It is currently Fri Feb 23, 2024 11:18 pm

All times are UTC - 8 hours [ DST ]




Post new topic Reply to topic  [ 23 posts ]  Go to page 1, 2  Next
Author Message
Offline
 Post subject: A special (new?) strategy in AGA field?
Post #1 Posted: Thu Nov 16, 2023 8:30 am 
Lives in sente

Posts: 1201
Liked others: 21
Was liked: 57
Rank: 1d
After a lot of work I managed to build a position for which the win need a special strategy I have never seen before.
Can you solve the following problem:

AGA rules, komi 14.5
Click Here To Show Diagram Code
[go]$$B Black to play and win
$$ ------------------------
$$| . . . . O X O O O . X |
$$| O O O O O X O O O X X |
$$| X X X X X X X X O . X |
$$| . . . . . X X O . O O |
$$| . . . . . . X O O O O |
$$| . X . . . . X X X X X |
$$| X X X . . . X O O O O |
$$| O O X . . . X O . O . |
$$| . O X X X X X O O X O |
$$| X O O O O X O O X X X |
$$| . X X . O X O X . X . |
$$ -----------------------[/go]


Edit :look at https://lifein19x19.com/viewtopic.php?p=279399#p279399 for a far better problem.


Last edited by Gérard TAILLE on Mon Nov 27, 2023 11:22 am, edited 1 time in total.
Top
 Profile  
 
Offline
 Post subject: Re: A special (new?) strategy in AGA field?
Post #2 Posted: Thu Nov 16, 2023 4:41 pm 
Dies in gote

Posts: 44
Liked others: 4
Was liked: 8
Gérard TAILLE wrote:
AGA rules, komi 14.5

May I ask the point of setting Komi to 14.5? Is it just to to ensure that a win vs loss depends on the solution?

Top
 Profile  
 
Offline
 Post subject: Re: A special (new?) strategy in AGA field?
Post #3 Posted: Thu Nov 16, 2023 6:08 pm 
Dies with sente

Posts: 111
Liked others: 33
Was liked: 12
Rank: IGS 4 dan
It's funny. Another superko beast.

Top
 Profile  
 
Offline
 Post subject: Re: A special (new?) strategy in AGA field?
Post #4 Posted: Fri Nov 17, 2023 6:07 am 
Lives in sente

Posts: 1201
Liked others: 21
Was liked: 57
Rank: 1d
hzamir wrote:
Gérard TAILLE wrote:
AGA rules, komi 14.5

May I ask the point of setting Komi to 14.5? Is it just to to ensure that a win vs loss depends on the solution?

Basically the komi is here to help you. If black plays the correct sequence black will win, otherwise black will lose.
I could have only said "what is the best result for black" but in that case you have no clue to know if you are close to the solution.

Top
 Profile  
 
Offline
 Post subject: Re: A special (new?) strategy in AGA field?
Post #5 Posted: Fri Nov 17, 2023 7:25 am 
Lives in sente

Posts: 1201
Liked others: 21
Was liked: 57
Rank: 1d
dany wrote:
It's funny. Another superko beast.

Yes Dany it is a really a beast.
Assuming white is allowed to play "unuseful" moves (e.g. by using the double ko when it is not necessary) but is not allowed to play "bad" moves (a move which loses points), how many moves are necessary before black can make the decisive capture (I mean a capture which is not an exchange in the double ko in the bottom right corner or in the sending 2 return 1 sequence)?

