Behind the scenes of some endgame tesuji

xela · Post by **xela** » Sun Dec 29, 2019 5:19 pm

I'm re-reading 200 Endgame Problems. The first time round, many years ago, I went through it with a "spot the key move" attitude, and thought it was pretty easy. This time round, I'm setting the bar higher in terms of understanding why the key move is good, and seeing more of the variations, and I'm finding it much more challenging. Great to have a book that works on more than one level! I wonder if Shirae is trying to nudge us in the direction of effortful practice, in the same way that JF makes explicit in his variation-free Genjo-Chitoku?

Anyway, enough waffling. I'd like to take a dozen or so problems from the book and dig deeper, find the insights that aren't in the two solution diagrams per problem that you get. First up is part 1 problem 13.

Click Here To Show Diagram Code: [go]$$B Black to play $$-----------------------+ $$ . . . . . . . . . . . | $$ . . . . . O . . X X . | $$ . O . . . O X X O O . | $$ . . . . . O O O X . . | $$ . . . . . . . . X . . | $$ . . . . . . . O X . . | $$ . . . . . . . . X . . | $$ . . . . . . . . . . . | $$ . . . . . . . . . . . | $$ . . . . . . . . . . . |[/go]

Summary of book solution

What's not discussed is this alternative move, a shape which appears as the solution to some later problems. What is white's reply to

in the next diagram?

Gomoto · Post by **Gomoto** » Sun Dec 29, 2019 7:31 pm

White's reply:

xela · Post by **xela** » Mon Dec 30, 2019 5:05 am

Yes, that's it. Took me some effort to understand why it's actually a good result for white.

Next up, part 1 problem 30.

Click Here To Show Diagram Code: [go]$$B Black to play $$-----------------------+ $$ . . . . . . . . . . . | $$ . . . . . . . O X . . | $$ . . O . . O . O X . . | $$ . . . O O X O O X . . | $$ . . . . . X X X . . . | $$ . . . . . . . . . . . | $$ . . . . . . . . . . . |[/go]

This is what not to do:

Click Here To Show Diagram Code: [go]$$B The ordinary moves $$-----------------------+ $$ . . . . . . 2 1 3 . . | $$ . . . . . . 4 O X . . | $$ . . O . . O . O X . . | $$ . . . O O X O O X . . | $$ . . . . . X X X . . . | $$ . . . . . . . . . . . | $$ . . . . . . . . . . . |[/go]

Here's the book solution:

Now it might not be obvious at a glance that the solution is actually better than the ordinary moves. (At least, it wasn't obvious to me.) So this is a good counting exercise: how many points has black gained in the book solution compared with the ordinary moves?

Gomoto · Post by **Gomoto** » Mon Dec 30, 2019 10:57 am

Black gains ...

jlt · Post by **jlt** » Mon Dec 30, 2019 11:17 am

@Gomoto: I think that Black gains more than that, because to capture the three stones, White has to take gote, but on the other hand Black can also take gote to save his three stones?

Kirby · Post by **Kirby** » Mon Dec 30, 2019 12:16 pm

jlt wrote:@Gomoto: I think that Black gains more than that, because to capture the three stones, White has to take gote, but on the other hand Black can also take gote to save his three stones?

My understanding in this situation is that...

I'm bad at endgame calculations, so I'd be interested in having my analysis corrected, if there are errors.

jlt · Post by **jlt** » Mon Dec 30, 2019 1:27 pm

Since I didn't study endgame theory seriously, it would be a miracle if my answer was correct, but here it is anyway. At least one of us is wrong.

Start from the book solution, and suppose White has no ko threats (one of my problems is that I don't know how to treat the ko). We count the score locally, so that the "wrong answer" in xela's post has score W+6.

