I tried analysing AlphaGo self-play game #38. It's a rather meandering and inconclusive for a review: some bits I think I understand what it's doing, others are still mysterious.

I learnt from a recent pro game that the meaning of the B3 probe is to make B8 sente (as B4 is threatened)

nice stuff,


it seems better for me to create a new sgf for comments, rather that add to your large file.




isn't the Q13 problem a seriously bugging question. I don't think I can believe that a ladder breaker is sente. And running leela for an hour didn't change its opinion that if W Q13, then 60% to W, if not then 40%

Andrew: It seems to me a lot of the surprise melts away if we make the surely not unreasonable supposition that AlphaGo makes mistakes, too. Top human pros seem united in thinking they are something like four stones away from perfect play, which would mean AG must be a good three stones away - plenty of scope for error.

Furthermore, in self-play it is making errors on both sides (i.e. not always exploiting mistakes). And conceivably the program, if the same version, is making the same errors from both sides of the board.

The fact that a human can't exploit an AG error doesn't mean it's not an error.

The latest issue of Go World gives huge space to the Future of Go Summit, with discussion led by Ohashi Hirofumi, O Meien and Ko Reibun (plus game commentaries by Ohashi). The cover photo of a despairing Ke Jie will surely go down in history.

One interesting comment by O Meien factors into your own comments. Ohashi had just made a comment about the frequency of the 3-3 invasion increasing in self play games (and Ke Jie playing it more often in his recent run). O said he initially thought it was a 場合の手 (here's your cue, Bill!), or move dictated by special circumstances. But looking at the self play games, the much greater frequency suggested the opposite of it being a special case move, and indeed it was perhaps more likely that NOT playing the invasion was the 場合の手. And Ko Reibun, who apparently spoke to the Google team, indicated that the change was something engineered between different versions of the program.

My speculation: is an early 3-3 enough to tilt the game (at pro level) in the invader's favour? After all, it's not just about splitting territory and influence, the usual way of assessing it. It also settles a significant portion of the game (both in area and time) and acts as a probe - two factors a pro is capable of exploiting, and a Monte Carlo program even more so?

Isn't it more that it guarantees that b1 will be sente, because if you make the hanging connection on the outside first then 1) black may atari in the corner, and more importantly 2) if black answers on the outside then when you play b1 black may tenuki, or push at b8 first. If you tenuki in this case then white's follow-up is capturing the 2-2 stone, certainly big but the corner isn't all dead, versus if you b3 first then then black can't tenuki or the 3 cutting stones get captured. There's also the argument that with the hanging connection first you are more willing to tenuki the b1 hane because the hanging connection then becomes an unnecessary move if you sacrifice the 2-2 stone. This is of course only valid if black is not going to play the tombstone exchange and is afraid of the ko.

5 is still sente here (locally speaking for corner shape, ignoring white lower group not safe)

Click Here To Show Diagram Code

[go]$$Wc
$$ | . . . , . . . . . ,
$$ | . . . . . . . . . .
$$ | . 5 O . . . . . . .
$$ | . X O . . . . . . .
$$ | . X O X X . . . . .
$$ | . . X O . . . . . .
$$ | . . X O . 2 . X . ,
$$ | . . X O . . . . . .
$$ | 4 X O . 1 . . . . .
$$ | . 3 . . . . . . . .
$$ +--------------------[/go]

If black ignores 3 he could push at 4:

Click Here To Show Diagram Code

[go]$$Wc
$$ | . . . , . . . . . ,
$$ | . . . . . . . . . .
$$ | . 4 O . . . . . . .
$$ | . X O . . . . . . .
$$ | . X O X X . . . . .
$$ | . . X O . . . . . .
$$ | . . X O . 2 . X . ,
$$ | . . X O . . . . . .
$$ | . X O . 1 . . . . .
$$ | . 3 . . . . . . . .
$$ +--------------------[/go]

if white answers then 6 lives more comfortably

Click Here To Show Diagram Code

[go]$$Wc
$$ | . . . , . . . . . ,
$$ | . . 5 . . . . . . .
$$ | . 4 O . . . . . . .
$$ | . X O . . . . . . .
$$ | . X O X X . . . . .
$$ | . . X O . . . . . .
$$ | . . X O . 2 . X . ,
$$ | . . X O . . . . . .
$$ | 6 X O . 1 . . . . .
$$ | . 3 . . . . . . . .
$$ +--------------------[/go]

