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 Post subject: How to answer the unsupported 4-2 submarine invasion?
Post #1 Posted: Fri Aug 24, 2018 3:15 am 
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How to answer the unsupported 4-2 submarine invasion?

Consider the large keima.


Attachment:
submarine.jpg
submarine.jpg [ 156.39 KiB | Viewed 743 times ]


possible continuation:

Attachment:
submarine2.jpg
submarine2.jpg [ 161.03 KiB | Viewed 743 times ]


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 Post subject: Re: How to answer the unsupported 4-2 submarine invasion?
Post #2 Posted: Fri Aug 24, 2018 3:27 am 
Judan

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Black's submarine seems kind of early to me, and the direction of white's shimari is odd too. The idea of playing from the outside with small knight move when your opponent plays 2-4 in inappropriate situations is something I was aware of before bots, but you probably don't see it so much in pro games (most common probably bump to keep corner) because they don't play the 2-4 in inappropriate situations so much (though probably more than we thought). What about if the submarine is played in more typical positions it is used? Also see similar idea from AG http://www.alphago-games.com/view/event ... 12/move/34.


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 Post subject: Re: How to answer the unsupported 4-2 submarine invasion?
Post #3 Posted: Fri Aug 24, 2018 4:54 am 
Judan

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Here's a pro game (black Ke Jie vs Zho Ruiyang) with a more typical usage. http://ps.waltheri.net/database/game/74620/. It's from 2016 and has the AlphaGo vs Lee Sedol game 5 opening which was popular back then but now seems so old fashioned! (small shimari, no 3-3 invasions). Black has the distant stone on the left side to support the submarine. Zhou played the classic bump to keep the corner, LZ #157 doesn't think it's so bad, just -1%, but on this position likes to take the outside with the small knight move. LZ thiks the submarine was the worst move of the game so far at -3.6% and preferred knight approach or a move on the top side.
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ke jie submarine.PNG
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 Post subject: Re: How to answer the unsupported 4-2 submarine invasion?
Post #4 Posted: Sat Aug 25, 2018 12:34 pm 
Tengen

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Today, I applied the OP move to win a qualification tournament, thanks! :)


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 Post subject: Re: How to answer the unsupported 4-2 submarine invasion?
Post #5 Posted: Tue Sep 11, 2018 6:45 am 
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Sometimes white will try this (suboptimal) move:

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

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 Post subject: Re: How to answer the unsupported 4-2 submarine invasion?
Post #6 Posted: Tue Sep 11, 2018 6:49 am 
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Possible continuations:

good for black:
Click Here To Show Diagram Code
[go]$$B
$$ ----------------------+
$$ . . . . . . . . . . . |
$$ . . . . . . . O . . . |
$$ . . . . X . 2 . . . . |
$$ . , . . . . O X . . . |
$$ . . . . . 3 1 . . . . |
$$ . . . . . . . . X . . |
$$ . . . . . . . . . . . |
$$ . . . . . . . . . . . |
$$ . . . . . . . . . . . |
$$ . , . . . . . , . . . |
$$ . . . . . . . . . . . |[/go]

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 Post subject: Re: How to answer the unsupported 4-2 submarine invasion?
Post #7 Posted: Tue Sep 11, 2018 6:54 am 
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also possible (still not good for white):

(after black connects at a, white can play tenuki)

Click Here To Show Diagram Code
[go]$$B
$$ ----------------------+
$$ . . . . . . . . . . . |
$$ . . . . . . . O . 9 . |
$$ . . . . X . 3 . 7 8 . |
$$ . , . . . . O X 2 . . |
$$ . . . . . . 1 5 4 . . |
$$ . . . . . . . a X 6 . |
$$ . . . . . . . . 0 . . |
$$ . . . . . . . . . . . |
$$ . . . . . . . . . . . |
$$ . , . . . . . , . . . |
$$ . . . . . . . . . . . |[/go]

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 Post subject: Re: How to answer the unsupported 4-2 submarine invasion?
Post #8 Posted: Tue Sep 11, 2018 6:58 am 
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Sometimes black can consider this:

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

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 Post subject: Re: How to answer the unsupported 4-2 submarine invasion?
Post #9 Posted: Tue Sep 11, 2018 7:04 am 
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Situational:

Blacks plays now at a!

Click Here To Show Diagram Code
[go]$$B
$$ ----------------------+
$$ . . . . . . . . . . . |
$$ . . . . . . 5 O . . . |
$$ . . . . X . 1 2 . 8 . |
$$ . , . . . 4 W X 6 0 . |
$$ . . . . . . 3 7 . 9 . |
$$ . . . . a . . . X . . |
$$ . . . . . . . . . . . |
$$ . . . . . . . . . . . |
$$ . . . . . . . . . . . |
$$ . , . . . . . , . . . |
$$ . . . . . . . . . . . |[/go]

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 Post subject: Re: How to answer the unsupported 4-2 submarine invasion?
Post #10 Posted: Tue Sep 11, 2018 8:23 am 
Judan

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Gomoto wrote:
Situational:

Blacks plays now at a!

Click Here To Show Diagram Code
[go]$$B
$$ ----------------------+
$$ . . . . . . . . . . . |
$$ . . . . . . 5 O . . . |
$$ . . . . X . 1 2 . 8 . |
$$ . , . . . 4 W X 6 0 . |
$$ . . . . . . 3 7 . 9 . |
$$ . . . . a . . . X . . |
$$ . . . . . . . . . . . |
$$ . . . . . . . . . . . |
$$ . . . . . . . . . . . |
$$ . , . . . . . , . . . |
$$ . . . . . . . . . . . |[/go]


What situations?

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 Post subject: Re: How to answer the unsupported 4-2 submarine invasion?
Post #11 Posted: Tue Sep 11, 2018 9:23 am 
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@Bill: Sometimes this move is best, but the continuation is heavily depending on the surrounding.


Attachments:
submarinev1.jpg
submarinev1.jpg [ 169.88 KiB | Viewed 454 times ]

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 Post subject: Re: How to answer the unsupported 4-2 submarine invasion?
Post #12 Posted: Tue Sep 11, 2018 9:33 am 
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possible continuations:


Attachments:
submarinev1b.jpg
submarinev1b.jpg [ 173.18 KiB | Viewed 452 times ]
submarinev1a.jpg
submarinev1a.jpg [ 171.76 KiB | Viewed 452 times ]
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 Post subject: Re: How to answer the unsupported 4-2 submarine invasion?
Post #13 Posted: Fri Sep 14, 2018 12:36 pm 
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2 times application of the move. (Move 46 and 52)

Poor black did not know I had a look at the 4-2 submarine already :twisted:


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