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L+1 with two hane

https://www.lifein19x19.com/viewtopic.php?t=12309

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L+1 with two hane

Posted: Wed Sep 30, 2015 12:35 pm
by emeraldemon
I was working through Haylee's Top 10 L&D shapes, and she mentions this shape:

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


She says it is alive (https://youtu.be/EyJa0rNrbho?t=4m57s) and gives this variation:

Click Here To Show Diagram Code
[go]$$B White lives.
$$ +-------------------+
$$ | . . . . . . . . . |
$$ | . . . . . . . . . |
$$ | . . , . . . , X . |
$$ | . . . . . . . . . |
$$ | . . . . , X X X O |
$$ | . . . . . X O O . |
$$ | . . , X . X O . . |
$$ | . . X . X O O 4 2 |
$$ | . . . . O 1 . 3 . |
$$ +-------------------+[/go]


The L+1 page on Sensei's Library calls this position 10,000 year ko, and gives this variation:
Click Here To Show Diagram Code
[go]$$B 10k ko?
$$ +-------------------+
$$ | . . . . . . . . . |
$$ | . . . . . . . . . |
$$ | . . , . . . , X . |
$$ | . . . . . . . . 3 |
$$ | . . . . , X X X O |
$$ | . . . . . X O O 4 |
$$ | . . , X . X O . . |
$$ | . . X . X O O 5 1 |
$$ | . . . . O 2 . 6 7 |
$$ +-------------------+[/go]


http://senseis.xmp.net/?L1Group#toc5

I have to trust a pro over SL, especially on what she considers a "basic" position. But my reading is weak and I can't refute SL's variation. Since she explicitly talks about 10,000 year ko for a different position, I don't think she'd just gloss over it here. What is correct?

Re: L+1 with two hane

Posted: Wed Sep 30, 2015 12:51 pm
by emeraldemon
Click Here To Show Diagram Code
[go]$$B Is this the answer?
$$ +-------------------+
$$ | . . . . . . . . . |
$$ | . . . . . . . . . |
$$ | . . , . . . , X . |
$$ | . . . . . . . . . |
$$ | . . . . , X X X O |
$$ | . . . . . X O O . |
$$ | . . , X . X O . . |
$$ | . . X . X O O 2 1 |
$$ | . . . . O . . . . |
$$ +-------------------+[/go]


Click Here To Show Diagram Code
[go]$$B White lives in seki?
$$ +-------------------+
$$ | . . . . . . . . . |
$$ | . . . . . . . . . |
$$ | . . , . . . , X . |
$$ | . . . . . . . . . |
$$ | . . . . , X X X O |
$$ | . . . . . X O O 4 |
$$ | . . , X . X O . 3 |
$$ | . . X . X O O 2 1 |
$$ | . . . . O 5 6 . 7 |
$$ +-------------------+[/go]


It still would surprise me if the answer was seki. :scratch:

Re: L+1 with two hane

Posted: Wed Sep 30, 2015 1:09 pm
by illluck
Funny - I saw a similar shape (without a stone on the outside that actually change the situation) on Baidu Tieba the other day and wanted to translate and post it here, but was too lazy and then forgot.

http://tieba.baidu.com/p/3849314787

Since I saw this post I'll take it as a sign and translate it later :p From what I can make out the ten thousand year ko is the strongest in this situation.

Re: L+1 with two hane

Posted: Wed Sep 30, 2015 1:21 pm
by leichtloeslich
It still would surprise me if the answer was seki.

That is not a seki, that is dead.

Also on the sensei page it says black can force an ungodly multistep ko for white. Kos like that (or a 10k year ko, which usually ends up seki) are considered "almost alive".

I have to trust a pro over SL, especially on what she considers a "basic" position.

Why? I find it quite conceivable Haylee glossed over those variations (they only work when all the outside libs are filled, so maybe she forgot about that).