White's follow-up in corner is only capture 2-2 stone, black's ok to come out at 8, stone at 1 now unnecessary

Click Here To Show Diagram Code

[go]$$Wc
$$ | . . . , . . . . . ,
$$ | . . 8 . . . . . . .
$$ | . 4 O . . . . . . .
$$ | . X O . . . . . . .
$$ | . X O X X . . . . .
$$ | . . X O . . . . . .
$$ | . 6 X O . 2 . X . ,
$$ | . 5 X O . . . . . .
$$ | 7 X O . 1 . . . . .
$$ | . 3 . . . . . . . .
$$ +--------------------[/go]

Or if black tenukis, then next a to live (leaving throw in ko for white) or crawl at b but then white gets the nice atari and it's a lot of 2nd line crawling to safety:

Click Here To Show Diagram Code

[go]$$Wc
$$ | . . . , . . . . . 4
$$ | . . . . . . . . . .
$$ | . b O . . . . . . .
$$ | . X O . . . . . . .
$$ | . X O X X . . . . .
$$ | a . X O . . . . . .
$$ | . 6 X O . 2 . X . ,
$$ | . 5 X O . . . . . .
$$ | 7 X O . 1 . . . . .
$$ | . 3 . . . . . . . .
$$ +--------------------[/go]

White 5 tries to kill all, but 6 is still ko

Click Here To Show Diagram Code

[go]$$Wc
$$ | . . . , . . . . . 4
$$ | . . . . . . . . . .
$$ | . 5 O . . . . . . .
$$ | . X O . . . . . . .
$$ | . X O X X . . . . .
$$ | . . X O . . . . . .
$$ | . 6 X O . 2 . X . ,
$$ | . . X O . . . . . .
$$ | . X O . 1 . . . . .
$$ | . 3 . . . . . . . .
$$ +--------------------[/go]

Whereas if we omit 1-2 exchange and play direct cut, of course black can't crawl or tenuki

Click Here To Show Diagram Code

[go]$$Wc
$$ | . . . , . . . . . 2
$$ | . . . . . . . . . .
$$ | . 2 O . . . . . . .
$$ | . X O . . . . . . .
$$ | . X O X X . . . . .
$$ | . 3 X O . . . . . .
$$ | . . X O . . . X . ,
$$ | . 1 X O . . . . . .
$$ | . X O .. . . . . .
$$ | . . . . . . . . . .
$$ +--------------------[/go]

yes, to clarify, I meant comparing between A3 and B4 responses, B4 leaves a ko, but A3 leaves C8. As I couldn't initially understand why sometimes alphago plays B4 - I couldn't see the negative side. As I would be surprised to see B tenuki the atari after B4 in this situation where B is cutting aggressively, so I didn't think that was the difference here.


I think W will not descend for tombstone as B will fight with B4, and W's shape isn't great, but rather W will squeeze immediately and W is happy.


Also we wonder why W doesn't atari B1 immediately, presumably it is to leave it as a ko threat in some variations, though it's not even that clear to me in the game that the atari is urgent. It becomes important as it is no longer sente when the 3 stones are captured, and helps W in the ko at the bottom right later.

Here are a few more notes from the Go World articles, in my own words and in no special order.

1. It seems the idea of an uchikomi series has been put into cold storage and the pros believe AG has effectively retired from playing humans, but it will continue doing go research. It seems AG will not release details of AG's analysis - too big a project.

2. O Meien especially doesn't seem to think we can learn to play like AG. Its play is just too different. He notes that go is above all a game of probes, but this is difficult to handle for humans whereas AG has no problems with this and can tenuki more (a point Andrew noted above). Similarly, AG is happy to make huge trades which a human may see but wouldn't dare try. AG is superior at evaluating trades and has no fear factor, he notes. He adds that he understand the results of what AG does but not the process.

