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Handling Inside Approaches - Sanrensei
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Author:  Monadology [ Fri Feb 07, 2014 12:02 pm ]
Post subject:  Handling Inside Approaches - Sanrensei
I play sanrensei a lot and my opponents often approach from the inside early. There is a pattern that occurs a lot and I'm not sure how to handle it. I've got a sense of how to deal with white extending to R8 or Q8 (descend to R10 and attack). It seems like in the below position I should descend to R10. Then when white pushes up to Q9 I should probably hane. After that I'm lost and white's group seems like it has a lot of options and doesn't seem to be under too much pressure. Basically, I'm forced into a contact fight with it which is good for white settling the invading group.

I've tried to find this pattern in pro games but it doesn't seem to show up. Similarly I can't find it in The Power of the Star Point or Patterns of the Sanrensei. This leads me to think that it's not a good choice for white but I can't see why.



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Author:  Uberdude [ Fri Feb 07, 2014 12:53 pm ]
Post subject:  Re: Handling Inside Approaches - Sanrensei
Yes you absolutely must block at r10. When white pushes up hane is best though extend is also good and maintains Black's advantage. Of course white will live but black gets strong around so it's good for you.
Author:  MagicMagor [ Fri Feb 07, 2014 1:20 pm ]
Post subject:  Re: Handling Inside Approaches - Sanrensei
Quote:
Basically, I'm forced into a contact fight with it which is good for white settling the invading group.

While keeping up the pressure on an invading group is good, letting white settle doesn't mean it's good for white.
You have to remember that you get something in return for whites invading group. Namely the two moves at the bottom, shaping good territory in the corner (the aji left at 3-3 can be eliminated with a descent at S6, which should be sente against the weak white group).
And you get R10 which works together with Q10 and Q16 to map out a potential moyo at the top-right.

White gets in return a weak group, that is probably just barely alive with maybe only 5 points.
Compared to a more normal approach from the outside, that exchange (invade vs influence) is clearly bad for white.

If an invasion is considered bad, it doesn't (always) mean that it is doomed to die, most often it just means the invasion isn't worth the influence it gives the other player. And i would say that is also the case here.
Author:  Monadology [ Fri Feb 07, 2014 1:24 pm ]
Post subject:  Re: Handling Inside Approaches - Sanrensei
Thanks! I definitely wasn't assuming that I could kill it, it just seems like it becomes stable too quickly for me to get equivalent compensation. I must either be underestimating the influence/strength I get from the contact exchanges or I just need to figure out the way to get enough influence/strength.

Just knowing, in general, the right way to approach it is a great help. It's trial-and-error time now!
Author:  DrStraw [ Fri Feb 07, 2014 1:28 pm ]
Post subject:  Re: Handling Inside Approaches - Sanrensei
One reason it does not show up in pro games is because it is bad for W. Your opponent was seeing the B potential on the right and panicking, instead of seeing the W potential on the left and expanding.

The way you played was ideal, and following up with R10 reenforces your advantage. W has a small life with strong B groups on each side. W has little potential for expansion and so those stone will contribute little to the rest of the game, but both B's groups are solid and have potential to expand and contribute to the game.

If this position were to appear in a pro game it would be a guaranteed win for B.
Author:  Uberdude [ Fri Feb 07, 2014 1:31 pm ]
Post subject:  Re: Handling Inside Approaches - Sanrensei
A further more advanced point though is that if black is already strong in the upper right area then that "armpit hit" at r9 can be a good move if you want to force black into overconcentration and settle yourself quickly. Here is an example from a pro game (searching the arpit hit push double hane and cut tesuji shape finds 24 hits in my GoGoD).



Sometimes you can even capture the outside stone:



That technique can be considered an invasion joseki. As it happens, I used it successfully in my last game in the European Team Go Championships (notice how it makes white's n3 poorly placed):



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Author:  Bill Spight [ Fri Feb 07, 2014 2:01 pm ]
Post subject:  Re: Handling Inside Approaches - Sanrensei
What Uberdude said. :)

BTW, the block at R-10 is an example of the tap, which is one of the most basic plays in go. See http://senseis.xmp.net/?BillSpight%2FTap :)
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