Problem Nr. 344 from Cho's intermediate Problems

Nagilum · #1

Click Here To Show Diagram Code: [go]$$c Black to live or make a ko i suppose. $$ --------------------------------------- $$ | . . . . . . . . . . . . . . . . . . . | $$ | . O . O X X O O . . . . . . . . . . . | $$ | . X . X X O X X O . . . . . . . . . . | $$ | . O X X O O . . O , . . . . . , . . . | $$ | . O O O . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ ---------------------------------------[/go]

Hi,
this is Problem Nr. 344 from Cho's intermediate Problems. http://tsumego.tasuki.org/?page=tsumego
i can't find the solution. Not even a ko. Any Suggestions?

HermanHiddema · #2

Click Here To Show Diagram Code: [go]$$Bc $$ --------------------------------------- $$ | . 6 . 7 . 8 1 . . . . . . . . . . . . | $$ | 3 O 4 O X X O O 2 . . . . . . . . . . | $$ | . X 5 X X O X X O . . . . . . . . . . | $$ | . O X X O O . . O , . . . . . , . . . | $$ | . O O O . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ ---------------------------------------[/go]

Eternal Life?

Nagilum · #3

Wow. Thanks for the answer. :salute:

Good to know that this game can still surprise me.

I really thought that there is no answer for this problem. (Indeed, this seems to be true under a ruleset with super-ko.)

IMO, not really an standard problem.

jts · #4

Under super-ko eternal life just becomes a regular ko, no? So it's not "no solution", in any case.

ez4u · #5

This is Cho Chikun's collection, so I think it is reasonable to assume you are using Japanese rules. Besides, if you can read out to this point, you have achieved the pedagogical objective.
:grumpy:

Solomon · #6

A good exercise is to consider this move as well, which doesn't lead to eternal life but still gives a satisfactory result for Black if he plays correctly:

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

gonut · #7

Be sure to remember that when a similar position arises in your AGA tournament games this weekend, that Black dies. The American Go Association rules have situational superko, which prohibits Black from repeating the position that Black 7 creates in HermanHiddema's diagram above.

jts · #8

gonut wrote:

Be sure to remember that when a similar position arises in your AGA tournament games this weekend, that Black dies. The American Go Association rules have situational superko, which prohibits Black from repeating the position that Black 7 creates in HermanHiddema's diagram above.

Even after making a ko threat?

Here is a problem which stumped me:

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

(Doubly embarrassing because either I got it right the first three times and I have since lost the ability to solve it, or I thought I had solved it three times and didn't see a really obvious problem with my "solution".)

entropi · #9

I still didn't have my morning coffee, so forgive me if I overlook something obvious. But I don't see why black c5 doesn't lead to a ko.

Click Here To Show Diagram Code: [go]$$c Black to live or make a ko i suppose. $$ --------------------------------------- $$ | . . . . . . 1 . . . . . . . . . . . . | $$ | . O 3 O X X O O 2 . . . . . . . . . . | $$ | . X . X X O X X O . . . . . . . . . . | $$ | . O X X O O . . O , . . . . . , . . . | $$ | . O O O . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ ---------------------------------------[/go]

Click Here To Show Diagram Code: [go]$$Wc Black to live or make a ko i suppose. $$ --------------------------------------- $$ | . . 1 2 . 3 X . . . . . . . . . . . . | $$ | 4 O X O X X O O O . . . . . . . . . . | $$ | . X . X X O X X O . . . . . . . . . . | $$ | . O X X O O . . O , . . . . . , . . . | $$ | . O O O . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ ---------------------------------------[/go]

Click Here To Show Diagram Code: [go]$$Wc Black to live or make a ko i suppose. $$ --------------------------------------- $$ | . 5 . 2 6 3 X . . . . . . . . . . . . | $$ | 4 O X O X X O O O . . . . . . . . . . | $$ | 1 X . X X O X X O . . . . . . . . . . | $$ | . O X X O O . . O , . . . . . , . . . | $$ | . O O O . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ ---------------------------------------[/go]

Click Here To Show Diagram Code: [go]$$Wc Black to live or make a ko i suppose. $$ --------------------------------------- $$ | . 3 . 1 4 . X . . . . . . . . . . . . | $$ | 2 O X O X X O O O . . . . . . . . . . | $$ | . X . X X O X X O . . . . . . . . . . | $$ | . O X X O O . . O , . . . . . , . . . | $$ | . O O O . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ ---------------------------------------[/go]

perceval · **#10**

jts wrote:

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

entropi · **#11**

jts wrote:

gonut wrote:

Be sure to remember that when a similar position arises in your AGA tournament games this weekend, that Black dies. The American Go Association rules have situational superko, which prohibits Black from repeating the position that Black 7 creates in HermanHiddema's diagram above.

Even after making a ko threat?

As soon as black plays 7 white can play 8 again leading to the same local situation. Then black is again obliged to play c6, white captures at e6 and then black needs to find another ko threat. Sooner or later black will run out of ko threats while white doesn't need to play any threat.

entropi · **#12**

perceval wrote:

jts wrote:

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

HermanHiddema · **#13**

entropi wrote:

I still didn't have my morning coffee, so forgive me if I overlook something obvious. But I don't see why black c5 doesn't lead to a ko.

