Level 2 (15 kyu - 5 kyu), Problem 4




I assume this ends in seki if black is to live. My question is, why is O19 so special? Doesn't seki occur with black moving on O18 or R18 as well?

And why doesn't my SGF load on this forum? I generated it using Drago.

Thank you,

Alizais

The other two options make a dead shape. Some 4 space shapes can be killed by throwing in. Try it out!

Ah, I can see it now. Black needs to be able to survive if white makes the first move after seki. If black can't survive, it's not really seki and black just loses. (Hopefully that makes sense...) Thanks!

Black lives in seki after playing @ 14-19. L-4 or "dogleg 4" shape is guaranteed if White plays one of the remaining inside liberties after surrounding Black completely.

If White plays fist at the above mentioned point, Black dies.

You should put http://www.lifein19x19.com/forum/download/file.php?id=3511 between the sgf-problem tags, like this:

This is correct, but it might be worth being specific about one minor point: after @ r19, white doesn't need to make another move to kill the group. After all, once black has removed his own liberty by playing r19, it's not like he can make his group live by coming back to play o19...

(This an important difference because some positions are "unsettled" - that is, black wins if black makes the first move, and white wins if white makes the first move. R19 would be a very bad move in any event, but what makes it completely unpalatable is that black dies and white gets sente.)

Level 2 (15 kyu - 5 kyu), Problem 38

Why is S18 wrong? How can white survive? How can white kill black? How can white cause seki?

Click Here To Show Diagram Code

[go]$$c Level 2 (15k-5k), Problem 38.
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . . O X X O . |
$$ | . . . . . . . . . . . . . . O X . Z O |
$$ | . . . . . . . . . . . . . . O X . . . |
$$ | . . . , . . . . . , . . . . O X X X X |
$$ | . . . . . . . . . . . . . . . O O O O |
$$ | . . . . . . . . . . . . . . . . . . . |[/go]

Your move is very obviously ko. If you can't read that out, do easier problems.

Cool! thanks for letting me know.

You're right. These problems are beyond my level. I am around 20 kyu but these problems are for above 15 kyu. However, so far, I have learned two things from asking these hard questions. I learned what seki is and I learned that for some reason, I want to avoid ko. I'll continue with this problem set and keep asking questions until it stops benefiting me.

You could have known that yourself had you looked at the obvious white move (the atari) and its continuations.

You seem to be in need of some very basics for tsumegos. Please take a look at http://senseis.xmp.net/?TsumegoConventions#toc2 .
(In a tsumego, ko is always worse than unconditional life/death.)

Also, the problem set in question contains a lot of seki problems, so you should take a look at http://senseis.xmp.net/?KillingShapes .

Some variations (I messed up making them, ignore the 2nd and 3rd variations starting at ), for practice figure out why alternative moves are worse, especially look for ones where white can create a dead shape.



Extra practice, confirm that the seki solution doesn't work if the Q16 stone is white not black and that Black dies if they go T17 first in the problem diagram.

The point is about what each side has to gain or lose in the ko. In a seki (usually, give or take), both sides have zero points. In effect if W can jump into B's corner and make seki, he has denied black the territory he would have gotten in the corner, but that is all.

When a corner situation becomes ko, all of the stones of one side will die. That means that the side with fewer stones profits more when he wins than the side with more stones does if he loses. In this case, black has 10 stones involved in the ko, and white has 4. That means that if white wins the ko, white scores ~20 points for the corner while if black wins, black scores ~8 points in the corner. One way of looking at it: by making ko rather than seki, black throws away 6 points (because he puts 20 pts at risk in order to have a shot at making 8 points). Another way to look at it; after black starts the ko, white will come out ahead (relative to the seki) if he can find ko threats worth more than 8 pts, but black can only come out ahead if he can find ko threats worth more than 20 pts.

As for learning - the main reason to do tsumego, imho, is to practice your reading. You are welcome to do whatever you enjoy and find productive, but eventually you should do tsumego to push your reading harder rather than to learn other things.

The second problem is interesting in that if it occurs fairly early in the game seki is correct, as a rule, even if Black can win the ko. The extra move will not be worth what it gains. Later in the game, which is when these corner L&D problems often arise, if Black can win the ko fight he should play the ko, otherwise he should make seki.

However, the convention in tsumego is life before ko. Seki is life, and that is why the ko is wrong, in tsumego if not in a real game.

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Everything with love. Stay safe.

i couldnt stop laughing,
they should ban you!!!

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