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 Post subject: Two questions about two moves from a pro game
Post #1 Posted: Fri Jun 15, 2018 2:58 pm 
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Hey,

So I went through an old kifu from a title match, and I can more or less understand the purpose behind every move made in the game - except for two.

In this first picture, fixing the cut in the bottom right corner is worth 4 points (I think). Is it really the most urgent move on the board? Isn't there any capping move or similar in top-mid section of the board for black to be able to claim more territory? Other moves?

Image

In this second picture black plays to the mid-bottom on the second line against the white wall. I understand it's most likely to secure a base, is that a vital (and most urgent) point to be played right now? It looks funny to the eyes of a beginner :-?

Image

Thanks up front!

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Post #2 Posted: Fri Jun 15, 2018 7:31 pm 
Honinbo
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Hi Sekibutsu,

My guesses:

Board 1: S2 is 5-point gote, for both :black: and :white: . ( Not 4, because :white: can capture S1. )

Board 2: the diagonal kick not only tries to make a base for :black:, but also M2 removes all eyespace for :white: ( there may be other :black: follow-ups, too ).

Now LZ/Elf can evaluate these moves. :study:

( The app's stones and board are quite nice: pleasing and not distracting. But the "randomly off-center" stones are more of a nuisance for me. The star points are also off-centered (to the right), which likely is an unintended bug. :)

Two independent parameters: probability p of each stone off-center, and the amount q off-center (as a percentage of the stone radius). Probably people will have different preferences. Currently it seems p ~= 100%, and q ~= 5%, both way too high for me. :) )

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 Post subject: Re: Two questions about two moves from a pro game
Post #3 Posted: Fri Jun 15, 2018 8:10 pm 
Judan

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First, good job for studying pro games like this. :tmbup:

1. Corner is more than 4 points. Let's make simplifying assumption Black won't play ko at 2-1. Then you probably got 4 points as the territory Black preserved if he defends at t3 after white's cut, but that forgets white's point for the capture and more importantly that would be gote for black so gives white 5 points in sente (aka for free). Black should tenuki at the end to make white spend a move for his gain, so then white can later hane at t3. If black blocks white can cut (can't connect) to make a big ko so let's simplify again and assume black pulls back. We can assume black later closes on 1st line t4 and white s1 so there is a ko currently valued as 1/3 point for black. He lost 2 extra points on row 4 so I count this as 6 2/3 point gote endgame.

So how about the centre? Can you mark 7 points you think will become Black territory with 1 move? It's going to be tough with that hole below. As a general (endgame) principle it's hard to surround centre points so they are often smaller than they look whilst corners/edges larger. Also note that Black's stick near tengen needs to connect home so white can use some threats against this to help nibble away at the centre. In fact this last point does make me think more about playing there as black, but more as a reverse sente prophylaxis than making territory move. Needs careful counting and reading of what white can do there. But my idea is if black could only make say 4 points there where the alternative is white reducing the whole area to dame in sente then that could be preferable to the corner move. This kind of thick centre play can be bigger than it looks :lol: . Something to ask Elf... (though komi will be wrong).

2. It's defending against white g3 which would scoop out all Black's eyespace. It also affects eyespace of white on the right. So move affecting base of 2 groups is usually pretty urgent. Also makes h4 less annoying. But it still leaves problems so I don't like the shape much, hard to find a better move though. I wonder why Black played the high approach to 4-4, this group is a bit cramped.

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 Post subject: Re: Two questions about two moves from a pro game
Post #4 Posted: Sat Jun 16, 2018 2:29 am 
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Thanks for the input both :bow:

EdLee wrote:
Board 1: S2 is 5-point gote, for both :black: and :white: . ( Not 4, because :white: can capture S1. )


Check, or then there are the ko possibilities that Uberdude mentioned.

EdLee wrote:
Board 2: the diagonal kick not only tries to make a base for :black:, but also M2 removes all eyespace for :white: ( there may be other :black: follow-ups, too ).

I seemed to be tired since I missed the clamp at M2 :grumpy: so it affects both white and black bases. Gotcha.

EdLee wrote:
But the "randomly off-center" stones are more of a nuisance for me...

I actually think that the stones become more alive by being off-center, so I really like it :lol: Didn't even notice that the star points are off, that I don't like either!

Uberdude wrote:
1. Corner is more than 4 points. Let's make simplifying assumption Black won't play ko at 2-1...


Yeah, didn't think about the second ko possibility that might make it nasty. I played it out as you explained. I’m always a bit scared of making a ko since I’m not sure if I'm capable of reading ko threats well enough (or in the little time that is in the clock). Also, I feel as if I’m really bad at judging the worth of a ko, I’m sometimes having a hard time understanding why they are so valuable even if they seem relatively small. I guess that comes with experience (and ability to read further). This went a little bit side track from the original question, but given that at some point white would play S2, would it be better for black to make a ko in the lower right in this situation? Any quick tips for ko’s in general?

Uberdude wrote:
So how about the centre? Can you mark 7 points you think will become Black territory...


Image

Somewhere along the lines of that region I was thinking could be turned to territory if black gets to start dictating the exchanges. Still I guess it was more of a feeling thing for me, as I can't really read it out properly in relation to other groups on the board due to my honest lack of skill. DDK power!


Uberdude wrote:
2. It's defending against white g3 which would scoop out all Black's eyespace. It also affects eyespace of white on the right...


Well this makes perfect sense now, I'm still having much trouble recognizing vital points to make a living shape.

Thank you so much for the help!

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