TFG9 Black Upper Left 2

    Keywords: Problem

Dave analyzed the following sequence extensively in TFG9 Black Upper Left and concluded that Black will live:

Line analyzed previously  

Let's look at an alternative for White 2:

An alternative for White 2  

White 2 here is severe.

Connection is not an option  

Connceting with Black 1 is not an option. Black has to try harder.

The fight for liberties  

Black 1 looks promising, but White simply captures at 2. And no matter what Black tries, he will end up with one liberty short.

Ko? (4 above 2)  

Black 1 invites a white capture at 2. After that all White needs to do is to connect the ko (assuming that the ko is large enough to win the game, and we only consider local ko threats).

One line is shown in the diagram. Black has no chance.

So looking at the above diagrams, it looks like Black 1 in the first diagram does not help Black at all: he doesn't even get a ko.

What else is there to do?


DaveSigaty: The problem here is that Black does have two internal ko threats. (Arno, note that in your original "Ko?" diagram you had inadvertently filled in the liberty at a so I fixed it - this changes the result greatly :-)

Ko? (4 above 2)  
  • Black 5 at the marked stone.
  • White 8 at 2
  • White 10 at 3. Note that 9 again raises the question of the game situation on the rest of the board. Here I assume that White answers the ko threat. If White connects at the marked stone and Black captures at 3 and connects next move (ignoring White's ko threat), who wins?
Ko? (4 above 2)  
  • White 4 recaptures at the marked stone.
  • Black 7 captures the ko at 3
  • White 8 might be somewhere else if there were a larger ko threat on the board.
  • Black 9 connects the ko

After the exchange of Black a for White b both sides have lived. Who is winning the game?

TFG9 Black Upper Left 2 last edited by Unkx80 on April 17, 2004 - 22:00
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