life & death studying material on carpenter's square

[macelee]

I am about to translate a large number of Go studying materials into English - first will be a serial of articles covering the life & death problem around so-called carpenter's square. These used to be published on an old Chinese version of Go4Go.net and has become quite popular on the internet. These are quite interesting but tricky L&D and I am not sure at what level of details I should present the materials. I've put an index page and a first article online and hope to get some feedback before working on more articles. If all works as planned, I should post one article per day and complete the series in about 1 month time. Here is the link:

http://www.go4go.net/go/carpenter_square

Thanks for reading. Your suggestions are highly appreciated.

[Shinkenjoe]

Hi there,

I'm looking forward to it, cause Im doing Cho's carpenter square section right now, so maybe i'll come up with some questions. Two of them I posted already in wise foresight in the study section.

http://www.lifein19x19.com/forum/viewto ... =15&t=7611

[macelee]

Hi there,

I'm looking forward to it, cause Im doing Cho's carpenter square section right now, so maybe i'll come up with some questions. Two of them I posted already in wise foresight in the study section.

http://www.lifein19x19.com/forum/viewto ... =15&t=7611

Yeah I am aware of that post. I will post in that thread to address your original question why there needs to be two ways to form ko for the original carpenter's square. I just read some pro's comments which I think should answer your question well.

[macelee]

I am half way through the articles.

It is a great experience. Every time I revisit these patterns I learn new things. I even found errors in rather authoritative life & death books. I will finish the whole series in about two weeks time.

http://www.go4go.net/go/carpenter_square

[SoDesuNe]

I somehow missed this thread until now... Nice articles! I'm sure to read through them - thank you very much for your effort!

[SmoothOper]

Do the carpenters square variations arise mostly out of attachment invasions on the hoshi shimari's?

[macelee]

Do the carpenters square variations arise mostly out of attachment invasions on the hoshi shimari's?

I think you are talking about the following invansion, which results in one of the shapes I discussed.

$$W
$$ --------------------+
$$ . . . . . . . . . . |
$$ . . . . . . 9 . . . |
$$ . . . . . 8 7 . . . |
$$ , . . . X . X 1 5 . |
$$ . . . . . . 4 2 3 . |
$$ . . . . . . . . 6 . |
$$ . . . . . . . . . . |
$$ . . . . . . . . . . |
$$ . . . . . . . . . . |
$$ , . . . . . , . . . |

Click Here To Show Diagram Code

[go]$$W
$$ --------------------+
$$ . . . . . . . . . . |
$$ . . . . . . 9 . . . |
$$ . . . . . 8 7 . . . |
$$ , . . . X . X 1 5 . |
$$ . . . . . . 4 2 3 . |
$$ . . . . . . . . 6 . |
$$ . . . . . . . . . . |
$$ . . . . . . . . . . |
$$ . . . . . . . . . . |
$$ , . . . . . , . . . |[/go]

There are a number of joseki or post-joseki patterns that create Carpenter Square-like shapes.

Carpenter Square can also be formed in mid-game, for example when a big corner is somehow under attack and its eyespace reduced. This will lead to a lot of different conditions (with/without external liberty, with/without hanes on first line). That's why it is interesting to consider all these situations.

[Bill Spight]

Some komaster analysis.

[John Fairbairn]

A reminder, if I may, that the carpenter's square (like the L shape and some other basic shapes) is rather easy to find in a database using Kombilo. GoGoD has 801 games with the standard shape, 1451 with the weak carpenter's square and 666 with the weak point occupied by the enemy. Not all are 100% useful. On the other hand, a little bit of fiddling will also give you the shapes with legs. In short, you can see how (and maybe more importantly: when) the pros played in this shape.

There has also been a lot of analysis over the years on the giant carpenter's square (10x10 black stones enclosing a corner: can White live inside?). As far as I know, the answer is no but the analysis is not conclusive. Maeda Nobuaki wrote about it quite a lot.

[macelee]

A reminder, if I may, that the carpenter's square (like the L shape and some other basic shapes) is rather easy to find in a database using Kombilo. GoGoD has 801 games with the standard shape, 1451 with the weak carpenter's square and 666 with the weak point occupied by the enemy. Not all are 100% useful. On the other hand, a little bit of fiddling will also give you the shapes with legs. In short, you can see how (and maybe more importantly: when) the pros played in this shape.

There has also been a lot of analysis over the years on the giant carpenter's square (10x10 black stones enclosing a corner: can White live inside?). As far as I know, the answer is no but the analysis is not conclusive. Maeda Nobuaki wrote about it quite a lot.

John. Can you please give a screen capture how the patterns are set up using Kombilo? Somehow I only found less than 30 games from 30000+ sgf. So my set up must be incorrect.

