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 Post subject: Opening problems for AI: Problem 26 #1 Posted: Fri Jul 10, 2020 2:07 am
 Honinbo

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Black's textbook play loses 28½% to par, according to Elf, assuming komi, as always.

`[go]\$\$Bcm23 Black to play\$\$ ---------------------------------------\$\$ | . . . . . . O . . . . . . . . . . . . |\$\$ | . . . O X O . O . . . . . . . . . . . |\$\$ | . . X O O X O O . . . . . . O . . . . |\$\$ | . . . , X X X . . , . . . . . , X . . |\$\$ | . . X . . . . . . . . . . . . . . . . |\$\$ | . . . . . . . . . . . . . . . . . . . |\$\$ | . . O . . . . . . . . . . . . . . . . |\$\$ | . . . . . . . . . . . . . . . . . . . |\$\$ | . . . . . . . . . . . . . . . . . . . |\$\$ | . . . , . . . . . , . . . . . , . . . |\$\$ | . . X . . . . . . . . . . . . . . . . |\$\$ | . . . . . . . . . . . . . . . . . . . |\$\$ | . . . . . . . . . . . . . . . . . . . |\$\$ | . . . . . . . . . . . . . . . . . . . |\$\$ | . . . . . . . . . . . . . . . . . . . |\$\$ | . . X , . . . . . , . . . . . , O . . |\$\$ | . . . . . . . . . . . . . . . . . . . |\$\$ | . . . . . . . . . . . . . . . . . . . |\$\$ | . . . . . . . . . . . . . . . . . . . |\$\$ ---------------------------------------[/go]`

Black to play.

There are lots of possible plays out there. Enjoy!

_________________
At some point, doesn't thinking have to go on?

Visualize whirled peas.

Everything with love. Stay safe.

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 Post subject: Re: Opening problems for AI: Problem 26 #2 Posted: Fri Jul 10, 2020 3:43 am
 Judan

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`[go]\$\$B moves possibly losing much\$\$ ---------------------------------------\$\$ | . . . . . . O . . . . . . . . . . . . |\$\$ | . . . O X O . O . . . . . . . . . . . |\$\$ | . . X O O X O O . . . . . . O . . . . |\$\$ | . . . C X X X . . , . . . . . , X . . |\$\$ | . . X . . . . . . . . . . . . . . . . |\$\$ | . . . . . . . . . . . . . . . . . . . |\$\$ | . . O . . . . . . . . . . . . . . . . |\$\$ | . . . . . . . . . . . . . . . . C . . |\$\$ | . . . . . . . . . . . . . . . . C . . |\$\$ | . . . , . . . . . , . . . . . , C . . |\$\$ | . . X . . . . . . . . . . . . . . . . |\$\$ | . . . . . . . . . . . . . . . . . . . |\$\$ | . . . . . . . . . . . . . . . . . . . |\$\$ | . . . . . . . . . . . . . . . . . . . |\$\$ | . . . . . . . . . . . . . . . . . . . |\$\$ | . . X , . . . . . , . . . . . , O . . |\$\$ | . . . . . . . . . . . . . . . . . . . |\$\$ | . . . . . . . . . . . . . . . . . . . |\$\$ | . . . . . . . . . . . . . . . . . . . |\$\$ ---------------------------------------[/go]`

`[go]\$\$B a possible choice\$\$ ---------------------------------------\$\$ | . . . . . . O . . . . . . . . . . . . |\$\$ | . . . O X O . O . . . . . . . . . . . |\$\$ | . . X O O X O O . . . . . . O 3 . . . |\$\$ | . . . , X X X . . , . . . . . , X . . |\$\$ | . . X . . . . . . . . . . . . . . . . |\$\$ | . . . . . . . . . . . . . . . . . . . |\$\$ | . . O . . . . . . . . . . . . . . . . |\$\$ | . . . . . . . . . . . . . . . . . . . |\$\$ | . . . . . . . . . . . . . . . . . . . |\$\$ | . . . , . . . . . , . . . . . , . . . |\$\$ | . . X . . . . . . . . . . . . . . . . |\$\$ | . . . . . . . . . . . . . . . . . . . |\$\$ | . . . . . . . . . . . . . . . . . . . |\$\$ | . . . . . . . . . . . . . . . . . . . |\$\$ | . . . . . . . . . . . . . . . 2 . . . |\$\$ | . . X , . . . . . , . . . . . , O . . |\$\$ | . . . . . . . . . . . . . . 1 . . . . |\$\$ | . . . . . . . . . . . . . . . . . . . |\$\$ | . . . . . . . . . . . . . . . . . . . |\$\$ ---------------------------------------[/go]`

