Bulky Eight in the Corner

Keywords: Life & Death, Ko
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 contentsMain lines Playing elsewhere Seki or ten thousand year ko White makes direct ko Can black avoid the direct ko and make seki? Without a Descent Table of diagramsBulky 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

Black first lives
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

White first

After 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

Seki in sente or 10,000 year ko

threatens to kill, as does . After White can play a to create a 10,000 year ko, and if White doesn't then Black can play either b to make seki. If black is komaster, white should leave the position as seki.

Ko

After , 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

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 .

Can black avoid the direct ko and make seki?

Can Black get a seki?

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

Mistake 1: Black gets seki ( at )
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.

White kills

Without a Descent

White first kills

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

White first kills

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

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 RickyDemer on February 26, 2018 - 08:30