It is currently Sun Apr 30, 2017 9:36 am

All times are UTC - 8 hours [ DST ]




Post new topic Reply to topic  [ 5 posts ] 
Author Message
Offline
 Post subject: Help with open ko (japanese rule)
Post #1 Posted: Mon Feb 01, 2016 4:25 pm 
Lives with ko

Posts: 176
Liked others: 0
Was liked: 30
Rank: kgs 6 kyu
KGS: Pio2001
Hi,
I've just played the following game in kgs, in japanese rule.

I guess that the black group on the right side is dead, but how do I prove it if Black doesn't connect the ko ?


Attachments:
open_ko.sgf [7.47 KiB]
Downloaded 183 times
Top
 Profile  
 
Offline
 Post subject: Re: Help with open ko (japanese rule)
Post #2 Posted: Mon Feb 01, 2016 4:30 pm 
Dies with sente

Posts: 118
Liked others: 2
Was liked: 13
Think about it similarly to the corner bent-four: one side can attempt to kill, but the other side cannot attempt to live.

Top
 Profile  
 
Offline
 Post subject:
Post #3 Posted: Mon Feb 01, 2016 5:53 pm 
Judan
User avatar

Posts: 7344
Location: Santa Barbara, CA
Liked others: 267
Was liked: 1646
GD Posts: 312
Hi Pio,
Click Here To Show Diagram Code
[go]$$
$$ -----------
$$ | O . O O |
$$ | . O O X |
$$ | O O X . |
$$ | O X X X |
$$ | O X . . |
$$ | O X O . |
$$ | O X . X |
$$ | O X X X |
$$ -----------[/go]
I don't know if this is helpful or more confusing --
for your particular board, you can think of it as reduced to the above situation.

White can, at any time she wishes, eventually remove all the Black stones off the board;
there is nothing Black can do to stop it from happening.

( If Black disagrees, you can easily play it out.
Of course, in the process to reduce Black's liberties,
White will have to sacrifice a few White stones --
but the local status of this Black group is dead. )

For your particular board, even if there are any ko threats elsewhere,
White can reply to every single one of them; even if Black wins the 0.5 ko and connects,
it doesn't change the status -- Black is still dead as a group.


This post by EdLee was liked by: Bill Spight
Top
 Profile  
 
Offline
 Post subject: Re: Help with open ko (japanese rule)
Post #4 Posted: Tue Feb 02, 2016 12:08 am 
Tengen

Posts: 4357
Liked others: 0
Was liked: 574
Verify the death of the black stones. Verify the life of the white stone. For each imagined verification, study the game tree and decicion-making. Necessarily, White can establish a white two-eye-formation on the intersections of and around the black group and the initial single white stone. Simply speaking, the basic ko rule applies. Whenever Black captures the ko, White plays an arbitrary move as a ko threat and next rcaptures the ko. Whenever Black plays a move elsewhere on the board, White recaptures the ko if possible. Black's plays elsewhere do not affect the local life verification because of not preventing White from establishing a local two-eye-formation.

See also my rules webpage. KGS-Japanese Rules are ambiguous so they require other Japanese rulesets as context rulesets. This is the real complication when assessing the life an death because it must be done for each existing Japanese ruleset and commentary ruleset. It turns out that each existing relevant ruleset assesses the statuses equally. However, for some of them, passes as ko threats and definitions of locality are relevant. For the details see my webpage.

Naive conclusion: treat it like a book life and death problem: the black group is dead. Detailed conclusion: KGS-Japanese Rules are ambiguous but many hours of rules expert analysis confirm the death of the black stones and the life of the white stone.

Top
 Profile  
 
Offline
 Post subject: Re: Help with open ko (japanese rule)
Post #5 Posted: Tue Feb 02, 2016 5:21 am 
Lives with ko

Posts: 176
Liked others: 0
Was liked: 30
Rank: kgs 6 kyu
KGS: Pio2001
Thank you all for the answers !

Top
 Profile  
 
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 5 posts ] 

All times are UTC - 8 hours [ DST ]


Who is online

Users browsing this forum: No registered users and 2 guests


You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot post attachments in this forum

Search for:
Jump to:  
Powered by phpBB © 2000, 2002, 2005, 2007 phpBB Group