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 Post subject: Invasion on 4-4, 7-3 enclosure: strange outcomes
Post #1 Posted: Sun Aug 25, 2019 10:34 am 
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Hi all.

I am studying invasion shapes and I am considering the invasion on the enclosure "44 73 with a stone under the star point on the side" (go to black 9). Now there are two kind of invasion

1) 3-3 invasion
2) 3-4 attachment

To summarize main outcomes...

3-3 invasion takes sente and about 6 point in the corner
3-4 attachment has the option to choose between "taking gote and 10 points" or "take sente reducing black moyo but living very small in the corner"

BUT analyzing a possible fuseki with Leela (see goban below) turns out that:

3-3 invasion isn't even a candidate move
3-4 invasion is ok for Leela, but it leads to a complicate position in which white concedes in my opinion too much thickness and leads to a hard fight for reducing it.

Can you please explain me why 3-3 invasion isn't that good and Leela prefers the attachment?

Thank you in advance


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 Post subject: Re: Invasion on 4-4, 7-3 enclosure: strange outcomes
Post #2 Posted: Sun Aug 25, 2019 1:02 pm 
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For the 3-3 invasion, you show black killing the single stone with P15 and claim white has sente. But my LZ says P15 is a 6.5% mistake! Did you not check this part with LZ? Or maybe yours says different?

So I think the answer is LZ thinks the 3-3 invasion is gote, while the 3-4 is sente.

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 Post subject: Re: Invasion on 4-4, 7-3 enclosure: strange outcomes
Post #3 Posted: Sun Aug 25, 2019 1:09 pm 
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How is the solid connection in the 3-3 actually worse? It gives the same shape without the exchange of Q19 for S19.

Anyway, I'm wondering how you can see the thickness of the 3-4 as any worse than what black would get with the 3-3 invasion, where he has, if he takes gote to capture the cutting stone (which he isn't obliged to so saying that this invasion end in sente seems misleading), black has a completely alive wall completely sealing white in the corner. It's hard to be thicker than this.

...Though the issue I have with the 3-4 attach is can white even live unconditionally if he tenuki? Though the kos I can read out seems to favor white and he has local ko threats so I guess on this board the AI wouldn't mind life by ko.

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 Post subject: Re: Invasion on 4-4, 7-3 enclosure: strange outcomes
Post #4 Posted: Sun Aug 25, 2019 1:58 pm 
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yoyoma wrote:
For the 3-3 invasion, you show black killing the single stone with P15 and claim white has sente. But my LZ says P15 is a 6.5% mistake! Did you not check this part with LZ? Or maybe yours says different?

So I think the answer is LZ thinks the 3-3 invasion is gote, while the 3-4 is sente.


Yes, LeelaZero prefers tenuki but for pratical human play p15 is almost forced, and in fact a joseki dictionary (EasyGO) says that move is pattern.

Unfortunately for me EasyGo doesn't explain much of the moves so I am still guessing but I would certainly play there if I were black. If you don't play there, then white plays P15 herself and cut black group and she easily reduces black framework and at the same time the cut group still has to settle: losing about 6% is worth playing a simpler game for black imo.

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 Post subject: Re: Invasion on 4-4, 7-3 enclosure: strange outcomes
Post #5 Posted: Sun Aug 25, 2019 2:16 pm 
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Bki wrote:
How is the solid connection in the 3-3 actually worse? It gives the same shape without the exchange of Q19 for S19.

Anyway, I'm wondering how you can see the thickness of the 3-4 as any worse than what black would get with the 3-3 invasion, where he has, if he takes gote to capture the cutting stone (which he isn't obliged to so saying that this invasion end in sente seems misleading), black has a completely alive wall completely sealing white in the corner. It's hard to be thicker than this.

...Though the issue I have with the 3-4 attach is can white even live unconditionally if he tenuki? Though the kos I can read out seems to favor white and he has local ko threats so I guess on this board the AI wouldn't mind life by ko.


