This 'n' that

Knotwilg · Post by **Knotwilg** » Thu Apr 09, 2020 12:37 am

Robert

Click Here To Show Diagram Code: [go]$$Wcm50 Switcheroo shocker $$ --------------------------------------- $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . X O . . . . | $$ | . . O . X O . . . . . . X O O O O . . | $$ | . . O X . X . . X , . . X X O X X . . | $$ | . . . . . . . . . . . . . O X . . . . | $$ | . . . O . . . . . . . . . O . X . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . X . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . , . . . . . , . . . . . , . . . | $$ | . . . . . . . . . . . . . . . O . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . 6 . . . . . . . . . . . . . O X . . | $$ | 8 3 4 . . . . . . . . . . O . O . . . | $$ | . 2 O O 5 . . . . , . . X O X O O . . | $$ | . 7 X X O . . . . . . . . X X X O X . | $$ | . . 9 . X 1 . . . . . . . . . . X O . | $$ | . . . . . . . . . . . . . . . . . X . | $$ ---------------------------------------[/go]

I believe the above is Cho's variation

Click Here To Show Diagram Code: [go]$$Wcm50 Switcheroo shocker $$ --------------------------------------- $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . X O . . . . | $$ | . . O . X O . . . . . . X O O O O . . | $$ | . . O X . X . . X , . . X X O X X . . | $$ | . . . . . . . . . . . . . O X . . . . | $$ | . . . O . . . . . . . . . O . X . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . X . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . , . . . . . , . . . . . , . . . | $$ | . . . . . . . . . . . . . . . O . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . O X . . | $$ | . . . . . . . . . . . . . O . O . . . | $$ | . . O O 3 . . . . , . . X O X O O . . | $$ | . . X X O 2 . . . . . . . X X X O X . | $$ | . . 7 5 X 1 4 . . . . . . . . . X O . | $$ | . . . . . 6 . . . . . . . . . . . X . | $$ ---------------------------------------[/go]

And this would be the benchmark diagram, which is 37% better.

Bill Spight · Post by **Bill Spight** » Thu Apr 09, 2020 2:13 am

RobertJasiek wrote:
Bill Spight wrote:
$$Wcm50 Switcheroo shocker
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . X O . . . . |
$$ | . . O . X O . . . . . . X O O O O . . |
$$ | . . O X . X . . X , . . X X O X X . . |
$$ | . . . . . . . . . . . . . O X . . . . |
$$ | . . . O . . . . . . . . . O . X . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . X . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . , . . . . . , . . . . . , . . . |
$$ | . . . . . . . . . . . . . . . O . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . 6 . . . . . . . . . . . . . O X . . |
$$ | 8 3 4 . . . . . . . . . . O . O . . . |
$$ | . 2 O O 5 . . . . , . . X O X O O . . |
$$ | . 7 X X O . . . . . . . . X X X O X . |
$$ | . . 9 . X 1 . . . . . . . . . . X O . |
$$ | . . . . . . . . . . . . . . . . . X . |
$$ ---------------------------------------
Click Here To Show Diagram Code
[go]$$Wcm50 Switcheroo shocker $$ --------------------------------------- $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . X O . . . . | $$ | . . O . X O . . . . . . X O O O O . . | $$ | . . O X . X . . X , . . X X O X X . . | $$ | . . . . . . . . . . . . . O X . . . . | $$ | . . . O . . . . . . . . . O . X . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . X . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . , . . . . . , . . . . . , . . . | $$ | . . . . . . . . . . . . . . . O . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . 6 . . . . . . . . . . . . . O X . . | $$ | 8 3 4 . . . . . . . . . . O . O . . . | $$ | . 2 O O 5 . . . . , . . X O X O O . . | $$ | . 7 X X O . . . . . . . . X X X O X . | $$ | . . 9 . X 1 . . . . . . . . . . X O . | $$ | . . . . . . . . . . . . . . . . . X . | $$ ---------------------------------------[/go]
Instead of capturing in the usual joseki, Cho opted to hane on the left side and capture . According to the Elf commentary, by comparison this decision cost Cho a whopping 37% in winrate!
I am unsure whether I understand you. Is the diagram above 37% better than Cho's variation? Please show Cho's variation with a diagram! What was the 37% mistake in it?