`[go]\$\$B variation\$\$ ---------------------------------------\$\$ | . . . . . . O . . . . . . . . . . . . |\$\$ | . . . O X O . O . . . . . . . . . . . |\$\$ | . . X O O X O O . . . . . . O . . . . |\$\$ | . . . , X X X . . , . . . . . , X . . |\$\$ | . . X . . . . . . . . . . . . 2 7 . . |\$\$ | . . . . . . . . . . . . . . . 8 . . . |\$\$ | . . O . . . . . . . . . . . . . 9 . . |\$\$ | . . . . . . . . . . . . . . . . . . . |\$\$ | . . . . . . . . . . . . . . . . . . . |\$\$ | . . . , . . . . . , . . . . . , . . . |\$\$ | . . X . . . . . . . . . . . . . . . . |\$\$ | . . . . . . . . . . . . . . . . . . . |\$\$ | . . . . . . . . . . . . . . . . 6 . . |\$\$ | . . . . . . . . . . . . . . . 5 . . . |\$\$ | . . . . . . . . . . . . . . . 3 4 . . |\$\$ | . . X , . . . . . , . . . . . , O . . |\$\$ | . . . . . . . . . . . . . . X . . . . |\$\$ | . . . . . . . . . . . . . . . . . . . |\$\$ | . . . . . . . . . . . . . . . . . . . |\$\$ ---------------------------------------[/go]`

 This post by RobertJasiek was liked by: Bill Spight
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 Post subject: Re: Opening problems for AI: Problem 26 #3 Posted: Fri Jul 10, 2020 3:57 pm
 Lives in sente

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My eyes get drawn to an enclosure (or how you want to call it) in the lower left. The upper right also looks big, so maybe like this?

`[go]\$\$Bcm23 Black to play\$\$ ---------------------------------------\$\$ | . . . . . . O . . . . . . . . . . . . |\$\$ | . . . O X O . O . . . . . . . . . . . |\$\$ | . . X O O X O O . . . . . . O . . . . |\$\$ | . . . , X X X . . , . . . . . , X . . |\$\$ | . . X . . . . . 7 . . . . . . 2 3 . . |\$\$ | . . . . . . . . . . . . . . . 4 5 . . |\$\$ | . . O . . . . . . . . . . . . 6 . . . |\$\$ | . . . . . . . . . . . . . . . . . . . |\$\$ | . . . . . . . . . . . . . . . . . . . |\$\$ | . . . , . . . . . , . . . . . , . . . |\$\$ | . . X . . . . . . . . . . . . . . . . |\$\$ | . . . . . . . . . . . . . . . . . . . |\$\$ | . . . . . . . . . . . . . . . . . . . |\$\$ | . . . . . . . . . . . . . . . . . . . |\$\$ | . . . . . . . . . . . . . . . . . . . |\$\$ | . . X , . 1 . . . , . . . . . , O . . |\$\$ | . . . . . . . . . . . . . . . . . . . |\$\$ | . . . . . . . . . . . . . . . . . . . |\$\$ | . . . . . . . . . . . . . . . . . . . |\$\$ ---------------------------------------[/go]`

might be a bit thin though… my first ideas always seem to be too greedy.

_________________
A good system naturally covers all corner cases without further effort.

 This post by Harleqin was liked by: Bill Spight
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 Post subject: Re: Opening problems for AI: Problem 26 #4 Posted: Fri Jul 10, 2020 5:07 pm
 Lives in gote

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Bill Spight wrote:

`[go]\$\$Bcm23 Black to play\$\$ ---------------------------------------\$\$ | . . . . . . O . . . . . . . . . . . . |\$\$ | . . . O X O . O . . . . . . . . . . . |\$\$ | . . X O O X O O . . . . . . O . . . . |\$\$ | . . . , X X X . . , . . . e . , X . . |\$\$ | . . X . . . . . c . . . . . . b . . . |\$\$ | . . . . . . . . . . . . . . . . . . . |\$\$ | . . O . d . . . . . . . . . . . . . . |\$\$ | . . . . . . . . . . . . . . . . . . . |\$\$ | . . . . . . . . . . . . . . . . . . . |\$\$ | . . . , . . . . . , . . . . . , . . . |\$\$ | . . X . . . . . . . . . . . . . . . . |\$\$ | . . . . . . . . . . . . . . . . . . . |\$\$ | . . . . . . . . . . . . . . . . . . . |\$\$ | . . . . . . . . . . . . . . . . . . . |\$\$ | . . . . . . . . . . . . . . . . . . . |\$\$ | . . X , . . . . . , . . . . . , O . . |\$\$ | . . . . . . . . . . . . . . a . . . . |\$\$ | . . . . . . . . . . . . . . . . . . . |\$\$ | . . . . . . . . . . . . . . . . . . . |\$\$ ---------------------------------------[/go]`

It's an interesting position. I found a move that I wanted to play fairly quickly, but it was a challenge to conceive of a pro-level move that loses 28%.

