All our findings that have an effect on the problem's final score -- and so led to the refutation of the known professional solutions -- are explained in the 2011 book.

All other -- later -- findings can be valued to be somewhat "technical" only, these do not affect the outcome of the problem any more.

Therefore, if you are not interested in

-- the correct order of moves,
-- professional validation of our ideas,
-- correction of further professional mistakes (as are in Cheng Xiaoliu's 2010 book on "Igo Hatsuyoron"),
-- stunning professional Tesuji,
-- further "natural looking" alternate moves that are extremely difficult to refute (on amateur level),
-- further "natural looking" alternate moves that benefit their initiator in "normal" games, but not in this very special problem, and
-- further insights in other aspects of the problem,

you will be fine with our 2011 book.

Cassandra · Post by **Cassandra** » Wed May 13, 2015 5:44 am

How to begin with ?

As a matter of course, Volume I contains many more variations than our 2011 book. Its structure is nested, complex, and somewhat confused.

It was a lot of work to re-organise the order of variations -- that has grown historically over a long period of time -- so that (with only a very few exceptions) the result of a higher-level variation is always better (for its initiator) than the result of the corresponding lower-level ones.

You will find maps of this structure, which hopefully will help cloudlessness:

These maps might be useful, especially if you ever find a mistake in one of our sub-variations that changes its outcome. You will be able to easily identify, whether there are implications on higher level variations.

There is the danger that you will find some of these sub-variations superfluous, or boring. However, it is very difficult for me to decide on the erasure of such a sub-variation. Due to the "cloudy", and complex, structure, it is not unlikely that there is a reference to just this sub-variation -- or any in its immediate surrounding.

Cassandra · Post by **Cassandra** » Wed May 13, 2015 6:06 am

The story of "Our Solution" is devided into three sections now:

-- The creation of the Hanezeki in the lower right corner, including the flight of the Hanezeki's Tail through the centre of the board (until shortly before its end).
-- The very decisive moment of the problem, with my Guzumi played in the upper right corner (no other move will win Black the problem).
-- The plain sailing rest of the solution sequence, wherein nothing decisive will happen any more (possibly with the exception of Yamada Shinji's Tsuke in the upper left corner).

Most voluminous is section 2, including a very extensive treatment of Joachim's Ko-Semeai (found in mid-2011). Section 2 also contains the discussion of an idea of Michael Redmond 9p, with respect to a Kikashi in the upper right corner (that "would 'naturally' come into a professional's mind", but does not really help in the problem).

Each section starts with "Technical Notes", i.e. a selection of technical aspects, which discussion we assessed to be too special for our general overview "A Summary of Our Solution" (slightly extended, compared to our 2011 book).

Cassandra · Post by **Cassandra** » Wed May 13, 2015 6:29 am

The correct order of moves

Prof. Jeong SooHyun 9p (from Myongji University), and Ōhashi Hirofumi 6p, kindly provided us with indications on the correct timing for starting the "endgame" of the problem (much earlier than in our 2011 book), and on the correct order of moves for filling the Nakade on the left side.

We also found that it is technically correct to play Harry's Hasami-Tsuke-sequence in the upper right corner before the Guzumi (and not the other way round, as in our 2011 book).

Professional validation of our ideas

Prof. Jeong SooHyun was so very kind to validate my idea of the "second Throw-in" in the Hanezeki (of which Fujisawa Hideyuki 9p originally said that it would be fatal). This move is also used by Cheng Xiaoliu 6p in his 2010 book.

Joachim's "late" Oki -- that put Fujisawa's originally solution into question -- is also used by Cheng now. Cheng gives the result of the problem as "Jigo" now, but he missed Yamada's Tsuke in the upper left corner, gaining two points for White.

Seen overall, Harry's Hasami-Tsuke-sequence is assessed to be a "natural" endgame sequence. However, its territorial effect (four points) is only valid in conjunction with my Guzumi; there is no effect with the "classical" line of play.

So far, no professional engaged found a flaw with my Guzumi.

