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 Post subject: Re: Following Iyama Yuta (no world ranking discussions)
Post #341 Posted: Sun Feb 03, 2019 2:04 pm 
Judan

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Kisei game 3, can you find Iyama's 42% mistake and Yamashita's 44% return of the favour; Iyama (white) won in the end. LZ's suggested move is the one I expected watching the game and its analysis appears sound to me. Is it missing something, or did the players really make such a big mistake?



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 Post subject: Re: Following Iyama Yuta (no world ranking discussions)
Post #342 Posted: Thu Feb 07, 2019 4:55 pm 
Judan

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Iyama has got off to a bad start in the Meijin league, so what may have been assumed as a foregone conclusion that he would top the league to challenge Cho U to regain his title may not be so certain. He started off with a win against Mutsuura Yuta 7d, but then lost to Suzuki Shinji 7d (who? you may ask) by half a point. And just today he lost to prodigal youngster Shibano Toramaru 7d by 1.5 so he's 1-2 so far, with 5 games left.

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 Post subject: Re: Following Iyama Yuta (no world ranking discussions)
Post #343 Posted: Fri Feb 08, 2019 6:17 am 
Lives with ko

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You can't leave us hanging... What was the 42% mistake?

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 Post subject: Re: Following Iyama Yuta (no world ranking discussions)
Post #344 Posted: Sat Feb 09, 2019 9:35 am 
Judan

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mhlepore wrote:
You can't leave us hanging... What was the 42% mistake?


Here is the position after move 189. White's stick on row 8 has just finished hassling the black group above and the fight resumed at the bottom left corner. White can push and cut with a-c to capture the cutting stones (each has 3 liberties but black needs to defend the g5 stones so white goes first), but would also like to kill the corner too if possible. LZ 203 says white is at 84%.
Click Here To Show Diagram Code
[go]$$Bc Iyama (white) vs Yamashita, White 84%
$$ ---------------------------------------
$$ | . . . . . . O . O X X . . . . . . . . |
$$ | . O X X . X O O O O X X X X X . O . . |
$$ | . . O X . X X O O X X O O O . X O . . |
$$ | . . O O X . . . O O X . X O X X O . . |
$$ | . . . . . X X X X O X X X X O X O . . |
$$ | . . O . . O . O X O O O X X O X X O . |
$$ | . O . . . O . O O X . O O O O X X O . |
$$ | . X O O . . . . . X . O . O O X O . . |
$$ | X . X . X . . X O . X X O O X O O . . |
$$ | . . . X . . X . . , X O X O X X . . . |
$$ | . X X O X X O X X X . O X X . X . . . |
$$ | . . O O O O O O O O O O . X X . . . . |
$$ | . O O . . . . . . . X O . X O O . . . |
$$ | . X O X X b c . . . X O . X O X . . . |
$$ | . . X O X a X . . . X X . X O . . . . |
$$ | . . X O O O X . . , . . . . O , . . . |
$$ | . . X O . X O O . . . . . . . X . . . |
$$ | . X O O X . X . . . . . . . . . . . . |
$$ | . . . . . X . . . . . . . . . . . . . |
$$ ---------------------------------------[/go]


First, what if white simply goes for the cut and capture. If white 7 takes a liberty black can connect under in sente and gets to play an important move like r4 next. White ends at 22%.
Click Here To Show Diagram Code
[go]$$Wc Direct cut. 22%
$$ ---------------------------------------
$$ | . . . . . . O . O X X . . . . . . . . |
$$ | . O X X . X O O O O X X X X X . O . . |
$$ | . . O X . X X O O X X O O O . X O . . |
$$ | . . O O X . . . O O X . X O X X O . . |
$$ | . . . . . X X X X O X X X X O X O . . |
$$ | . . O . . O . O X O O O X X O X X O . |
$$ | . O . . . O . O O X . O O O O X X O . |
$$ | . X O O . . . . . X . O . O O X O . . |
$$ | X . X . X . . X O . X X O O X O O . . |
$$ | . . . X . . X . . , X O X O X X . . . |
$$ | . X X O X X O X X X . O X X . X . . . |
$$ | . . O O O O O O O O O O . X X . . . . |
$$ | . O O 7 9 . 5 . . . X O . X O O . . . |
$$ | . X O X X 2 3 4 . . X O . X O X . . . |
$$ | . . X O X 1 X . . . X X . X O . . . . |
$$ | . . X O O O X . 6 , . . . . O , . . . |
$$ | . . X O . X O O . . . . . . . X . . . |
$$ | . X O O X . X . . . . . . . . . . . . |
$$ | . . 0 8 . X . . . . . . . . . . . . . |
$$ ---------------------------------------[/go]


