Home > Steve > Go > Problem of the month
White is alive (as explained in J Davies "Life and Death&).
"Life and Death" covers Black attacks at A and B.
In a recent tournament game I was white and had this shape when my
opponent invaded at C. I replied at D and it developed into a seki.
Several questions:
First lets review answering A and B.
White 2 is the essential reply. There are then three pairs of miai points which leave White with two eyes (at the 1,1 point and the 2,3 point).
However there is a potential shortage of liberties if White plays this scheme blindly, the exception being shown below.
White can't play 8 at 
.
Using 8 to capture 3 only leads to a ko.
If instead 8 is played at one of the 
to gain an extra liberty, Black may
play at and White
still has insufficient liberties. It turns out that capturing at the
other as well
is sufficient. Black can't make a bent four in the corner as the next
diagram shows.
(Despite this, the simple solution to the liberty shortage is to
have played 6 at
.)
Black 13
at , White 14
throws-in at 11, Black 15 captures at , White 16 at 9 guarantees two eyes.
Alternatively White could take one eye in the corner and use the hane stones to run away for a second eye.
In this case White 2 is the essential reply. There are then two
pairs of miai points and also A & B which are normally miai.
Sometimes B and the upper need care.
In this situation White must not mindlessly play 8 at in answer to 7.
Otherwise Black will capture 2 with 9 and then it is ko.
All White needs to do is to capture 5 with 8 for 2 real eyes.
Moves 2 to 6 force a seki.
If 7' is at 8, then White worms out at the top instead of down at the
left.
The remaining moves demonstrate a possible advantage of the seki -
namely that White can push into one of the two sides (Black's choice of
which one). Compared to living in the corner, this appears be
better by around 7 points, but you have to deduct the territory not
gained in corner.
Jim Cox emailed me pointing out that here, Dia 7, White has sente after
Black plays 15 and he has "7" points (IE Black has lost 7
points.) In Dia 8, White 6 is gote (and the remaining moves are not
urgent and won't be played until later) and he only gets 4 points.
So the seki is 3 points better for White and, more importantly, is
sente.
Two eyes and four points. No apparent way to push at all.
The game which this occurred in was an interesting one. I was Black. White played mirror go for many moves, then I played in the central point and started playing mirror go following his moves! Around move 60 I deviated from mirrorring and a battle occurred in the corner with the above seki resulting. Due to the strange fuseki, his surrounding stones were eventually captured thus un-seki-ing the corner. :-)
Home >
Steve >
Go >
Problem of the month
British Go Association
Last updated 2004-08-10
This page is part of http://www.stocton.org/
Email: webmaster@stocton.org