[Bill Spight]

Extras.

$$ Diagram 1
$$ . . . . . . . |
$$ . . . . . . . |
$$ . . O O O O O |
$$ . . O X X X X |
$$ . . O X . O . |
$$ . . O X . O O |
$$ . . O X X X . |
$$ --------------

Click Here To Show Diagram Code

[go]$$ Diagram 1
$$ . . . . . . . |
$$ . . . . . . . |
$$ . . O O O O O |
$$ . . O X X X X |
$$ . . O X . O . |
$$ . . O X . O O |
$$ . . O X X X . |
$$ --------------[/go]

Under AGA equivalence scoring ("territory" scoring by area rules), how much is this corner worth?

$$ Diagram 2
$$ . . . . . . . |
$$ . . . . . . . |
$$ . . O O O O O |
$$ . . O X X X X |
$$ . . O X . . . |
$$ . . O X O O O |
$$ . . O X X X . |
$$ --------------

Click Here To Show Diagram Code

[go]$$ Diagram 2
$$ . . . . . . . |
$$ . . . . . . . |
$$ . . O O O O O |
$$ . . O X X X X |
$$ . . O X . . . |
$$ . . O X O O O |
$$ . . O X X X . |
$$ --------------[/go]

How about this one?

Enjoy!

[John Fairbairn]

John. Can you please give a screen capture how the patterns are set up using Kombilo? Somehow I only found less than 30 games from 30000+ sgf. So my set up must be incorrect.

Maybe I did something wrong but I just put 5 black stones in an L-shape centred on the 4-4 point and then highlighted a 4x4 corner. As I said, this is not 100% reliable but it should capture a lot more than 30 examples.

If you want to filter out a portion before you sift through the results for, say, the standard shape, you can do things like put a white stone on the 5-2 point, make a 5x2 rectangle, then search 4x4 only on the results that gives.

In fact, it would be useful to start a thread for creative solutions with Kombilo searches.

[Dusk Eagle]

Extras.

$$ Diagram 1
$$ . . . . . . . |
$$ . . . . . . . |
$$ . . O O O O O |
$$ . . O X X X X |
$$ . . O X . O . |
$$ . . O X . O O |
$$ . . O X X X . |
$$ --------------

Click Here To Show Diagram Code

[go]$$ Diagram 1
$$ . . . . . . . |
$$ . . . . . . . |
$$ . . O O O O O |
$$ . . O X X X X |
$$ . . O X . O . |
$$ . . O X . O O |
$$ . . O X X X . |
$$ --------------[/go]

Under AGA equivalence scoring ("territory" scoring by area rules), how much is this corner worth?

$$ Diagram 2
$$ . . . . . . . |
$$ . . . . . . . |
$$ . . O O O O O |
$$ . . O X X X X |
$$ . . O X . . . |
$$ . . O X O O O |
$$ . . O X X X . |
$$ --------------

Click Here To Show Diagram Code

[go]$$ Diagram 2
$$ . . . . . . . |
$$ . . . . . . . |
$$ . . O O O O O |
$$ . . O X X X X |
$$ . . O X . . . |
$$ . . O X O O O |
$$ . . O X X X . |
$$ --------------[/go]

How about this one?

Enjoy!

1) Black can't play at all without dying; white gets two free moves, so the position is worth -2 (black score is positive, white negative).

2) If black plays first, there is a double gote move for both worth the same amount, so we'll just cancel that out. So a black play gains 1.
If white plays first, then there is a further move which only he can play, so a white play gains -2.
Thus, the position is worth -1.

I think I'm doing this right . Though maybe I'm forgetting some detail about AGA rules, as I've never actually played with them.

[Bill Spight]

1) Black can't play at all without dying; white gets two free moves, so the position is worth -2 (black score is positive, white negative).

2) If black plays first, there is a double gote move for both worth the same amount, so we'll just cancel that out. So a black play gains 1.
If white plays first, then there is a further move which only he can play, so a white play gains -2.
Thus, the position is worth -1.

I think I'm doing this right . Though maybe I'm forgetting some detail about AGA rules, as I've never actually played with them.

1) Right. The two free moves (one-way dame) yield two points for White, even though they are not territory as we know it.

2) You are counting the stones. OC, that is fine for area scoring, but equivalence scoring is a little trickier. Let me put your analysis in the form of a game tree, with / indicating a Black play and \ indicating a White play.

Code: Select all

               A
              / \
             1  -2

The value of A is (1 - 2)/2, the average of the gote results. That comes to -1/2. So each play gains 1 1/2 points by area scoring.

With equivalence scoring each play gains 1 point less, and the tree looks this way:

Code: Select all

               A
              / \
             0  -1

The value is the same, -1/2.