This is Cho's variation. I.e., what he played in the game. Thanks to Knotwilg for showing the usual joseki for comparison.

Elf does not indicate a single mistake by Cho.

was a mistake, and

was a blunder. It cost more because Black could have reversed course and captured

. But we humans tend to be consistent, except when we are not. Cho played

with the intention of capturing

.

Bill Spight · Post by **Bill Spight** » Thu Apr 09, 2020 2:19 am

These are not happy times, but I hope everyone is well and reasonably happy, given the circumstances. I have been at home, holding down the fort, for almost five weeks now. It is good to talk with my friends here on L19.

Take care.

SoDesuNe · Post by **SoDesuNe** » Thu Apr 09, 2020 2:27 am

Thanks, Bill!

I'm also home (and working from home) for five weeks. Good thing is: without commuting I have more time for go!

And thanks for your "fuseki analysis"! I always read them with great interest but saldy have nothing to contribute ^^

Wishing the best to you and all of L19 =)

RobertJasiek · Post by **RobertJasiek** » Thu Apr 09, 2020 7:11 am

Let us assume the C15 and N3 ajis are siimilsr. Cho's variation is better for W because B does not have a later forcing move on the outside. In the joseki, B has some. We know that 37% is not an absolute number; it simply indicates a clear mistake in the program's opinion.

Bill Spight · Post by **Bill Spight** » Tue Apr 28, 2020 8:24 pm

Personal update.

Going on 8 weeks now. Doing OK.

Toilet paper may be delivered tomorrow, we'll see.

In the US, we are told, the food chain is in peril. Without sitdown business, restaurants are not buying food like they have been doing. A potato farmer had tons of potatoes that he could not sell and said that anyone who wanted some could come and get them. I am reminded of pictures of grain rotting by the side of the road during the great depression, as supply outstripped demand before the dustbowl hit. Today, at least, farmers are getting Federal subsidies.

OTOH, the demand for meat is apparently now higher than supply, because processing plants have closed because they have become Covid-19 hotspots. The President has issued an executive order for them to reopen, safeguards or no, damn the virus.

I now believe that I should do my part to reduce the demand for meat by going vegetarian for the foreseeable future.

P.S. Many tons of that farmer's potatoes ended up in food banks, where demand is quite high for food, but funds are low. They have all or nearly all been consumed by now.

jlt · Post by **jlt** » Wed Apr 29, 2020 12:25 am

I think you live in California? It seems you've passed the peak one week ago. Probably you will be back to almost normal life before the end of May, except that you will need to wear masks and apply social distancing: avoid crowded places, restrict traveling.

Bill Spight · Post by **Bill Spight** » Wed Apr 29, 2020 12:34 am

Thanks, jlt.

We shall see what we shall see.

Yakago · Post by **Yakago** » Wed Apr 29, 2020 5:27 am

Bill Spight wrote: In the US, we are told, the food chain is in peril. Without sitdown business, restaurants are not buying food like they have been doing. A potato farmer had tons of potatoes that he could not sell and said that anyone who wanted some could come and get them. I am reminded of pictures of grain rotting by the side of the road during the great depression, as supply outstripped demand before the dustbowl hit. Today, at least, farmers are getting Federal subsidies.

Stuff like this always strikes me as weird, because in general I don't believe we stopped eating.

I guess the basic principle is that it takes time for the supply/demand to rearrange itself, but it could also showcase how we eat differently at home vs. at restaurants. I.e. it might be that we eat less french fries when home cooking

Also says something about how much food waste/surplus there is, because as far as I know, people are not starving. The calories not eaten from the potatoes must be found in something that would not have been eaten otherwise.