Correction of further professional mistakes (as are in Cheng Xiaoliu's 2010 book on "Igo Hatsuyoron")

We discuss all the "new" variations, given by Cheng in his 2010 book (as compared with his first 1988 / 2003 book), also correcting some of his oversights.

Stunning professional Tesuji

Michael Redmond was so kind to provide us with some stunning Tesuji, when commenting White's strongest Tenuki-option after my Guzumi.

Cassandra · Post by **Cassandra** » Wed May 13, 2015 6:35 am

Volume II begins with the treatment of all the professional solutions that are known to us, including their sub-variations.

Herein, you will find all the (sub-) variations that are special to the professional line of play.

"The Evolution of Professionals' Knowledge" explains the historical professional path -- from Fujisawa to Cheng.

Cassandra · Post by **Cassandra** » Wed May 13, 2015 6:53 am

The second part of Volume II (= part 3 seen overall) discusses the "Evolution of Amateur's Knowledge".

In principle,

-- The History of the Problem's Final Score (1999 - 2011),
-- The Decisive Moment in the Historical Line of Play (2002 - 2007),
-- Guzumi at Top Right (2007 - 2009), and
-- Various Kikashi in the Hanezeki (2007 - 2011; 2014)

can also be found in our 2011 book.

In 2014, Harry revealed some very interesting aspects in one of the "classical" Hanezeki-problems (containg the well-known "basic" shape"), which we explain in detail.

Joachim's Ko-Semeai is not trivial at all.

We encountered massive difficulties in browsing through all the possible variations, in order to "prove" that this Ko-Semeai is no valid option for Black. As "usual" with Dosetsu's masterpiece, Black has one liberty too few to be successful and / or one Ko-threat too few.

Therefore, we tried some kind of "reverse engineering" -- starting with a later moment in these sequences -- for comparative studies in "Joachim's Ko-Semeai -- Putting the Cart Before the Horse (2013 - 2015)". This second, different approach helped us a lot to find mistakes in our earlier sequences.

Cassandra · Post by **Cassandra** » Wed May 13, 2015 7:01 am

The third part of Volume II (= part 4 seen overall) contains further topics.

Amoung the further structural elements of the problem,

-- About Approach-Move Liberties (2009)
-- About Hanezeki (2009; 2015)

can be also found in our 2011 book (in principle).
There is a supplement on Hanezeki, due to Harry's findings, mentioned above.

"About Ko in a Semeai Between Two One-Eyed Groups (2012)" was my first attempt to create a different approach on Joachim's Ko-Semeai, using simplified positions. However, there were some rumours that this chapter might be too mathematical orientated, thus I finally developed "Putting the cart before the horse".

"Igo Hatsuyōron 120 and Go Playing Programs (2009 - 2011)" explains my trials with Many Faces of Go during the investigations in White's Tenuki-variations after my Guzumi.

Cassandra · Post by **Cassandra** » Wed May 13, 2015 7:09 am

All the contents described above, which has been developed until mid-2013, can be found in our 300th Anniversary Edition "The most difficult problem ever: Igo Hatsuyōron 120" with SmartGo Books.

Cassandra · Post by **Cassandra** » Sat Aug 05, 2017 12:29 am

A few days ago, Harry Fearnley of our amateur research team found a mistake in our previous solution to Igo Hatsuyoron 120.

Harry revealed an AlphaGo-ish large trade on the board that we hadn't considered before.

Details can be found at our website.

