tesuji problem

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macelee
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tesuji problem

Post by macelee »

A tesuji problem: how can white break into the left side?
Click Here To Show Diagram Code
[go]$$B
$$ +---------------------------------------+
$$ | . . . X X O . . . . . . . . . . . . . |
$$ | . . X X O O . . . . . . . . O X . . . |
$$ | . . X O O X . O O O O X X O O X . . . |
$$ | . . X O . . O X X X X O O O . X X X . |
$$ | . . . O . . . . . . O X X O X . O O . |
$$ | . . X O . . . . . . X . X X O . . . . |
$$ | . . X O . O . . X . X X O . O . . . . |
$$ | . . . . . X O . O O O O O . O . . . . |
$$ | . . X O O X . . O X X X X X O . O . . |
$$ | . . . O . X . O . , . . . X X , . . . |
$$ | . 1 O . . . . . O X . X O . . X X . . |
$$ | . . X O . X X O X . . X O O O O . . . |
$$ | . . X O O . . O X X . . O X X . O O . |
$$ | . . . X . X X O O X X . . O X . . X . |
$$ | . . . X . X O O X X O O . O X X X X . |
$$ | . . X , . . O X X O . . . . . , O O . |
$$ | . . X O . O . X O O . O O X X X O . . |
$$ | X X O O . . . . . . . . X O O O X X . |
$$ | . O . . . . . . . . . . . . . . . . . |
$$ +---------------------------------------+[/go]
Answer is in this pro game: http://www.go4go.net/go/games/sgfview/42420
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leichtloeslich
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Re: tesuji problem

Post by leichtloeslich »

Since I don't have an account for that site I'll just post my sketchy Sunday morning reading.
Click Here To Show Diagram Code
[go]$$Bc
$$ +---------------------------------------+
$$ | . . . X X O . . . . . . . . . . . . . |
$$ | . . X X O O . . . . . . . . O X . . . |
$$ | . . X O O X . O O O O X X O O X . . . |
$$ | . . X O . . O X X X X O O O . X X X . |
$$ | . 5 4 O . . . . . . O X X O X . O O . |
$$ | . . X O . . . . . . X . X X O . . . . |
$$ | . 6 X O . O . . X . X X O . O . . . . |
$$ | . . . . . X O . O O O O O . O . . . . |
$$ | . 3 X O O X . . O X X X X X O . O . . |
$$ | . . 2 O . X . O . , . . . X X , . . . |
$$ | . 1 O . . . . . O X . X O . . X X . . |
$$ | . . X O . X X O X . . X O O O O . . . |
$$ | . . X O O . . O X X . . O X X . O O . |
$$ | . . . X . X X O O X X . . O X . . X . |
$$ | . . . X . X O O X X O O . O X X X X . |
$$ | . . X , . . O X X O . . . . . , O O . |
$$ | . . X O . O . X O O . O O X X X O . . |
$$ | X X O O . . . . . . . . X O O O X X . |
$$ | . O . . . . . . . . . . . . . . . . . |
$$ +---------------------------------------+[/go]
This looks forced, and from here I don't see a way to defend white breaking in.

b14 looks like the best defense, minimizing the damage.
If black tries to be stubborn with c12, white can capture some stones.
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Uberdude
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Re: tesuji problem

Post by Uberdude »