3. Kato Hideki (DeepZen developer) says AG is not all that great at reading (it looks at 10,000 moves a second but compare that to 200 million in chess). It copes with this by simplifying into thickness. This is similar to the point Andrew made about AG liking to make two eyes quickly, but O has a slightly different slant - he considers AG is putting emphasis on being able to connect (which is what is meant by thickness here - solidity), which is a different way of ensuring safety. AG is apparently using linkability to prune the lookahead tree.

4. Pros seem to be coming round to the view that 7.5 komi is a mite too much.

5. Of the three big AI machines, DeepZen is the one that humans will find easiest to imitate (and it is still going great guns in the Japanese National Squad training games, which will apparently last till end December).

I have responded to Uberdude in This 'n' That: viewtopic.php?p=221591#p221591 . Now let me reply to John.



I think, in the relatively near future, we will see young players, especially, imitate AlphaGo and other programs, as other programs get better than humans. Even at my level I am sensitive to the drops in local temperature, but I would have trouble handling the remaining stones that lack a base. Young pros would not have that problem.



Go Seigen, anyone? Again, like Go Seigen did in his day, young pros could, and I believe, would develop that judgement and the skills to go with it. The next decade or two will, I think, be very exciting for the development of go.



Not just to prune the tree, I think. Long ago I surmised that Monte Carlo based programs liked to play in the center because connecting to other stones was the easiest way to live by random play. (Large dragons never die. ) AlphaGo still uses Monte Carlo rollouts as part of its evaluation, and for that reason may put some premium on being able to connect.



Maybe so, but I think that AlphaGo is showing us the future of go, and the relatively near future, at that. It's too bad that we don't have Go Seigen commenting on AlphaGo. He might say, I told you so. Oh, wait! I live near Berkeley, California. Maybe I can find a psychic to channel Go Seigen!

_________________
The Adkins Principle:
At some point, doesn't thinking have to go on?
— Winona Adkins

Visualize whirled peas.

Everything with love. Stay safe.

A game of probes? An interesting viewpoint. Is this a common one expressed by other pros?

It is notable that a pro would feel that AlphaGo is too far ahead, but I gather quite a few do. It echos the sentiment that I think many of us amateurs share that it's hard to learn from pro games (especially some of the more modern violent games) until one's reading is already approaching pro level. I am reminded of advice often given along the lines of: study the more accessible games from this pro (e.g., Otake, Takagawa, Chang Hao) not that pro whose games are hard for anyone to understand (e.g., Go Seigen or many current young pros).

Many Kahneman System 1 surfaces a lot of moves my brain somehow notices from replaying many pro games, but many of them I wouldn't be able to handle tactically or even strategically. Is playing them, then, cargo cult go? Maybe.

This is the conversation that goes on in my head:

Logical Brain: Look, Intuitive Brain. You have one job and only one job: to suggest moves that I wouldn't otherwise consider. You don't actually make the moves because you make basic mistakes that get us in trouble, so don't let me catch you doing that.

Intuitive Brain: Shut up. I'm stronger than you.

Logical Brain: Only today. Not forever.

It will be interesting see how pro's own imitation of AlphaGo differs from the way previous generations of pros learned from their masters.

Time for a little update: I won the Isle of Man Go festival main tournament (beautiful place btw, highly recommended). The competition wasn't so tough (only 2 dans and below under the stricter new British rank rules) but some games were uncomfortably close (e.g. I forgot to gain a liberty in sente in an ~90 point semeai so lost by 1 liberty in my first game but managed to catch up, and 2nd game was also losing but won by 1.5 in the end) so I need to play better in the British title match in 2 weeks.

Anyway, in my 3rd game I tried out AlphaGo's double attachment from the 1st self play game (though Alex had pincered my approach on the left side instead of back off to a so maybe the premise of counter hane to develop there was less valid). 13 was maybe too soft, but Alex said if hane that side he didn't like my 2 counter hanes inside to settle there but I wasn't actually so keen on that thinking it was cramped. Interestingly Michael Redmond said in his recent review of the AlphaGo game that he wanted to hane there too (AG played inside hane) and wasn't sure how white would show that was not so good for black.

