Problem No. 120 from Igo Hatsuyoron
Created by Inoue Dosetsu Inseki (1646 - 1719)



Black to play and win
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Contents

 What this problem is really about.
 Highlights (our key-results; highly recommended for a better overview).
 Main Path of the "official" solution in detail.
 Table "Main Path" (summary of the variations of the Main Path).
 Table "The second Throw-in" (summary of the results of our investigations).
 Several questions from 2007 (= the path to the Guzumi).
 Variations of the Main Path in detail.
 Variations after the second Throw-in in detail.

 Research on the move that probably solves the problem. THIS PAGE.

 TIME - what distinguishes between amateurs and professionals (or joins them together ?).





Research on the move that probably solves the problem.



Sub variation for B 67

Dia. 67p.1: B 67 - W 76

B 67:
This seems to be the last possible moment to play that "bad shape"-move in the upper right before action starts on the left side of the board.

W 68:
White starts the "usual" sequence on the left side, because answering immediately in the top right will lose White the game, as we have seen already
(please refer to the variation for B 93).

Update 2011:
Without second Throw-in, White will get the closest result, when she prevents two Black eyes immediately with a move above 67.

Update 2009:
To start attacking the black stones on the left with 68 is alternative "L" of the research on my "bad-shape" move.

Perhaps a White answer in the top left corner would be stronger.

Update 2011:
In the meantime we found that White's answers in the top left corner do not favour White, as we supposed before.


B 73:
Black now takes the opportunity to live in the top right.
Black will not be successful if he returns to the Main Path here.

[ see variation ]

Saving the stones on the left may look big, but will lose the game for Black.

[ see variation ]

W 76:
White captures the Black group.
But it would be better to start the Endgame in the top left instead.

[ see variation ]

Yamada Shinji's Tsuke is not possible here, because the surroundings are far more open than in the Main Path.

[ see variation ]

 


Dia. 67p.2: B 77 - W 86

B 77, 79:
Black answers in the top left, getting points while threatening the second eye of the White centre group.

B 81:
What follows is an amateurish idea of the Endgame. Black seems to be about five points ahead.

Update 2009:
B 85:
A Hasami-Tsuke at 86 will give Black a further advantage of one point.



Dia. 67p.3: B 87 - W 96


 

Dia. 67p.4: B 97 - W 106



Dia. 67p.5: B 107 - W 116



Dia. 67p.6: B 117 - W 126


Dia. 67p.7: "The Score"

Black wins by 6 points.


Black may perhaps be 1 point better if he does not play the second Throw-in with B 19. The Seki in the lower right is not resolved, so this proves as a lost move now.

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Sub² variation #1 for B 73


Dia. 67p.8: B 73 - W 82

B 73:
Black follows the Main Path.

B 79:
Now it is clear that Black has lost one move on the right side.

B 81:
Black is forced to make two eyes for his upper right group because White lives on the left side.



Dia. 67p.9: B 83 - W 92

W 84:
What follows is an amateurish idea for the Endgame again.

 

Dia. 67p.10: B 93 - W 102



Dia. 67p.11: B 103 - W 112


 

Dia. 67p.12: B 113 - W 122


 

Dia. 67p.13: B 123 - W 126


 

Dia. 67p.14: B 127 - W 138


 

Dia. 67p.15: "The Score"

White wins by 5 points.


Black may perhaps be 1 point better if he does not play the second Throw-in with B 19. The Seki in the lower right is not resolved, so this proves as a lost move now.

back to the sub variation for B 67
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Sub² variation #2 for B 73


Dia. 67p.16: B 73 - W 82

B 73:
Black saves his stones on the left side.

W 74:
White deprives Black of two eyes on the right side.

B 75:
So Black has to return to the Main Path again.

B 81:
Necessary to prevent two eyes for Whites left side group.

W 82:
White can enter Blacks weak top left corner now.



Dia. 67p.17: B 83 - W 92

B 83:
Black cannot give up his stone in Atari.


Dia. 67p.18: B 93 - B 97

B 95:
If played at 96 (see below), there will result a "normal" Ko, this will be won by White, too.

 

Dia. 67p.19: W 98 - B 99

W 98:
White starts a Double Ko that Black cannot win.

 

Dia. 67p.20: W 100 - B 103

B 103:
Sooner or later Black has to capture that White stone in the corner.

 

Dia. 67p.21: W 104 - W 108

W 108:
White lives in the top left and therefore wins the game by a large margin.

 





Dia. 67p.51: B 95 - B 99

B 95:
Black connects and gets a "normal" Ko.

