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Intriguing problem

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Intriguing problem

Posted: Thu May 05, 2011 2:44 am
by SoDesuNe
This is a problem from a local Dan-player, which I find very intriguing because it looks like a simple situation. So I assume in a real game a lot of players will play by instinct, which might result in a inferior outcome.

Click Here To Show Diagram Code
[go]$$Bc
$$ . . . . . . . . . . . |
$$ . . . . . . . . . . . |
$$ . . . . . . . . . . . |
$$ . X X X X X X X . . . |
$$ . X O O O O O X X . . |
$$ . X O X O X . O O X . |
$$ . . O . O . . . . 1 . |
$$ ----------------------[/go]


First question: Is :b1: Sente against White's group (why/why not)?

Second question: How much points has White to gain elsewhere, if he does not respond to :b1: ?

Re: Intriguing problem

Posted: Thu May 05, 2011 2:57 am
by Solomon
Really bad with questions like the 2nd one, so I'll just try to answer the first:
Pretty sure White can live if he plays elsewhere:
Click Here To Show Diagram Code
[go]$$Bc
$$ . . . . . . . . . . . |
$$ . . . . . . . . . . . |
$$ . . . . . . . . . . . |
$$ . X X X X X X X . . . |
$$ . X O O O O O X X . . |
$$ . X O X O X 1 O O X . |
$$ . . O . O 5 4 2 3 X . |
$$ ----------------------[/go]

Click Here To Show Diagram Code
[go]$$Wc
$$ . . . . . . . . . . . |
$$ . . . . . . . . . . . |
$$ . . . . . . . . . . . |
$$ . X X X X X X X . . . |
$$ . X O O O O O X X . . |
$$ . X O X O X X 1 . X . |
$$ . . O . O X . . X X . |
$$ ----------------------[/go]

Re: Intriguing problem

Posted: Thu May 05, 2011 4:39 am
by Magicwand
SoDesuNe wrote:This is a problem from a local Dan-player, which I find very intriguing because it looks like a simple situation. So I assume in a real game a lot of players will play by instinct, which might result in a inferior outcome.

Click Here To Show Diagram Code
[go]$$Bc
$$ . . . . . . . . . . . |
$$ . . . . . . . . . . . |
$$ . . . . . . . . . . . |
$$ . X X X X X X X . . . |
$$ . X O O O O O X X . . |
$$ . X O X O X . O O X . |
$$ . . O . O . . . . 1 . |
$$ ----------------------[/go]


First question: Is :b1: Sente against White's group (why/why not)?

Second question: How much points has White to gain elsewhere, if he does not respond to :b1: ?

very intresting endgame question :)
i am curious what bill has to say about this :)
Click Here To Show Diagram Code
[go]$$Bc :6: = :wc:
$$ . . . . . . . . . . . |
$$ . . . . . . . . . . . |
$$ . . . . . . . . . . . |
$$ . X X X X X X X . . . |
$$ . X O O O O O X X . . |
$$ . X O X O X 1 W O X . |
$$ . . O . O 5 4 2 3 B . |
$$ ----------------------[/go]

for second question.. i got 2 and 1/2 point gote point gain for black.
so if white can play something bigger than 3 or greater...white can tenuki.

Re: Intriguing problem

Posted: Thu May 05, 2011 6:29 am
by perceval
my attempt (i figure after that people lower than 3d will dare post their thoughts. it is sometime difficult posting your opinion after someone 10 stone stronger than you did)

i start from araban var (which i didnt found i did not thought of W 1) were B has captured 4 stones

Click Here To Show Diagram Code
[go]$$Wc :w5: at :bc:
$$ . . . . . . . . . . . |
$$ . . . . . . . . . . . |
$$ . . . . . . . . . . . |
$$ . X X X X X X X . . . |
$$ . X O O O O O X X . . |
$$ . X O X O X B 1 2 X . |
$$ . . O . O X 3 4 X X . |
$$ ----------------------[/go]




i count 5+3-4 =4 point for W.

if W answer:
Click Here To Show Diagram Code
[go]$$
$$ . . . . . . . . . . . |
$$ . . . . . . . . . . . |
$$ . . . . . . . . . . . |
$$ . X X X X X X X . . . |
$$ . X O O O O O X X . . |
$$ . X O X O X . O O X . |
$$ . b O . O . 2 . a 1 . |
$$ ----------------------[/go]