Click Here To Show Diagram Code

[go]$$Wcm8 Andrew Simons 4d (white) vs Alex Rix 2d
$$ +---------------------------------------+
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . 0 4 . . . . X 6 . . . X . . . . . |
$$ | . . X 3 8 . . . 5 , . . . . . O . . . |
$$ | . . 7 9 . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . O . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . , . . . . . , . . . . . , . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . 2 . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . 1 . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . X . . . . . , . . . . . O . . . |
$$ | . . . . . a . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ +---------------------------------------+[/go]

I would think that's a too deterministic view on how AI works but I'm not a specialist myself. (Agree with the rest of what you said)

The hypothesis seems reasonable to me. Say that AlphaGo undervalues influence. As White it might play suboptimal moves that allow Black to gain an unreasonable amount of influence, thinking that it's not important; but then as Black it would not punish those moves by playing the influence-gaining response, for the same reason.

Ideally reinforcement learning would take care of this problem eventually, but it can be hard when you're just playing yourself and there's no one who plays in a different style to show you the error of your ways.

I hope you didn't fall off the island.

(Seriously, looks like a beautiful place to visit.)

I also agree with dfan in his comment about how are you supposed to improve if there's nobody to show you the error of your ways.

Some of my games. 1st one features my ~90 point blunder on move 114!

Something amusing I noticed today: my play against Pavol Lisy earlier this year can't have been too bad as Sonoda Yuichi 9p just played pretty much the same in the Kansai Kiin championship yesterday! http://www.go4go.net/go/games/sgfview/69946

Click Here To Show Diagram Code

[go]$$Bc Me (white) vs Pavol Lisy 1p
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . 0 . . . . . . . . . . . . . . . . . |
$$ | . 9 4 O . . . . . , . . . . . X . . . |
$$ | . 3 . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . 1 . . . . . . . . . . . . . . . . |
$$ | . . . 7 . . . . . . . . . . . . . . . |
$$ | . . 2 5 . . . . . , . . . . . , . . . |
$$ | . . . 6 8 . . . . . . . . . . . X . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . O . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . O O O O O . O . . . . . , . . . |
$$ | . . . . X X O X . . . . . . . X . . . |
$$ | . . . X X O X . X . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------[/go]

Click Here To Show Diagram Code

[go]$$Bcm11 Me (white) vs Pavol Lisy 1p cont.
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . 4 3 . . . . . . . . . . . . . . . |
$$ | . O 6 5 . 1 9 . . . . . . . . . . . . |
$$ | . X O O . . 8 0 . , . . . . . X . . . |
$$ | . X . . . . . . . . . . . . . . . . . |
$$ | . . 7 2 . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . X . . . . . . . . . . . . . . . . |
$$ | . . . X . . . . . . . . . . . . . . . |
$$ | . . O X . . . . . , . . . . . , . . . |
$$ | . . . O O . . . . . . . . . . . X . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . O . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . O O O O O . O . . . . . , . . . |
$$ | . . . . X X O X . . . . . . . X . . . |
$$ | . . . X X O X . X . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------[/go]

Click Here To Show Diagram Code

[go]$$Bcm21 Me (white) vs Pavol Lisy 1p cont.
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . O X . . . . 1 . . . . . . . . . . |
$$ | . O O X . X X . . . . . . . . . . . . |
$$ | . X O O . . O O . 7 . . . . . X . . . |
$$ | . X . . . . . . . . . . . . . . . . . |
$$ | . . X O . . . . . . . . . . . . . . . |
$$ | . . . 2 . . . . . . . . . . . . . . . |
$$ | . . X . . . . . . . . . . . . . . . . |
$$ | . . 5 X . 6 . . . . . . . . . . . . . |
$$ | 9 3 O X . . . . . , . . . . . , . . . |
$$ | . 8 4 O O . . . . . . . . . . . X . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . O . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . O O O O O . O . . . . . , . . . |
$$ | . . . . X X O X . . . . . . . X . . . |
$$ | . . . X X O X . X . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------[/go]

And Sonoda Yuichi 9p (white) vs Kiyonari Tetsuya 9p yesterday, the key difference is black kept on pushing instead of slide to the 2nd line, and Sonoda didn't surround the group so early (it's not sente) so black didn't have a change to come up like Pavol did with 27. Also when Catalin Taranu reviewed my game he criticised the direction of my checking extension as being from the thickness, Sonoda does the same direction though it's true his moyo to the left is more developed with the marked stones so there's more reason to do it in his game.

