BQM 394

    Keywords: Question

From a recently finished game on DGS, I play black:

Moves 60 to 69  

LukeNine45 (later): I think B2 and W3 are both mistakes because the white stones are small. I think B4 is a mistake because white is dead as it stands (though I could be wrong on that). Tapir says the other things I wanted to say. I would say that W1 is sente and black needs to defend both the center group and the corner group, they're both in danger.

Moves 70 to 79  

LukeNine45: I think 12 probably is a mistake, but really the mistake was not defending it sooner. B2 would have been a good time to defend it.

Moves 80 to 89  

I hope that's not too many diagrams, but I wanted to give the full context. Basically, I think I lose the game because my group in the upper left dies. In particular, was move 12 above my mistake? It seems like I should be able to kill the invading white group, but maybe not. Any help would be great.


Kill the white group in the upper left corner? It can not be done if White plays properly. The white group in the upper left corner is alive as the position stands. If there was a black stone at the point marked with a square AND it was Black's turn, then Black could attack and create a two stage ko. If there was a white stone at the point marked with a square, the white group would be the L+2 group which is unconditionally alive. Black needs two moves here and still the best Black can get is a two stage ko. Its a good reading problem. The answer is detailed in Life and Death by James Davies, Chapter 23 The L+2 Group, problem 5, page 103 OR 4. Weak Leg on the L+2 Group page.

Positional judgement after 65

Moves 60 to 65  

Tapir: Imho, after B4 Black has a huge lead in actual territory (the marked white stones are dead). W5 split and black has now a weak group. But the white one above is weak as well. The exchanges of a against b strengthened white (and granted secure territory in the corner) without gaining anything (it doesn't even make an eye, as far as i read) and prepared the white attack against the corner. What about simply c as B6?

Can black kill?  

White corner without B4 and White playing at that point in plcae of Black...

White has an sure eye at the squared point and can make another eye in gote at the circled point... In my opinion W1 is an eye in sente, threatening to make another eye on the edge. Black at a and c should not work, I'm not sure about b. (This is an 4kyu analysis)

emeraldemon: Thanks for everyone's replies. Let me see if I understand what's being said:

Black kills  

Looking closer, it looks like Black perhaps can kill without that extra move (B4 in the original diagram), so it was probably not necessary. Similarly B2 above wasn't needed. The reason I played B6, B8 and B10 above was to make an eye or maybe even two, but from comments above I guess those exchanges might have hurt more than they helped? Tapir's response of playing B6 (or maybe B2) at c makes sense; perhaps I worried about the health of the side group too soon? As for my other question, I meant more generally does B12 give me enough to kill White's invasion at 13. I guess the answer is no?

Tapir: If u can capture such a big group which should make winning the game easy, but cannot read it out. Don't mind and play the extra move. (This works out at my level as well.) ->B4 in the original diagram. Nothing is more embarassing than an opponent making life with such a group in the endgame... by just trying. W3 in your diagram is not enough. White can't win by making an eye in gote, but white can try to play at B4 or B6. Later he can try to capture the lone black stone, the threat to cut the three marked stones off might be useful. --> Tsumego from Games 84

Can Black kill?  

LukeNine45: Not only can black not kill, Black will have to do well to live! You might be able to find a better B12 but even so, black is so thin you can't expect much here. If White were a little thicker on the outside white could probably just invade with W11 and quite possibly kill.

kb: Since we've been bantering over whether or not Black is ahead after killing White in the bottom right, let's count actual territory and then try to estimate influence. White has just played white+circle.

After move 65, Black to move  

Count actual territory for both (I'm using x's for Black and o's for White), I get 18 points on the bottom left, 12 points on the top, and 4 points on the side, plus 6.5 points komi for a total of 40.5 points for White. Black has 71 points on the bottom right, about 8 points on the top left side, and 12 points in the top right corner for an amazing 91 points.

The conclusion: White needs more than 50 points from his influence. Wow! However, it's Black's move next... not looking so good for White.

Black needs to decide what to do with black+circle, since giving them up is big, but making them live is very hard given all of that White influence around. If he can make them live the game is over, but if the can give them up and still win, then Black will have a much easier game, since he essentially leaves chance out of it.

The first thing Black needs to do is strengthen the top left side, or it will get invaded. One simple continuation is the following:

What can Black do to secure victory?  

The first thing Black needs to do is strengthen the top left side, or it will get invaded. One simple continuation is the following:

What can Black do to secure victory?  

If White resists, some complications may come up, though.

What can Black do to secure victory? (2), B9 at black+circle  
What can Black do to secure victory? (2), B9 at black+circle  

If White connects at a, immediately play 3-3 at b and White has no territory to win. If White goes for the ko, at c, take at a and don't look back (White doesn't have a big enough threat, even living in the bottom right, for you to ignore this ko. Just take at W2 and be done with it).

White cannot possibly get enough points out of his moyo now:

After move 73, Black to move  

Black has 71, 12 and 18 points a total of 101 points. White has about 17 + 4 + 63 + 6.5 points komi, for 90.5 points, with Black to move in the beginning of the large endgame. I estimate a 10-15 point Black win.

BQM 394 last edited by Dieter on July 5, 2008 - 12:49
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