Life-and-death solution: what am I missing?

singular · #1

I've been using a life-and-death app that makes its own moves and tells me if my solution is WRONG or SOLVED!
There is a solution I have found for two separate problems that looks alive and well, but the app has told me I was WRONG.

So, I had a problem, and this is my first solution, for which I was told: WRONG. I am black.

Click Here To Show Diagram Code: [go]$$B Wrong $$ ------------------ $$ | . O X O . . . . . $$ | O . X O . O . . . $$ | X X X O . . . . . $$ | X . X O . . . . . $$ | X X O . . . . . . $$ | O O O . . . . . . $$ | . . . . . . . . . $$ | . O . . . . . . . $$ | . . . . . . . . .[/go]

This is the problem:

Click Here To Show Diagram Code: [go]$$B Problem $$ ------------------ $$ | . . . . . . . . . $$ | O . X O . O . . . $$ | . X X O . . . . . $$ | X . X O . . . . . $$ | . X O . . . . . . $$ | . O O . . . . . . $$ | . . . . . . . . . $$ | . O . . . . . . . $$ | . . . . . . . . .[/go]

The next solution I found, for which I was told: SOLVED!

Click Here To Show Diagram Code: [go]$$B Solved $$ ------------------ $$ | . . . . . . . . . $$ | O X X O . O . . . $$ | . X X O . . . . . $$ | X . X O . . . . . $$ | X X O . . . . . . $$ | O O O . . . . . . $$ | . . . . . . . . . $$ | . O . . . . . . . $$ | . . . . . . . . .[/go]

I can see why the second solution is better, because black gets an extra point.

However, I stumbled upon the same solution in another problem . . .

PROBLEM NUMBER TWO

My first solution, for which I was told: WRONG.

Click Here To Show Diagram Code: [go]$$B Wrong $$ ------------------ $$ | . O X O . . . . . $$ | O . X O . . . . . $$ | X X X O . . . . . $$ | X . X O . . . . . $$ | X X O . . . . . . $$ | O O O . . . . . . $$ | . . . . . . . . . $$ | . . . . . . . . . $$ | . . . . . . . . .[/go]

It's pretty much the same as the solution for the first problem. I was wrong again, when it seems to me the shape is alive and well.
So, I assumed I could find a more profitable solution.

The problem

Click Here To Show Diagram Code: [go]$$B Problem $$ ------------------ $$ | X . X O . . . . . $$ | O . X O . . . . . $$ | . . X O . . . . . $$ | . . X O . . . . . $$ | X X O . . . . . . $$ | O O O . . . . . . $$ | . . . . . . . . . $$ | . . . . . . . . . $$ | . . . . . . . . .[/go]

The next solution I found, for which I was told: SOLVED!

Click Here To Show Diagram Code: [go]$$B Solved $$ ------------------ $$ | X . X O . . . . . $$ | . X X O . . . . . $$ | X X X O . . . . . $$ | O O X O . . . . . $$ | . . O . . . . . . $$ | O O O . . . . . . $$ | . . . . . . . . . $$ | . . . . . . . . . $$ | . . . . . . . . .[/go]

This solution for this second problem doesn't seem more profitable. Black gets only two points (and some of black's stones were taken).

Is there something I'm missing in my appraisal of the original solutions?

tj86430 · #2

singular wrote:

it seems to me the shape is alive and well.

What is the status of the two white stones in the corner?

DrStraw · #3

It is not at all obvious what you are asking because you don't show any sequences.

Jarmo · #4

For the first problem, I like your second solution more because it is worth more points. For the second problem, I like your first solution more. I don't understand why it is wrong and the second solution is correct. The first solution seems to be worth more. Maybe the app assumes some rules I am not familiar with. I don't know how seki is handled with chinese counting.

Mike Novack · #5

OK, let's look at the first one. I am assuming that the problem was "black to play and live". Well in your solution, yes, black is alive (in seki) but with no points (black gets one point but so does white). In the solution market correct, black lives with two eyes and gets at least five points (four points plus a prisoner).

Generally with these problems, if the goal is to live, a solution that is live in seki will be marked wrong if life with two eyes is possible. Similarly living with ko will be marked wrong if uncinditional life is possible.

As you get to more advanced problems, you will usually just be told whose move it is and asked "what is the status?" << and you have to show how to get that >>

Bill Spight · #6

Here are a couple of possibilities for the second problem.

Click Here To Show Diagram Code: [go]$$B Problem 2, var. 1 $$ ------------------ $$ | X 2 X O . . . . . $$ | O . X O . . . . . $$ | 1 3 X O . . . . . $$ | 5 4 X O . . . . . $$ | X X O . . . . . . $$ | O O O . . . . . . $$ | . . . . . . . . . $$ | . . . . . . . . . $$ | . . . . . . . . .[/go]

Net local territory: 0

Net local area: 7

Click Here To Show Diagram Code: [go]$$B Problem 2, var. 2 $$ ------------------ $$ | B 2 X O . . . . . $$ | O 3 X O . . . . . $$ | 1 7 X O . . . . . $$ | 6 4 X O . . . . . $$ | X X O . . . . . . $$ | O O O . . . . . . $$ | . . . . . . . . . $$ | . . . . . . . . . $$ | . . . . . . . . .[/go]

at

Net local territory: -1 (1 pt. for White)

Net local area: 6

Variation 1 is better for Black.

----

Click Here To Show Diagram Code: [go]$$B Problem2, var. 3 $$ ------------------ $$ | X . X O . . . . . $$ | O 3 X O . . . . . $$ | 1 5 X O . . . . . $$ | 4 2 X O . . . . . $$ | X X O . . . . . . $$ | O O O . . . . . . $$ | . . . . . . . . . $$ | . . . . . . . . . $$ | . . . . . . . . .[/go]

is better for White. This is the correct result, unless Black is komaster. Maybe that is why the program said that the other result is wrong.