Instead of 7 white can put in the sente hane in the corner to prevent black's connection, but then black can make a comb group to live in the corner. White 40%.
Click Here To Show Diagram Code
[go]$$Wcm7 No connection, but a comb life. 40%
$$ ---------------------------------------
$$ | . . . . . . O . O X X . . . . . . . . |
$$ | . O X X . X O O O O X X X X X . O . . |
$$ | . . O X . X X O O X X O O O . X O . . |
$$ | . . O O X . . . O O X . X O X X O . . |
$$ | . . . . . X X X X O X X X X O X O . . |
$$ | . . O . . O . O X O O O X X O X X O . |
$$ | . O . . . O . O O X . O O O O X X O . |
$$ | . X O O . . . . . X . O . O O X O . . |
$$ | X . X . X . . X O . X X O O X O O . . |
$$ | . . . X . . X . . , X O X O X X . . . |
$$ | . X X O X X O X X X . O X X . X . . . |
$$ | . . O O O O O O O O O O . X X . . . . |
$$ | . O O 3 5 . O . . . X O . X O O . . . |
$$ | 6 X O X X X O X . . X O . X O X . . . |
$$ | . . X O X O X . . . X X . X O . . . . |
$$ | . . X O O O X . X , . . . . O , . . . |
$$ | . . X O 4 X O O . . . . . . . X . . . |
$$ | 2 X O O X . X . . . . . . . . . . . . |
$$ | . 1 . . . X . . . . . . . . . . . . . |
$$ ---------------------------------------[/go]


Starting with the hane in the corner seems pretty natural to me (and is the correct move says LZ), those white stones are weaker than the wall above so it makes sense to play from that direction, and that hane can often gain you a liberty in a semeai. If black extends with 2 (not best) to make the possibility of a comb group life, white captures a stone with b5 (not best), black ataris with b4 (not best) then white has, in sente, reduced the corner to one eye and got the b1 hane. White up to 96% with black's cooperation.
Click Here To Show Diagram Code
[go]$$Wc Sente moves on corner before cut. 96%.
$$ ---------------------------------------
$$ | . . . . . . O . O X X . . . . . . . . |
$$ | . O X X . X O O O O X X X X X . O . . |
$$ | . . O X . X X O O X X O O O . X O . . |
$$ | . . O O X . . . O O X . X O X X O . . |
$$ | . . . . . X X X X O X X X X O X O . . |
$$ | . . O . . O . O X O O O X X O X X O . |
$$ | . O . . . O . O O X . O O O O X X O . |
$$ | . X O O . . . . . X . O . O O X O . . |
$$ | X . X . X . . X O . X X O O X O O . . |
$$ | . . . X . . X . . , X O X O X X . . . |
$$ | . X X O X X O X X X . O X X . X . . . |
$$ | . . O O O O O O O O O O . X X . . . . |
$$ | . O O . . . . . . . X O . X O O . . . |
$$ | 5 X O X X . . . . . X O . X O X . . . |
$$ | . 3 X O X . X . . . X X . X O . . . . |
$$ | 6 4 X O O O X . . , . . . . O , . . . |
$$ | . . X O . X O O . . . . . . . X . . . |
$$ | 2 X O O X . X . . . . . . . . . . . . |
$$ | . 1 . . . X . . . . . . . . . . . . . |
$$ ---------------------------------------[/go]

Note that 4 above is a mistake, it's better at 6, then white pushes and captures a stone and black gets to defend at f5 and the corner will be a ko. So 3 was also a mistake, it should be at the vital point of 6 too and white is then successful in turning the black corner into 1 eye in sente as before and f5 push and cut. So 2 was also a mistake, see later.