Top
 Profile  
 
Offline
 Post subject: Re: A special (new?) strategy in AGA field?
Post #6 Posted: Sat Nov 18, 2023 2:16 pm 
Lives in sente

Posts: 1201
Liked others: 21
Was liked: 57
Rank: 1d
I have just discovered a dual solution for the problem I showed in this topic. By just adding a black stone and a white stone in the upper left corner this dual issue is fixed:

AGA rules, komi 14.5
Click Here To Show Diagram Code
[go]$$B Black to play and win
$$ ------------------------
$$| X . O . O X O O O . X |
$$| O O O O O X O O O X X |
$$| X X X X X X X X O . X |
$$| . . . . . X X O . O O |
$$| . . . . . . X O O O O |
$$| . X . . . . X X X X X |
$$| X X X . . . X O O O O |
$$| O O X . . . X O . O . |
$$| . O X X X X X O O X O |
$$| X O O O O X O O X X X |
$$| . X X . O X O X . X . |
$$ -----------------------[/go]

Top
 Profile  
 
Offline
 Post subject: Re: A special (new?) strategy in AGA field?
Post #7 Posted: Sun Nov 19, 2023 3:36 am 
Lives in sente

Posts: 1201
Liked others: 21
Was liked: 57
Rank: 1d
After more work I have discovered the black attack is far stronger than what I believed initialy. As a consequence the win for black in my previous positions is not very interesting because almost any black moves (including a pass!) is winning.
Though the results I claimed are good it is not satisfactory and I have to change the position in order to have a quite interesting solution. Here it is with a more usual komi:

AGA rules, komi 6.5
Click Here To Show Diagram Code
[go]$$B Black to play and win
$$ ------------------------
$$| . O . O . O . O . O . |
$$| O O O O O O O O O O X |
$$| X X X X X X O . O . . |
$$| . . . . . X X O . O . |
$$| . . . . . . X O O O O |
$$| . X . . . . X X X X X |
$$| X X X . . . X O O O O |
$$| O O X . . . X O . O . |
$$| . O X X X X X O O X O |
$$| X O O O O X O O X X X |
$$| . X X . O X O X . X . |
$$ -----------------------[/go]

This time I am quite happy. The position seems quite simple, without weaknesses (with japanese rules it is even an endgame position) but with AGA rules, this apparently losing position is a winning one due to a very surprising sequence!
Take pleasure.

Top
 Profile  
 
Offline
 Post subject: Re: A special (new?) strategy in AGA field?
Post #8 Posted: Sun Nov 19, 2023 11:45 pm 
Judan

Posts: 6081
Liked others: 0
Was liked: 786
Gérard TAILLE wrote:
endgame position


I think you mean "settled position".

Top
 Profile  
 
Offline
 Post subject: Re: A special (new?) strategy in AGA field?
Post #9 Posted: Sun Nov 19, 2023 11:56 pm 
Lives in gote

Posts: 388
Liked others: 416
Was liked: 198
Gérard TAILLE wrote:
Black to play and win


I must be missing something, what is the number of prisoners on each side?
At first sight, assumming no prisoners, black has 22 points, white has 14, so with komi 6.5 black won already.

Top
 Profile  
 
Offline
 Post subject: Re: A special (new?) strategy in AGA field?
Post #10 Posted: Mon Nov 20, 2023 3:04 am 
Lives in sente

Posts: 1201
Liked others: 21
Was liked: 57
Rank: 1d
RobertJasiek wrote:
Gérard TAILLE wrote:
endgame position


I think you mean "settled position".

Yes Robert. I mean it is a position for which both players can easily decide to pass and go in the confirmation phase instead of playing the loop made of a single pass followed by an exchange in the double ko.

Top
 Profile  
 
Offline
 Post subject: Re: A special (new?) strategy in AGA field?
Post #11 Posted: Mon Nov 20, 2023 3:22 am 
Lives in sente

Posts: 1201
Liked others: 21
Was liked: 57
Rank: 1d
sorin wrote:
Gérard TAILLE wrote:
Black to play and win


I must be missing something, what is the number of prisoners on each side?
At first sight, assumming no prisoners, black has 22 points, white has 14, so with komi 6.5 black won already.

I assume AGA rules that means area counting. The number of prisoners is irrelevant.

