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 Post subject: Counting question
Post #1 Posted: Wed Feb 22, 2017 7:53 am 
Dies in gote

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Hi! This is a very, very simple counting question. But bear with me - I'm just a beginner.



The question is: "What is the value of playing at B1". I get 3+4 = 7 points. The "book" says 8 (no explanation). What did I miss?

Thanks in advance!

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 Post subject: Re: Counting question
Post #2 Posted: Wed Feb 22, 2017 7:57 am 
Dies with sente

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If black gets it, white a3 is not going to be a point, he will have to connect there later. That is the point you forgot to count.

Edit: actually, in this case, I think the move is even bigger, beacause after white b1, a later play at d1 is sente for white, so we cannot count the exchange black d1 white c1 as sente for black.
Edit2, ah I see, you also didnt count in the fact, that after black gets b1, he will later have to take the white stone out. So I now count 9 points, your 7 +1 the one above, plus 2 more for white d1 in sente -1 for that. It seems it's not that simple;)

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 Post subject: Re: Counting question
Post #3 Posted: Wed Feb 22, 2017 8:09 am 
Dies in gote

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Wow, that was fast!

> If black gets it, white a3 is not going to be a point,
> he will have to connect there later. That is the point
> you forgot to count.

I was thinking about that. But if black plays at B1 first he can't play A1 because of the white stone at C2. He would first have to capture that stone, reducing his territory by 1. Only then white would have to defend at A3. So the count wouldn't change.

Did I get that right?

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 Post subject: Re: Counting question
Post #4 Posted: Wed Feb 22, 2017 8:13 am 
Dies with sente

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Baywa wrote:
Wow, that was fast!

> If black gets it, white a3 is not going to be a point,
> he will have to connect there later. That is the point
> you forgot to count.

I was thinking about that. But if black plays at B1 first he can't play A1 because of the white stone at C2. He would first have to capture that stone, reducing his territory by 1. Only then white would have to defend at A3. So the count wouldn't change.

Did I get that right?

Yes that seems right(what I only noticed by edit 2). I at the moment do not count the move to be 8 points(but rather 9), so maybe if 8 is right, someone should explain it to the both of us:)

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 Post subject: Re: Counting question
Post #5 Posted: Wed Feb 22, 2017 8:34 am 
Tengen

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If black plays first, we will eventually end up with:
Click Here To Show Diagram Code
[go]$$Bc
$$ -------------------
$$ | . . . . . . . . . |
$$ | . . . . . . . . . |
$$ | . . , O . . , . . |
$$ | . . . O X . . . . |
$$ | . O . O X . . . . |
$$ | . . O O X . . . . |
$$ | O O X X . X , . . |
$$ | O X . X . . . . . |
$$ | O X X . . . . . . |
$$ -------------------[/go]

If white, then:
Click Here To Show Diagram Code
[go]$$Wc
$$ -------------------
$$ | . . . . . . . . . |
$$ | . . . . . . . . . |
$$ | . . , O . . , . . |
$$ | . . . O X . . . . |
$$ | . O . O X . . . . |
$$ | . . O O X . . . . |
$$ | . O X X . X , . . |
$$ | O . O X 2 . . . . |
$$ | . O 5 1 4 . . . . |
$$ -------------------[/go]

Note that when counting a gote move like this you give each player their expected sente follow-ups, so white could get 1 for 2 above, and then later black 4 for 5 (there's actually a tiny chance that white could play at 4 but that's gote, whereas black's 4 is sente to capture 1 stone and more in ko so it should be his sente move later in the game).

So now you can count the difference between these 2 positions.

The way I would actually do this in my head is (knowing those terminal positions) look what intersections become points for black if he gets it (triangles) and what become points for white (squares). Remember captured stones count for 2 so there's a difference of 9 here.
Click Here To Show Diagram Code
[go]$$Bc
$$ -------------------
$$ | . . . . . . . . . |
$$ | . . . . . . . . . |
$$ | . . , O . . , . . |
$$ | . . . O X . . . . |
$$ | . O . O X . . . . |
$$ | . . O O X . . . . |
$$ | S O X X . X , . . |
$$ | O # Q X T . . . . |
$$ | S . . T T . . . . |
$$ -------------------[/go]

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 Post subject: Re: Counting question
Post #6 Posted: Wed Feb 22, 2017 9:18 am 
Dies in gote

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Thanks a lot for that detailed response, Uberdude! My counting based on the exchange Wb1 (captures), Bd1, Wc1. Bd1 doesn't seem to be worth much but if W ignores, then Bc1 and W has to connect at b2, loosing one point. But it all depends on what other endgame moves there are, doesn't it?

BTW: This problem is from the online course on 321go.org, Chapter 5.7.2.

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 Post subject: Re: Counting question
Post #7 Posted: Wed Feb 22, 2017 10:12 am 
Judan

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I prepared an SGF file, but Uberdude beat me to it. :)

Just a couple of small points.

Click Here To Show Diagram Code
[go]$$Bc Black first
$$ -------------------
$$ | . . . . . . . . . |
$$ | . . . . . . . . . |
$$ | . . , O . . , . . |
$$ | . . . O X . . . . |
$$ | . O . O X . . . . |
$$ | . . O O X . . . . |
$$ | W O X X . X , . . |
$$ | O X O X b . . . . |
$$ | x 1 B b b . . . . |
$$ -------------------[/go]


After :b1: :bc: and :wc: are later protective plays. x is a dame.

Local result for Black: +5

Click Here To Show Diagram Code
[go]$$Wc White first
$$ -------------------
$$ | . . . . . . . . . |
$$ | . . . . . . . . . |
$$ | . . , O . . , . . |
$$ | . . . O X . . . . |
$$ | . O . O X . . . . |
$$ | . . O O X . . . . |
$$ | w O X X . X , . . |
$$ | O X O X 4 . . . . |
$$ | w 1 7 3 6 . . . . |
$$ -------------------[/go]


After :w1: :w3: is later sente. Black normally replies with :b4: Later, :b6: is sente.

Local result for Black: -4

Swing = 9

Initial local value for Black: 0.5

Each gote play gains 4.5.

Click Here To Show Diagram Code
[go]$$Wc Black komaster
$$ -------------------
$$ | . . . . . . . . . |
$$ | . . . . . . . . . |
$$ | . . , O . . , . . |
$$ | . . . O X . . . . |
$$ | . O . O X . . . . |
$$ | . . O O X . . . . |
$$ | . O X X . X , . . |
$$ | O . O X 6 . . . . |
$$ | . O 5 3 4 . . . . |
$$ -------------------[/go]


If Black is komaster she can play :b4:. The result is the same as the main line.

Click Here To Show Diagram Code
[go]$$Wc White komaster
$$ -------------------
$$ | . . . . . . . . . |
$$ | . . . . . . . . . |
$$ | . . , O . . , . . |
$$ | . . . O X . . . . |
$$ | . O . O X . . . . |
$$ | . . O O X . . . . |
$$ | . O X X . X , . . |
$$ | O . O X 5 . . . . |
$$ | . O 6 3 4 7 . . . |
$$ -------------------[/go]


If White is komaster :w5: - :w7: is very bad for Black.

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