Click Here To Show Diagram Code

[go]$$B Sonoda Yuichi 9p (white) vs Kiyonari Tetsuya 9p
$$ +---------------------------------------+
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . X O X X . . . . . . . . . . |
$$ | . . . X X X X O . . . . . O . X . . . |
$$ | . . . , . X O . O O . . . . . , X . . |
$$ | . . . . . . O O . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . X X X X . . . . . . . . . . . . . |
$$ | . . . O X . X . . . . . . . . . . . . |
$$ | . . . , O X . W . , . . . . . , . . . |
$$ | . . X . O W . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . X O . . . . . . . . . . . . . . . |
$$ | . . O . . . . . 6 . . . . . . . . . . |
$$ | . . . O . . . . 4 3 5 . . . . O . . . |
$$ | . . . . . O . . . 2 . 1 . . . 8 . . . |
$$ | . . . . . . . . . . . . . . 9 7 0 . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ +---------------------------------------+[/go]

That Black answered 14 immediately suggests he may have thought peeping in the corner immediately white may do well do resist with the attachment at a in which case white may sacrifice the corner and gobble up the lower side. I did consider this in my game but the cutting point of 12 was not defended yet which made it harder, I think Kiyonari's earlier exchange of 11 for 12 actually makes those stones heavier so makes this exchange easier to consider for white. If white is going to extend at 16 immediately though it doesn't really matter, but white did have a choice to play something on the right at that point to prevent the peep.

Click Here To Show Diagram Code

[go]$$Bcm11 Sonoda Yuichi 9p (white) vs Kiyonari Tetsuya 9p cont.
$$ +---------------------------------------+
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . X O X X . . . . . . . . . . |
$$ | . . . X X X X O . . . . . O . X . . . |
$$ | . . . , . X O . O O . . . . . , X . . |
$$ | . . . . . . O O . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . X X X X . . . . . . . . . . . . . |
$$ | . . . O X . X . . . . . . . . . . . . |
$$ | . . . , O X . O . , . . . . . , . . . |
$$ | . . X . O O . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . X O . . . . . . . . . . . . 3 . . |
$$ | . . O . . . . . O . . . . . . . . . . |
$$ | . . . O . . . . O X X . 6 4 . O 9 7 . |
$$ | . . . . . O . . 2 O . X . 5 . O 0 8 . |
$$ | . . . . . . . . . 1 . . . a X X O . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ +---------------------------------------+[/go]

Sonoda didn't spend a move at a after 23 like I did, so can stay ahead of black with the pushing on the right side. That he also went for the shoulder hit of 24 rather than something softer validates my view it was not too thin but a reasonable pressing move.

Click Here To Show Diagram Code

[go]$$Bcm21 Sonoda Yuichi 9p (white) vs Kiyonari Tetsuya 9p cont.
$$ +---------------------------------------+
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . X O X X . . . . . . . . . . |
$$ | . . . X X X X O . . . . . O . X . . . |
$$ | . . . , . X O . O O . . . . . , X . . |
$$ | . . . . . . O O . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . X X X X . . . . . . . . . . . . . |
$$ | . . . O X . X . . . . . . . . . . . . |
$$ | . . . , O X . O . , . . . . . 0 . . . |
$$ | . . X . O O . . . . . . . . . 8 9 . . |
$$ | . . . . . . . . . . . . . . . 6 7 . . |
$$ | . . . . . . . . . . . . . . . 4 5 . . |
$$ | . . X O . . . . . . a . . . . . X . . |
$$ | . . O . . . . . O . . . . . . . . . . |
$$ | . . . O . . . . O X X . O O . O X X . |
$$ | . . . . . O . . O O 1 X . X . O O O . |
$$ | . . . . . . . . 2 X . . . . X X O . . |
$$ | . . . . . . . . . 3 . . . . . . . . . |
$$ +---------------------------------------+[/go]

In the end Sonoda does enclose at 38 which also helps deal with the bad aji of the 31 stone. The lower group ends up being a seki. But my lesson is I did indeed play this move too early, my move 26 above should have been jump or press on the top side as closing wasn't sente so too slow.