So next white pushes and cuts, and that handy b1 hane means black can no longer connect under in sente, only gote. A big difference.
Click Here To Show Diagram Code
[go]$$Wcm7 Gote connection under. 96%.
$$ ---------------------------------------
$$ | . . . . . . O . O X X . . . . . . . . |
$$ | . O X X . X O O O O X X X X X . O . . |
$$ | . . O X . X X O O X X O O O . X O . . |
$$ | . . O O X . . . O O X . X O X X O . . |
$$ | . . . . . X X X X O X X X X O X O . . |
$$ | . . O . . O . O X O O O X X O X X O . |
$$ | . O . . . O . O O X . O O O O X X O . |
$$ | . X O O . . . . . X . O . O O X O . . |
$$ | X . X . X . . X O . X X O O X O O . . |
$$ | . . . X . . X . . , X O X O X X . . . |
$$ | . X X O X X O X X X . O X X . X . . . |
$$ | . . O O O O O O O O O O . X X . . . . |
$$ | . O O . 9 7 5 . . . X O . X O O . . . |
$$ | O . O X X 2 3 4 . . X O . X O X . . . |
$$ | . O X O X 1 X . . . X X . X O . . . . |
$$ | X X X O O O X . 6 , . . . . O , . . . |
$$ | . . X O . X O O . . . . . . . X . . . |
$$ | X X O O X . X . . . . . . . . . . . . |
$$ | 0 O . 8 . . X . . . . . . . . . . . . . |
$$ ---------------------------------------[/go]


So if white hanes in the corner it's better for black to make the hanging connection. Now if white wants to reduce it to 1 eye (best) its gote instead of sente like it was with the descent. If black f5 white can tenuki as the corner is still a ko, so black probably plays in lower right.
Click Here To Show Diagram Code
[go]$$Wc Hanging. 85%
$$ ---------------------------------------
$$ | . . . . . . O . O X X . . . . . . . . |
$$ | . O X X . X O O O O X X X X X . O . . |
$$ | . . O X . X X O O X X O O O . X O . . |
$$ | . . O O X . . . O O X . X O X X O . . |
$$ | . . . . . X X X X O X X X X O X O . . |
$$ | . . O . . O . O X O O O X X O X X O . |
$$ | . O . . . O . O O X . O O O O X X O . |
$$ | . X O O . . . . . X . O . O O X O . . |
$$ | X . X . X . . X O . X X O O X O O . . |
$$ | . . . X . . X . . , X O X O X X . . . |
$$ | . X X O X X O X X X . O X X . X . . . |
$$ | . . O O O O O O O O O O . X X . . . . |
$$ | . O O . . . . . . . X O . X O O . . . |
$$ | 5 . O X X . . . . . X O . X O X . . . |
$$ | . 3 X O X . X . . . X X . X O . . . . |
$$ | . 4 X O O O X . . , . . . . O , . . . |
$$ | 2 . X O . X O O . . . . . . . X . . . |
$$ | . X O O X . X . . . . . . . . . . . . |
$$ | . 1 . . . X . . . . . . . . . . . . . |
$$ ---------------------------------------[/go]


If instead of 3 above white pushes and cuts then black can sort-of live in the corner next (thought lower right may be bigger).
Click Here To Show Diagram Code
[go]$$Wc Hanging then cut. 76%
$$ ---------------------------------------
$$ | . . . . . . O . O X X . . . . . . . . |
$$ | . O X X . X O O O O X X X X X . O . . |
$$ | . . O X . X X O O X X O O O . X O . . |
$$ | . . O O X . . . O O X . X O X X O . . |
$$ | . . . . . X X X X O X X X X O X O . . |
$$ | . . O . . O . O X O O O X X O X X O . |
$$ | . O . . . O . O O X . O O O O X X O . |
$$ | . X O O . . . . . X . O . O O X O . . |
$$ | X . X . X . . X O . X X O O X O O . . |
$$ | . . . X . . X . . , X O X O X X . . . |
$$ | . X X O X X O X X X . O X X . X . . . |
$$ | . . O O O O O O O O O O . X X . . . . |
$$ | . O O . . 9 7 . . . X O . X O O . . . |
$$ | . X O X X 4 5 6 . . X O . X O X . . . |
$$ | . . X O X 3 X . . . X X . X O . . . . |
$$ | . . X O O O X . 8 , . . . . O , . . . |
$$ | 2 . X O 0 X O O . . . . . . . X . . . |
$$ | . X O O X . X . . . . . . . . . . . . |
$$ | . 1 . . . X . . . . . . . . . . . . . |
$$ ---------------------------------------[/go]