In the end I decided that I could see a pro playing 'b'. It would stop white from playing 'b' himself and then continuing with 'c' to build up the top, reduce black's left and aim at nuisances like 'd'. By comparison when black gets 'b' first then he can aim at pressing at 'e', indirectly making 'd' less appealing and trying to overconcentrate white on the top.

Myself, I want to play 'a'. It's a low approach, which St. Leela blesses and even pre-AI it was generally considered a good move to approach first when there are opposing 3-4 points.

I must say that something bothers me about Black's left side position, although it's difficult to explain why. I think the problem, to my eyes, is that black's two stones on the bottom left are low and black's top left isn't thick (John, thickness discussion?) and doesn't control the white pincer stone very well. Taken together it feels like black still owes moves on the left, and if he's not careful he might not secure enough compensation for the investment. This feels like an area that an AI, with its talent for making shapes overconcentrated, might handle very well as white.

 This post by pwaldron was liked by: Bill Spight
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 Post subject: Re: Opening problems for AI: Problem 26 #5 Posted: Fri Jul 10, 2020 5:36 pm
 Oza

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My equilibrium theory predicts D16, which apart from fitting the theory also fits human concerns of perfecting thickness which has a strong likelihood of being usable as thickness, and leaving a small but tasty follow-up move in the corner.

While I'm confident about that, I find it hard to follow that the actual move (which I know) is rated as so bad by Elf. Or, more precisely, I think there is an inferior but acceptable move in that area, and I'm surprised that Elf rates the actual move as much worse even than that one.

 This post by John Fairbairn was liked by: Bill Spight
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 Post subject: Re: Opening problems for AI: Problem 26 #6 Posted: Fri Jul 10, 2020 7:31 pm
 Honinbo

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A brief word on the extreme differences in Elf's estimated winrates. In theory they are estimates of the probabilities of winning from particular positions in self play games. But, AFAICT, nobody has ever checked those estimates to see how accurate they are. They are only indirectly validated by the overall strength of the program. None of the bots' winrate estimates apply to human play, although there is a tendency to interpret them that way. Nor do they apply between bots. If Elf estimates Black's winrate in a certain position as 90%, Leela Zero might estimate it as 72%. That does not mean that they disagree, because they are estimating different things. Elf's estimate applies, in theory, anyway, to Elf's self play and Leela Zero's estimate applies, in theory, to Leela Zero's self play. They could both be right. My guess is that they are both wrong. But that kind of difference between the bots is typical. Elf makes more extreme estimates than other top bots, and the differences in its estimates for different plays tend to be greater, as well. It is important to keep in mind that Elf's estimates apply only to its own self play, not to any other bot, and certainly not to human vs. human play.

Some years ago I came up with a rule of thumb for estimated winrate differences for Leela 11, that their margin of error was about 3%. Leela Zero is far stronger, but that does not mean that its margin of error is smaller. It may even be larger, quien sabe? My rule of thumb for Elf was 5%, but I have recently raised it to 6%, but maybe that's too high. Anyway. a difference of 28% means that the play with the lower evaluation is almost certainly worse than the other play, and hence is a mistake. Most likely a blunder. If Leela Zero calculates a difference of 10%, that does not mean that that smaller difference does not indicate a blunder.

_________________
At some point, doesn't thinking have to go on?

Visualize whirled peas.

Everything with love. Stay safe.

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 Post subject: Re: Opening problems for AI: Problem 26 #7 Posted: Fri Jul 10, 2020 9:18 pm
 Judan

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Harleqin wrote:
`[go]\$\$Bcm23 Black to play\$\$ ---------------------------------------\$\$ | . . . . . . O . . . . . . . . . . . . |\$\$ | . . . O X O . O . . . . . . . . . . . |\$\$ | . . X O O X O O . . . . . . O . . . . |\$\$ | . . . , X X X . . , . . . . . , X . . |\$\$ | . . X . . . . . 7 . . . . . . 2 3 . . |\$\$ | . . . . . . . . . . . . . . . 4 5 . . |\$\$ | . . O . . . . . . . . . . . . 6 . . . |\$\$ | . . . . . . . . . . . . . . . . . . . |\$\$ | . . . . . . . . . . . . . . . . . . . |\$\$ | . . . , . . . . . , . . . . . , . . . |\$\$ | . . X . . . . . . . . . . . . . . . . |\$\$ | . . . . . . . . . . . . . . . . . . . |\$\$ | . . . . . . . . . . . . . . . . . . . |\$\$ | . . . . . . . . . . . . . . . . . . . |\$\$ | . . . . . . . . . . . . . . . . . . . |\$\$ | . . X , . 1 . . . , . . . . . , O . . |\$\$ | . . . . . . . . . . . . . . . . . . . |\$\$ | . . . . . . . . . . . . . . . . . . . |\$\$ | . . . . . . . . . . . . . . . . . . . |\$\$ ---------------------------------------[/go]`