Click Here To Show Diagram Code: [go]$$B (one white stone captured) $$-----------------------+ $$ . . . . . X . X . . . | $$ . . . . O X X O X . . | $$ . . O . O O O O X . . | $$ . . . O O X O O X . . | $$ . . . . . X X X . . . | $$ . . . . . . . . . . . | $$ . . . . . . . . . . . |[/go]

Consider the following positions :

Click Here To Show Diagram Code: [go]$$W Position W $$-----------------------+ $$ . . . . 1 X . X . . . | $$ . . . . O X X O X . . | $$ . . O . O O O O X . . | $$ . . . O O X O O X . . | $$ . . . . . X X X . . . | $$ . . . . . . . . . . . | $$ . . . . . . . . . . . |[/go]

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

Click Here To Show Diagram Code: [go]$$W Position WW $$-----------------------+ $$ . . . . O . 1 X . . . | $$ . . . . O . . O X . . | $$ . . O . O O O O X . . | $$ . . . O O X O O X . . | $$ . . . . . X X X . . . | $$ . . . . . . . . . . . | $$ . . . . . . . . . . . |[/go]

Click Here To Show Diagram Code: [go]$$B Position WB=BW $$-----------------------+ $$ . . . . O X . X 1 . . | $$ . . . . O X X O X . . | $$ . . O . O O O O X . . | $$ . . . O O X O O X . . | $$ . . . . . X X X . . . | $$ . . . . . . . . . . . | $$ . . . . . . . . . . . |[/go]

Click Here To Show Diagram Code: [go]$$B Position WBB: B+1 $$-----------------------+ $$ . . . . O X X X X . . | $$ . . . . O X X O X . . | $$ . . O . O O O O X . . | $$ . . . O O X O O X . . | $$ . . . . . X X X . . . | $$ . . . . . . . . . . . | $$ . . . . . . . . . . . |[/go]

Click Here To Show Diagram Code: [go]$$W Position WWW: W+7 $$-----------------------+ $$ . . . . O . O 3 1 2 . | $$ . . . . O . . O X 4 . | $$ . . O . O O O O X . . | $$ . . . O O X O O X . . | $$ . . . . . X X X . . . | $$ . . . . . . . . . . . | $$ . . . . . . . . . . . |[/go]

Click Here To Show Diagram Code: [go]$$B Position WWB=WBW: W+5 $$-----------------------+ $$ . . . . O . O X 1 . . | $$ . . . . O . . O X . . | $$ . . O . O O O O X . . | $$ . . . O O X O O X . . | $$ . . . . . X X X . . . | $$ . . . . . . . . . . . | $$ . . . . . . . . . . . |[/go]

Click Here To Show Diagram Code: [go]$$B Position BB: B+3 $$-----------------------+ $$ . . . 2 1 X 3 X X . . | $$ . . . 4 O X X O X . . | $$ . . O . O O O O X . . | $$ . . . O O X O O X . . | $$ . . . . . X X X . . . | $$ . . . . . . . . . . . | $$ . . . . . . . . . . . |[/go]

White's score at the final positions is:

WWW=7, WWB=WBW=5, WBB=-1, BB=-3.
So WW=(WWW+WWB)/2=6
BW=WB=(WBW+WBB)/2=2
W=4
B=-0.5
(the book's position) = 1.75

On the other hand, the wrong answer had a score equal to 6. So compared to the wrong answer, the book answer gains 4.25 points.

Gomoto · Post by **Gomoto** » Mon Dec 30, 2019 2:19 pm

I am a simple man. With the optimal answer black gains at least 1 point. And there is the additional potential for even more gains (Related to the rest of the board position.)

That is enough endgame theory for my needs

Tryss · Post by **Tryss** » Mon Dec 30, 2019 2:33 pm

In pure area scoring, Black only gain sente

xela · Post by **xela** » Mon Dec 30, 2019 3:10 pm

Gomoto wrote:That is enough endgame theory for my needs :-)

Well, I'm posting these because I'm interested in endgame theory and want to learn more :-) It's not that I need more endgame theory though, what I really need is to not lose all those middlegame fights, but that's a different conversation...

So for this one I get the same as Kirby. Of course that doesn't mean I'm correct, I'm still learning this stuff too. My first impression of jlt's analysis was that in the 1-2-3 sequences, move 1 reverses. So the WWW and BB diagrams should never happen with correct play.

It's the same as the basic hane-connect:

Click Here To Show Diagram Code: [go]$$B Three-move sequence $$ X X X O O O $$ . . 3 1 2 . $$ -------------[/go]

You'd never analyse the following position:

Click Here To Show Diagram Code: [go]$$B White to play $$ X X X O O O $$ . . . 1 2 . $$ -------------[/go]

because for black to play 1 and then abandon the position is a loss for black. If black 1 goes on the board and both players are making the best moves, then you'll always see 1-2-3 as a unit.

