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August 1998's Go Answer of the Month

This is problem 23 from "Graded Go Problems for Beginners Volume 2".

GGP's question is "How does Black play?"

My question is inspired by a dissatisfaction with their answer. I am happy with GGP's black 1, but feel that GGP's white 2 is poor. I suspect white 2 is used just to demonstrate a point.

Dia 1 - Black 1 and White 2?

Find black 1, both white 2s and then work out the relative value of them.

Dia 2 - The book answer.

"Black 1 and 3 catch two white stones. White's territory has been devastated."

Note that the answers published here are my 2 kyu thoughts and may well be incorrect - especially if sente and gote are taken properly into account, concepts I am only starting to get to grips with properly.

Dia 3 - Devastated.

This is what would be likely to happen if both players played on from Dia 2. It shows the white territory significantly reduced.

What is each move worth?

Working backwards ...

• 11 is forced, else 12' puts Black 1, 3, 5 etc into atari and captures them, recovering about 20 points.
• 10's block is worth 1 point in sente.
• 9 is gote for the two points.
• 8 prevents Black haneing followed by a double atari, which would be a loss of about ten points.
• 7 is two points in sente.
• 6 prevents nasty double ataris.
• 4 is damage limitation.
  How much more damage can occur if 4 is omitted? Yet to be determined.

Given this, I would expect the above sequence to be played with either White omitting 4 or Black omitting 9 to take sente elsewhere.

Dia 4 - The other "2".

Here Black gains a net 2 prisoners and 1 point from pushing with 5.

Dia 5 - Counting.

If we count the territory surrounded (and including) the points, we come up with the answer:

• Dia 3 (as drawn). Black gote.
  • White has 9 territory + 1 prisoner points = 10
  • Black has 5 territory + 2 prisoner points = 7
  • Net 3 points to White.
• Dia 3 (Black plays 9 elsewhere, White 10' at 9). Black sente.
  • White has 9 territory + 1 prisoner points = 10
  • Black has 3 territory + 2 prisoner points = 5
  • Net 5 points to White.
• Dia 4. Black sente.
  • White has 14 territory + 1 prisoner points = 15
  • Black has 4 territory + 3 prisoner points = 7
  • Net 8 points to White.

Conclusion: Dia 4, the other "2" is better for White by 3 (or 5) points than the book answer. The choice is white's privilege.
I am not sure at present how to evaluate what happens if White tenukis with 4' in dia 3.

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