As an example if
Click Here To Show Diagram Code
[go]$$B :b3: pass, :b5: pass, :w6: pass
$$ ------------------------
$$| . O . O . O . O . O 4 |
$$| O O O O O O O O O O X |
$$| X X X X X X O . O . 2 |
$$| . . . . . X X O . O . |
$$| . . . . . . X O O O O |
$$| . X . . . . X X X X X |
$$| X X X . . . X O O O O |
$$| O O X . . . X O . O . |
$$| . O X X X X X O O X O |
$$| X O O O O X O O X X X |
$$| 1 X X . O X O X . X . |
$$ -----------------------[/go]

black count : 38 stones + 24 territory = 62 points
white count : 45 stones + 12 territory = 57 points
with a 6.5 komi black loses the game by 1.5 points


This post by Gérard TAILLE was liked by: sorin
Top
 Profile  
 
Offline
 Post subject: Re: A special (new?) strategy in AGA field?
Post #12 Posted: Mon Nov 20, 2023 12:51 pm 
Dies in gote

Posts: 35
Liked others: 2
Was liked: 1
If I'm right with my solution idea, it's a pretty nasty superko beast. A kind of "pass fight", and at the same time an example of the difference between situational superko and positional superko, isn't it?
And I think maaany moves are necessary before black can make the decisive capture...

Top
 Profile  
 
Offline
 Post subject: Re: A special (new?) strategy in AGA field?
Post #13 Posted: Mon Nov 20, 2023 1:22 pm 
Lives in sente

Posts: 1201
Liked others: 21
Was liked: 57
Rank: 1d
jmeinh wrote:
If I'm right with my solution idea, it's a pretty nasty superko beast. A kind of "pass fight", and at the same time an example of the difference between situational superko and positional superko, isn't it?
And I think maaany moves are necessary before black can make the decisive capture...

You are 100% right jmeinh.
Do you think you have discovered the right sequence allowing to apply your idea?

Top
 Profile  
 
Offline
 Post subject: Re: A special (new?) strategy in AGA field?
Post #14 Posted: Mon Nov 20, 2023 2:41 pm 
Dies in gote

Posts: 35
Liked others: 2
Was liked: 1
Well, I think so.
I'm not good at creating images, so I use coordinates.
B A3, W A1, B L4, W J1, B A2.
Now White has a choice:
a. W pass, B A3 , and W A1 is forbidden.
b. W L9 (or elsewhere), B A3 (repeating the loop until W cannot make a move without damaging himself).
c. W L3, B H1 (SSK allows this, in contrast to PSK), W L9 or elsewhere (SSK forbids passing - is that right? I'm not an SSK expert...), B A3 and the same idea as b.

Top
 Profile  
 
Offline
 Post subject: Re: A special (new?) strategy in AGA field?
Post #15 Posted: Mon Nov 20, 2023 3:27 pm 
Lives in sente

Posts: 1201
Liked others: 21
Was liked: 57
Rank: 1d
jmeinh wrote:
Well, I think so.
I'm not good at creating images, so I use coordinates.
B A3, W A1, B L4, W J1, B A2.
Now White has a choice:
a. W pass, B A3 , and W A1 is forbidden.
b. W L9 (or elsewhere), B A3 (repeating the loop until W cannot make a move without damaging himself).
c. W L3, B H1 (SSK allows this, in contrast to PSK), W L9 or elsewhere (SSK forbids passing - is that right? I'm not an SSK expert...), B A3 and the same idea as b.


The basic idea is correct and I confirm the SSK allows such sequence. Congratulation for that ajmeinh.
Unfortunetly the execution is not correct.

You forgot to take into account the white attack against the black center group.
Click Here To Show Diagram Code
[go]$$B
$$ ------------------------
$$| . O . O . O . O . O . |
$$| O O O O O O O O O O X |
$$| X X X X X X O . O . . |
$$| W W W W W X X O . O . |
$$| . W . . . W X O O O O |
$$| W X W . . W X X X X X |
$$| X X X W . W X O O O O |
$$| O O X W W W X O . O . |
$$| . O X X X X X O O X O |
$$| X O O O O X O O X X X |
$$| . X X . O X O X . X . |
$$ -----------------------[/go]
In my mind this attack is the main difficulty of this problem.