Click Here To Show Diagram Code

[go]$$Bcm31 Sonoda Yuichi 9p (white) vs Kiyonari Tetsuya 9p cont.
$$ +---------------------------------------+
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . X O X X . . . . . . . . . . |
$$ | . . . X X X X O . . . . . O . X . . . |
$$ | . . . , . X O . O O . . . . . , X . . |
$$ | . . . . . . O O . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . X X X X . . . . . . . . . . 7 . . |
$$ | . . . O X . X . . . . . . . . 6 5 . . |
$$ | . . . , O X . O . , . . . . . O . . . |
$$ | . . X . O O . . . . . . . . . O X . . |
$$ | . . . . . . . . . . . . . . . O X . . |
$$ | . . . . . . . . . . . . . . . O X . . |
$$ | . . X O . . . . . . 8 . . . 4 3 X . . |
$$ | . . O . . . . . O . . . . . 1 2 . . . |
$$ | . . . O . . . . O X X . O O . O X X . |
$$ | . . . . . O . . O O X X . X . O O O . |
$$ | . . . . . . . . O X . . . . X X O . . |
$$ | . . . . . . . . . X . . . . . . . . . |
$$ +---------------------------------------+[/go]

Great minds think alike.

The question I had for your play was , allowing .

_________________
The Adkins Principle:
At some point, doesn't thinking have to go on?
— Winona Adkins

Visualize whirled peas.

Everything with love. Stay safe.

https://www.youtube.com/watch?v=g10AoGQNFFM

You should check out this similar game on the AGA channel

Tong Yulin 4p vs Cao Youyin 3p.

Cao criticises her play at the end, saying the shoulder hit is too soft and they suggest the attach crosscut.

a series of tewaris

You say on move 25:

Maybe, but I'm not convinced yet. The territory on the left side is not yet secure (as you say yourself two moves later), and at present the Black corner has to be counted as less than 20 points. But Black has played one extra move in the corner (not to mention having also an extra move in the game). If we take the usual rule of thumb that a big point in fuseki is worth 15 points, and that is White's right, that almost cancels out the corner, but in addition White has thickness from the corner exchange, so it hardly seems "terrible".

On top of that, I got the impression that Sonoda was trying to play in an AlphaGo way, so he was probably satisfied from that standpoint anyway.

Hmm, I still think W is terrible, but you have a point that tewari is a delicate business. And I've only embraced tewari so fully post-alphago, needing to judge different positions comparing to alphago's variations. It is also often hard to point out which move was wrong.

Pondering on it more:

In the move 25 tewari, B does end up with only a one space jump, and the second line keima seems overly obsessed with territory, having to spend another move to fix, when the normal move is to extend. But B's corner aji has been resolved, B is very thick and most beautifully, the C12 side extension seems a perfectly wide extension from it. Whereas I would say W is not thick, and the O17 approach looks very aji-keshi, giving up a large corner rather heavily for a stone that is not connected, and undercut. And the dumb efficiency of the K16 stone remains almost enough to dismiss this variation for W by itself.

You say that B has an extra move here. But the value of O17 seems 20% wasted, and B seems very efficient for territory with the wide extension to C12 and it still has potential to expand to L17. Perhaps the corner is counted at around 17 points but that is completely ignoring C12, which should be worth at least 80% of a move right now. (Though part of that needs to count as reducing the W influence). NB I suspect B would most rather C12 be at C4 for comparison.

I also think perhaps B's moves 27 and 29 are in no way as bad as I first thought, and it is big to get out into the centre here, since W covering does create a large centre potential (and W will end up looking very thick, so reducing will be tricky). (I won't be too surprised if these moves are in fact the best moves) So my opinion is that B only really goes wrong with move 33. Since investing in that move in the centre makes W a lot more solid and kills off aji with C6 which seems more important to me. I would much rather preserve the aji of extending with D6. Since 27 and 29 have already done a good job of removing W's centre potential and good shape. Also 35 and 37 seem over-solid and B should be able to fight more strongly with such thickness.


Hmm, I just used percentages twice to explain how I feel about the position, but I wonder if there is any way to actually quantify these feelings more precisely.