Re: L+1 with two hane

Posted: Wed Sep 30, 2015 2:08 pm
by Bill Spight
emeraldemon wrote:I was working through Haylee's Top 10 L&D shapes, and she mentions this shape:

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


She says it is alive (https://youtu.be/EyJa0rNrbho?t=4m57s) and gives this variation:

Click Here To Show Diagram Code
[go]$$B White lives.
$$ +-------------------+
$$ | . . . . . . . . . |
$$ | . . . . . . . . . |
$$ | . . , . . . , X . |
$$ | . . . . . . . . . |
$$ | . . . . , X X X O |
$$ | . . . . . X O O . |
$$ | . . , X . X O . . |
$$ | . . X . X O O 4 2 |
$$ | . . . . O 1 . 3 . |
$$ +-------------------+[/go]


The L+1 page on Sensei's Library calls this position 10,000 year ko, and gives this variation:
Click Here To Show Diagram Code
[go]$$B 10k ko?
$$ +-------------------+
$$ | . . . . . . . . . |
$$ | . . . . . . . . . |
$$ | . . , . . . , X . |
$$ | . . . . . . . . 3 |
$$ | . . . . , X X X O |
$$ | . . . . . X O O 4 |
$$ | . . , X . X O . . |
$$ | . . X . X O O 5 1 |
$$ | . . . . O 2 . 6 7 |
$$ +-------------------+[/go]


http://senseis.xmp.net/?L1Group#toc5

I have to trust a pro over SL, especially on what she considers a "basic" position. But my reading is weak and I can't refute SL's variation. Since she explicitly talks about 10,000 year ko for a different position, I don't think she'd just gloss over it here. What is correct?


Sensei's is correct. :b3: in the 10,000 year ko diagram is not easy to find. For reference, see http://www.h-eba.com/heba/JITEN/jiten2-7.html . Eba is an amateur, but Takemiya wrote an endorsement at the beginning of the book. :)

Re: L+1 with two hane

Posted: Wed Sep 30, 2015 3:11 pm
by Bill Spight
emeraldemon wrote:
Click Here To Show Diagram Code
[go]$$B Is this the answer?
$$ +-------------------+
$$ | . . . . . . . . . |
$$ | . . . . . . . . . |
$$ | . . , . . . , X . |
$$ | . . . . . . . . . |
$$ | . . . . , X X X O |
$$ | . . . . . X O O . |
$$ | . . , X . X O . . |
$$ | . . X . X O O 2 1 |
$$ | . . . . O . . . . |
$$ +-------------------+[/go]


Click Here To Show Diagram Code
[go]$$B White lives in seki?
$$ +-------------------+
$$ | . . . . . . . . . |
$$ | . . . . . . . . . |
$$ | . . , . . . , X . |
$$ | . . . . . . . . . |
$$ | . . . . , X X X O |
$$ | . . . . . X O O 4 |
$$ | . . , X . X O . 3 |
$$ | . . X . X O O 2 1 |
$$ | . . . . O 5 6 . 7 |
$$ +-------------------+[/go]


It still would surprise me if the answer was seki. :scratch:


Click Here To Show Diagram Code
[go]$$B
$$ +-------------------+
$$ | . . . . . . . . . |
$$ | . . . . . . . . . |
$$ | . . , . . . , X . |
$$ | . . . . . . . . 9 |
$$ | . . . . , X X X O |
$$ | . . . . . X O O 6 |
$$ | . . , X . X O . 3 |
$$ | . . X . X O O 2 1 |
$$ | . . . . O 7 8 5 4 |
$$ +-------------------+[/go]

Re: L+1 with two hane

Posted: Wed Sep 30, 2015 5:04 pm
by Shaddy
emeraldemon wrote:
Click Here To Show Diagram Code
[go]$$B Is this the answer?
$$ +-------------------+
$$ | . . . . . . . . . |
$$ | . . . . . . . . . |
$$ | . . , . . . , X . |
$$ | . . . . . . . . . |
$$ | . . . . , X X X O |
$$ | . . . . . X O O . |
$$ | . . , X . X O . . |
$$ | . . X . X O O 2 1 |
$$ | . . . . O . . . . |
$$ +-------------------+[/go]


Click Here To Show Diagram Code
[go]$$B White lives in seki?
$$ +-------------------+
$$ | . . . . . . . . . |
$$ | . . . . . . . . . |
$$ | . . , . . . , X . |
$$ | . . . . . . . . . |
$$ | . . . . , X X X O |
$$ | . . . . . X O O 4 |
$$ | . . , X . X O . 3 |
$$ | . . X . X O O 2 1 |
$$ | . . . . O 5 6 . 7 |
$$ +-------------------+[/go]


It still would surprise me if the answer was seki. :scratch:


That's bent 4, not seki. :D

Re: L+1 with two hane

Posted: Wed Sep 30, 2015 5:09 pm
by emeraldemon
Thanks guys, I learned a lot from this thread. It seems like I need to study the L+1 group.