Top
 Profile  
 
Offline
 Post subject: Re: A special (new?) strategy in AGA field?
Post #16 Posted: Tue Nov 21, 2023 5:18 am 
Dies in gote

Posts: 35
Liked others: 2
Was liked: 1
Is that really a problem?
I think it's enough for Black to make the appropriate defence moves when necessary; then he continues the interrupted loop, and W can't defend against that.
Or am I missing something?

Top
 Profile  
 
Offline
 Post subject: Re: A special (new?) strategy in AGA field?
Post #17 Posted: Tue Nov 21, 2023 6:44 am 
Lives in sente

Posts: 1201
Liked others: 21
Was liked: 57
Rank: 1d
jmeinh wrote:
Is that really a problem?
I think it's enough for Black to make the appropriate defence moves when necessary; then he continues the interrupted loop, and W can't defend against that.
Or am I missing something?

Yes it is a problem
The problem is due to the subtilities of SSK : at the moment black makes the appropiate defence move then white passes and after this pass the loop can no longer work!

Top
 Profile  
 
Offline
 Post subject: Re: A special (new?) strategy in AGA field?
Post #18 Posted: Tue Nov 21, 2023 7:37 am 
Dies in gote

Posts: 35
Liked others: 2
Was liked: 1
I see. Then my idea doesn't work as intended.

Top
 Profile  
 
Offline
 Post subject: Re: A special (new?) strategy in AGA field?
Post #19 Posted: Tue Nov 21, 2023 7:48 am 
Dies in gote

Posts: 44
Liked others: 4
Was liked: 8
sorin wrote:
Gérard TAILLE wrote:
Black to play and win


I must be missing something, what is the number of prisoners on each side?
At first sight, assumming no prisoners, black has 22 points, white has 14, so with komi 6.5 black won already.



While not especially necessary, AGA still counts with prisoners as a convention.
Black to play, means an equal number of moves have been made.
43 White stones on the board
38 Black stones on the board
White has thus captured 5 more prisoners than black. Even in unlike event of an early pass in the game, player would still have to hand over a prisoner in AGA.

Top
 Profile  
 
Offline
 Post subject: Re: A special (new?) strategy in AGA field?
Post #20 Posted: Tue Nov 21, 2023 8:38 am 
Lives in sente

Posts: 1201
Liked others: 21
Was liked: 57
Rank: 1d
hzamir wrote:
sorin wrote:
Gérard TAILLE wrote:
Black to play and win


I must be missing something, what is the number of prisoners on each side?
At first sight, assumming no prisoners, black has 22 points, white has 14, so with komi 6.5 black won already.



While not especially necessary, AGA still counts with prisoners as a convention.
Black to play, means an equal number of moves have been made.
43 White stones on the board
38 Black stones on the board
White has thus captured 5 more prisoners than black. Even in unlike event of an early pass in the game, player would still have to hand over a prisoner in AGA.


Yes hzamir, providing you count 5 more prisoners for white you can count by territory the initial position:
Click Here To Show Diagram Code
[go]$$B Black to play and win
$$ ------------------------
$$| T O T O T O T O T O T |
$$| O O O O O O O O O O Y |
$$| X X X X X X O T O T T |
$$| M M M M M X X O T O T |
$$| M M M M M M X O O O O |
$$| M X M M M M X X X X X |
$$| X X X M M M X O O O O |
$$| O O X M M M X O T O T |
$$| . O X X X X X O O X O |
$$| X O O O O X O O X X X |
$$| M X X . O X O X M X M |
$$ -----------------------[/go]

black : 25 territory = 25 points
white : 14 territory + 1 prisoner (upper right corner) + 5 prisoners (to reach the initial position) = 20 points
With a komi of 6.5 black loses by 1.5 points (same result under https://lifein19x19.com/viewtopic.php?p=279412#p279412)

Top
 Profile  
 
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 23 posts ]  Go to page 1, 2  Next

All times are UTC - 8 hours [ DST ]


Who is online

Users browsing this forum: No registered users and 1 guest


You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot post attachments in this forum

Search for:
Jump to:  
Powered by phpBB © 2000, 2002, 2005, 2007 phpBB Group