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 Post subject: Re: This 'n' that #441 Posted: Wed Oct 04, 2017 11:33 pm
 Tengen

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Bill Spight wrote:
What do you want to call the difference between S and 0?

Call it "the difference between S and 0".

But "the difference between the count of S and 0 (which is the count of a leaf)" we call the "the negative of the [net] profit" aka "the negative of the gain", right?

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 Post subject: Re: This 'n' that #442 Posted: Thu Oct 05, 2017 8:31 am
 Judan

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RobertJasiek wrote:
The profit is the value change from the count of S to the count 0. Why do you instead say that the profit is the change from the game S to the count 0?

In CGT a game is a value, and numbers are games. Non-numerical games are fuzzy values. The count of a go position is a number, which is the mean value of its game (adjusted in modern go according to the specific rule set).

You are the one to introduce the term, profit. If you wish to use it only for numbers, be my guest. But gain and loss, in English, are not restricted to numbers. One may gain understanding or lose confidence.

The gain from playing with sente from S to 0 is 0 - S, which is the game, -S, which is greater than 0, even though its mean value is 0.

If you want to say that the profit from playing S with sente is 0, that accords with the saying, Sente gains nothing.

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 Post subject: Re: This 'n' that #443 Posted: Thu Oct 05, 2017 9:47 am
 Tengen

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Actually, you introduced 'profit value' for one move's profit and 'net profit' for the alternating difference of a sequence's profit values quite some time ago, although you did not provide such definitions explicitly, AFAIK. I have found these terms very useful when expressing the change from a starting count to a follower's count.

'Profit' used alone is also used in different, informal go meanings ("A player takes profit here, then tenukis."). Therefore, using 'profit value' and 'net profit' as the terms for CGT or endgame theory avoids ambiguity. Besides, 'profit value' reminds us of the close relation to the term 'move value'.

There seems to be no consensus yet on whether 'gain' might occur as another term. I hope that not because profit and gain are so similar to create confusion that is better avoided.

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 Post subject: Re: This 'n' that #444 Posted: Thu Oct 05, 2017 11:17 am
 Judan

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RobertJasiek wrote:
Actually, you introduced 'profit value' for one move's profit and 'net profit' for the alternating difference of a sequence's profit values quite some time ago, although you did not provide such definitions explicitly, AFAIK. I have found these terms very useful when expressing the change from a starting count to a follower's count.

Well, your memory is better than mine on that score. (Edit: I did a search here and did not find that I used it here.) Possibly that happened on rec.games.go or, perhaps more likely, in the lost archives of Godiscussions before 2010. Back in the 1990s I pushed for Western players to learn and use miai values for moves instead of deiri values, in an attempt to help clarify evaluation. I seem to have caused more confusion, however. John Fairbairn has pointed out that the term, deiri in accounting refers to profit and loss. It could be that I tried the term, profit value, as an English equivalent to miai value. That seems to be how you are using the term. But eventually I decided to simply use the term, gain, despite some ambiguity. Unless you get really technical, you don't have to distinguish between the difference in counts and the difference in games. Here I was getting really technical, because I wanted to show that sente in the technical sense can gain something, just not points.

Quote:
There seems to be no consensus yet on whether 'gain' might occur as another term. I hope that not because profit and gain are so similar to create confusion that is better avoided.

Yes, I see other people using "miai value", but neither "profit value" nor "gain" seems to have generally caught on yet.

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 Post subject: Re: This 'n' that #445 Posted: Thu Oct 05, 2017 12:10 pm
 Tengen

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Maybe on Sensei‘s? You used profit value in contrast to move value to describe the different behaviour of sente and the different values of starting a sente sequence or playing reverse sente. Precision is needed and I did some related proofs because I could not find such quickly from others, except that OC you paved the conceptual way.

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 Post subject: Re: This 'n' that #446 Posted: Sat Oct 07, 2017 11:41 am
 Judan

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Yet another post on Kano's Beauty

Code:
A              +            D
/ \ \                       / \
/   \ \_____ -1             1  -1
/     \
B       C
/ \     / \
BIG  D   0  -BIG'
/ \
1  -1

Kano's Beauty is A + D (normalized to have a count of 0). As we know, A + D = A - D < 0. Which means that White gets the last play in Kano's Beauty, no matter who plays first. It is rather interesting that the sum of two games that are confused with 0 is less than 0. But that is not all that unusual.

Here is something that I find interesting.

A < D, so
A + A < D + D = 0

So two copies of A is less than 0. Here is an SGF file that illustrates that. Note that when White plays first he could easily make a mistake.

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 Post subject: Re: This 'n' that #447 Posted: Mon Oct 16, 2017 10:01 pm
 Judan

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Tsumego from an actual game

`[go]\$\$Wc Status?\$\$ --------------------\$\$ | . . X . X X . . . .\$\$ | . O O X X . X O . .\$\$ | X . O X X X O X X X\$\$ | X O . , O O O O . ,\$\$ | O X O O O X X O X X\$\$ | . X X X O O X O X O\$\$ | . X . X . O X O X X\$\$ | O O O X . O X O X O\$\$ | . X X . X O X X X X\$\$ | . X . , O O O X O ,\$\$ | . O O O . X . X O O\$\$ | . O X X X . X X X X\$\$ | . O X . . X X . O O\$\$ | . O O X X . X X O X[/go]`

What is the status of the Black group on the left side? Can White to play kill? (The surrounding White stones are alive, OC.)