This one breaks into the side, but the white group gets cut off and dies so I don't think that counts as a solution :lol:
Click Here To Show Diagram Code
[go]$$B
$$ +---------------------------------------+
$$ | . . . X X O . . . . . . . . . . . . . |
$$ | . . X X O O . . . . . . . . O X . . . |
$$ | . . X O O X . O O O O X X O O X . . . |
$$ | . . X O . . O X X X X O O O . X X X . |
$$ | . 3 2 O . . . . . . O X X O X . O O . |
$$ | . 7 X O . . . . . . X . X X O . . . . |
$$ | . 6 X O . O . . X . X X O . O . . . . |
$$ | . 5 4 9 . X O . O O O O O . O . . . . |
$$ | . 8 X O O X . . O X X X X X O . O . . |
$$ | . 0 . O . X . O . , . . . X X , . . . |
$$ | . 1 O . . . . . O X . X O . . X X . . |
$$ | . . X O . X X O X . . X O O O O . . . |
$$ | . . X O O . . O X X . . O X X . O O . |
$$ | . . . X . X X O O X X . . O X . . X . |
$$ | . . . X . X O O X X O O . O X X X X . |
$$ | . . X , . . O X X O . . . . . , O O . |
$$ | . . X O . O . X O O . O O X X X O . . |
$$ | X X O O . . . . . . . . X O O O X X . |
$$ | . O . . . . . . . . . . . . . . . . . |
$$ +---------------------------------------+[/go]
(If black 7 at 9 then white 7 and she can get the 2 stones but the lower tail dies again which is bigger, and black's corner still lives.)

Click Here To Show Diagram Code
[go]$$Bm11
$$ +---------------------------------------+
$$ | . . . X X O . . . . . . . . . . . . . |
$$ | . . X X O O . . . . . . . . O X . . . |
$$ | . . X O O X . O O O O X X O O X . . . |
$$ | . . X O . . O X X X X O O O . X X X . |
$$ | . X O O . . . . . . O X X O X . O O . |
$$ | . X X O . . . . . . X . X X O . . . . |
$$ | . O X O . O . . X . X X O . O . . . . |
$$ | . X . X 1 X O . O O O O O . O . . . . |
$$ | 5 O X O O X . . O X X X X X O . O . . |
$$ | . O . O . X . O . , . . . X X , . . . |
$$ | 4 X O . . . . . O X . X O . . X X . . |
$$ | . 2 X O . X X O X . . X O O O O . . . |
$$ | . 3 X O O . . O X X . . O X X . O O . |
$$ | . . . X . X X O O X X . . O X . . X . |
$$ | . . . X . X O O X X O O . O X X X X . |
$$ | . . X , . . O X X O . . . . . , O O . |
$$ | . . X O . O . X O O . O O X X X O . . |
$$ | X X O O . . . . . . . . X O O O X X . |
$$ | . O . . . . . . . . . . . . . . . . . |
$$ +---------------------------------------+[/go]
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gogameguru
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Re: tesuji problem

Post by gogameguru »

leichtloeslich wrote:Since I don't have an account for that site I'll just post my sketchy Sunday morning reading.
Click Here To Show Diagram Code
[go]$$Bc
$$ +---------------------------------------+
$$ | . . . X X O . . . . . . . . . . . . . |
$$ | . . X X O O . . . . . . . . O X . . . |
$$ | . . X O O X . O O O O X X O O X . . . |
$$ | . . X O . . O X X X X O O O . X X X . |
$$ | . 5 4 O . . . . . . O X X O X . O O . |
$$ | . . X O . . . . . . X . X X O . . . . |
$$ | . 6 X O . O . . X . X X O . O . . . . |
$$ | . . . . . X O . O O O O O . O . . . . |
$$ | . 3 X O O X . . O X X X X X O . O . . |
$$ | . . 2 O . X . O . , . . . X X , . . . |
$$ | . 1 O . . . . . O X . X O . . X X . . |
$$ | . . X O . X X O X . . X O O O O . . . |
$$ | . . X O O . . O X X . . O X X . O O . |
$$ | . . . X . X X O O X X . . O X . . X . |
$$ | . . . X . X O O X X O O . O X X X X . |
$$ | . . X , . . O X X O . . . . . , O O . |
$$ | . . X O . O . X O O . O O X X X O . . |
$$ | X X O O . . . . . . . . X O O O X X . |
$$ | . O . . . . . . . . . . . . . . . . . |
$$ +---------------------------------------+[/go]
This looks forced, and from here I don't see a way to defend white breaking in.