`[go]\$\$W\$\$ ---------------------------------------\$\$ | . . . . . . O . . . . . . . . . . . . |\$\$ | . . . O X O . O . . . . . . . . . . . |\$\$ | . . X O O X O O . . . . . . O . . . . |\$\$ | . . . 1 X X X 3 . , . . . . . , X . . |\$\$ | . . X 2 . . . 4 X . . . . . . O X . . |\$\$ | . . . . . 5 . . . . . . . . . O X . . |\$\$ | . . O . . . . . . . . . . . . O . . . |\$\$ | . . . . . . . . . . . . . . . . . . . |\$\$ | . . . . . . . . . . . . . . . . . . . |\$\$ | . . . , . . . . . , . . . . . , . . . |\$\$ | . . X . . . . . . . . . . . . . . . . |\$\$ | . . . . . . . . . . . . . . . . . . . |\$\$ | . . . . . . . . . . . . . . . . . . . |\$\$ | . . . . . . . . . . . . . . . . . . . |\$\$ | . . . . . . . . . . . . . . . . . . . |\$\$ | . . X , . X . . . , . . . . . , O . . |\$\$ | . . . . . . . . . . . . . . . . . . . |\$\$ | . . . . . . . . . . . . . . . . . . . |\$\$ | . . . . . . . . . . . . . . . . . . . |\$\$ ---------------------------------------[/go]`

Harleqin, how do you want to follow-up your sequence?

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 Post subject: Re: Opening problems for AI: Problem 26 #8 Posted: Sat Jul 11, 2020 10:50 am
 Honinbo

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Textbook blunder (joseki)

Black's blunder was the simple joseki response in the top right corner, making a base.

`[go]\$\$Bcm23 Nakamura Doseki (W) - Yasui Santetsu, 1620-00-00bd\$\$ ---------------------------------------\$\$ | . . . . . . O . . . . . . . . . . . . |\$\$ | . . . O X O . O . . . . . . . . . . . |\$\$ | . . X O O X O O . . . . . . O . . . . |\$\$ | . . . 2 X X X . . , . . . . . , X . . |\$\$ | . . X 3 5 . . . . . . . . . . . . . . |\$\$ | . . . . 4 c . . . . . . . . . . . . . |\$\$ | . . O . . . . . . . . . . . . . 1 . . |\$\$ | . . . . . . . . . . . . . . . . . . . |\$\$ | . . . . . . . . . . . . . . . . . . . |\$\$ | . . . d . . . . . , . . . . . , . . . |\$\$ | . . X . . . . . . . . . . . . . . . . |\$\$ | . . . . . . . . . . . . . . . . . . . |\$\$ | . . . . . . . . . . . . . . . . . . . |\$\$ | . . . . . . . . . . . . . . . . . . . |\$\$ | . . . . . . . . . . . . . . . . . . . |\$\$ | . . X , a . . . . , . . . . . , O . . |\$\$ | . . . . b . . . . . . . . e . . . . . |\$\$ | . . . . . . . . . . . . . . . . . . . |\$\$ | . . . . . . . . . . . . . . . . . . . |\$\$ ---------------------------------------[/go]`

After Doseki pushed out with and played kikashi with , forcing . These last four moves are also Elf's top choices. White now has 5 good moves with winrate estimates within 0.1%, a - e, ordered by the number of rollouts, greatest to least. In the game Doseki played the corner approach at b.

