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?

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.

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.

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".


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).

Sensei's is correct. 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.

_________________
The Adkins Principle:
At some point, doesn't thinking have to go on?
— Winona Adkins

Visualize whirled peas.

Everything with love. Stay safe.

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]

_________________
The Adkins Principle:
At some point, doesn't thinking have to go on?
— Winona Adkins

Visualize whirled peas.

Everything with love. Stay safe.

That's bent 4, not seki.

Thanks guys, I learned a lot from this thread. It seems like I need to study the L+1 group.

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]

_________________
Dave Sigaty
"Short-lived are both the praiser and the praised, and rememberer and the remembered..."
- Marcus Aurelius; Meditations, VIII 21

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 immediately after . (The local temperature has dropped, unless Black can make a regular ko and kill the corner.) So we should compare the both diagrams after . 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 ) 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 will be bigger than making the 10,000 year ko immediately. But the 10,000 year ko is the tsumego solution.

_________________
The Adkins Principle:
At some point, doesn't thinking have to go on?
— Winona Adkins

Visualize whirled peas.

Everything with love. Stay safe.

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.

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

_________________
The Adkins Principle:
At some point, doesn't thinking have to go on?
— Winona Adkins

Visualize whirled peas.

Everything with love. Stay safe.

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

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.

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.)

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?

Very common shapes are practical to know since they enforce knowledge of the shape, and it'll be easy to deal with in your game.

Practicing the art of searching for a solution to a less common shape has value, too, because you will see many non-common shapes in your games. It may not be this particular "less-common" shape, but getting good at iterating through the unknown is undoubtably valuable.

To give an analogy, it's very practical to learn multiplication tables to get good at multiplying. You'll often have to multiply single digit numbers, such as 7x6 or 9x3. But it's also important to practice multiplying larger numbers, too. You probably won't often have to multiply 358x147, but you need to practice the process of multiplying uncommon numbers. That particular uncommon set of numbers may not be something you have to multiply on a regular basis, but you'll surely have to multiply other uncommon numbers, and you need to practice doing it.

_________________
be immersed

I could only really imagine seki or komi issues. Japanese players fill dame at the end to score. They're just not kept in the game records.

Gee, what I heard was that mastery of the capenter's square indicated shodan strength. Evidence of rank inflation?



I remember a yose ko occurring in a game once, and I was a dan player, too. I did not know how to handle it. Mannen kos have been more frequent, but I did not handle them right, either. In my case it was not because of a conscious decision not to study them, but because of negligence and lack of study material. Oh, I saw them being played in pro games, but without commentary, or without sufficient commentary.



In another recent thread Bantari suggested that he preferred to play games and study them to studying problems. I am pretty much of the same school. Such an approach is pragmatic. However, in my case it has led to uneven development. If I had understood approach kos better, I expect that I would have played more of them, for instance.

_________________
The Adkins Principle:
At some point, doesn't thinking have to go on?
— Winona Adkins

Visualize whirled peas.

Everything with love. Stay safe.

Though these shapes are not common in pro games, it's my impression that the L+ type shapes occur often in kyu-rank players' games. In that case studying this family of shapes could be of use to these players.

Deflation if anything. You didn't actually mishear, but that form of the saying came from the early 20th century when there was no distinction between pro and amateur ranks, or kyus. Top amateurs were routinely called 1-dan, i.e. nominally same as pro 1-dans.

Nowadays the saying is usually expressed as evidence of 5-dan or 6-dan strength, which is maybe deflation, as 7- or 8-dan amateur seems a better fit with beginning pro.

Before the war especially, bit even after, Kido and other magazines would run long series on the carpenter's square every two or three years, but next to nothing on other positions. They really did think it was important. How many western amateurs can truthfully say they know how to play the CS? If you can't, then is it not reasonable to suggest that spending time on mannen-ko instead is a little self-indulgent?

But I think gowan's point about kyu players is a good one.



Not common in my world, though I can do it without a calculator if I have to. But I don't think the analogy quite fits anyway. At school I learnt how to do things like find the square root of a number using paper and pencil. That might be a better fit with learning some of the weirder positions. The point then is that I don't think I have ever had to use that now lost skill in over 50 years, even though as a technical translator I've been heavily involved in scientific work, and for quite a time I was also a reporter on the UK's most well known science magazine and wrote for engineering magazines. I didn't even cheat and use a calculator. The issue, like hanezeki, just never came up.