Cassandra · Post by **Cassandra** » Wed Sep 27, 2017 6:56 am

Click Here To Show Diagram Code: [go]$$Wcm94 During the course of the published professional solution $$ +---------------------------------------+ $$ | . . . . . . . . . . . 6 . . . . O X . | $$ | . . . . . . . X O O . X O 5 . . . O . | $$ | . . . . . X . O . . . X 4 . . 3 O . . | $$ | . X O , . . . . . O . X . O O 2 . . . | $$ | . . X X X X O O O . O X X . X X O O . | $$ | . X . O O O X X X O . . X . X O . . . | $$ | O O O O . X O O X X O O . O X . 7 1 . | $$ | O X . X . X . O O X O . . . X X X X X | $$ | O X . X . . . O X X O . X X X X O O O | $$ | O O O 8 . X . O X O O X X O O O O X . | $$ | X O O O X . . O X O . X O O O . X X X | $$ | X X O O X . . O X O . X O O X X X O O | $$ | X . O . X . . O X O . X O . O . X X O | $$ | . O O X O X . O X O . X X O O O X O O | $$ | O O X . . X . O X O X . O X X X O O O | $$ | O 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 the published professional solution, W 94 occupies the guzumi-point at the right, AFTER the Nakade Sequence at the left has been played to its very end.
Thereafter, Black reduces White's upper right corner by playing at B 95 first, followed by the second push of B 97, and the final sagari at B 99.
W 100, and B 101, start the mutual occupation of opponent's liberties in the Main Semeai.

Click Here To Show Diagram Code: [go]$$Wcm38 Yamada Shinji's tsuke gains one point of territory in the upper left and ... $$ +---------------------------------------+ $$ | . . . . . 6 . 7 . . O X O . . . O X . | $$ | . . . . 2 1 3 X O O O X O O . . . O . | $$ | . . . 8 5 X 4 O . . O X X O . O O . . | $$ | . X 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 . . . O . O X X X O . . . | $$ | O O O O X X O O . . O O O O X O O O O | $$ | O X X X . X . O O . O . . . X X X X X | $$ | O X X X . . . O . . O O X X X X O O O | $$ | O O O X . X . O . O O X X O O O O X . | $$ | . O O O X . . O . O . X O O O . X X X | $$ | X . O O X . . O . O . X O O X X X O O | $$ | . O O X X . . O . O . X O . O . X X O | $$ | O O O X O X . O . O O X X O O O X O O | $$ | O O X . . X . O . O . O O X X X O O O | $$ | O X X , X . . O . O O O O X . X O O X | $$ | O X . . O X . O . . . . X . O X X O X | $$ | O X X . 0 9 X O O O O O O X . X X O X | $$ | X X . . . . . O . . . . O X X X . O . | $$ +---------------------------------------+[/go]

However, after White captured the hanezeki's tail (and Black played some moves of the dissolution of the hanezeki), Cheng Xiaoliu 6p apparently did not consider the tsuke W 138 of Yamada Shinji 6p that results in a local gain of one point, and ...

Click Here To Show Diagram Code: [go]$$Wcm48 ... another point of territory in the centre, winning her the game $$ +---------------------------------------+ $$ | . . . . . X . O . . O X O . . . O X . | $$ | . . . . X O O . O O O X O O . . . O . | $$ | . . . X O X X O . . O X X O . O O . . | $$ | . X O , 6 . 4 5 . 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 . . . O . O X X X O . . . | $$ | O O O O X X O O . . O O O O X O O O O | $$ | O X X X . X . O O . O . a . X X X X X | $$ | O X X X . 0 . O . . O O X X X X O O O | $$ | O O O X . X 9 O . O O X X O O O O X . | $$ | . O O O X . . O . O . X O O O . X X X | $$ | X . O O X . . O . O . X O O X X X O O | $$ | . O O X X . . O . O . X O . O . X X O | $$ | O O O X O X . O . O O X X O O O X O O | $$ | O O X . . X . O . O . O O X X X O O O | $$ | O X X , X 8 . O . O O O O X . X O O X | $$ | O X . . O X 7 O . . . . X . O X X O X | $$ | O X X . X O X O O O O O O X . X X O X | $$ | X X . . 2 1 3 O . . . . O X X X . O . | $$ +---------------------------------------+[/go]

... another gain of one point in the centre (W 158 @ a).
Compared to the published professional solution that ends in a drawn game (jigo), White is two points better now, and will win the game by that margin.

So much for the introduction ...