But actually, jlt's diagrams are not quite the same thing, because the 1-2 exchanges there don't actually make the position worse for the first player, they just make the position no better. I think that in a whole-board position where the other moves are small enough that 1 is the best local move, then 2 would be sente, which is why you'd still treat 1-2-3 as a unit for counting purposes (although in practice you could play 1, leave it alone for a while, then do 2-3 later). So not technically a "reverse", but same effect.

I haven't read it yet, but I believe Robert Jasiek's Endgame 3 has some theory on "long sequences" which goes into this in more depth. And someone please tell me if I'm overthinking this.

Shaddy · Post by **Shaddy** » Mon Dec 30, 2019 5:40 pm

You could actually analyze that position, xela; it is useful to know sometimes how much a lossy ko threat loses.

RobertJasiek · Post by **RobertJasiek** » Tue Dec 31, 2019 12:31 am

xela wrote:
$$B White to play
$$ X X X O O O
$$ . . . 1 2 .
$$ -------------
Click Here To Show Diagram Code
[go]$$B White to play $$ X X X O O O $$ . . . 1 2 . $$ -------------[/go]
because for black to play 1 and then abandon the position is a loss for black. [...]
I haven't read it yet, but I believe Robert Jasiek's Endgame 3 has some theory on "long sequences" which goes into this in more depth.

See viewtopic.php?p=252422#p252422

jlt · Post by **jlt** » Tue Dec 31, 2019 1:11 am

Still confused.

Well, I should really read some endgame books. I am currently working on tesuji but after that I should learn to count.

Uberdude · Post by **Uberdude** » Tue Dec 31, 2019 2:12 am

Simple mistake way White has 6 points to baseline.
Tesuji variation White has 0 or 6 points depending who gets the gote. So currently worth 3. Black has 1 extra from throw in. So white net 3-1=2.
6-2=4. Black gained 4 points from the tesuji endgame.

Kirby · Post by **Kirby** » Tue Dec 31, 2019 7:58 am

jlt wrote:Since I didn't study endgame theory seriously, it would be a miracle if my answer was correct, but here it is anyway. At least one of us is wrong.

Start from the book solution, and suppose White has no ko threats (one of my problems is that I don't know how to treat the ko). We count the score locally, so that the "wrong answer" in xela's post has score W+6.

$$B (one white stone captured)
$$-----------------------+
$$ . . . . . X . X . . . |
$$ . . . . O X X O X . . |
$$ . . O . O O O O X . . |
$$ . . . O O X O O X . . |
$$ . . . . . X X X . . . |
$$ . . . . . . . . . . . |
$$ . . . . . . . . . . . |
Click Here To Show Diagram Code
[go]$$B (one white stone captured) $$-----------------------+ $$ . . . . . X . X . . . | $$ . . . . O X X O X . . | $$ . . O . O O O O X . . | $$ . . . O O X O O X . . | $$ . . . . . X X X . . . | $$ . . . . . . . . . . . | $$ . . . . . . . . . . . |[/go]
Consider the following positions :

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

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

$$W Position WW
$$-----------------------+
$$ . . . . O . 1 X . . . |
$$ . . . . O . . O X . . |
$$ . . O . O O O O X . . |
$$ . . . O O X O O X . . |
$$ . . . . . X X X . . . |
$$ . . . . . . . . . . . |
$$ . . . . . . . . . . . |
Click Here To Show Diagram Code
[go]$$W Position WW $$-----------------------+ $$ . . . . O . 1 X . . . | $$ . . . . O . . O X . . | $$ . . O . O O O O X . . | $$ . . . O O X O O X . . | $$ . . . . . X X X . . . | $$ . . . . . . . . . . . | $$ . . . . . . . . . . . |[/go]

$$B Position WB=BW
$$-----------------------+
$$ . . . . O X . X 1 . . |
$$ . . . . O X X O X . . |
$$ . . O . O O O O X . . |
$$ . . . O O X O O X . . |
$$ . . . . . X X X . . . |
$$ . . . . . . . . . . . |
$$ . . . . . . . . . . . |
Click Here To Show Diagram Code
[go]$$B Position WB=BW $$-----------------------+ $$ . . . . O X . X 1 . . | $$ . . . . O X X O X . . | $$ . . O . O O O O X . . | $$ . . . O O X O O X . . | $$ . . . . . X X X . . . | $$ . . . . . . . . . . . | $$ . . . . . . . . . . . |[/go]