Knotwilg · Post by **Knotwilg** » Wed Apr 29, 2020 5:35 am

Yakago wrote:
Bill Spight wrote: In the US, we are told, the food chain is in peril. Without sitdown business, restaurants are not buying food like they have been doing. A potato farmer had tons of potatoes that he could not sell and said that anyone who wanted some could come and get them. I am reminded of pictures of grain rotting by the side of the road during the great depression, as supply outstripped demand before the dustbowl hit. Today, at least, farmers are getting Federal subsidies.
Stuff like this always strikes me as weird, because in general I don't believe we stopped eating.

I guess the basic principle is that it takes time for the supply/demand to rearrange itself, but it could also showcase how we eat differently at home vs. at restaurants. I.e. it might be that we eat less french fries when home cooking

Also says something about how much food waste/surplus there is, because as far as I know, people are not starving. The calories not eaten from the potatoes must be found in something that would not have been eaten otherwise.

The answer may lie in that food is thrown away all along the food chain, it just happens sooner now. There's less processed and packaged food in our litterbins.

Bill Spight · Post by **Bill Spight** » Wed Apr 29, 2020 6:12 am

Yakago wrote:Also says something about how much food waste/surplus there is, because as far as I know, people are not starving. The calories not eaten from the potatoes must be found in something that would not have been eaten otherwise.

In the US, people are starving, if not actually starving to death. Which is why we are seeing long lines at food banks. At least temporarily we are living under Depression conditions, because a lot of people are not working or are producing less than normal. As we are able to reopen economic activity, people have to have money so they can buy goods and services, pay rent, pay debts, pay taxes, avoid bankruptcy and foreclosure, and so on. I think that the US is doing pretty well in that regard.

Bill Spight · Post by **Bill Spight** » Wed Apr 29, 2020 6:50 am

Back to go stuff.

Recently moha has, IIUC, raised the question of board parity under Button Go. Most of my readers will know that I am an advocate of button go as a hybrid of area and territory scoring. Button go has already been used in international competition, not by using a physical button, but by having special pass rules. For simplicity, let's assume that there is a button, worth ½ pt. under area scoring, that a player may take instead of playing a stone on the board. The normal effect of the button is to make who gets the last dame irrelevant. OC, kos can complicate things.

It turns out that there is no interaction between the button and board parity, except perhaps under unusual circumstances involving ko. For instance, suppose that the territory score on the board is 7 for Black. With odd parity, White will get the last dame and so Black will take the button, for a button score of 7½. With even parity, Black will get the last dame and White will take the button, for a button score of 7 + 1 - ½ = 7½. Now let's suppose that the territory score is an even number, like 6. With odd parity Black will get the last dame and White will take the button, for a button score of 6 + 1 - ½ = 6½. With even parity White will get the last dame and Black will take the button, for a button score of 6½. All same same.

Bill Spight · Post by **Bill Spight** » Mon May 18, 2020 10:55 am

Like Cheating on an Exam

Recently I watched this talk by Yasser Seirawan on an endgame ( https://www.youtube.com/watch?v=YI5CQL_ ... 3&frags=wn ). At about 5 min. in he asks his audience how many people spend 10% of their time devoted to chess, both play and study, studying endgames? 25%? 50%? We don't see the audience, but Seirawan notes that a lot of them spend 25% of their time studying endgames. (OC, this was an endgame lecture, so that's probably high for the chess playing population as a whole.) He goes on to relate something that Michael J. Franett, Washington State Champion in the early 1970s, told him early in his career. "Yasser," he said, "studying endgames is like cheating on an exam. because you know you're going to be asked the questions down the road."

OC, the endgame at go is not as consequential as the endgame at chess, but there are many predictable situations in go, such as standard corner life and death positions, common endgames, and ladders. I have stated that I think that dan players should be able to play the late endgame almost perfectly. Not that unfamiliar positions don't arise, but they are usually easy to analyze in a matter of seconds. Even 5 kyus are A+ at filling dame, where the shortage of liberties can potentially lead to big swings. Playing the last 30 moves correctly is not too difficult, if you have put in a little study. But who does?

Recently I was surprised

to find that one of my endgame problems has an 8 dan rating on goproblems.com. Here it is.