13 doesn't work because black can connect under with 16, and although there is a ko at a2 black winning it is atari so nigh on impossible for white to fight.
Click Here To Show Diagram Code
[go]$$Wcm11 Hanging then cut contd. 76%
$$ ---------------------------------------
$$ | . . . . . . O . O X X . . . . . . . . |
$$ | . O X X . X O O O O X X X X X . O . . |
$$ | . . O X . X X O O X X O O O . X O . . |
$$ | . . O O X . . . O O X . X O X X O . . |
$$ | . . . . . X X X X O X X X X O X O . . |
$$ | . . O . . O . O X O O O X X O X X O . |
$$ | . O . . . O . O O X . O O O O X X O . |
$$ | . X O O . . . . . X . O . O O X O . . |
$$ | X . X . X . . X O . X X O O X O O . . |
$$ | . . . X . . X . . , X O X O X X . . . |
$$ | . X X O X X O X X X . O X X . X . . . |
$$ | . . O O O O O O O O O O . X X . . . . |
$$ | 6 O O . 1 O O . . . X O . X O O . . . |
$$ | 2 X O X X X O X . . X O . X O X . . . |
$$ | . 4 X O X O X . . . X X . X O . . . . |
$$ | 5 3 X O O O X . X , . . . . O , . . . |
$$ | X . X O X X O O . . . . . . . X . . . |
$$ | . X O O X . X . . . . . . . . . . . . |
$$ | . O . . . X . . . . . . . . . . . . . |
$$ ---------------------------------------[/go]


So that's what white should do. But Iyama didn't hane in the corner but just captured the outside stone directly. LZ says this lost 42%, white down from 85 to 43%.
Click Here To Show Diagram Code
[go]$$Wc Capture a stone. 43%
$$ ---------------------------------------
$$ | . . . . . . O . O X X . . . . . . . . |
$$ | . O X X . X O O O O X X X X X . O . . |
$$ | . . O X . X X O O X X O O O . X O . . |
$$ | . . O O X . . . O O X . X O X X O . . |
$$ | . . . . . X X X X O X X X X O X O . . |
$$ | . . O . . O . O X O O O X X O X X O . |
$$ | . O . . . O . O O X . O O O O X X O . |
$$ | . X O O . . . . . X . O . O O X O . . |
$$ | X . X . X . . X O . X X O O X O O . . |
$$ | . . . X . . X . . , X O X O X X . . . |
$$ | . X X O X X O X X X . O X X . X . . . |
$$ | . . O O O O O O O O O O . X X . . . . |
$$ | . O O . . . . . . . X O . X O O . . . |
$$ | 3 . O X X . . . . . X O . X O X . . . |
$$ | . 1 X O X . X . . . X X . X O . . . . |
$$ | . 2 X O O O X . . , . . . . O , . . . |
$$ | . . X O . X O O . . . . . . . X . . . |
$$ | . X O O X . X . . . . . . . . . . . . |
$$ | . . . . . X . . . . . . . . . . . . . |
$$ ---------------------------------------[/go]