Here the full explanation why solid connection is worse: he gives a powerful ko threat against white group


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 Post subject: Re: Invasion on 4-4, 7-3 enclosure: strange outcomes
Post #6 Posted: Sun Aug 25, 2019 3:06 pm 
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Well that's only an approach ko if white answer correctly :). The hane (and white S18) would have been a better threat since that actually threaten to kill unconditionally. And for the S18 connection well :

Click Here To Show Diagram Code
[go]$$B Black played the circled stone, white tenuki
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . . . X 3 4 . |
$$ | . . . . . . . . . . . . . . X O O O 5 |
$$ | . . . . . . . . . . . . . X . X O . 1 |
$$ | . . . , . . . . . , . . . . . X O O 2 |
$$ | . . . . . . . . . . . . . . . O X O B |
$$ | . . . . . . . . . . . . . . . . X X . |
$$ | . . . . . . . . . . . . . . . . X . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . , . . . . . , . . . . . , . . . |[/go]


(Any other :w2: and black play there.)

And it's not like black can't keep the atari at Q19 in reserve in case he needs a ko threat. Since that's sente it's his privilege to play as long as he doesn't wait to long to do so. So I'm not convinced by this explanation.

Quote:

Yes, LeelaZero prefers tenuki but for pratical human play p15 is almost forced, and in fact a joseki dictionary (EasyGO) says that move is pattern.

Unfortunately for me EasyGo doesn't explain much of the moves so I am still guessing but I would certainly play there if I were black. If you don't play there, then white plays P15 herself and cut black group and she easily reduces black framework and at the same time the cut group still has to settle: losing about 6% is worth playing a simpler game for black imo.


If white play p15 immediately he will be the one getting attacked and black can easily get ample compensation from that and the tenuki. Of course, if the board is such that the R15 group is made weak by the cut then by all means black should protect against it. P15 is simply the proper solid move that doesn't leave any aji. It can be ignored if the fight isn't threatening and the value of tenuki is high enough.

Also in this era of komi favoring white black has no reason to be the one to want a simple game (unless this is handicap, but come one you would play the tighter small knight enclosure in a handicap game for that exact reason).

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 Post subject: Re: Invasion on 4-4, 7-3 enclosure: strange outcomes
Post #7 Posted: Sun Aug 25, 2019 3:23 pm 
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In the OP you mentioned why you did the tiger's mouth but you didn't mention you decided to ignore LZ's suggestion about not doing P15. But now it's clear, you don't agree with that particular move. Sounds like instead of doubting LZ's judgement, you feel for your level of play it's better to play safe and accept a loss. I understand that, everyone has their own feeling for how much LZ says you lost vs how difficult LZ's proposed sequence is. But let's consider a sequence where white does move the stone.

I entered an example sequence from LZ's suggestions. LZ usually prefers to tenuki, but these continuing moves are not big mistakes either. I picked a simple variation where black sacrifices a stone to kill the two white stones. The overall result is: Black was first to extend on the right side -- this seems very big since white has a high shimari facing it. White broke the area immediately next to the big black wall. But Black got two jumps building the area on the other side. The upper left side was 5 spaces wide, and the upper right side was 3 spaces wide. So it seems like a good deal for Black? There are other variations where Black doesn't play so simple and keeps an attack on the white stones.

Black Q10 focuses on the valuable part of the board, the border of two moyos, and also shores up black's stones in case white does move the single stone. On the other side, white P15 black O16 -- that is a 3 space extension from a 2 stone wall, and the 2 white stones are still behind the 2 stone wall. That seems very safe to me, no reason to worry.

