Wednesday, December 21, 2005

Conundrums: Empty triangle and territorial reduction

Did W-O3 really have to collapse my moyo on the bottom?

I had a good game (SGF link) against goisart (19k) this evening but I still lost by 16.5 moku. My lower moyo collapsed when I responded to W-O3 with B-O4. In hindsight, I think B-N4 might have been better even though it created an empty triangle.

White has almost perfected his moyo. How to invade or reduce?

My opening moves were poorly coordinated. I played B-G17 (Move 21) in gote and so White was able to extend with W-D10 (Move 22). I think Move 21 was wholly unnecessary and Move 22 was obviously big for White. Had Black taken D10, it might have helped neutralize the influence of White's wall.

White also limited my shimari at B-R5 (Move 31) with his extension to W-K3 (Move 32). After B-M3 (Move 33) I tried to reduce White's moyo with B-H4 but this probably wasn't the right move. I couldn't see an exit path that was reinforcible. Maybe there was a better way? Maybe B-J5 would have worked instead?

Perhaps I should have launched my invasion at C7 at this point but, judging from White's strength, I expected to live small and only give White more central influence.

I also wonder whether it was wise not to have played my 3rd move at R9 to create a Chinese opening.


At 7:03 AM, December 21, 2005, Anonymous Anonymous said...

might i humbly suggest B N2 in response? if w plays anywhere but O2 in response, you play O2 and connect. If w plays O2, you then push through at N4 and w is toast :)

(and of course it's fine to not make the chinese opening :)

At 7:25 AM, December 21, 2005, Blogger ChiyoDad said...

Many thanks! That's a good suggestion. B-N2 seems to be sente and creates strong options if W doesn't play O2.

I wonder though if the push of B-N4 is more immediate and efficient. I'm at a loss as to how best to respond after B-N2, W-M2, B-N4 and W-N3. It would seem as if N2 was a wasted move. Or is it really a forcing move which makes it a necessary (potential) sacrifice?

At 9:42 AM, December 21, 2005, Anonymous Anonymous said...

you're right, n2 would become a wasted move; after B-n2, w-o2, b-n4, w-o4, b-o5, w-m2, black can't connect and has to capture the two white stones, allowing white to capture the n2 stone and connect.
Better just to cut with b-n4.

--- a fellow go player

At 2:20 PM, December 21, 2005, Anonymous Shawn McHorse said...

After B-N2, W-M2, B-N4 white can capture directly with the forcing sequence W-O4, B-N3, W-O2.

My personal inclination (as a DDK though) would be to treat the stones at M3 and M4 as sacrifice stones allowing me to form a good wall. The sequence B-O5, W-N4, B-O4, W-N3, B-P3 jumps to mind.

As white in response to B-N4, I'd aim at connecting underneath with W-M2. If B-O4, then W-N3 connects. If instead B-N2 (a mistake), then W-O4, B-N3, W-O2 captures directly.

At 5:53 AM, December 22, 2005, Anonymous MrOoijer said...

(a) B O4 directly does not work, because of dame zumari after W N4, B N3 then W N2.
(b) First the N2 O2 exchange does not make B O4 work, there is still a shortage of liberties.
(c) Then maybe directly B N4? No, because after W O4, B O5 W M2, B N2 W N3, B N6 W O2 connects underneath.
(d) Then lets try B N2, W O2 first and then B N4. There is now still a shortage of liberties and after W O4, B O5, W M2 will connect underneath.

So this move by white really blows up that part of your territory.

Going a lot back in this game, white 6 is a strange move that Black should have answered at C15. Always split your opponents stone. White will become busy to defend his corner, so he can never build a wall with 6, he will not have the time. A couple of moves later Black played 13 but should have moved into the center (for instance with a one point jump) from 11. The point is that white has now spent too many moves capturing that one stone without any other compensation. In return, Black is strong towards the center. That would have been a very good situation for Black.

At 7:12 PM, December 22, 2005, Anonymous yoyoma said...

I think it's a lot of fuss over the wrong move. On black 145, you should defend the weaker stones (M4/M3) by playing O4.

Also after your H4 shoulder hit, you should move out to the center by playing H5. After perhaps one more move out (H6), if white doesn't defend you can cut L3 by playing H3. If white does defend L3 by connecting under, then you turn towards the left and reduce more. This is a very common reduction technique, see


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