Solid thickness

`[go]\$\$Bcm23 Strong wall\$\$ ---------------------------------------\$\$ | . . . . . . O . . . . . . . . . . . . |\$\$ | . . a O X O . O . . . . . . . . . . . |\$\$ | . . X O O X O O . . . . . . O . . . . |\$\$ | . . . 1 X X X . . , . . . . . , X . . |\$\$ | . . X . . . . . . . . . . . . . . . . |\$\$ | . . . . . . . . . . . . . . . . . . . |\$\$ | . . W . . . . . . . . . . . . . . . . |\$\$ | . . . . . . . . . . . . . . . . . . . |\$\$ | . . . . . . . . . . . . . . . . . . . |\$\$ | . . . , . . . . . , . . . . . , . . . |\$\$ | . . X . . . . . . . . . . . . . . . . |\$\$ | . . . . . . . . . . . . . . . . . . . |\$\$ | . . . . . . . . . . . . . . . . . . . |\$\$ | . . . . . . . . . . . . . . . . . . . |\$\$ | . . . . . . . . . . . . . . . . . . . |\$\$ | . . X , . . . . . , . . . . . , O . . |\$\$ | . . . . . . . . . . . . . . . . . . . |\$\$ | . . . . . . . . . . . . . . . . . . . |\$\$ | . . . . . . . . . . . . . . . . . . . |\$\$ ---------------------------------------[/go]`

solidifies Black's wall, weakening the pincered stone. The fact that White now has no kikashi is significant. In addition, a in the corner becomes big.

`[go]\$\$Bcm23 Mainline variation for \$\$ ---------------------------------------\$\$ | . . . . . . O . . . . . . . . . . . . |\$\$ | . . 8 O X O . O . . . . . . 4 . . . . |\$\$ | . . X O O X O O . . . . . . O 3 . . . |\$\$ | . . . 1 X X X . . , . . . . . , X . . |\$\$ | . . X . . . . . . . . . . . . 2 5 . . |\$\$ | . . . . . . . . . . . . . . . 6 . . . |\$\$ | . . O . . . . . . . . . . . . . 7 . . |\$\$ | . . . 9 . . . . . . . . . . . . . . . |\$\$ | . . . . . . . . . . . . . . . . . . . |\$\$ | . . . , . . . . . , . . . . . , . . . |\$\$ | . . X . . . . . . . . . . . . . . . . |\$\$ | . . . . . . . . . . . . . . . . . . . |\$\$ | . . . . . . . . . . . . . . . . . . . |\$\$ | . . . . . . . . . . . . . . . . . . . |\$\$ | . . . . . . . . . . . . . . . . . . . |\$\$ | . . X , . . . . . , . . . . . , O . . |\$\$ | . . . . 0 . . . . . . . . . . . . . . |\$\$ | . . . . . . . . . . . . . . . . . . . |\$\$ | . . . . . . . . . . . . . . . . . . . |\$\$ ---------------------------------------[/go]`

After White plays the press in the top right corner, making outside strength with sente, and then plays the big turn in the top left corner. The shoulder hit, , is also big.

Elf also regards in the game as a 15½% mistake. It thinks that White should play the push and peep instead. Here is its mainline for

`[go]\$\$Wcm22 Push and peep\$\$ ---------------------------------------\$\$ | . . . . 9 . O . . . . . . . . . . . . |\$\$ | . . 6 O X O . O . . . . . . . . . . . |\$\$ | . . X O O X O O . . . . . . . . . . . |\$\$ | . . 8 1 X X X . . , . . . 0 . , X . . |\$\$ | . . X 2 5 . . . . . . . . . . . . . . |\$\$ | . . . . 3 . . . . . . . . . . . . . . |\$\$ | . . O . . . . . . . . . . . . . . . . |\$\$ | . . . . 7 . . . . . . . . . . . . . . |\$\$ | . . . . . . . . . . . . . . . . . . . |\$\$ | . . . , . . . . . , . . . . . , . . . |\$\$ | . . X . . . . . . . . . . . . . . . . |\$\$ | . . . . . . . . . . . . . . . . . . . |\$\$ | . . . . . . . . . . . . . . . . . . . |\$\$ | . . . . . . . . . . . . . . . . . . . |\$\$ | . . . . . . . . . . . . . . . . . . . |\$\$ | . . X , . . . . . , . . . . . , O . . |\$\$ | . . . . . . . . . . . . . . 4 . . . . |\$\$ | . . . . . . . . . . . . . . . . . . . |\$\$ | . . . . . . . . . . . . . . . . . . . |\$\$ ---------------------------------------[/go]`

Instead of submitting to the peep Black approaches the bottom right corner. White cuts off Black's four stones but Black takes sente and encloses the top right corner.

Elf also prefers to solidify the wall right away with . The pincer is only a minor error, losing 9½% to par. Here is Elf's mainline variation for .