b14 looks like the best defense, minimizing the damage.
If black tries to be stubborn with c12, white can capture some stones.
I second leichtloeslich's solution :)
Click Here To Show Diagram Code
[go]$$Wc
$$ +---------------------------------------+
$$ | . . . X X O . . . . . . . . . . . . . |
$$ | . . X X O O . . . . . . . . O X . . . |
$$ | . . X O O X . O O O O X X O O X . . . |
$$ | . . X O . . O X X X X O O O . X X X . |
$$ | . X O O . . . . . . O X X O X . O O . |
$$ | . 2 X O . . . . . . X . X X O . . . . |
$$ | . 1 X O . O . . X . X X O . O . . . . |
$$ | . . 7 . . X O . O O O O O . O . . . . |
$$ | . X X O O X . . O X X X X X O . O . . |
$$ | 4 3 O O . X . O . , . . . X X , . . . |
$$ | 6 X O . . . . . O X . X O . . X X . . |
$$ | . 5 X O . X X O X . . X O O O O . . . |
$$ | . . X O O . . O X X . . O X X . O O . |
$$ | . . . X . X X O O X X . . O X . . X . |
$$ | . . . X . X O O X X O O . O X X X X . |
$$ | . . X , . . O X X O . . . . . , O O . |
$$ | . . X O . O . X O O . O O X X X O . . |
$$ | X X O O . . . . . . . . X O O O X X . |
$$ | . O . . . . . . . . . . . . . . . . . |
$$ +---------------------------------------+[/go]
Click Here To Show Diagram Code
[go]$$Wc A and B are miai
$$ +---------------------------------------+
$$ | . . . X X O . . . . . . . . . . . . . |
$$ | . . X X O O . . . . . . . . O X . . . |
$$ | . . X O O X . O O O O X X O O X . . . |
$$ | . . X O . . O X X X X O O O . X X X . |
$$ | . X O O . . . . . . O X X O X . O O . |
$$ | . X X O . . . . . . X . X X O . . . . |
$$ | . O X O . O . . X . X X O . O . . . . |
$$ | . 2 1 4 a X O . O O O O O . O . . . . |
$$ | 5 X X O O X . . O X X X X X O . O . . |
$$ | X O O O . X . O . , . . . X X , . . . |
$$ | X X O . . . . . O X . X O . . X X . . |
$$ | 3 O X O . X X O X . . X O O O O . . . |
$$ | . . X O O . . O X X . . O X X . O O . |
$$ | . . b X . X X O O X X . . O X . . X . |
$$ | . . . X . X O O X X O O . O X X X X . |
$$ | . . X , . . O X X O . . . . . , O O . |
$$ | . . X O . O . X O O . O O X X X O . . |
$$ | X X O O . . . . . . . . X O O O X X . |
$$ | . O . . . . . . . . . . . . . . . . . |
$$ +---------------------------------------+[/go]
Click Here To Show Diagram Code
[go]$$Wc If :b8: @ :w5: then :w9: @ the marked stone. A and B are miai.
$$ +---------------------------------------+
$$ | . . . X X O . . . . . . . . . . . . . |
$$ | . . X X O O . . . . . . . . O X . . . |
$$ | . . X O O X . O O O O X X O O X . . . |
$$ | . b X O . . O X X X X O O O . X X X . |
$$ | . X O O . . . . . . O X X O X . O O . |
$$ | a X X O . . . . . . X . X X O . . . . |
$$ | 2 O X O . O . . X . X X O . O . . . . |
$$ | 4 3 1 . . X O . O O O O O . O . . . . |
$$ | 5 6 B O O X . . O X X X X X O . O . . |
$$ | X O O O . X . O . , . . . X X , . . . |
$$ | X X O . . . . . O X . X O . . X X . . |
$$ | 7 O X O . X X O X . . X O O O O . . . |
$$ | . . X O O . . O X X . . O X X . O O . |
$$ | . . . X . X X O O X X . . O X . . X . |
$$ | . . . X . X O O X X O O . O X X X X . |
$$ | . . X , . . O X X O . . . . . , O O . |
$$ | . . X O . O . X O O . O O X X X O . . |
$$ | X X O O . . . . . . . . X O O O X X . |
$$ | . O . . . . . . . . . . . . . . . . . |
$$ +---------------------------------------+[/go]
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macelee
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Re: tesuji problem