Click Here To Show Diagram Code: [go]$$Bcm97 Harry's hasami-tsuke and Michael Redmond's kikashi $$ +---------------------------------------+ $$ | . . . . . . . . . . . . 3 . . . O X . | $$ | . . . . . c d X O O . X O 1 4 . . O . | $$ | . . . . . X . O . . . X 2 a b O O . . | $$ | . X O , . . . . . O . X . O O X . . . | $$ | . . X X X X O O O . O X X 5 X X O O . | $$ | . 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 | $$ | O X . X . . . O X X O . X X X X O O O | $$ | O O O , . X . O X O O X X O O O O X . | $$ | X O O O X . . O X O . X O O O . X X X | $$ | X X O O X . . O X O . X O O X X X O O | $$ | X . O . X . . O X O . X O . O . X X O | $$ | . O O X O X . O X O . X X O O O X O O | $$ | O O X . . X . O X O X . O X X X O O O | $$ | O 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]

At the time when the defusing of a 1.5-ton bomb from the Second World War was being prepared in Frankfurt, Joachim brought his own "bomb" to burst:
Joachim addressed the question whether playing the kikashi B 101 of Michael Redmond 9p might be feasible for Black, after he had chosen the Hasami-Tsuke Sequence B 97, B 99 (instead of the classical push / sagari shown above) for reducing White's top right corner.
This idea provides White with a difficult choice, as well as Black later.

White might choose between answering locally (a, b) or playing tenuki to start with the reduction of Black's upper left corner (c, d), but none of these options will lead to success.
According to our amateurish analysis, Black will indeed win by at least two points, after White had allowed Black to play the kikashi in the bamboo joint.

A main factor for Black's success is the still non-outplayed top left corner that Black will want to defend at an appropriate moment for a large territorial gain. Therefore, we had to consider how White could take this opportunity out of Black's hands.

Click Here To Show Diagram Code: [go]$$Wcm86 White must start the endgame in the upper left corner "early", with the atari $$ +---------------------------------------+ $$ | . . . . . . . . . . . . . . . . O X . | $$ | . . . . . b 1 X O O . X O . . . . O . | $$ | . . . . . X . O . . . X . . . . O . . | $$ | . X O , . . . . . O . X . O O , . . . | $$ | . . X X X X O O O . O X X . X X O O . | $$ | . X . O O O X X X O . . X . X O . . . | $$ | O O O O . X O O X X O O . O X . . . . | $$ | O X . X . X . O O X O . . . X X X X X | $$ | O X . X . . . O X X O . X X X X O O O | $$ | X O O , . X . O X O O X X O O O O X . | $$ | X X O O X . . O X O . X O O O . X X X | $$ | X X a O X . . O X O . X O O X X X O O | $$ | X X O . X . . O X O . X O . O . X X O | $$ | X O O X O X . O X O . X X O O O X O O | $$ | X O X . . X . O X O X . O X X X O O O | $$ | O 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]

The first chance for doing so arises with W 86.
In the professional solution, White captures Black's nine-stone nakade at the left with this move. However, playing at a is not mandatory at this moment (completing the nine-stone nakade was gote for Black).
White is forced to play the "classical" atari W 86 at the top left, starting the endgame "early".

Please note that choosing Yamada Shinji's tsuke at b, instead, will not lead to success, as it is a bit too soft (with regard to potential follow-up moves in the corner).

Click Here To Show Diagram Code: [go]$$Bcm87 Black must follow the "usual" course of the professional solution $$ +---------------------------------------+ $$ | . . . . 3 2 4 6 . . . . . . . . O X . | $$ | . . . . 7 1 O X O O . X O . . . . O . | $$ | . . . . . X 5 O . . . X . . . . O . . | $$ | . X O , . . . . . O . X . O O a . . . | $$ | . . X X X X O O O . O X X . X X O O . | $$ | . X . O O O X X X O . . X . X O . . . | $$ | O O O O . X O O X X O O . O X . . 8 . | $$ | O X . X . X . O O X O . . . X X X X X | $$ | O X . X . . . O X X O . X X X X O O O | $$ | X O O , . X . O X O O X X O O O O X . | $$ | X X O O X . . O X O . X O O O . X X X | $$ | X X . O X . . O X O . X O O X X X O O | $$ | X X O . X . . O X O . X O . O . X X O | $$ | X O O X O X . O X O . X X O O O X O O | $$ | X O X . . X . O X O X . O X X X O O O | $$ | O 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, on the other hand, is also bound to follow the "usual" course.

