Intriguing problem

SoDesuNe · Post by **SoDesuNe** » Thu May 05, 2011 2:44 am

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:

?

Post by **Solomon** » Thu May 05, 2011 2:57 am

Really bad with questions like the 2nd one, so I'll just try to answer the first:

Magicwand · Post by **Magicwand** » Thu May 05, 2011 4:39 am

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.

$$Bc
$$ . . . . . . . . . . . |
$$ . . . . . . . . . . . |
$$ . . . . . . . . . . . |
$$ . X X X X X X X . . . |
$$ . X O O O O O X X . . |
$$ . X O X O X . O O X . |
$$ . . O . O . . . . 1 . |
$$ ----------------------

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 Sente against White's group (why/why not)?

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

very intresting endgame question

i am curious what bill has to say about this

perceval · Post by **perceval** » Thu May 05, 2011 6:29 am

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]$$Wc at $$ . . . . . . . . . . . | $$ . . . . . . . . . . . | $$ . . . . . . . . . . . | $$ . X X X X X X X . . . | $$ . 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]$$Wc is sente $$ . . . . . . . . . . . | $$ . . . . . . . . . . . | $$ . . . . . . . . . . . | $$ . X X X X X X X . . . | $$ . 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]

Magicwand · Post by **Magicwand** » Thu May 05, 2011 9:49 am

perceval wrote:
7 or 8 depending of who gets the gote at a so 7.5 so the diff is 7.5-4 =3

SoDesuNe · Post by **SoDesuNe** » Thu May 05, 2011 9:59 am

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.

Bill Spight · Post by **Bill Spight** » Thu May 05, 2011 10:46 am

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

sente?

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

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]

ataris at

captures at :w4:

Note:

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

correct?

Magicwand · Post by **Magicwand** » Thu May 05, 2011 10:53 am

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.

Bill Spight · Post by **Bill Spight** » Thu May 05, 2011 11:27 am

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.

Magicwand · Post by **Magicwand** » Thu May 05, 2011 12:33 pm

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.

Bill Spight · Post by **Bill Spight** » Thu May 05, 2011 1:02 pm

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.

Magicwand · Post by **Magicwand** » Thu May 05, 2011 1:27 pm

i see what i am missing.
you rock Bill!!!

Bill Spight · Post by **Bill Spight** » Thu May 05, 2011 3:56 pm

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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