ETA: I did some database searches. Many pros do play P15. I don't know enough to say, but maybe black's nearby stone K17 has a big impact on this. But I changed the position a few times and couldn't find one where LZ really wanted to play P15. For myself I would skip P15 in this specific case because of K17 so close, and the right side seems important. For the other cases... well I'm a bot fan so I will try to follow it if it doesn't seem too crazy. :cool:




Click Here To Show Diagram Code
[go]$$Bc
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . . . X . . . |
$$ | . . . . . . . . . . . . . . X O O O . |
$$ | . . . X . . . . . X . . . X . X O . . |
$$ | . . . , . . . . . , . O . X . X O O . |
$$ | . . X . . . . . . . . . O X O O X O . |
$$ | . . . . . . . . . X . O . O X . X X . |
$$ | . . . . . . . . . . . . O . X . X . . |
$$ | . . . . . . . . . X . O . . O . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . , . . . . . , . . . . . X . . . |
$$ | . . . . . . . . . . . . . . . . X . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . O . . . . . . . . . . . . . . . . |
$$ | . . . , . . . . . , . . . O . , O . . |
$$ | . . . O . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------[/go]


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 Post subject: Re: Invasion on 4-4, 7-3 enclosure: strange outcomes
Post #8 Posted: Wed Aug 28, 2019 2:50 am 
Judan

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Bki wrote:
Well that's only an approach ko if white answer correctly :). The hane (and white S18) would have been a better threat since that actually threaten to kill unconditionally. And for the S18 connection well :

Click Here To Show Diagram Code
[go]$$B Black played the circled stone, white tenuki
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . . . X 3 4 . |
$$ | . . . . . . . . . . . . . . X O O O 5 |
$$ | . . . . . . . . . . . . . X . X O . 1 |
$$ | . . . , . . . . . , . . . . . X O O 2 |
$$ | . . . . . . . . . . . . . . . O X O B |
$$ | . . . . . . . . . . . . . . . . X X . |
$$ | . . . . . . . . . . . . . . . . X . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . , . . . . . , . . . . . , . . . |[/go]


(Any other :w2: and black play there.)

And it's not like black can't keep the atari at Q19 in reserve in case he needs a ko threat. Since that's sente it's his privilege to play as long as he doesn't wait to long to do so. So I'm not convinced by this explanation.


Bki, the idea of the hanging connection at s18 instead of solid r18 is a pretty subtle one, but is theoretically sound. Your point about t15 being sente is true but irrelevant, we can assume white will answer that move to live (if black plays it at a correct time). If white solid connects then black has 2 sente move choices on the top (we assume sente for step ko is sente enough). If a, white will answer at b to live. If c, white will also answer at b to live (as we are assuming white doesn't want ko). In terms of points white has the same. But black c is closer to the outside and so can be more useful than a in future sequences on the upper side; it's pretty neglible with o17 there, but for example the 1st line jump to L19 is better connected when black has a stone at p19. This could be useful if white is trying to make an alive group in the l18 area for example. So black has 2 choices of the sente move to use here, and may choose p19 if it's useful for him. The hanging connection forces black to choose q19, which he may not want.

Click Here To Show Diagram Code
[go]$$Bc
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . . c a . . . |
$$ | . . . . . . . . . . . . . . X O O b . |
$$ | . . . . . . . . . . . . . X . X O . . |
$$ | . . . , . . . . . , . . . . . X O O . |
$$ | . . . . . . . . . . . . . . . O X O . |
$$ | . . . . . . . . . . . . . . . . X X . |
$$ | . . . . . . . . . . . . . . . . X . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . , . . . . . , . . . . . , . . . |[/go]


There is another complication too:
Quote:
And it's not like black can't keep the atari at Q19 in reserve in case he needs a ko threat. Since that's sente it's his privilege to play as long as he doesn't wait to long to do so.

White might not connect, but ko at r19. If white has lots of ko threats, black may be afraid to atari. Say he just defends at o17, white might not even spend another move to live but leave it as a ko, and even if black takes at s16 white can still live. So the hanging connection gives white more choices and flexibility, and black fewer.


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 Post subject: Re: Invasion on 4-4, 7-3 enclosure: strange outcomes
Post #9 Posted: Wed Aug 28, 2019 3:21 am 
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Thank you for the explanation. I didn't really think that the hanging connection was a mistake, just that I didn't see why it was supposed to be better and the reason given felt unconvincing.

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