$$B Position WBB: B+1
$$-----------------------+
$$ . . . . O X X X X . . |
$$ . . . . O X X O X . . |
$$ . . O . O O O O X . . |
$$ . . . O O X O O X . . |
$$ . . . . . X X X . . . |
$$ . . . . . . . . . . . |
$$ . . . . . . . . . . . |
Click Here To Show Diagram Code
[go]$$B Position WBB: B+1 $$-----------------------+ $$ . . . . O X X X X . . | $$ . . . . O X X O X . . | $$ . . O . O O O O X . . | $$ . . . O O X O O X . . | $$ . . . . . X X X . . . | $$ . . . . . . . . . . . | $$ . . . . . . . . . . . |[/go]

$$W Position WWW: W+7
$$-----------------------+
$$ . . . . O . O 3 1 2 . |
$$ . . . . O . . O X 4 . |
$$ . . O . O O O O X . . |
$$ . . . O O X O O X . . |
$$ . . . . . X X X . . . |
$$ . . . . . . . . . . . |
$$ . . . . . . . . . . . |
Click Here To Show Diagram Code
[go]$$W Position WWW: W+7 $$-----------------------+ $$ . . . . O . O 3 1 2 . | $$ . . . . O . . O X 4 . | $$ . . O . O O O O X . . | $$ . . . O O X O O X . . | $$ . . . . . X X X . . . | $$ . . . . . . . . . . . | $$ . . . . . . . . . . . |[/go]

$$B Position WWB=WBW: W+5
$$-----------------------+
$$ . . . . O . O X 1 . . |
$$ . . . . O . . O X . . |
$$ . . O . O O O O X . . |
$$ . . . O O X O O X . . |
$$ . . . . . X X X . . . |
$$ . . . . . . . . . . . |
$$ . . . . . . . . . . . |
Click Here To Show Diagram Code
[go]$$B Position WWB=WBW: W+5 $$-----------------------+ $$ . . . . O . O X 1 . . | $$ . . . . O . . O X . . | $$ . . O . O O O O X . . | $$ . . . O O X O O X . . | $$ . . . . . X X X . . . | $$ . . . . . . . . . . . | $$ . . . . . . . . . . . |[/go]

$$B Position BB: B+3
$$-----------------------+
$$ . . . 2 1 X 3 X X . . |
$$ . . . 4 O X X O X . . |
$$ . . O . O O O O X . . |
$$ . . . O O X O O X . . |
$$ . . . . . X X X . . . |
$$ . . . . . . . . . . . |
$$ . . . . . . . . . . . |
Click Here To Show Diagram Code
[go]$$B Position BB: B+3 $$-----------------------+ $$ . . . 2 1 X 3 X X . . | $$ . . . 4 O X X O X . . | $$ . . O . O O O O X . . | $$ . . . O O X O O X . . | $$ . . . . . X X X . . . | $$ . . . . . . . . . . . | $$ . . . . . . . . . . . |[/go]
White's score at the final positions is:

WWW=7, WWB=WBW=5, WBB=-1, BB=-3.
So WW=(WWW+WWB)/2=6
BW=WB=(WBW+WBB)/2=2
W=4
B=-0.5
(the book's position) = 1.75

On the other hand, the wrong answer had a score equal to 6. So compared to the wrong answer, the book answer gains 4.25 points.

I have a little more confidence now that some other folks also got the same answer, so I'll give my interpretation as to why I have a different answer than this one:

As usual, I'm open to critique in this analysis.

Life In 19x19

Behind the scenes of some endgame tesuji

Behind the scenes of some endgame tesuji

Re: Behind the scenes of some endgame tesuji

Re: Behind the scenes of some endgame tesuji

Re: Behind the scenes of some endgame tesuji

Re: Behind the scenes of some endgame tesuji

Re: Behind the scenes of some endgame tesuji

Re: Behind the scenes of some endgame tesuji

Re: Behind the scenes of some endgame tesuji

Re: Behind the scenes of some endgame tesuji

Re: Behind the scenes of some endgame tesuji

Re: Behind the scenes of some endgame tesuji

Re: Behind the scenes of some endgame tesuji

Re: Behind the scenes of some endgame tesuji

Re: Behind the scenes of some endgame tesuji

Re: Behind the scenes of some endgame tesuji