Life In 19x19

So this happened in a recent game, where I got a L+2 group (in theory alive with points) and played endgame descents thinking this was enough to get 8 points in that corner. Then my opponent played this :

Click Here To Show Diagram Code

[go]$$B Black to play
$$ ------------------
$$ | . . a . X O . . .
$$ | b W . X X O . . .
$$ | . X X X O O . . .
$$ | X X O O O . . . .
$$ | O O O . . . . . .
$$ | . . . . . . . . .
$$ | . . . . . . . . .
$$ | . . . . . . . . .
$$ | . . . . . . . . .[/go]

And it seems that a and b are miai, and black is left with the choice of either fighting a ko (which I couldn't win in this game) or a seki (since white can either make B's eye false or make an eye himself and black is short of liberties). Fortunately even with the loss of point it was still enough to win the game, but clearly this shouldn't have happened.

Well first, I think I'm reading this corner correctly, but if I missed a way to live with points I do hope someone stronger will point it out. More importantly, then, is what would have been a better way to play the endgame to maximize the points I got from this corner.

I think you are correct about the seki (or ko). To avoid it, just make an eye before your liberties are filled.

Let me refer you to this Sensei's page. https://senseis.xmp.net/?L2GroupWithDescent

Bki wrote:...black is left with the choice of either fighting a ko (which I couldn't win in this game) or a seki ...but clearly this shouldn't have happened...

Actually, it should happen. If you have inadequate ko threats, the best play by both sides is a seki.

Look at it this way: a pro could not have played it better than you did. For several moves, you were playing like a pro.

Joaz Banbeck wrote:

Bki wrote:...black is left with the choice of either fighting a ko (which I couldn't win in this game) or a seki ...but clearly this shouldn't have happened...

Actually, it should happen. If you have inadequate ko threats, the best play by both sides is a seki.

Look at it this way: a pro could not have played it better than you did. For several moves, you were playing like a pro.

Actually, at least one of the descents was probably a mistake.

Bill Spight wrote:

Joaz Banbeck wrote:

Bki wrote:...black is left with the choice of either fighting a ko (which I couldn't win in this game) or a seki ...but clearly this shouldn't have happened...

Actually, it should happen. If you have inadequate ko threats, the best play by both sides is a seki.

Look at it this way: a pro could not have played it better than you did. For several moves, you were playing like a pro.

Actually, at least one of the descents was probably a mistake.

My comment was about the play starting from the OPs diagram.

Joaz Banbeck wrote:

Bki wrote:...black is left with the choice of either fighting a ko (which I couldn't win in this game) or a seki ...but clearly this shouldn't have happened...

Actually, it should happen. If you have inadequate ko threats, the best play by both sides is a seki.

Look at it this way: a pro could not have played it better than you did. For several moves, you were playing like a pro.

Joaz Banbeck wrote:

Bill Spight wrote:Actually, at least one of the descents was probably a mistake.

My comment was about the play starting from the OPs diagram.

Thanks for making that clear.

It has been suggested that the problem arose only after he ignored White filling the last dame. It was probably before that.

Bki wrote:...but clearly this shouldn't have happened...

I think Bki is simply saying that, had he known that the corner could become a seki, black playing a move there to ensure it is ~7 points of territory is thus a ~7 point gote move and bigger than the presumably smaller moves he played instead during this phase of the endgame. (This is correct.)

Bki wrote:More importantly, then, is what would have been a better way to play the endgame to maximize the points I got from this corner.

Well, what is outside the corner matters for the endgame.

Click Here To Show Diagram Code

[go]$$Bc Black to play
$$ ------------------
$$ | . . . . b . . . .
$$ | . . . X X O . . .
$$ | . X X X O O . . .
$$ | a X O O O . . . .
$$ | c O O . . . . . .
$$ | . . . . . . . . .
$$ | . . . . . . . . .
$$ | . . . . . . . . .
$$ | . . . . . . . . .[/go]

For instance, a, b, or c is sente for White, but then, after securing the corner Black has a sente hane-connect.

Click Here To Show Diagram Code

[go]$$Bc Black to play
$$ ------------------
$$ | . . . . . . . . .
$$ | . . . X X O . . .
$$ | . X X X O . O . .
$$ | . X O O O . . . .
$$ | . O , . . . . . .
$$ | . . O . . . . . .
$$ | . . . . . . . . .
$$ | . . . . . . . . .
$$ | . . . . . . . . .[/go]

For reference, here is a simpler position where Black has no sente. What is Black's play?

Click Here To Show Diagram Code

[go]$$Bc Black to play
$$ ------------------
$$ | . a . . . . . . .
$$ | . 1 . X X O . . .
$$ | . X X X O . O . .
$$ | . X O O O . . . .
$$ | . O , . . . . . .
$$ | . . O . . . . . .
$$ | . . . . . . . . .
$$ | . . . . . . . . .
$$ | . . . . . . . . .[/go]

After or Ba, the rest is miai.

Click Here To Show Diagram Code

[go]$$Bc Miai
$$ ------------------
$$ | C C C 3 2 4 C . .
$$ | C B C X X O . . .
$$ | C X X X O . O . .
$$ | 7 X O O O . . . .
$$ | 5 O , . . . . . .
$$ | 6 . O . . . . . .
$$ | . . . . . . . . .
$$ | . . . . . . . . .
$$ | . . . . . . . . .[/go]

In the marked region, Black gets 6 pts. in the corner and WHite gets 1 pt. outside, for a net result to Black of 5 pts.

What is the result if Black plays a descent instead?