 

Dia. 67p.52: W 100 - W 102


 

Dia. 67p.53: B 103 - B 105


 

Dia. 67p.54: W 106 - W 108


 

Dia. 67p.55: B 109 - B 111


 

Dia. 67p.56: W 112 - W 114


 

Dia. 67p.57: B 115 - B 117


 

Dia. 67p.58: W 118 - W 120


 

Dia. 67p.59: B 121 - W 124

B 121:
Black does not have any real Ko-threat left.

W 122, W124:
White finishes the Ko and saves her group on the left. Her group on the lower side has only one eye, so she must resolve the Hanezeki; but despite of this loss White will win anyway by approximately 20 points.

 

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Sub² variation #1 for W 76


Dia. 67p.22: W 76 - B 85

W 76:
White starts the endgame in the upper left before returning to the Black group on the left with 84.

B 85:
The moves from here on follow the suggestion of Yoon Young-Sun 5p from Korea, now living in Hamburg, Germany. Special thanks to Yoon Sensei, who was so kind to help me with the correct Endgame here.

 

Dia. 67p.23: W 86 - B 95

W 86 - 94:
It does not profit White to Tenuki with one of these moves to play in the centre.

[ see variations ]

Update 2009:
B 89: A Hasami-Tsuke at 90 might be possible and give Black a further advantage of one point.



Dia. 67p.24: W 96 - B 105

B 103:
The biggest point remaining on the board.

W 104:
Sente. The follow-up move at A would be unbearable for Black.

 

Dia. 67p.25: W 106 - B 115

W 114:
It is the correct order of moves to play here first and then at 116.


Dia. 67p.26: W 116 - B 125

B 119:
Hereafter only 1-point Endgames are available.

B 121:
It would be a mistake to follow the Main Path instead. The captured White stone compensates for the point Black has lost below.

[ see variation ]


 

Dia. 67p.27: W 126 - B 131
W 130, B 131:
No Ko fight will start here, because two Ko of different colours are open.


Dia. 67p.28: "The Score"

Black wins by 1 point.


Black may perhaps be 1 point better if he does not play the second Throw-in with B 19. The Seki in the lower right is not resolved, so this proves as a lost move now.

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Sub² variation #2 for W 76


Dia. 67p.22: W 76 - B 85

W 76:
Yamada Shinji's Tsuke is not possible here.

B 77:
This black answer threatens to connect the string of black stones to the outside and is absolute Sente.

W 82:
Is no threat any more against the right part of Black's stones, so Black can answer with 83 in the corner.

Should White play at A instead (what she did in the Seki-sequence after Black 83, White B, Black C), she will lose the Semeai by at least one move. White has lost the Sente move of B (77 had been white, not black), which forced Black to take himself one liberty by connecting at C in the Seki-sequence.

Black wins the game.


back to the sub variation for B 67
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Sub² variation for W 86


Dia. 67p.29: W 86 - B 91

W 86:
If White plays in the centre, she has this 8-point Endgame, according to Yoon Sensei.

B 87:
But Black gets much more profit in the upper right corner.

 





Dia. 67p.30: W 88 - B 91

W 88:
White is unable to capture some Black stones in the centre.

 




Sub² variation for W 88


Dia. 67p.31: W 88 - B 89

B 89:
This Endgame in the top right corner is worth about 12 points for Black. So White is 4 points worse.

 




Sub² variation for W 90


Dia. 67p.32: W 90 - B 99

B 91:
This Black Endgame in the top right corner has a value of 8 points, too. So the result remains unchanged.

 




Sub² variation for W 92


Dia. 67p.33: W 92 - B 99

B 93:
Again, the Black Endgame in the top right corner has a value of 8 points. So the result remains unchanged.

 




Sub² variation for W 94


Dia. 67p.34: W 94 - B 101

B 95:
For the third time there is a Black Endgame in the top right corner with a value of 8 points. So the result remains unchanged.

 

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Sub³ variation for B 121


Dia. 67p.35: B 121 - W 130

B 121:
Black follows the Main Path.

W 122:
White connects. This move endangers one point of Black territory as well, but leaves no open Ko behind.

W 128:
Sente. And takes one Black Ko threat away, what will be very important later.

 

Dia. 67p.36: B 131 - W 140

B 131:
Black captures a White stone, but will be unable to win the following Ko fight.
(Moves not shown in the diagrams here take Ko.)

