Opening problems for AI: Problem 26

Bill Spight · #1

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

Click Here To Show Diagram Code: [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!

RobertJasiek · #2

Click Here To Show Diagram Code: [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]

Click Here To Show Diagram Code: [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]

Click Here To Show Diagram Code: [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]

Harleqin · #3

pwaldron · #4

Bill Spight wrote:

Click Here To Show Diagram Code: [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.

John Fairbairn · #5

Bill Spight · #6

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.

RobertJasiek · #7

Harleqin wrote:

Click Here To Show Diagram Code: [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]

Click Here To Show Diagram Code: [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?

Bill Spight · #8

Knotwilg · #9

Without looking at the other answers:

Click Here To Show Diagram Code: [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?

Click Here To Show Diagram Code: [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 :w26:

sente?

Well, if Black doesn't answer again but follows up in the lower right with the press, then cutting at A meets :b27:

as a ladder breaker. But ...

Click Here To Show Diagram Code: [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 :w28:

for

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

Click Here To Show Diagram Code: [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 :w26:

has made good profit in sente. Next, :w28:

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.

Click Here To Show Diagram Code: [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.

Uberdude · **#10**

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.

Bill Spight · **#11**

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.

dhu163 · **#12**

Opening problems for AI: Problem 26

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