Post by macelee »

Well done! guys.

Uberdude's solution shows the most natual thinking process, although he proved that's not working. By saving one exchange from that sequence, magic happens.

BTW, sorry for those of you who don't have an account at Go4Go. It's really easy to create one. The site was recently targeted by somebody (apparently a Go player) who insisted he having the right to mass downloading everything. His technical skill was akin to a hacker because he somehow used a large range of distributed IPs to target my site. Protecting the game pages by login is by far the easiest defense.
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Re: tesuji problem

Post by logan »

macelee wrote:Well done! guys.

Uberdude's solution shows the most natual thinking process, although he proved that's not working. By saving one exchange from that sequence, magic happens.

BTW, sorry for those of you who don't have an account at Go4Go. It's really easy to create one. The site was recently targeted by somebody (apparently a Go player) who insisted he having the right to mass downloading everything. His technical skill was akin to a hacker because he somehow used a large range of distributed IPs to target my site. Protecting the game pages by login is by far the easiest defense.
It should be possible to separate viewing permissions from downloading permissions. Right now it's not possible to even replay (view) a game without creating an account or logging in.
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gogameguru
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Re: tesuji problem

Post by gogameguru »

logan wrote:It should be possible to separate viewing permissions from downloading permissions. Right now it's not possible to even replay (view) a game without creating an account or logging in.
That sounds logical and I agree that not even being able to view a game without logging in is very unfortunate. The problem is that there's fundamentally no difference between viewing a game and downloading the data. Whoever is doing this would then just download all the games anyway, by using a script to 'view' them and extract the data they're interested in.

Normally you might solve this by throttling the rate of requests per IP address (which Mace has probably tried already). It sounds to me like someone is accessing go4go using TOR (which is abusing TOR as well as Mace's server, really) and blocking TOR exit nodes is something that some sites do to deal with this sort of thing.

At GGG, we just gave up participating in the arms race (except against those damn spammers!), because we didn't have time for it and 'winning' it eventually involves inconveniencing normal readers in some way (as you've just seen). Requiring users to login is another reasonable compromise once you realize the full context of the problem. Anyway, it's a difficult problem for the person running the website :(

EDIT: Actually Mace, if you're using PHP, this might help: http://bad-behavior.ioerror.us/
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macelee
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Re: tesuji problem

Post by macelee »

Thanks David for giving a very accurate description of the problem I am facing. No matter what technique is used to present the games, if a game is viewable online, so is the data behind it. It is just a matter of time for the data to be decoded.

I will look into the bad-behavior package. The idea behind it sounds great because it not only stops spam but also saves bandwidth, which is in practice often the biggest issue.
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Re: tesuji problem

Post by logan »

Thank-you for the explanation David, I'm sorry for my ignorance regarding these issues. I wish I was an expert at these things so I could help you with them, macelee.
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Mef
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Re: tesuji problem

Post by Mef »

gogameguru wrote: At GGG, we just gave up participating in the arms race (except against those damn spammers!), because we didn't have time for it and 'winning' it eventually involves inconveniencing normal readers in some way (as you've just seen). Requiring users to login is another reasonable compromise once you realize the full context of the problem. Anyway, it's a difficult problem for the person running the website :(

If memory serves, this is very same problem that made gobase start to require logins (even if they were free ones) several years ago...seems like some things never change )=
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