Click Here To Show Diagram Code

[go]$$Bc Black to play
$$ ------------------
$$ | . 4 2 . 1 . . . .
$$ | 6 3 . X X O . . .
$$ | . X X X O . O . .
$$ | 5 X O O O . . . .
$$ | . O , . . . . . .
$$ | . . O . . . . . .
$$ | . . . . . . . . .
$$ | . . . . . . . . .
$$ | . . . . . . . . .[/go]

If , causes difficulties for Black. leads to seki, possibly ko later. at 4 lets White make ko. This descent is not good.

Click Here To Show Diagram Code

[go]$$Bc Black to play
$$ ------------------
$$ | . 4 5 . 6 . C . .
$$ | 3 2 . X X O . . .
$$ | C X X X O . O . .
$$ | 1 X O O O . . . .
$$ | 7 O , . . . . . .
$$ | 8 . O . . . . . .
$$ | . . . . . . . . .
$$ | . . . . . . . . .
$$ | . . . . . . . . .[/go]

If , threatens the corner. Black keeps sente, but the net result is 4 pts. for Black, 5 pts. for Black in the corner minus 1 pt. outside for White. This descent may be correct, depending on the rest of the board.

Click Here To Show Diagram Code

[go]$$Wc White to play
$$ ------------------
$$ | C C C 4 3 5 C . .
$$ | C 2 C X X O . . .
$$ | 6 X X X O . O . .
$$ | 1 X O O O . . . .
$$ | 7 O , . . . . . .
$$ | C . O . . . . . .
$$ | . . . . . . . . .
$$ | . . . . . . . . .
$$ | . . . . . . . . .[/go]

White to play can hold the net result for Black to 3 pts., 5 pts. for Black in the corner minus 2 pts. for White outside. The Black descent at 1 prevents that with sente. This position is ambiguous, as Black can choose to play sente or gote.

Click Here To Show Diagram Code

[go]$$Wc White to play, II
$$ ------------------
$$ | . 2 . 6 1 7 . . .
$$ | . . . X X O . . .
$$ | 4 X X X O . O . .
$$ | 3 X O O O . . . .
$$ | 5 O , . . . . . .
$$ | . . O . . . . . .
$$ | . . . . . . . . .
$$ | . . . . . . . . .
$$ | . . . . . . . . .[/go]

here is an alternative, leading to the same net result.

Bill Spight wrote:
What is the result if Black plays a descent instead?

$$Bc Black to play
$$ ------------------
$$ | . 4 2 . 1 . . . .
$$ | 6 3 . X X O . . .
$$ | . X X X O . O . .
$$ | 5 X O O O . . . .
$$ | . O , . . . . . .
$$ | . . O . . . . . .
$$ | . . . . . . . . .
$$ | . . . . . . . . .
$$ | . . . . . . . . .

Click Here To Show Diagram Code

[go]$$Bc Black to play
$$ ------------------
$$ | . 4 2 . 1 . . . .
$$ | 6 3 . X X O . . .
$$ | . X X X O . O . .
$$ | 5 X O O O . . . .
$$ | . O , . . . . . .
$$ | . . O . . . . . .
$$ | . . . . . . . . .
$$ | . . . . . . . . .
$$ | . . . . . . . . .[/go]

If , causes difficulties for Black. leads to seki, possibly ko later. at 4 lets White make ko. This descent is not good.

what about at ?

Schachus wrote:

Bill Spight wrote:
What is the result if Black plays a descent instead?

$$Bc Black to play
$$ ------------------
$$ | . 4 2 . 1 . . . .
$$ | 6 3 . X X O . . .
$$ | . X X X O . O . .
$$ | 5 X O O O . . . .
$$ | . O , . . . . . .
$$ | . . O . . . . . .
$$ | . . . . . . . . .
$$ | . . . . . . . . .
$$ | . . . . . . . . .

Click Here To Show Diagram Code

[go]$$Bc Black to play
$$ ------------------
$$ | . 4 2 . 1 . . . .
$$ | 6 3 . X X O . . .
$$ | . X X X O . O . .
$$ | 5 X O O O . . . .
$$ | . O , . . . . . .
$$ | . . O . . . . . .
$$ | . . . . . . . . .
$$ | . . . . . . . . .
$$ | . . . . . . . . .[/go]

If , causes difficulties for Black. leads to seki, possibly ko later. at 4 lets White make ko. This descent is not good.

what about at ?

You're right. I goofed. Thanks.

Click Here To Show Diagram Code

[go]$$Bc Black to play
$$ ------------------
$$ | C C C C 1 4 C .
$$ | 3 C C X X O . . .
$$ | . X X X O . O . .
$$ | 2 X O O O . . . .
$$ | . O , . . . . . .
$$ | C . O . . . . . .
$$ | . . . . . . . . .
$$ | . . . . . . . . .
$$ | . . . . . . . . .[/go]

So I guess is next, then , assuming that Black cannot afford to play at 4. The net result is 4 pts. to Black with sente. Or, if plays elsewhere, 5 pts. to Black with gote. This descent is fine as far as points go, but the drawback is that White decides whether it is sente or gote, not Black.

Uberdude wrote:

Bki wrote:...but clearly this shouldn't have happened...

I think Bki is simply saying that, had he known that the corner could become a seki, black playing a move there to ensure it is ~7 points of territory is thus a ~7 point gote move and bigger than the presumably smaller moves he played instead during this phase of the endgame. (This is correct.)

Yes this is exactly what I mean. Clearly given that the descent allowed for a seki and weren't really sente, playing an inside move to make sure I was alive with points instead of one of them would have been better. Instead I was greedy and naively thought that they were enough to secure points. It's made even worse by the fact that there was no white point on one of the side so it's not like I even had a follow-up to descending.