Re: L+1 with two hane

Posted: Thu Oct 01, 2015 1:52 am
by ez4u
Below is the answer in the old (Cho Chikun) version of the Basic L&D Dictionary where the starting position is marked as 'not dead'. The comment says that since the marked stone prevents Black from connecting, White simply connects at 2.
Click Here To Show Diagram Code
[go]$$Bc Cho Chikun L&D
$$ +-------------------+
$$ | . . . . . . . . . |
$$ | . . . . . . . . . |
$$ | . . , . . . , X . |
$$ | . . . . . . . . . |
$$ | . . . . , X X X W |
$$ | . . . . . X O O 4 |
$$ | . . , X . X O . 3 |
$$ | . . X . X O O 6 1 |
$$ | . . . . O 2 . 5 . |
$$ +-------------------+[/go]


Black 1 below is noted as "urusai" (annoying). However, White ends up living in double-ko.
Click Here To Show Diagram Code
[go]$$Bc 10 recaptures 5 and 9 at 4.
$$ +-------------------+
$$ | . . . . . . . . . |
$$ | . . . . . . . . . |
$$ | . . , . . . , X . |
$$ | . . . . . . . . . |
$$ | . . . . , X X X O |
$$ | . . . . . X O O 2 |
$$ | . . , X . X O 8 1 |
$$ | . . X . X O O 3 6 |
$$ | . . . . O 5 9 4 7 |
$$ +-------------------+[/go]

Click Here To Show Diagram Code
[go]$$Bc double-ko
$$ +-------------------+
$$ | . . . . . . . . . |
$$ | . . . . . . . . . |
$$ | . . , . . . , X . |
$$ | . . . . . . . . 3 |
$$ | . . . . , X X X O |
$$ | . . . . . X O O O |
$$ | . . , X . X O O X |
$$ | . . X . X O O X 4 |
$$ | . . . . O 2 1 O X |
$$ +-------------------+[/go]

Re: L+1 with two hane

Posted: Thu Oct 01, 2015 9:29 am
by Bill Spight
ez4u wrote:Below is the answer in the old (Cho Chikun) version of the Basic L&D Dictionary where the starting position is marked as 'not dead'. The comment says that since the marked stone prevents Black from connecting, White simply connects at 2.
Click Here To Show Diagram Code
[go]$$Bc Cho Chikun L&D
$$ +-------------------+
$$ | . . . . . . . . . |
$$ | . . . . . . . . . |
$$ | . . , . . . , X . |
$$ | . . . . . . . . . |
$$ | . . . . , X X X W |
$$ | . . . . . X O O 4 |
$$ | . . , X . X O . 3 |
$$ | . . X . X O O 6 1 |
$$ | . . . . O 2 . 5 . |
$$ +-------------------+[/go]


The 10,000 year ko sequence has two advantages over this sequence for Black.

Click Here To Show Diagram Code
[go]$$B 10,000 year ko
$$ +-------------------+
$$ | . . . . . . . . . |
$$ | . . . . . . . . . |
$$ | . . , . . . , X . |
$$ | . . . . . . . . 3 |
$$ | . . . . , X X X O |
$$ | . . . . . X O O 4 |
$$ | . . , X . X O . . |
$$ | . . X . X O O 5 1 |
$$ | . . . . O 2 . 6 7 |
$$ +-------------------+[/go]


First, the 10,000 year ko sequence blocks off the White corner in one direction. Second, in a real game Black is unlikely to play :b7: immediately after :w6:. (The local temperature has dropped, unless Black can make a regular ko and kill the corner.) So we should compare the both diagrams after :w6:. In the Cho sequence White has the option of making a regular ko or leaving a seki. In the 10,000 year ko sequence Black has the option of making a 10,000 year ko (and at least picking up the White stone at :w6:) and White has the option of making a seki (with sente). Clearly the advantage in each case goes to the player who has the option to make the ko instead of seki.