Click Here To Show Diagram Code: [go]$$Wc White to play and win. No komi. $$ ----------------------- $$ | . . . . . . . . . . . | $$ | . . . . . . . . . . . | $$ | . . O O O X X X X . . | $$ | . . O , O . . . X , . | $$ | . . O . O X X . X . . | $$ | . . O . X X . X . X . | $$ | . . O . . O O X . . . | $$ | . . O O O O X X X X X | $$ | . . O . . X X . X O X | $$ | . . . O O O X X O , O | $$ | . . . . . O O X X O . | $$ -----------------------[/go]

Now, reading the solution out may take a little time, but an SDK who has studied chilled go infinitesimals should see the first few plays almost instantaneously. This really should not be an 8 dan problem. Mathematical Go came out in 1994, and the SL material on go infinitesimals has been available for many years.

As for smaller plays, the prototypes for them are corridors. True, complicated positoins can arise, but usually they are easy to calculate. For instance,

Click Here To Show Diagram Code: [go]$$Wc Corridors $$ ----------------------- $$ | . . . . . . . . . . . | $$ | . . . . . . . . . . . | $$ | . . O O O X X X X . . | $$ | . . O W O . . . X , . | $$ | . . O . O X X B X . . | $$ | . . O . X X . X . X . | $$ | . . O . . O O X . . . | $$ | . . O O O O X X X X X | $$ | . . O . . X X . X O X | $$ | . . . O O O X X O , O | $$ | . . . . . O O X X O . | $$ -----------------------[/go]

I have add a Black stone and a White stone to the position, so that the plays in the center each gain less than 1 pt. of territory. Everybody knows that the 2 space White corridor is worth -½ pt. from Black's point of view. The 3 space Black corridor is worth 1¼ pt. for Black. To see that, Black to play closes the corridor for 2 pts. and White to play advances into the corridor for a position worth ½ pt. Both of these plays are gote, so we take their average to get the territorial value of 1¼. The White shape in the center is not a corridor, but it is not hard to calculate its value.

Hint:

----

Speaking of corridors, there is a kind of diagram that appears in nearly every endgame book, of corridors of increasing length, side by side. Like so.

As everybody learns, the correct play is in the longest corridor. And we learn that the territorial value of each corridor is the length of the corridor minus 2 plus a fraction. The value of a length 2 corridor is ½, the value of a length 3 corridor is 1¼, the value of a length 4 corridor is 2⅛, etc. What the textbooks don't teach, not the ones I have seen, anyway, is that after White enters the longest corridor, the result is a kind of miai. That is, the corridors taken together have a territorial score which is the same, no matter who plays first in the combination. This SGF file illustrates that fact.

This fact has been discovered independently, it seems, by Antti Tormanen, David Wolfe, myself, and, I am sure, many others.

I discovered that fact by considering the miai of the two longest corridors, which, when played, yield another miai in the two longest corridors, and so on. From David's Theorem 8 in Mathematical Go, I suspect that David figured it out by noting that the fractions all add up to 1.

David went even further and noticed that if the fractions add up to more than 1, then there will be some number of corridors whose fractions add up to exactly 1, and form this kind of miai. Well done, sir!

Bill Spight · Post by **Bill Spight** » Mon May 18, 2020 11:29 am

Corner L&D, endgame

There is a myth that in the endgame life and death are settled, that the endgame is just about points. Not so. In fact, there are frequently unsettled positions, especially in the corner, especially involving ko, that are the right size to play in the early and middle endgame. And life and death battles can occur, particularly with mutual damage positions.

Here is a simple endgame corner position. Per convention, the outside White stones are alive. Territory scoring, counting territory in seki.

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

Easy questions.

1) What is the usual territorial value of the corner?

2) How much does a gote or reverse sente gain?

Maybe not so easy questions. Usually, Black cannot afford to fight a ko in such corners because she has too much at stake. However, assume that Black is komaster, and can win a ko in this corner. (Assume that the komaster has just enough large enough ko threats to win the ko without ignoring the opponent's threat.)