 

Dia. 67p.37: B 141 - W 150


 

Dia. 67p.38: B 151 - W 160


 

Dia. 67p.39: B 161 - W 170


 

Dia. 67p.40: B 171 - W 180


 

Dia. 67p.41: B 181 - W 188


 

Dia. 67p.42: B 189 - W 190

B 189:
Black passes. There is no Ko threat anywhere.


Dia. 67p.43: "The Score"

Jigo !


Black may perhaps be 1 point better if he does not play the second Throw-in with B 19. The Seki in the lower right is not resolved, so this proves as a lost move now.

Update 2009:
Black might be a further 1 point better if he had played Hasami-Tsuke in the top right corner with 89.



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Research on the "Bad-Shape" Move B 67


Dia. 67r.1:

For research purposes we can divide the board into four areas and look at these one after another.

Lower right (light brown):
If the big Black group on the right gets two eyes, the temporary Seki will remain unresolved until the end of the game.

Upper right (light yellow):
White will not get additional points here.

Lower left (orange):
It is possible for Black to save his five stones on the left edge. And the end of this procedure the two Black stones on the fourth line perhaps might be in danger of being captured.

Upper left (yellow):
This is the most interesting (and most difficult) area.
To win the game, White must destroy Black points in the corner and get own points in such an amount that can compensate for the loss in the lower left quadrant.

Precondition of this research is:
With 68 White plays a move that forces Black to make two eyes for his upper right group and at the same time threatens the upper left Black corner.
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Upper Right Quadrant


Dia. 67r.2:

According to Yoon Young-Sun (please refer to her endgame suggestion), each of the Black Sente moves in the top right corner (71 to 79) would threat to capture some White stones (with the side effect of providing Black with his second eye).
So they could be played - if necessary - before securing the second eye inside the Black eye space with 81.

Update 2009:
Perhaps Black can play 75 at 76, what is one point better for him.

Update 2011:
Our thoughts about the correct order of moves in the top right corner can be found [ here. ]

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Lower Left Quadrant


Dia. 67r.3:

It takes White two moves (68 and 76) to capture the Black stones on the left side.
White gets 6 points of territory and 7 prisoners here, 13 points in total.
White ends in Gote.

But White must have Sente to start the sequence beginning with 68.

If Black gets to play at 68 himself, he will capture the White stones below outright (two liberties to four) and spare most of the Teire shown. That would be too much a burden for White.

But White cannot play 68 before forcing Black's top right group to make two eyes, as she loses Sente here with 72. Black thereafter will prevent White's intrusion into the top left corner.

On the other side Black must follow White on the "usual" Main Path sequence for the time being. That means as long as his big group on the right does not have two eyes.

Question: Why does White not play Atari with 91 before connecting at 72 ?

In the Main Path sequence that may be disadvantageous because White takes herself a liberty. But here the connection of these stones to the centre group would have been secured already. Black would lose one additional point by saving his single stone in Atari and White would get one additional point of territory at 92.

But: Black could capture at 72 outright. This move contains the threat to cut off all of the White stones here. So perhaps White cannot Tenuki thereafter and Black will have the change to play some defensive move.


Dia. 67r.4:

Should Black ever be able to save his stones on the left side, he gets 2 points of territory and 3 prisoners.
This time Black ends in Gote.

So saving or capturing the Black stones on the left side is worth 13 + 5 = 18 points in Gote.

But really Black will lose some more points, if White will be able to play in the centre of the board first.

A White move there threatens to cut off the two Black stones above the Hoshi on the left - and is worth about 2 or 3 points.

Perhaps Black 77 will have another consequence. Depending on the future development in the top left corner White may be able to separate and capture this two Black stones with the sequence from A to G (suppose that a Geta with Black D at F will not work), because a Black move at C is no threat against the White stones below any longer.

If the top is played out, the sequence here is a one way street, once started. Black ends in Gote, but it had been White's turn from the very beginning.

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Upper Left Quadrant


Dia. 67r.5:

This is the final position in the top left corner in the variation with Young-Sun's endgame suggestion.

Black has 16 points of territory and 1 prisoner, 17 points in total.

White must get more additional points here than Black can keep in this area to compensate for the abovementioned loss of 18 points in the lower left.

Dia. 67r.6:

This White 68 (= H as White follow-up move after Black 67) was the move that looked the most straightforward to us. This move does not leave any threat in the centre for Black, so he must make two eyes for his group in the upper right.

Update 2009:
In the meantime we found, that playing F with 68 might be preferable for White.

Update 2011:
Amoung White's possible alternatives, B, C, and F seem to be strongest.