`[go]\$\$Bcm21 Strong wall\$\$ ---------------------------------------\$\$ | . . . . . . O . . . . . . . . . . . . |\$\$ | . . 4 O X O . O . . . . . . . . . . . |\$\$ | . . X O O X O O . . . . . . . . . . . |\$\$ | . . . 1 X X X . . , . . . . . , X . . |\$\$ | . . X . . . . . . . . . . . . . . . . |\$\$ | . . . . . . . . . . . . . . . . . . . |\$\$ | . . O . . . . . . . . . . . . . . . . |\$\$ | . . . . . . . . . . . . . . . . . . . |\$\$ | . . . . . . . . . . . . . . . . . . . |\$\$ | . . 2 , . . . . . , . . . . . , . . . |\$\$ | . . . . . . . . . . . . . . . . . . . |\$\$ | . . 3 . . . . . . . . . . . . . . . . |\$\$ | . . . . . . . . . . . . . . . . . . . |\$\$ | . . . . . . . . . . . . . . . . 0 . . |\$\$ | . . . . . . . . . . . . . . . . . . . |\$\$ | . . X , . . . . . , . . . 9 5 , O . . |\$\$ | . . . . . . . . . . . . . 7 6 8 . . . |\$\$ | . . . . . . . . . . . . . . . . . . . |\$\$ | . . . . . . . . . . . . . . . . . . . |\$\$ ---------------------------------------[/go]`

After White makes a base with . Black attacks the White group with . (Thickness for attack!) takes the big play in the corner, and then Black plays the high approach to the bottom right corner.

`[go]\$\$Bcm31 Mainline for , continued\$\$ ---------------------------------------\$\$ | . . . . . . O . . . . . . . . . . . . |\$\$ | . . O O X O . O . . . . . . . . . . . |\$\$ | . . X O O X O O . . . . . . . . . . . |\$\$ | . . . X X X X . . , . . . . . , X . . |\$\$ | . . X . . . . . . . . . . . . . . . . |\$\$ | . . . . . . . . . . . . . . . . . . . |\$\$ | . . O . 2 . 3 . . . . . . . . . . . . |\$\$ | . . . . . . . . . . . . . . . . . . . |\$\$ | . . . . . 4 . . . . . . . . . . . . . |\$\$ | . . O , . . . . . , . . . . . , . . . |\$\$ | . . . . 5 . . . . . . . . . . . . . . |\$\$ | . . X . . . . . . . . . . . . . . . . |\$\$ | . . . . . . . . . . . . . . . . . . . |\$\$ | . . . . . . . . . . . . . . . . O . . |\$\$ | . . . . . . . . . . . . . . . . . . . |\$\$ | . . X , . . . . . , . . . X X , O . . |\$\$ | . . . . . . . 1 . . . . . X O O . . . |\$\$ | . . . . . . . . . . . . . . . . . . . |\$\$ | . . . . . . . . . . . . . . . . . . . |\$\$ ---------------------------------------[/go]`

stakes out a micro-Chinese style position on the bottom side. joins battle with Black on the left side. prevents a second White jump there, which would be painful for the Black wall after the turn in the corner. OC, it also attacks the White group. defends, and continues the attack while also extending Black's framework.

To summarize

The pedestrian extension of was a blunder, because it allowed White to play kikashi against Black's wall and bolster White's pincered stone on the left side. Black should have solidified and strengthened the wall instead.

Instead of approaching the top right corner White should have played the push and peep right away. Black then ignores the peep, allowing White to cut in exchange for approaching the bottom right corner and enclosing the top right corner. But allowing the cut raises doubts about the efficacy of the pincer on the left side.

Better, then, to solidify the wall instead of playing the immediate pincer. Even though doing so lets White make a base on the left side, Black still has a good attack against the White group.

There is, I think, a general theme here. There is a good play on the side which has a good follow-up in the corner. It is often better to make the corner play first and let the play on the side be the good follow-up.

I confess that I had a blind spot about D-16, so all of this is after the fact. Hats off to John Fairbairn's equilibrium theory.

_________________
At some point, doesn't thinking have to go on?

Visualize whirled peas.

Everything with love. Stay safe.

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 Post subject: Re: Opening problems for AI: Problem 26 #9 Posted: Sat Jul 11, 2020 12:12 pm
 Oza

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Without looking at the other answers:

`[go]\$\$Bcm23 Black to play\$\$ ---------------------------------------\$\$ | . . . . . . O . . . . . . . . . . . . |\$\$ | . . . O X O . O . . . . . . . . . . . |\$\$ | . . X O O X O O . . . . . . O . . . . |\$\$ | . . . d X X X . . , . . . . . , X . . |\$\$ | . . X . . . . . . . . . . . . . . . . |\$\$ | . . . . . . . . . . . . . . . c . . . |\$\$ | . . O . . . . . . . . . . . . . . . . |\$\$ | . . . . . . . . . . . . . . . . . . . |\$\$ | . . . . . . . . . . . . . . . . . . . |\$\$ | . . . , . . . . . , . . . . . , . . . |\$\$ | . . X . . . . . . . . . . . . . . . . |\$\$ | . . . . . . . . . . . . . . . . . . . |\$\$ | . . . . . . . . . . . . . . . . . . . |\$\$ | . . . . . . . . . . . . . . . . . . . |\$\$ | . . . . . . . . . . . . . . . . . . . |\$\$ | . . X , . b . . . , . . . . . , O . . |\$\$ | . . . . . . . . . . . . . . a . . . . |\$\$ | . . . . . . . . . . . . . . . . . . . |\$\$ | . . . . . . . . . . . . . . . . . . . |\$\$ ---------------------------------------[/go]`

From LZ's opening gospel, we know the big moves are A, closely followed by B (side stone present) and then C (avoiding the press).

The big question is: how urgent is D? Is it urgent enough to go before the big opening moves?

`[go]\$\$Bcm23 Black to play\$\$ ---------------------------------------\$\$ | . . . . . . O . . . . . . . . . . . . |\$\$ | . . . O X O . O . . . . . . . . . . . |\$\$ | . . X O O X O O . . . . . . O . . . . |\$\$ | . . 4 2 X X X . . , . . . . . , X . . |\$\$ | . . X 3 a . . . . . . . . . . . . . . |\$\$ | . . . . . . . . . . . . . . . . . . . |\$\$ | . . O . . . . . . . . . . . . . . . . |\$\$ | . . . . . . . . . . . . . . . . . . . |\$\$ | . . . . . . . . . . . . . . . . . . . |\$\$ | . . . , . . . . . , . . . . . , . . . |\$\$ | . . X . . . . . . . . . . . . . . . . |\$\$ | . . . . . . . . . . . . . . . . . . . |\$\$ | . . . . . . . . . . . . . . . . . . . |\$\$ | . . . . . . . . . . . . . . . . . . . |\$\$ | . . . . . . . . . . . . . . . 5 . . . |\$\$ | . . X , . . . . . , . . . . . , O . . |\$\$ | . . . . . . . . . . . . . . 1 . . . . |\$\$ | . . . . . . . . . . . . . . . . . . . |\$\$ | . . . . . . . . . . . . . . . . . . . |\$\$ ---------------------------------------[/go]`

Since is surely sente, the question becomes: is sente?

Well, if Black doesn't answer again but follows up in the lower right with the press, then cutting at A meets as a ladder breaker. But ...

`[go]\$\$Bcm23 Black to play\$\$ ---------------------------------------\$\$ | . . . . . . O . . . . . . . . . . . . |\$\$ | . . . O X O . O . . . . . . . . . . . |\$\$ | . . X O O X O O . . . . . . O . . . . |\$\$ | . . 4 2 X X X . . , . . . . . , X . . |\$\$ | . . X 3 7 . . . . . . . . . . . . . . |\$\$ | . . . . 6 . . . . . . . . . . . . . . |\$\$ | . . O . . . . . . . . . . . . . . . . |\$\$ | . . . . . . . . . . . . . . . . . . . |\$\$ | . . . . . . . . . . . . . . . . . . . |\$\$ | . . . , . . . . . , . . . . . , . . . |\$\$ | . . X . . . . . . . . . . . . . . . . |\$\$ | . . . . . . . . . . . . . . . . . . . |\$\$ | . . . . . . . . . . . . . . . . 0 . . |\$\$ | . . . . . . . . . . . . . . . 9 . . . |\$\$ | . . . . . . . . . . . . . . . 5 8 . . |\$\$ | . . X , . . . . . , . . . . . , O . . |\$\$ | . . . . . . . . . . . . . . 1 . . . . |\$\$ | . . . . . . . . . . . . . . . . . . . |\$\$ | . . . . . . . . . . . . . . . . . . . |\$\$ ---------------------------------------[/go]`

White can exchange for before returning to the lower side. Black's original influence has been turned into a liability. So ...