3) When Black is komaster, what is the territorial value of the corner?

4) How much does each play in the ko gain, on average?

5) How much does Black gain by winning the ko versus the territorial value of the corner?

6) How should White play this corner?

Enjoy!

jlt · Post by **jlt** » Tue May 19, 2020 5:39 am

$$Wc White to play and win. No komi.
$$ -----------------------
$$ | . . . . . . . . . . . |
$$ | . . . . . . . . . . . |
$$ | . . O O O X X X X . . |
$$ | . . O , O . . . X , . |
$$ | . . O . O X X . X . . |
$$ | . . O . X X . X . X . |
$$ | . . O . . O O X . . . |
$$ | . . O O O O X X X X X |
$$ | . . O . . X X . X O X |
$$ | . . . O O O X X O , O |
$$ | . . . . . O O X X O . |
$$ -----------------------
Click Here To Show Diagram Code
[go]$$Wc White to play and win. No komi. $$ ----------------------- $$ | . . . . . . . . . . . | $$ | . . . . . . . . . . . | $$ | . . O O O X X X X . . | $$ | . . O , O . . . X , . | $$ | . . O . O X X . X . . | $$ | . . O . X X . X . X . | $$ | . . O . . O O X . . . | $$ | . . O O O O X X X X X | $$ | . . O . . X X . X O X | $$ | . . . O O O X X O , O | $$ | . . . . . O O X X O . | $$ -----------------------[/go]

Attempt:

Click Here To Show Diagram Code: [go]$$Wc W32, B31. a and b are miai for White $$ ----------------------- $$ | . . . . . 9 7 8 . . . | $$ | . . . . 3 1 2 . . . . | $$ | . . O O O X X X X . . | $$ | . . O , O 5 6 . X , . | $$ | . . O a O X X . X . . | $$ | . . O 4 X X . X . X . | $$ | . . O . . O O X . . . | $$ | . . O O O O X X X X X | $$ | . . O . b X X . X O X | $$ | . . . O O O X X O , O | $$ | . . . . . O O X X O . | $$ -----------------------[/go]

Click Here To Show Diagram Code: [go]$$Wc W31, B30. :w11: is at a ; b and c miai for White. $$ ----------------------- $$ | . . . . 7 6 8 . . . . | $$ | . . . . 3 1 2 . . . . | $$ | . . O O O X X X X . . | $$ | . . O , O 5 9 b X , . | $$ | . . O a O X X . X . . | $$ | . . O 4 X X c X . X . | $$ | . . O . . O O X . . . | $$ | . . O O O O X X X X X | $$ | . . O . 0 X X . X O X | $$ | . . . O O O X X O , O | $$ | . . . . . O O X X O . | $$ -----------------------[/go]

Click Here To Show Diagram Code: [go]$$Wc W31, B30. :w11: is at a ; b and c miai for White. $$ ----------------------- $$ | . . . . 5 4 6 . . . . | $$ | . . . . 3 1 2 . . . . | $$ | . . O O O X X X X . . | $$ | . . O , O 7 9 b X , . | $$ | . . O a O X X . X . . | $$ | . . O 8 X X c X . X . | $$ | . . O . . O O X . . . | $$ | . . O O O O X X X X X | $$ | . . O . 0 X X . X O X | $$ | . . . O O O X X O , O | $$ | . . . . . O O X X O . | $$ -----------------------[/go]

Click Here To Show Diagram Code: [go]$$Wc W33, B32. a and b are miai for White $$ ----------------------- $$ | . . . . 5 4 6 . . . . | $$ | . . . . 3 1 2 . . . . | $$ | . . O O O X X X X . . | $$ | . . O , O 7 8 . X , . | $$ | . . O . O X X . X . . | $$ | . . O 9 X X . X . X . | $$ | . . O . a O O X . . . | $$ | . . O O O O X X X X X | $$ | . . O . b X X . X O X | $$ | . . . O O O X X O , O | $$ | . . . . . O O X X O . | $$ -----------------------[/go]

Life In 19x19

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