Playing tenuki in the upper left corner, in order to start the Hasami-Tsuke Sequence with a move at a, and to play the guzumi at 94 thereafter, will not lead to success.

Finally, W 94 occupies the guzumi-point.

Click Here To Show Diagram Code: [go]$$Bcm95 Black must choose the "classical" push / sagari combination $$ +---------------------------------------+ $$ | . . . . X O O O . . . 5 a . . . O X . | $$ | . . . . X X O . O O . X O 4 b . . O . | $$ | . . . . . X X O . . . X 3 . . 2 O . . | $$ | . X O , . . . . . O . X . O O 1 . . . | $$ | . . X X X X O O O . O X X c X X O O . | $$ | . X . O O O X X X O . . X . X O . . . | $$ | O O O O . X O O X X O O . O X . 6 O . | $$ | O X . X . X . O O X O . . . X X X X X | $$ | O X . X . . . O X X O . X X X X O O O | $$ | X O O 7 . X . O X O O X X O O O O X . | $$ | X X O O X . . O X O . X O O O . X X X | $$ | X X d O X . . O X O . X O O X X X O O | $$ | X X O . X . . O X O . X O . O . X X O | $$ | X O O X O X . O X O . X X O O O X O O | $$ | X O X . . X . O X O X . O X X X O O O | $$ | O 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 . . e X O O O O O O X O X . O X | $$ | . X . . . . . O . . . . O X X X . O . | $$ +---------------------------------------+[/go]

The following reduction of White's corner territory must again follow the "usual" course of the professional solution.

Black will lose by one point, if he chooses Harry's Hasami-Tsuke Sequence B 98, W 97, B a, W b, followed by Michael Redmond's kikashi of c, instead.

Later, White will capture the nakade, with a move at d, and also start the remaining endgame at the left side of board, with a move at e.

It results a change in the order of moves with the published professional solution, but White never got the opportunity to successfully play Yamada Shinji's tsuke.
Now, the professional solution will really end in a draw.

You might want to take this result of our amateurish analysis with a grain of salt, as there is no professional confirmation yet.

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

Details can be found at our website:

Variations:
Michael Redmond's Kikashi in the Professional Solution
How to Prevent Michael Redmond's Kikashi in the Professional Solution

Theory:
Michael Redmond's Kikashi in the Professional Solution
How to Prevent Michael Redmond's Kikashi in the Professional Solution

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

For your convenience, I uploaded a SGF that contains most of the variations from the website:

Please note that this SGF does NOT contain any detailed commentaries, but displays only the final scores of forthcoming alternative moves (labeled with A, B, ..., instead of EidoGo's 1, 2, ...) for easier orientation at the branching points.

Please also note that I was not very attentive with the order of moves during the sequences, especially with the mutual occupation of liberties in the Main Semeai.

Life In 19x19

The most difficult problem ever. Igo Hatsuyoron 120

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Re: The most difficult problem ever. Igo Hatsuyoron 120

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Re: The most difficult problem ever. Igo Hatsuyoron 120

Re: The most difficult problem ever. Igo Hatsuyoron 120

Re: The most difficult problem ever. Igo Hatsuyoron 120

Re: The most difficult problem ever. Igo Hatsuyoron 120

Re: The most difficult problem ever. Igo Hatsuyoron 120

Re: The most difficult problem ever. Igo Hatsuyoron 120

Re: The most difficult problem ever. Igo Hatsuyoron 120

Re: The most difficult problem ever. Igo Hatsuyoron 120

Re: The most difficult problem ever. Igo Hatsuyoron 120

Re: The most difficult problem ever. Igo Hatsuyoron 120

Re: The most difficult problem ever. Igo Hatsuyoron 120

Re: The most difficult problem ever. Igo Hatsuyoron 120