Moves that now come into mind for White 72 are:

A - "Standard" Osae of the Main Path.
Seems to be too direct and too small.
B - Yamada Shinji's Tsuke.
C - Oki.
May perhaps run into B with a change in the order of moves.
D - Peep.
Looks like the most interesting alternative for White. And seems to be the vital point in this position.
E - Atari from the right.
Seems to be too direct and too small.
F - Atari from below.
Will run into E with a change in the order of moves.

We did not find any sequence for White that damages the Black corner as much as would be necessary to change the tables. Black will win the game.

Surprisingly the strongest move for White seems to be that one on the right side, preventing the Black eye there immediately and then following the known Main Path (resulting in a 1-point win for Black respectively 2-points-win without the second Throw-in).


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Dia. 67r.7:

Variation A:

Black will keep about 15 points in the corner.

White will get some additional points in the centre.

The two Black stones in the left centre cannot be cut by White.

Black gets about 10 points in this area and therefore will win the game.

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Dia. 67r.8:

Variation B:

Black will keep about 12 points in the corner.

White will get about 7 additional points.

The two Black stones in the left centre cannot be cut by White.

Black gets about 5 points in this area and therefore will win the game.

Dia. 67r.9:

White cannot cut with 74. Black wins the Semeai in the corner.

Dia. 67r.10:

Pulling back with 73 is possible for Black, too, and might be the safer variation.

Black will keep about 12 points in the corner.

White will get about 7 additional points.

The two Black stones in the left centre cannot be cut by White.

Black gets about 5 points in this area and therefore will win the game.

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Dia. 67r.11:

Variation C:

If Black plays at 73 and let White connect to the outside (White 74 at 75 is not possible), it will result a change in the order of moves with the diagram before.

The two Black stones in the left centre cannot be cut by White.

Black gets about 5 points in this area and therefore will win the game.

Dia. 67r.12:

Answering the Oki White 72 with 73 might a bit dangerous for Black.

Black plays 77 from the lower side (and not at 78) to prevent weakening his two centre stones.

Black will keep about 11 points in the corner.

White will get about a few additional points.

The two Black stones in the left centre cannot be cut by White.

Black gets about 10 points in this area and therefore will win the game.

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Dia. 67r.13:

Variation D:

It seems to be best for Black to play a purely defensive move with 73.

Black will keep about 9 points in the corner.

Perhaps White will not play at 82 at once.
White will get about a few additional points.

The two Black stones in the left centre cannot be cut by White.

Black gets more than about 5 points in this area and therefore will win the game.

Dia. 67r.14:

White has the option to play at 74 at the outside immediately.

Black will keep about 9 points in the corner.

White will get 8 points later by separating the two Black stones on the left (due to the connection with 80).

But even this one remaining point in this area will Black enable to win the game.

Dia. 67r.15:

If White plays inside with 74, it might be dangerous for Black to shut White in with 78.

The safety-first measure for Black is to give way with 75 here.

Black will keep about 10 points in the corner.

White will get 8 points later by separating the two Black stones on the left (due to the connection with 82).

But some remaining points in this area will Black enable to win the game.

Dia. 67r.16:

Perhaps White will connect with 78.

Dia. 67r.17:

Black has 5 outside liberties left - and White cannot take two of them direct. So it cannot be said that the approach-move Ko around 97 is really a Ko for White.

Dia. 67r.18:

Connecting the second time on the outside with 75 looks to be extremely dangerous for Black at first sight.

But it results a change in the order of moves to something we have already seen before.

Dia. 67r.19:

Black has three effective liberties against White's two, so there is no need to play at 101 immediately.

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Dia. 67r.20:

Variation E:

Black will keep about 16 points in the corner.

White will get about additional 6 points in the centre.

The two Black stones in the left centre cannot be cut by White.

Black gets about 10 points in this area and therefore will win the game.

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Dia. 67r.21:

Variation F:

Black will keep about 16 points in the corner.

White will get about additional 6 points in the centre.

The two Black stones in the left centre cannot be cut by White.

Black gets about 10 points in this area and therefore will win the game.

Update 2009:
This move at 72 opens much better continuations for White in the top left corner, if the area of the top right corner is not played out before.

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The diagram-pictures were created with "SGF conversion" on Jan van der Steen's GoBase.org.
Compiled by Thomas Redecker.

For a blog on East-Asian books on Go, please refer to Tchan001's Blog..

(c) DGoB -  letzte Aktualisierung: 2011-08-22 20:00, TRMDPE@t-online.de