It is wrong, but it is wrong because White (the program) made a mistake.

----

Click Here To Show Diagram Code: [go]$$B Problem2, var. 4, Black komaster $$ ------------------ $$ | X 4 X O . . . . . $$ | O 3 X O . . . . . $$ | 2 1 X O . . . . . $$ | . . X O . . . . . $$ | X X O . . . . . . $$ | O O O . . . . . . $$ | . . . . . . . . . $$ | . . . . . . . . . $$ | . . . . . . . . .[/go]

Black can also play to make ko.

Edit:

Click Here To Show Diagram Code: [go]$$B Problem2, var. 5, Black komaster $$ ------------------ $$ | X 4 X O . . . . . $$ | O . X O . . . . . $$ | 5 1 X O . . . . . $$ | 2 3 X O . . . . . $$ | X X O . . . . . . $$ | O O O . . . . . . $$ | . . . . . . . . . $$ | . . . . . . . . . $$ | . . . . . . . . .[/go]

is an option when Black is komaster.

Bill Spight · #7

A couple of more variations.

Click Here To Show Diagram Code: [go]$$B Problem2, var. 6 $$ ------------------ $$ | X 2 X O . . . . . $$ | O 4 X O . . . . . $$ | 1 . X O . . . . . $$ | . 3 X O . . . . . $$ | X X O . . . . . . $$ | O O O . . . . . . $$ | . . . . . . . . . $$ | . . . . . . . . . $$ | . . . . . . . . .[/go]

If White (the program) makes the mistake of capturing with :w2:

,

lives in sente.

Click Here To Show Diagram Code: [go]$$B Problem2, var. 7 Black komaster $$ ------------------ $$ | X . X O . . . . . $$ | O 3 X O . . . . . $$ | 2 . X O . . . . . $$ | . 1 X O . . . . . $$ | X X O . . . . . . $$ | O O O . . . . . . $$ | . . . . . . . . . $$ | . . . . . . . . . $$ | . . . . . . . . .[/go]

If Black is komaster, :b1:

can lead to a 10,000 year ko.

Click Here To Show Diagram Code: [go]$$B Problem2, var. 8 Black komaster $$ ------------------ $$ | X 4 X O . . . . . $$ | O 2 X O . . . . . $$ | 3 . X O . . . . . $$ | . 1 X O . . . . . $$ | X X O . . . . . . $$ | O O O . . . . . . $$ | . . . . . . . . . $$ | . . . . . . . . . $$ | . . . . . . . . .[/go]

If Black is komaster, White can avoid the ko with :w2:

. Now

takes the vital point, and then :w4:

makes seki.

Click Here To Show Diagram Code: [go]$$B Problem2, var. 9 Black komaster $$ ------------------ $$ | X . X O . . . . . $$ | O 1 X O . . . . . $$ | 2 . X O . . . . . $$ | . 3 X O . . . . . $$ | X X O . . . . . . $$ | O O O . . . . . . $$ | . . . . . . . . . $$ | . . . . . . . . . $$ | . . . . . . . . .[/go]

If

prevents that seki, this line leads to the 10,000 year ko.

Click Here To Show Diagram Code: [go]$$B Problem2, var. 10 Black komaster $$ ------------------ $$ | X . X O . . . . . $$ | O 1 X O . . . . . $$ | 3 5 X O . . . . . $$ | 4 2 X O . . . . . $$ | B B O . . . . . . $$ | O O O . . . . . . $$ | . . . . . . . . . $$ | . . . . . . . . . $$ | . . . . . . . . .[/go]

But if Black is komaster, :b1:

is a mistake. :w2:

captures the :bc:

stones in sente.

So many variations!

singular · #8

Click Here To Show Diagram Code: [go]$$B Seki $$ ------------------ $$ | . O X O . . . . . $$ | O . X O . . . . . $$ | X X X O . . . . . $$ | X . X O . . . . . $$ | X X O . . . . . . $$ | O O O . . . . . . $$ | . . . . . . . . . $$ | . . . . . . . . . $$ | . . . . . . . . .[/go]

I see there's more to this problem than I thought, especially with Bill's diagrams. Sheesh! I didn't provide sequences because it's really just the status of the first solutions I'm wondering about -- apparently it's a seki. I was under the impression that it's not a seki. I think that was my misunderstanding -- the two white stones in the corner just look dead to me. Of course black won't play inside this eye, and white probably wouldn't bother, which is a seki-like situation ... but the shape has two eyes. When I encounter a seki it's usually the attacker filling up a single eye, and if the attacker plays again, the defender can take and make two eyes. If the defender plays again, the attacker can prevent two eyes.

Like this:

Click Here To Show Diagram Code: [go]$$ ------------------ $$ | . X X X . O . X . $$ | O O O O O O . X . $$ | . . . . . . . X . $$ | X X X X X X X . . $$ | . . . . . . . X . $$ | . . . . . . . . .[/go]

I got the above position from sensei's library and came upon a bunch of information on seki, which showed me how in the dark I am about it. Time to clear up some misconceptions.

I'm still not 100% clear on why my solutions are seki, but I'll get there.

Thanks for your help!

singular · #9

I just found this page on sensei's which I think describes the type of seki I have here: http://senseis.xmp.net/?SekiInTheCornerExample1

tj86430 · **#10**

singular wrote:

I just found this page on sensei's which I think describes the type of seki I have here: http://senseis.xmp.net/?SekiInTheCornerExample1

yes

Life-and-death solution: what am I missing?

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