[nandemo]

> In this game, black playing 3-3 (bottom right corner invasion) would have never been played before AlphaGo in the state of human theory. I was taught 15 years ago in my first beginner class how bad doing that is.

There are lots of 3-3 invasion joseki, though. Sometimes the context makes the invasion bad (e.g. when you end up giving a lot thickness to the opponent), but I don't see it here. What is it about the neighbouring corners that make the invasion bad?

[GabrielBen]

The 3-3 joseki is not considered even. It is supposed to be played in circumstances where thickness is inefficient, or an invasion/normal approach is attractive.

Conventional theory is to play the approach move from the right hand, extending the top right formation.

Note; something Michael Redmond mentioned in the commentary which is false is that joseki is even. Its not correct: josekis are not even, but are the best recognized patterns given a specific purpose.

In a way, straying from joseki means that you failed to apply the best possible sequence for the pattern you wanted to play. There is some subtlety around this topic.

[kyyni]

Whether a joseki is even or not depends on the context. However, when a joseki is played, it is considered to produce an even result by both players in that specific situation; otherwise, trivially, they would not play that way. The latter was precisely Redmond's point.

[conanbatt]

> Whether a joseki is even or not depends on the context

The whole point of joseki is its locality. Josekis do not depend on context to be joseki: it could be a bad joseki choice, but what they are, they are locally.

When you deviate from joseki you are; a) creating a new joseki b) recognizing that joseki is not applicable in the context, and its better to take a local loss to get a global gain.

Josekis are filled with non-even results, but that given a tactical goal, they are the best choice possible.

[nandemo]

Thanks for explanation.

I haven't studied AlphaGo games against Lee Sedol. I wonder if Ke Jie played that way because he saw AlphaGo playing a good counter to the more usual moves (an approach on the right side).

[inverse_pi]

3-3 invasion means you're giving thickness to 2 sides. After studying the 60 master games I concluded that 3-3 invasion only makes sense if you can make the thickness on BOTH sides inefficient (AG only played it when it has stones on both sides)