7 or 8 depending of who gets the gote at a so 7.5 so the diff is 7.5-4 =3
so W should play elsewhere if he has a 3 pts gote or 2 point sente
Note that if there is a Big B territory on the right b might be bigger as it is a 5 pt for W sente ? or maybe i am still totally confused about this notion ?

ie
Click Here To Show Diagram Code
[go]$$Wc :b2: is sente
$$ . . . . . . . . . . . |
$$ . . . . . . . . . . . |
$$ . . . . . . . . . . . |
$$ . X X X X X X X . . . |
$$ . X O O O O O X X . . |
$$ . X O X O X X 1 . X . |
$$ . 2 O . O X 3 . X X . |
$$ ----------------------[/go]


this prevent W 5 point sente (continuation from the first diag)
Click Here To Show Diagram Code
[go]$$Wc
$$ . . . . . . . . . . . . |
$$ . . . . . . . . . . . . |
$$ . . . . . . . . . . . . |
$$ . . X X X X X X X . . . |
$$ . 6 X O O O O O X X . . |
$$ 2 5 X O X O . O O X X . |
$$ 4 3 1 O . O . O X X X . |
$$ ----------------------[/go]

Re: Intriguing problem

Posted: Thu May 05, 2011 9:49 am
by Magicwand
perceval wrote:
7 or 8 depending of who gets the gote at a so 7.5 so the diff is 7.5-4 =3

correct me if i am wrong on this..

i dont think that statement is right because white has greater force on the endgame it should be white's right to play there. so you should count as 7.

also...below seems correct play if white has to play there.
Click Here To Show Diagram Code
[go]$$
$$ . . . . . . . . . . . |
$$ . . . . . . . . . . . |
$$ . . . . . . . . . . . |
$$ . X X X X X X X . . . |
$$ . X O O O O O X X . . |
$$ . X O X O X 2 O O X . |
$$ . b O . O . . . a 1 . |
$$ ----------------------[/go]

Re: Intriguing problem

Posted: Thu May 05, 2011 9:59 am
by SoDesuNe
I just got corrected by the very Dan-player, that there should be a black stone at H2 (which is not shown in the original diagram ^^)

Click Here To Show Diagram Code
[go]$$Bc
$$ . . . . . . . . . . . . . |
$$ . . . . . . . . . . . . . |
$$ . . . . . . . . . . . . . |
$$ . . . X X X X X X X . . . |
$$ . . . X O O O O O X X . . |
$$ . B . X O X O X . O O X . |
$$ . . . . O . O . . . . 1 . |
$$ ----------------------[/go]


Sorry!
Answers have been correct so far.

White should play something worth three points or more.

Re: Intriguing problem

Posted: Thu May 05, 2011 10:46 am
by Bill Spight
Click Here To Show Diagram Code
[go]$$Bc
$$ . . . . . . . . . . . . . |
$$ . . . . . . . . . . . . . |
$$ . . . . . . . . . . . . . |
$$ . . . X X X X X X X . . . |
$$ . . . X O O O O O X X . . |
$$ . B . X O X O X . O O X . |
$$ . . . . O . O . . . . 1 . |
$$ --------------------------[/go]


Note: I have added a stone which, I think, preserves the idea of the problem and avoids complications if White threatens to escape. :)

Edit: Ah! I see that that was part of the original problem. :) :) :)

Is :b1: sente?

No.

As everybody else has indicated. :)


How much does a reply by White gain?

3.5 points.

Click Here To Show Diagram Code
[go]$$Wc White reply
$$ . . . . . . . . . . . . . |
$$ . . . . . . . . . . . . . |
$$ . . . . . . . . . . . . . |
$$ . . . X X X X X X X . . . |
$$ . . . X O O O O O X X . . |
$$ . X . X O B O B 1 O O X . |
$$ . . 6 5 O C O C C 7 4 X . |
$$ --------------------------[/go]


White replies with :w1:. Later :b4: is ambiguous. White interposes a sente before replying. The local score is -7.

Click Here To Show Diagram Code
[go]$$Bc Black continuation
$$ . . . . . . . . . . . . . |
$$ . . . . . . . . . . . . . |
$$ . . . . . . . . . . . . . |
$$ . . . X X X X X X X . . . |
$$ . . . X O O O O O X X . . |
$$ . X . X O X O X 1 W O X . |
$$ . . . 7 O . O 5 4 2 3 X . |
$$ --------------------------[/go]


:w6: ataris at :wc: :w8: captures at :w4:

Note: :b7: can be played later.