`[go]\$\$Bcm23 Black to play\$\$ ---------------------------------------\$\$ | . . . . . . O . . . . . . . . . . . . |\$\$ | . . . O X O . O . . . . . . . . . . . |\$\$ | . . X O O X O O . . . . . . O . . . . |\$\$ | . . 4 2 X X X . . , . . . . . , X . . |\$\$ | . . X 3 . . . . . . . . . . . . . . . |\$\$ | . . . . . 5 . . . . . . . . . . . . . |\$\$ | . . O . . . . . . . . . . . . . . . . |\$\$ | . . . . . . . . . . . . . . . . . . . |\$\$ | . . . . . . . . . . . . . . . . . . . |\$\$ | . . . , . . . . . , . . . . . , . . . |\$\$ | . . X . . . . . . . . . . . . . . . . |\$\$ | . . . . . . . . . . . . . . . . . . . |\$\$ | . . . . . . . . . . . . . . . . . . . |\$\$ | . . . . . . . . . . . . . . . . . . . |\$\$ | . . . . . . . . . . . . . . . . . . . |\$\$ | . . X , 6 . . . . , . . . . . , O . . |\$\$ | . . . . . . . . . . . . . . 1 . . . . |\$\$ | . . . . . . . . . . . . . . . . . . . |\$\$ | . . . . . . . . . . . . . . . . . . . |\$\$ ---------------------------------------[/go]`

makes shape, but this means has made good profit in sente. Next, takes the next big point and it's not clear Black has gained much from taking the biggest point first.

Let's compare this to Black playing the upper left.

`[go]\$\$Bcm23 Black to play\$\$ ---------------------------------------\$\$ | . . . . . . O . . . . . . . . . . . . |\$\$ | . . a O X O . O . . . . . . . . . . . |\$\$ | . . X O O X O O . . . . . . O . . . . |\$\$ | . . . 1 X X X . . , . . . . . , X . . |\$\$ | . . X . . . . . . . . . . . . 4 5 . . |\$\$ | . . . . . . . . . . . . . . . 6 . . . |\$\$ | . . O . . . . . . . . . . . . . 7 . . |\$\$ | . . . . . . . . . . . . . . . . . . . |\$\$ | . . . . . . . . . . . . . . . . . . . |\$\$ | . . . , . . . . . , . . . . . , . . . |\$\$ | . . X . . . . . . . . . . . . . . . . |\$\$ | . . . . . . . . . . . . . . . . . . . |\$\$ | . . . . . . . . . . . . . . . . . . . |\$\$ | . . . . . . . . . . . . . . . . . . . |\$\$ | . . . . . . . . . . . . . . . . . . . |\$\$ | . . X , . 3 . . . , . . . . . , O . . |\$\$ | . . . . . . . . . . . . . 2 . . . . . |\$\$ | . . . . . . . . . . . . . . . . . . . |\$\$ | . . . . . . . . . . . . . . . . . . . |\$\$ ---------------------------------------[/go]`

In this diagram, White will get sente to play first in the upper right. Later, A is probably Black's prerogative rather than White's, taking a large corner. The difference between getting this 10-ish corner, vs White taking a 10-ish corner in the previous variation, is probably well worth giving up the right to play first in the upper right.

So, for once, giving up sente may be the right thing to do here.

 This post by Knotwilg was liked by 2 people: Bill Spight, Harleqin
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 Post subject: Re: Opening problems for AI: Problem 26 #10 Posted: Sun Jul 12, 2020 3:43 am
 Judan

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Elf wanting to defend solidly as black, and push and peep as white, is another example of how much bots hate letting the opponent make profitable exchanges in sente, so it's worth playing the reverse sente to avoid that. And bonus if your reverse sente actually had a big follow-up too (the corner atari) such that it might even be sente, in which case it's a double sente and those are even better.

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 Post subject: Re: Opening problems for AI: Problem 26 #11 Posted: Sun Jul 12, 2020 4:06 am
 Honinbo

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Uberdude wrote:
Elf wanting to defend solidly as black, and push and peep as white, is another example of how much bots hate letting the opponent make profitable exchanges in sente, so it's worth playing the reverse sente to avoid that. And bonus if your reverse sente actually had a big follow-up too (the corner atari) such that it might even be sente, in which case it's a double sente and those are even better.

I was struck how it seems that the approach to the top right corner made the peep sente.

_________________
At some point, doesn't thinking have to go on?

Visualize whirled peas.

Everything with love. Stay safe.

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 Post subject: Re: Opening problems for AI: Problem 26 #12 Posted: Fri Jun 04, 2021 10:30 am
 Lives in gote

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Rank: UK 2d Dec15
KGS: mathmo 4d
IGS: mathmo 4d
Speculatively:
Current position:
1. Where else but P3? As B has moyo, P4 also seems good.
2. D16 might be good, aiming at C18 or something like G11.
3. F4 big
4. Q14/Q15 still big as W thick enough to turn upper side into territory.

Opp to play
1. D16 D15 E4 (perhaps E13 better?)

Past:
1. On upper left B seems to have sacrificed two stones prematurely. Though C13 is weak, B isn't completely solid. I think W is slightly ahead.

Check:
1. close enough

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