Click Here To Show Diagram Code
[go]$$B Real game sequence (?)
$$ +-------------------+
$$ | . . . . . . . . . |
$$ | . . . . . . . . . |
$$ | . . , . . . , X . |
$$ | . . . . . . . . 3 |
$$ | . . . . , X X X O |
$$ | . . . . . X O O 4 |
$$ | . . , X . X O . . |
$$ | . . X . X O O 5 1 |
$$ | . . . 7 O 2 . 6 . |
$$ +-------------------+[/go]


Often closing off the corner with :b7: will be bigger than making the 10,000 year ko immediately. But the 10,000 year ko is the tsumego solution. :)

Re: L+1 with two hane

Posted: Thu Oct 01, 2015 9:57 am
by John Fairbairn
How important is this? In the 86,000 games in the GoGoD database this liberty-short double-hane shape has apparently never come up (I didn't check some freakish configurations). The hane-free L group with 1 leg makes only 6 appearances and the simple (dead) L-group just 11 times.

However, the L + 2 with no hanes does come up a few dozen times, presumably because it forms part of a couple of josekis.

Re: L+1 with two hane

Posted: Thu Oct 01, 2015 10:08 am
by Bill Spight
John Fairbairn wrote:How important is this? In the 86,000 games in the GoGoD database this liberty-short double-hane shape has apparently never come up (I didn't check some freakish configurations).


So? How many tsumego problems come up in real games? Moi, I think that it is good to understand corner play. :)

Re: L+1 with two hane

Posted: Thu Oct 01, 2015 11:00 am
by jeromie
John Fairbairn wrote:How important is this? In the 86,000 games in the GoGoD database this liberty-short double-hane shape has apparently never come up.


Apparently the professionals know the position well enough to ensure it does not occur. :D

Seriously, I would imagine there are many shapes that don't occur in professional games because they do not lead to a good result for one side. Knowledge of those shapes may very well impact the choice of moves well before they show up on the board.

Re: L+1 with two hane

Posted: Thu Oct 01, 2015 11:38 am
by John Fairbairn
So? How many tsumego problems come up in real games? Moi, I think that it is good to understand corner play.


I was asking a question (how important is this?), not making a statement. There were two things behind this. One is that certain corner positions do come up an awful lot in actual play, and the commonest may well be the carpenter's square. That may in turn be why pros keep telling us that mastery of the CS indicates you are 5-dan, which I take to be a PR way of saying the CS is common and therefore important - or at least more important than the L+1 + 2 hanes.

The second thing is that I've experienced many times cases where even dan players come up against things like yose-kos, double kos, mannen-kos and don't know how to handle them. I presume they've made a previous conscious decision not to study these things because they are relatively rare.

In a more extreme way, pros are "guilty" of similar pragmatic decisions. For example, in the early days of Sino-Japanese games, there were cases of embarrassment because a player (e.g. Kobayashi) had not bothered to spend time on learning the other player's ruleset.

jeromie: I had hoped I'd covered your point about shapes not occurring but still being worth knowing by including the phrase "the simple (dead) L-group [occurred] just 11 times." Sorry to have been so oblique.

Sure, it is interesting to study weird corners, and even though you may win a game only once in your lifetime with direct knowledge of them (ever had a hanezeki?), it's unlikely to be wasted time as regards keeping your go brain ticking over. But, in the scale of things, I repeat, how important is it? Is it not more efficient to study other things? (And again, I'm not making a statement - I don't know the answer.)

Re: L+1 with two hane

Posted: Thu Oct 01, 2015 11:46 am
by Abyssinica
John Fairbairn wrote:In a more extreme way, pros are "guilty" of similar pragmatic decisions. For example, in the early days of Sino-Japanese games, there were cases of embarrassment because a player (e.g. Kobayashi) had not bothered to spend time on learning the other player's ruleset.


Can I see this example? Do I assume the Japanese player kept passing when the Chinese player filled the dame and won the game he should have lost?
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