But this is only if black descends at the vital point in the corner. White can then push and cut as before, but black connects underneath in sente and can move to the lower right. Admittedly black doesn't actually connect to an alive group as he can't get e3 too and LZ might throw away the whole group later in a trade for p4 group later... LZ gives black 52% now.
Click Here To Show Diagram Code
[go]$$Bcm4 Descend, connect under, 48%.
$$ ---------------------------------------
$$ | . . . . . . O . O X X . . . . . . . . |
$$ | . O X X . X O O O O X X X X X . O . . |
$$ | . . O X . X X O O X X O O O . X O . . |
$$ | . . O O X . . . O O X . X O X X O . . |
$$ | . . . . . X X X X O X X X X O X O . . |
$$ | . . O . . O . O X O O O X X O X X O . |
$$ | . O . . . O . O O X . O O O O X X O . |
$$ | . X O O . . . . . X . O . O O X O . . |
$$ | X . X . X . . X O . X X O O X O O . . |
$$ | . . . X . . X . . , X O X O X X . . . |
$$ | . X X O X X O X X X . O X X . X . . . |
$$ | . . O O O O O O O O O O . X X . . . . |
$$ | . O O . b 0 6 . . . X O . X O O . . . |
$$ | O . O X X 3 4 5 . . X O . X O X . . . |
$$ | . O X O X 2 X . . . X X . X O . . . . |
$$ | 8 X X O O O X . 7 , . . . . O , . . . |
$$ | . 9 X O . X O O . . . . . . . X . . . |
$$ | . X O O X . X . . . . . . . . . . . . |
$$ | . 1 . a . X . . . . . . . . . . . . . |
$$ ---------------------------------------[/go]


But instead Yamashite played the a4 decent to prevent that atari, -47% says LZ, but then Iyama got to hane in the corner and it ends up sort of like if white played the hane first. If black plays a2 white can just push and cut and black only has the pathetic gote connection like before, so black defended f5 and the corner will be a ko, but white gets sente and is at 91%.

Click Here To Show Diagram Code
[go]$$Bcm4 Yamashita's counter-mistake. White 91%.
$$ ---------------------------------------
$$ | . . . . . . O . O X X . . . . . . . . |
$$ | . O X X . X O O O O X X X X X . O . . |
$$ | . . O X . X X O O X X O O O . X O . . |
$$ | . . O O X . . . O O X . X O X X O . . |
$$ | . . . . . X X X X O X X X X O X O . . |
$$ | . . O . . O . O X O O O X X O X X O . |
$$ | . O . . . O . O O X . O O O O X X O . |
$$ | . X O O . . . . . X . O . O O X O . . |
$$ | X . X . X . . X O . X X O O X O O . . |
$$ | . . . X . . X . . , X O X O X X . . . |
$$ | . X X O X X O X X X . O X X . X . . . |
$$ | . . O O O O O O O O O O . X X . . . . |
$$ | . O O . . . . . . . X O . X O O . . . |
$$ | O . O X X . . . . . X O . X O X . . . |
$$ | . O X O X 3 X . . . X X . X O . . . . |
$$ | 1 X X O O O X . . , . . . . O , . . . |
$$ | . . X O . X O O . . . . . . . X . . . |
$$ | . X O O X . X . . . . . . . . . . . . |
$$ | . 2 . . . X . . . . . . . . . . . . . |
$$ ---------------------------------------[/go]


So is there something wrong in this analysis, a move LZ overlooked or dubious judgement? I don't think Iyama could have been scared of the ko in LZ's correct answer, seeing as he went for a ko in the game anyway.


This post by Uberdude was liked by 4 people: Elom, mhlepore, sorin, Waylon
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 Post subject: Re: Following Iyama Yuta (no world ranking discussions)
Post #345 Posted: Sat Feb 09, 2019 12:22 pm 
Lives with ko

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Ah very cool - thanks Uberdude. There was a messy fight right from the start so I really had no idea of the goof was earlier or not.

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 Post subject: Re: Following Iyama Yuta (no world ranking discussions)
Post #346 Posted: Sat Feb 09, 2019 1:10 pm 
Judan

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LZ thought there were some mistakes in the early fights around 10%, but it's quite rare to have almost 50% ones in pro games.

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 Post subject: Re: Following Iyama Yuta (no world ranking discussions)
Post #347 Posted: Thu Feb 14, 2019 1:58 am 
Judan

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Iyama beat Yamashita in the 4th Kisei game to take a 3-1 lead.

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