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October 1998's Go Answer of the Month

This month's problem is taken from a professional game between Takagawa Kaku and Handa Dogen which I have been studying as part of Matthew Macfadyen's correspondence course.

Dia 1 - What happened next?

Dia 1
Black has captured 6 prisoners, White 4 and the komi to White is 5½.

In this diagram I show three moves: 180-182. This month's question is what are the next two moves and more importantly why?

The first thing to do when presented with a whole board situation like this (and indeed in your own games after some major status change) is to evaluate the situation - who has what.

White has territory at the top, with a bulge into the centre. Exactly how far the bulge goes will need to be determined. Black has the top right corner, and upon closer inspection the right side, having captured 6 stones. Black also has the lower right corner. White has the lower side and the bottom left corner. Black has a small group on the left side and the rest of the centre is a muddle which needs resolving.

Dia 2 - Counting.

Dia 2

Let's count the territories which are defined and see what is left.
White A: 38, B: 15, E: 27, prisoners & komi 9.5. Total: 89.5
Black C: 58, D: 13, F: 8, prisoners 6. Total: 85
So the countable area is fairly close.

What is happening in the middle?
There are 10 black stones towards the right under attack and six white stones also under attack. The upper black group is solidly connected to the F group on the left edge. There are another 6 white stones between B and F which look to be floating.
There is a ko in the middle of the area.

If all of these groups live, the score will not change much from that counted.
If the black group dies, White will win easily.
If the black group lives, it looks hard for the white stones (as 2 groups or joined as 1 large group) to connect out. This would be a win for Black, even if only the upper white stones were captured and the lower 6 linked out.

So it seems to all come down to a capturing race for the black stones.

Black 183 and White 184

Black therefore played 183 to capture the White stone and link his stones out towards the lower left.

White 184 resigned.

This result surprised me as I thought White could connect his central stones out the the E group whilst cutting an even larger Black group off, or at least managing something with the central ko.

The following sequence (including the move 183 actually made) demonstrates White's problem.

Dia 3 - White's problem.

Dia 3

The game record as an Ishi format file is available.

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