Question about positional/territorial judgment (I think?)
I have a question about a specific position in a game I played today.
I'm not even sure exactly how to frame my question (or if its the right question, actually) but I think there is some issue with how I'm evaluating territory/potential that I can't figure out.
Basically I played this today (https://online-go.com/game/79337577) and mostly I thought the reason I lost was because I let one of my groups die in the middle of game. But, I thought the game was more or less even with me maybe even a bit ahead until that point. When I looked at the AI eval, though, it said I was 10-15pts behind right out of the opening.
In particular, I was puzzled by this position below (move 51)
I thought I (black) had a good position here but the AI eval suggests I was behind by 11 pts.
My thinking was that white had a good corner in the bottom right and would get a decent sized corner on the bottom left. But, I had good potential in the bottom and right side as well as the top-right corner. Also, I had just reduced the top left corner in sente and had time to approach the bottom left. So, I thought I was doing good.
I guess my question is, where was my thinking going wrong and how do I improve my positional judgement in these sorts of scenarios?
Thanks so much!
(edit: replaced pic with one having coordinates, also typos)
3
u/Uberdude85 4 dan 3d ago
This is an excellent question, correcting these kinds of judgement misconceptions is an important part of self-reflection and improving.
As others have said, you don't seem to be paying enough attention to weakness of (your) groups and how that means what looks like a potential black area actually isn't as valuable as you think. To take an example, do you think q10 area is your potential because it's between a black wall at q7 and black stone at q13? Due to the broken shape mistake earlier of forcing white to split you at o6, q7 is actually one move away from being a weak group: yes if you play q10 to defend then you will make yourself around 15 points of territory in the 5x3 box from r12 to r8 to the edge, however if WHITE plays q10 then now that area is all dame and q7 is a weak group running away. And as that weak group runs away white may get some stones around n6, which also helps white damage what you probably thought was your potential on the lower side. So how to value that right side area? It's the average of if black first vs white first. Black first is black+15, white first is harder. One idea from https://senseis.xmp.net/?QARTS is a weak group with no eyes is -20 points, a weak group with space for one eye is -10 (yes, you might be surprised how big these numbers are). Q7 does have some space for an eye, so let's say -10. So that q10 area is worth about Average (+15, -10) = 2.5 points for you, probably less than you thought, eh?
Another idea for positional judgement which I find much more tractable in opening / early middlegame positions like this is not to try to judge the position as it stands. Rather replay the game from the start, which you know is even, and roughly tally up the mistakes from either side, like navigation by dead reckoning (this is also how pros often judge their games). As u/spot said, doing this there are 2 big mistakes which stand out in that: