The three star point formation or so called “Sanrensei” have always been my favorite one among all fusekis.
Alexander Dinerstein 3p reviewed a game of mine a week ago and during the review he pointed out this reducing move saying that an AI would play it.
Well, it seems like the latest 40 blocks of Leela is definitely convinced that it is the best reducing move although probably any other move would be just fine.
Personally I really like this attachment and I would play this if I get a chance, however, this move is not quite easy to understand or deal with, but it is really exciting and beautiful.
Let’s explore it!
According to ps.waltheri.net in professional games white never played this attachment, instead white makes Sanrensei position for himself on left and now black has two choices, either to make the moyo bigger or to approach on the left.
Leela Zero 40 blocks, thinks that approaching on the left side is good, however, it does not really think of playing move 2 showed in Waltheri – played by professional.
Normally, most of people would invade like this, which is pretty much ordinary, surprising to me here is that AI would not kick as I would do instantly without hesitation. It would attach instead (would take me quite some time to understand it).
The more interesting thing is that after attachment, it does not want to continue playing in the area, it would simply tenuki and play any corner enclosure on top or lower side. The reason not to play on right side is probably because it does not know exactly what to play, since black will not kill the stone immediately, white can decide what to do with it later.
I would kick without hesitation, how many of you would do the same? Wishful thinking of mine was to expect white to extend, white will play keima of course!
If white extends, black will press as usual and this way black will build thickness, while white will be worrying about it’s own group. Catalin Taranu 5p was always telling me to pay attention to the strength of my stones, because they give me invisible points, which magically appear later. When your stones are weak, it is hard to build points, when your stones are strong – you build points easier, however, the points do not always show up immediately as some people might expect.
To the keima black will push and white can escape more flexible and easier than with the simple extension above. Wonderful plan.
I have seen this exact position played not just once by strong players, I did not expect to find only one professional game with this opening, although you can see that it is pretty much “even” according to Leela, white has slight advantage in percentage.
So after our attachment, black can either hane which I can call “active” move and the extension which is “passive”, both ways are playable of course.
If black simply extends, the first intuition is to jump looking forward to make tiger mouth shape, simply extending would not be that flexible.
Once white extends, the two most played moves are wedge and extension, I was surprised to see keima to be a good move too. Well, at least for Sinan Zero (laugh) it was a 0 visits move, it did not appear in my mind at all. Did any of the readers thought about the keima in this situation?
When you extend, white should make a shape. Personally I would play two space jump, instead of the one space blue move showed in the picture, but both are fine.
If black wedges, which is the most ordinary way to play, white would make a shape by playing tiger mouth (blue). We can make tewari with the situation above, in this picture it looks like black pushed unnecessary and strengthened white. So, can we say that extension in this situation is slightly better?
Instead of tiger mouth, you can consider keima as well, black will treat the situation as finished and he will continue playing somewhere else, the game is totally fine.
If just keima which got 0 visits in my mind : – ), white will make a shape by playing anything in the center or just the blue suggested move. I do not like this keima, it is too passive in my opinion.
Playing extension is probably not a bad move, however it would give black the initiative to attack, I am not quite sure how many people enjoy being attacked, although Leela says it is 50/50, I would not extend any time soon. It is important to push, because if white takes the blue move, white will have easier time settling inside, it is like a key point for strength of the stones in the current area.
Leela pushed once again and white jumped, black tries to attack white and this fight starts, even though white can settle easy, it gives black power outside, which is quite good development in my opinion.
I wouldn’t push once again as Leela does, my move would be to attack immediately and it looks fine according to the AI.
But, what if your opponent goes into the complicated variation? Hane back is normal intuition and LZ agrees indeed, although we have something special in the other hane, which we will check out later.
Yoah, what a beautiful move suggested, hanes never end. I want to play this !
Black connection would probably be too passive, but this hane is just beautiful.
As I said – Hanes never end, LZ really likes them.
It looks like all three moves are good, let’s check them one by one.
Probably this is the move we all thought about first, isn’t it ? It looks like after black captures with 3, white will Atari at 4 and settle his shape with 6, if black does not block at 7, white will take it. So, black blocks at 7, but white takes the vital point of black’s shape at 8, settling the base with 10 is quite comfortable result for white. Giving a ponnuki to black seems not that painful once you reduce all of his moyo.
Connection seems to make a complicated fight, however, after black starts the big fight with 5, white just ignores and plays 6 taking black’s shape. Finally, white sacrifices the stone on the top, but manages to connect in a good way.
This seems to be the most severe move of black. White plays 4 and black extends at 5 to secure his territory, white extension at 6 is just to make more aji inside the territory for later and with move 8 he threatens to use the aji while strengthening his own group. As we can see, in this variation black managed to pretty much take the right side, while white got a group outside and managed to cut the lower side stone. I am not completely sure how to judge this situation since I really like the cash black has, however, white is not bad at all too, white can build more with the potential.
The variations after this hane are the highlight of this article. Black connection would be too passive, so black has to fight by playing Atari and splitting white into two.
To hane back in this position would be a bit too much, white will make quite comfortable shape in the center, do not make your opponent too happy.
After Atari and connect, white high-level technique would be to play a ladder breaker, playing the blue move would also be good, but there is a better move. LZ saw it on top, however, it does not see it on lower side? Weird AI’s.
It seems like it just does not like it, however, there is something it blind spots.
If black just answers passively and defends his cutting point, white will capture in ladder and it would be a quite good result for white.
Black will extend and instead of the cut immediately, white will first make a test to see how black will respond.
After this attachment test, we can see that white will cut black stone at 2, I like this result for white, this attachment test probably helps white to know what moves it can use later in the current situation. So it is even game.
This whole variation, reminded me of Go Seigen who recommended a similar move. Humans tends to play an invasion on lower side in this position instead of san-san.
After this invasion, people also mostly Atari from below instead of above, same as what AI thinks.
The reason is that if black plays from above, it is too easy for white to deal with the situation, white just makes live on the lower side comfortably.
However, Go Seigen pointed out the beautiful attachment here, which seems to not be the first choice according to LZ after 310 000 visits.
This is the same story, if black defends his stone, white will play Atari and Atari again for which black will never connect, but if black does, white will just capture the stone in ladder. We can say this is already success for white.
Black most active answer would be to play this hane and to fight, although white will still manage to cut black’s stone.
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I hope this article was helpful and it showed a great way to reduce Sanrensei, although I am sure some of these tactics can be applied to many other situations !