AlesCieply wrote:I agree with your comments, finding debatable only the point about analysis of the whole game. In particular, the first game moves are practically meaningless for the analysis and so are joseki sequences. And as it was already noted here, the analysis loses its merit when one side is already winning so much that even relatively big mistake does not alter the outcome of the game (and does not affect the winrate significantly). So, I prefer to start the analysis "after fuseki" but I am less sure when exactly stop it.
This is actually an easy question to address. The basic rule is simple:
Do not discard any data. Now it is true, under some circumstances, that you may decide not to use, or sometimes even to alter data, to reach your conclusions. But you have to make the case, given the data.
For instance, let's look at the early fuseki in the Metta-Ben David game.
$$Bc Ben David (W) vs. Metta
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . 1 . . |
$$ | . . . 2 . . . . . , . . . . . , . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . , . . . . . , . . . . . , . . . |
$$ | . . 6 . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . 5 . . . . . . . . . . . . . . . . |
$$ | . . . , 7 9 . . . , . . . . . , . . . |
$$ | . . a 4 8 . 0 . . . . . . . . . 3 . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------
- Click Here To Show Diagram Code
[go]$$Bc Ben David (W) vs. Metta
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . 1 . . |
$$ | . . . 2 . . . . . , . . . . . , . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . , . . . . . , . . . . . , . . . |
$$ | . . 6 . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . 5 . . . . . . . . . . . . . . . . |
$$ | . . . , 7 9 . . . , . . . . . , . . . |
$$ | . . a 4 8 . 0 . . . . . . . . . 3 . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------[/go]
The first five moves are standard options; we may consider them good enough.

is a bit lenient, but we are concerned with Metta's play.

is worthy of comment. Traditionally, tenuki is normal. But Black's choice of joseki is significant. AlphaGo likes

, even though Black makes a wall without much prospect of attacking

. (Probably Leela likes it, too, but neither you nor Bojanic analyzed this play.) Certainly

at "a" would be questionable, since there is no rush for Black to make territory or eyes. I have used the AlphaGo Teaching Tool at
https://alphagoteach.deepmind.com for my comments about these plays. In a similar position, with the two Black stones on the 4-4 pts. instead of the 3-3 pts., AlphaGo reckons that "a" would lose almost 6%. Even thought

and

are preferred, we can ignore them in our analysis, since copying them from AlphaGo or other bots is normal. (Making the case.)
$$Bcm11 Mistake?
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . a . . . . . . . . . . . . . X . . |
$$ | . . . O . . . . . , . . . . . , . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . , . . . . . , . . . . . , . . . |
$$ | . . O . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . X . . . . . . . . . . . . . . . . |
$$ | . . . , X X . . . , . . . . . , . . . |
$$ | . . 1 O O . O . . . . . . . . . X . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------
- Click Here To Show Diagram Code
[go]$$Bcm11 Mistake?
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . a . . . . . . . . . . . . . X . . |
$$ | . . . O . . . . . , . . . . . , . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . , . . . . . , . . . . . , . . . |
$$ | . . O . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . X . . . . . . . . . . . . . . . . |
$$ | . . . , X X . . . , . . . . . , . . . |
$$ | . . 1 O O . O . . . . . . . . . X . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------[/go]
But if this 3-3 attachment was a mistake for

, isn't it a mistake for

? In the similar position, AlphaGo says that it loses 7% by comparison with the invasion at "a" in the top left corner. The extra loss may be accounted for by the fact that

and

have already strengthened Black in the lower left, so that Black has even less need to make a base here. An error of around 7%, if that is the result of evaluating this exact position, is significant. But if we on principle ignore the fuseki we will miss it.
Now let us consider

.
$$Wcm26 Black to play, move 27
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . X O . . . . . . . . . . . . |
$$ | . . X X X O . . . . . . . . . . X . . |
$$ | . c O O X O . . . , . . . . . , . . . |
$$ | . . . b W a . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . , . . . . . , . . . . . , . . . |
$$ | . . O . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . O . . X . . |
$$ | . . X . . . . . . . . . . . . . . . . |
$$ | . . . X X X O . . , . . . . . , . . . |
$$ | . . X O O . O . . . . . . O . . X . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------
- Click Here To Show Diagram Code
[go]$$Wcm26 Black to play, move 27
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . X O . . . . . . . . . . . . |
$$ | . . X X X O . . . . . . . . . . X . . |
$$ | . c O O X O . . . , . . . . . , . . . |
$$ | . . . b W a . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . , . . . . . , . . . . . , . . . |
$$ | . . O . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . O . . X . . |
$$ | . . X . . . . . . . . . . . . . . . . |
$$ | . . . X X X O . . , . . . . . , . . . |
$$ | . . X O O . O . . . . . . O . . X . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------[/go]
White has just played

. Where to play? Waltheri indicates that "a", "b", and "c" are all joseki. But surely we are not indifferent to these choices. Just because Black plays joseki does not mean that we can ignore his choice.
$$Bcm27 Joseki deviation
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . X O . . . . . . . . . . . . |
$$ | . . X X X O . . . . . . . . . . X . . |
$$ | . a O O X O . . . , . . . . . , . . . |
$$ | . . . . O 1 3 . . . . . . . . . . . . |
$$ | . . . . 2 . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . , . . . . . , . . . . . , . . . |
$$ | . . O . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . O . . X . . |
$$ | . . X . . . . . . . . . . . . . . . . |
$$ | . . . X X X O . . , . . . . . , . . . |
$$ | . . X O O . O . . . . . . O . . X . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------
- Click Here To Show Diagram Code
[go]$$Bcm27 Joseki deviation
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . X O . . . . . . . . . . . . |
$$ | . . X X X O . . . . . . . . . . X . . |
$$ | . a O O X O . . . , . . . . . , . . . |
$$ | . . . . O 1 3 . . . . . . . . . . . . |
$$ | . . . . 2 . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . , . . . . . , . . . . . , . . . |
$$ | . . O . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . O . . X . . |
$$ | . . X . . . . . . . . . . . . . . . . |
$$ | . . . X X X O . . , . . . . . , . . . |
$$ | . . X O O . O . . . . . . O . . X . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------[/go]

and

are Waltheri's most frequent choices, but

is not in its database. "a" is its most frequent choice. How bad is

? With no analysis, we cannot say.
There are likely to be significant choices of plays in the fuseki, even as there are likely to be choices that we can afford to ignore. But we have to consider each choice on its merits. Don't discard data.