Click Here To Show Diagram Code: [go]$$c Black to live or make a ko i suppose. $$ --------------------------------------- $$ | . . . . . . 1 . . . . . . . . . . . . | $$ | . O 3 O X X O O 2 . . . . . . . . . . | $$ | . X . X X O X X O . . . . . . . . . . | $$ | . O X X O O . . O , . . . . . , . . . | $$ | . O O O . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ ---------------------------------------[/go]

Click Here To Show Diagram Code: [go]$$c Double ko death $$ --------------------------------------- $$ | 8 9 . 5 . 6 1 . . . . . . . . . . . . | $$ | 7 O 3 O X X O O 2 . . . . . . . . . . | $$ | 4 X 0 X X O X X O . . . . . . . . . . | $$ | . O X X O O . . O , . . . . . , . . . | $$ | . O O O . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ ---------------------------------------[/go]

After the sequence shown, black dies in double ko:

Click Here To Show Diagram Code: [go]$$c End position $$ --------------------------------------- $$ | O X a X . O X . . . . . . . . . . . . | $$ | b W X . X X O O O . . . . . . . . . . | $$ | O a O X X O X X O . . . . . . . . . . | $$ | . O X X O O . . O , . . . . . , . . . | $$ | . O O O . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ ---------------------------------------[/go]

Because of the two kos labeled a, the marked stone can never be captured. Note that black may take the corner stone, but it doesn't give him an eye.

jts · **#14**

entropi wrote:

jts wrote:

gonut wrote:

Be sure to remember that when a similar position arises in your AGA tournament games this weekend, that Black dies. The American Go Association rules have situational superko, which prohibits Black from repeating the position that Black 7 creates in HermanHiddema's diagram above.

Even after making a ko threat?

As soon as black plays 7 white can play 8 again leading to the same local situation. Then black is again obliged to play c6, white captures at e6 and then black needs to find another ko threat. Sooner or later black will run out of ko threats while white doesn't need to play any threat.

Ah, ok. So under situational superko, this functions in the same way as a double ko - unwinnable by black, but an infinite source of 30 pt. ko threats?

HermanHiddema · **#15**

jts wrote:

entropi wrote:

jts wrote:

Even after making a ko threat?

As soon as black plays 7 white can play 8 again leading to the same local situation. Then black is again obliged to play c6, white captures at e6 and then black needs to find another ko threat. Sooner or later black will run out of ko threats while white doesn't need to play any threat.

Ah, ok. So under situational superko, this functions in the same way as a double ko - unwinnable by black, but an infinite source of 30 pt. ko threats?

No, actually you can play it as a regular ko, but it is a little more tricky to remember which positions have already occurred.

There are four positions in the cycle:

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

In the last one, if black captures, it returns to the first one.

Now lets examine how ko is played here. In the example from the problem, position 1 is the first to arise, after :b7:

That means, that after playing through positions 2,3 and 4, black cannot return to position 1.

So Black makes a ko threat, and White responds.

Now, we are still at position 4, but two new stones elsewhere have been played. So position 4 is the first one that cannot be repeated from here.

Black captures (goes to position 1), white throws in (position 2), black pushes in (position 3).

At this point, white is not allowed to capture, as that would return to the position we had after the ko threat and response had been played (position 4).

So White plays a ko threat, and Black responds.

We are then at position 3, which is now the first one that cannot be repeated.

Move through positions 4, 1 and 2 (W, B, W) and it is Black who needs a threat.

Etcetera.

jts · **#16**

Hmm, so one was able to solve that tsumego? I wonder if it's a misprint. Two more:

Click Here To Show Diagram Code: [go]$$c Black must be completely dead, right? $$ --------------------------------------- $$ | . O . . O O . . . . . . . . . . . . . | $$ | . . X O X O . . . . . . . . . . . . . | $$ | . X X X X O . . . . . . . . . . . . . | $$ | O O O O O O . . . , . . . . . , . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . |[/go]

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

The second one looks soluble, but the best solution I found for B was

Josh Hatch · **#17**

jts wrote:

Hmm, so one was able to solve that tsumego? I wonder if it's a misprint. Two more:

Click Here To Show Diagram Code: [go]$$c Black must be completely dead, right? $$ --------------------------------------- $$ | . O . . O O . . . . . . . . . . . . . | $$ | . . X O X O . . . . . . . . . . . . . | $$ | . X X X X O . . . . . . . . . . . . . | $$ | O O O O O O . . . , . . . . . , . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . |[/go]

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

The second one looks soluble, but the best solution I found for B was

I don't know about the first one but here's the second problem:

jts · **#18**

Ah, ok. I hallucinated a shortage of liberties like so:

cyclops · **#19**

HermanHiddema wrote:

Click Here To Show Diagram Code: [go]$$Bc $$ --------------------------------------- $$ | . 6 . 7 . 8 1 . . . . . . . . . . . . | $$ | 3 O 4 O X X O O 2 . . . . . . . . . . | $$ | . X 5 X X O X X O . . . . . . . . . . | $$ | . O X X O O . . O , . . . . . , . . . | $$ | . O O O . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ ---------------------------------------[/go]

Eternal Life?

I tried to search on google with "eternal live" +"japanese rules". But I only found how the Japanese make eternal love ;-)

. Though interesting I really wondered what the rules in different versions say about this position if they don't have the super ko rule.
Well, after correcting the spelling of my search, I found some answers in http://senseis.xmp.net/?EternalLife.

edit: herman is right, just click on his link. :oops:

HermanHiddema · **#20**

@cyclops: did you try clicking the link I made of "Eternal Life" in my post? ;-)

Problem Nr. 344 from Cho's intermediate Problems

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