Click Here To Show Diagram Code
[go]$$Bc Position after Black continues
$$ . . . . . . . . . . . . . |
$$ . . . . . . . . . . . . . |
$$ . . . . . . . . . . . . . |
$$ . . . X X X X X X X . . . |
$$ . . . X O O O O O X X . . |
$$ . X . X O B O C a O . X . |
$$ . . C X O C O C O . X X . |
$$ --------------------------[/go]


In this position White has 5 points of secure territory, plus 3 captured stones, and we can count a as 1/2 point for White, for a total of 8.5 points. Black has 1 point of territory plus 4 captured stones, for a total of 5 points. The local count is 5 - 8.5 = -3.5.

Since Black's continuation was sente, this is also the count after :b1: in the original diagram. White's reply is a reverse sente that gains 3.5 points. :)


Is :b1: correct?

I don't think so.

Click Here To Show Diagram Code
[go]$$Bc Sente
$$ . . . . . . . . . . . . . |
$$ . . . . . . . . . . . . . |
$$ . . . . . . . . . . . . . |
$$ . . . X X X X X X X . . . |
$$ . . . X O O O O O X X . . |
$$ . X . X O X O X 1 O O X . |
$$ . . . . O . O . . 2 . a . |
$$ --------------------------[/go]


:b1: is sente, forcing :w2:. If Black waits until after White plays at a, then White will not reply at :w2: to :b1:, but will atari.

Re: Intriguing problem

Posted: Thu May 05, 2011 10:53 am
by Magicwand
Bill Spight wrote:Since Black's continuation was sente, this is also the count after in the original diagram. White's reply is a reverse sente that gains 3.5 points.


i disagree because one point on left is not a part of the problem.
it is white's sente anyway..so you dont count that as a point.

so the answer is 2.5 gain.

Re: Intriguing problem

Posted: Thu May 05, 2011 11:27 am
by Bill Spight
Magicwand wrote:
Bill Spight wrote:Since Black's continuation was sente, this is also the count after in the original diagram. White's reply is a reverse sente that gains 3.5 points.


i disagree because one point on left is not a part of the problem.
it is white's sente anyway..so you dont count that as a point.

so the answer is 2.5 gain.


In the Black continuation it becomes Black's sente instead of White's. That's why we count it. :)

Re: Intriguing problem

Posted: Thu May 05, 2011 12:33 pm
by Magicwand
Bill Spight wrote:
Magicwand wrote:
Bill Spight wrote:Since Black's continuation was sente, this is also the count after in the original diagram. White's reply is a reverse sente that gains 3.5 points.


i disagree because one point on left is not a part of the problem.
it is white's sente anyway..so you dont count that as a point.

so the answer is 2.5 gain.


In the Black continuation it becomes Black's sente instead of White's. That's why we count it. :)


wow.. i missed it ;)
thanks..

but..if black plays that one point in sente (which equal in value as 2 point gote) then he will lose gote 2.5 endgame at right so you dont want to play that side first.

can you recheck if you made a mistake? i still think i am correct.

Re: Intriguing problem

Posted: Thu May 05, 2011 1:02 pm
by Bill Spight
Magicwand wrote:but..if black plays that one point in sente (which equal in value as 2 point gote) then he will lose gote 2.5 endgame at right so you dont want to play that side first.

can you recheck if you made a mistake? i still think i am correct.


It is the play on the right that sets up the sente on the left.

Click Here To Show Diagram Code
[go]$$Bc Wrong sente
$$ . . . . . . . . . . . . . |
$$ . . . . . . . . . . . . . |
$$ . . . . . . . . . . . . . |
$$ . . . X X X X X X X . . . |
$$ . . . X O O O O O X X . . |
$$ . X . X O X O X X O . X . |
$$ . . 5 4 O . O X 2 1 X X . |
$$ --------------------------[/go]


If Black chooses the sente on the right, White gets a total of 8 points and Black gets a total of 4, for a local count of -4 instead of -3.5. Black loses 1/2 point. :)

Re: Intriguing problem

Posted: Thu May 05, 2011 1:27 pm
by Magicwand
i see what i am missing.
you rock Bill!!!

Re: Intriguing problem

Posted: Thu May 05, 2011 3:56 pm
by Bill Spight
Magicwand wrote:i see what i am missing.


I missed it myself, at first. :)

And thank you for the compliment, oh, Master of Malkovich. :)
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