Bulky Eight in the Corner

    Keywords: Life & Death, Ko
[Diagram]
Bulky Eight in the corner  

This is the basic bulky eight in the corner. a is the vital point. If black plays there, he is alive with 7 points in the corner.

If white plays a, he can achieve either ko or seki, but cannot kill outright. Optimal play depends upon the ko threat situation.

This position is proof against the idea that an eight point eye in the corner without cutting points is alive.

-- Analysis by Bill Spight.


Table of contents Table of diagrams
Bulky Eight in the corner
Black first lives
White first makes [10,000 year ko] or better
White first
Seki in sente or [10,000 year ko]
Ko
White makes ko
Can Black get a seki?
Mistake 1: Black gets seki (B8 at B2)
Mistake 2: Black gets seki (See [seki inside the bulky five])
White kills
White first kills
White first kills
White first kills

Main lines

[Diagram]
Black first lives  
[Diagram]
White first makes 10,000 year ko or better  

Next we shall show play when White plays first and discuss which choices white should make depending on who is komaster.

Playing elsewhere

[Diagram]
White first  

After W1 the temperature drops, which means black can choose to play elsewhere. Next White could kill Black, but White typically does better to wait. Giving black two moves elsewhere in exchange for this corner is usually not good enough. Either Black or White will then come back to this position later in the game, when it is big enough.


Seki or ten thousand year ko

[Diagram]
Seki in sente or 10,000 year ko  

W1 threatens to kill, as does W3. After B4 White can play a to create a 10,000 year ko. If black is komaster, white should leave the position as seki

[Diagram]
Ko  

After W5, the position is a ten thousand year ko. Black will often start the ko immediately, and may choose to lose it in exchange for a play elsewhere. This is usually better than waiting until the end of the game, when White can often win the ko for free.

White makes direct ko

[Diagram]
White makes ko  

This way, white gets a direct ko for the life of the black group. This line of play is usually not best for White, normally a is better than W3.


Can black avoid the direct ko and make seki?

[Diagram]
Can Black get a seki?  

B4 here is a trick play. The idea behind this move is that White might make a mistake with W5 and settle for a seki, as shown in the following two diagrams.


[Diagram]
Mistake 1: Black gets seki (B8 at B2)  
[Diagram]
Mistake 2: Black gets seki (See seki inside the bulky five)  


But White can play better-- the following line kills the Black group. Hence, Black has to settle for the direct two stage ko.

[Diagram]
White kills  


Without a Descent

[Diagram]
White first kills  

What happens if black is missing a descent? In this case, Black is dead...

[Diagram]
White first kills  

In this case, 4 and 5 are miai to kill for white.

[Diagram]
White first kills  

And black playing on the other side is no better. (Black has a shortage of liberties and cannot play at 6.)




Bulky Eight in the Corner last edited by 64.85.251.110 on August 13, 2014 - 05:37
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