It is currently Thu Mar 28, 2024 7:39 am

All times are UTC - 8 hours [ DST ]




Post new topic Reply to topic  [ 3 posts ] 
Author Message
Offline
 Post subject: Dieter's ABC of mistakes - 6
Post #1 Posted: Thu Apr 01, 2021 8:16 am 
Oza
User avatar

Posts: 2408
Location: Ghent, Belgium
Liked others: 359
Was liked: 1019
Rank: KGS 2d OGS 1d Fox 4d
KGS: Artevelde
OGS: Knotwilg
Online playing schedule: UTC 18:00 - 22:00
Click Here To Show Diagram Code
[go]$$c Mistake 6
$$ ---------------------------------------
$$ | . . . O . . . . a . . . . . . . . . . |
$$ | . X O X X O O X X O . . . . X X X X . |
$$ | . X O X . O X . X O . . X X O X . . X |
$$ | X X O X . O X . X O . O X O O O X X . |
$$ | . O X X X O X . . X X O O X O X O O . |
$$ | O . O O O O X . b X O O . . O X O . . |
$$ | . O . O . O . X X O X O . . O X O . . |
$$ | X . O . X O O X O O . . X . . X . . . |
$$ | X O . . X . X O . . . . . O X X X O . |
$$ | . X X , . . X O . O . . . O O X O . . |
$$ | 1 O X . . . X O . O X . . . . O O . . |
$$ | O . O X . . X X . X O . . . . . . . . |
$$ | . O O . . . . . . X O . . . . . . . . |
$$ | . . . . . . . . . X O . O . . . . . . |
$$ | . . . O . . X . O O X O . . . . . . . |
$$ | . . O , . . . . . , X X O O O O O O . |
$$ | . . O X . . X . . . . X X O X X X X . |
$$ | . X X . . . . . . . . . c X . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------[/go]


A [ko] has developed along the left side. Which ko threat should White play, ''a'', ''b'' or ''c''?


Last edited by Uberdude on Mon Apr 12, 2021 11:27 pm, edited 1 time in total.
Added coordinates

Top
 Profile  
 
Offline
 Post subject: Re: Dieter's ABC of mistakes - 6
Post #2 Posted: Fri Apr 02, 2021 3:02 pm 
Gosei
User avatar

Posts: 1753
Liked others: 177
Was liked: 491
If White wins the ko then White kills 3 black stones and connects two groups which become completely safe.

If Black wins the ko and White can't connect his group, then Black kills 18 white stones, gets a few extra points of territory, and puts pressure on the lower left white group.

I don't know how to calculate the value K of the ko but it must be at least 50 points. That's gigantic.

White has two local ko threats at "b", one at E19 and one at "a". The moves at "b" threaten to save 18 white stones, kill 14 black stones and make a few intersection switch hands. There may be a capturing race but anyway it is clear that the value of the ko threats at "b" is larger than K. The ko threat at E19 is a bit smaller but still maybe larger than K. On the other hand, a move at "a" only threatens to save 18 white stones, so is worth about 36 points. The ko threat at "c" is of similar size.

On the other hand, Black has 2 big ko threats around O14 which are worth about 40 points, and otherwise nothing very big. So in principle White should win the ko.

In general the players start with the largest ko threat but this is not always true. If several ko threats that work (i.e. to which the opponent will necessarily respond) are available then it is better to use the smallest ko threat that work, and save larger ones for the future.

The ko threats at "b" certainly work, maybe the one at E19 too, but I am not sure that the ko threats at "a" and "c" are enough.


This post by jlt was liked by: Knotwilg
Top
 Profile  
 
Offline
 Post subject: Re: Dieter's ABC of mistakes - 6
Post #3 Posted: Mon Apr 12, 2021 4:42 pm 
Oza
User avatar

Posts: 2408
Location: Ghent, Belgium
Liked others: 359
Was liked: 1019
Rank: KGS 2d OGS 1d Fox 4d
KGS: Artevelde
OGS: Knotwilg
Online playing schedule: UTC 18:00 - 22:00
Solution

B, the ko threat that threatens to capture and creates a subsequent ko threat at D

Click Here To Show Diagram Code
[go]$$ Mistake 6
$$ ---------------------------------------
$$ | . . . O . . . . a . . . . . . . . . . |
$$ | . X O X X O O X X O . . . . X X X X . |
$$ | . X O X . O X . X O . . X X O X . . X |
$$ | X X O X . O X . X O . O X O O O X X . |
$$ | . O X X X O X . 3 X X O O X O X O O . |
$$ | O . O O O O X . 2 X O O . . O X O . . |
$$ | . O . O . O d X X O X O . . O X O . . |
$$ | X . O . X O O X O O . . X . . X . . . |
$$ | X O . . X . X O . . . . . O X X X O . |
$$ | . X X , . . X O . O . . . O O X O . . |
$$ | 1 O X . . . X O . O X . . . . O O . . |
$$ | O . O X . . X X . X O . . . . . . . . |
$$ | . O O . . . . . . X O . . . . . . . . |
$$ | . . . . . . . . . X O . O . . . . . . |
$$ | . . . O . . X . O O X O . . . . . . . |
$$ | . . O , . . . . . , X X O O O O O O . |
$$ | . . O X . . X . . . . X X O X X X X . |
$$ | . X X . . . . . . . . . c X . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------[/go]

Top
 Profile  
 
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 3 posts ] 

All times are UTC - 8 hours [ DST ]


Who is online

Users browsing this forum: No registered users and 1 guest


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