Enjoy!

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 Post subject: Re: This 'n' that #448 Posted: Mon Oct 16, 2017 10:14 pm
 Lives in sente

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Universal go server handle: speedchase
`[go]\$\$W1\$\$ --------------------\$\$ | . . X . X X . . . .\$\$ | . O O X X . X O . .\$\$ | X . O X X X O X X X\$\$ | X O . , O O O O . ,\$\$ | O X O O O X X O X X\$\$ | 3 X X X O O X O X O\$\$ | . X . X . O X O X X\$\$ | O O O X . O X O X O\$\$ | 2 X X . X O X X X X\$\$ | 1 X . , O O O X O ,\$\$ | . O O O . X . X O O\$\$ | . O X X X . X X X X\$\$ | . O X . . X X . O O\$\$ | . O O X X . X X O X[/go]`

`[go]\$\$W1\$\$ --------------------\$\$ | . . X . X X . . . .\$\$ | . O O X X . X O . .\$\$ | X . O X X X O X X X\$\$ | X O . , O O O O . ,\$\$ | O X O O O X X O X X\$\$ | . X X X O O X O X O\$\$ | 2 X 4 X . O X O X X\$\$ | O O O X . O X O X O\$\$ | 3 X X . X O X X X X\$\$ | 1 X . , O O O X O ,\$\$ | 5 O O O . X . X O O\$\$ | . O X X X . X X X X\$\$ | . O X . . X X . O O\$\$ | . O O X X . X X O X[/go]`

This seems to work pretty well. Anything I am missing?

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 Post subject: Re: This 'n' that #449 Posted: Tue Oct 17, 2017 1:21 am
 Gosei

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speedchase wrote:
`[go]\$\$W1\$\$ --------------------\$\$ | . . X . X X . . . .\$\$ | . O O X X . X O . .\$\$ | X . O X X X O X X X\$\$ | X O . , O O O O . ,\$\$ | O X O O O X X O X X\$\$ | 3 X X X O O X O X O\$\$ | . X . X . O X O X X\$\$ | O O O X . O X O X O\$\$ | 2 X X . X O X X X X\$\$ | 1 X . , O O O X O ,\$\$ | . O O O . X . X O O\$\$ | . O X X X . X X X X\$\$ | . O X . . X X . O O\$\$ | . O O X X . X X O X[/go]`

`[go]\$\$W1\$\$ --------------------\$\$ | . . X . X X . . . .\$\$ | . O O X X . X O . .\$\$ | X . O X X X O X X X\$\$ | X O . , O O O O . ,\$\$ | O X O O O X X O X X\$\$ | . X X X O O X O X O\$\$ | 2 X 4 X . O X O X X\$\$ | O O O X . O X O X O\$\$ | 3 X X . X O X X X X\$\$ | 1 X . , O O O X O ,\$\$ | 5 O O O . X . X O O\$\$ | . O X X X . X X X X\$\$ | . O X . . X X . O O\$\$ | . O O X X . X X O X[/go]`

This seems to work pretty well. Anything I am missing?

Black has resources in the first diagram. Think about it before peeking!
Black answers 3 with 4, threatening to capture both white strings with 'a'. The capture threatens to make too many eyes. White can't prevent Black from living.
`[go]\$\$W1\$\$ --------------------\$\$ | . . X . X X . . . .\$\$ | . O O X X . X O . .\$\$ | X . O X X X O X X X\$\$ | X O . , O O O O . ,\$\$ | O X O O O X X O X X\$\$ | 3 X X X O O X O X O\$\$ | a X 4 X . O X O X X\$\$ | O O O X . O X O X O\$\$ | 2 X X . X O X X X X\$\$ | 1 X . , O O O X O ,\$\$ | . O O O . X . X O O\$\$ | . O X X X . X X X X\$\$ | . O X . . X X . O O\$\$ | . O O X X . X X O X[/go]`

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 This post by ez4u was liked by: Bill Spight
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 Post subject: Re: This 'n' that #450 Posted: Thu Nov 09, 2017 3:57 pm
 Judan

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A not so easy problem

Most of my problems and illustrations are easy. This one, however. . . .

`[go]\$\$Wc White to play\$\$ ---------------------------\$\$ | X X X X X X X X X X X X . |\$\$ | . O . O . O . O . O . O X |\$\$ | . O . O . O . O . O . O X |\$\$ | . O . O . O . O . O . O X |\$\$ | . O . O . O . O O O O O X |\$\$ | . O . O . O O O X O X X X |\$\$ | . O . O . O X X X X . . . |\$\$ | . O . O X . . . . X . X . |\$\$ | . O X X X X X X X X O X . |\$\$ | X O . . . . . X O O O O . |\$\$ | X X X X X X X X O . . . . |\$\$ | . . . . . . . . X O . O . |\$\$ | . . . . . . . X . . . . . |\$\$ ---------------------------[/go]`

No komi. White to play and win.

Enjoy!

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Last edited by Bill Spight on Mon Nov 13, 2017 2:20 pm, edited 1 time in total.
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 Post subject: Re: This 'n' that #451 Posted: Mon Nov 13, 2017 1:33 pm
 Judan

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Well, nobody has bitten so far. Here is an unhelpful hint.

Black gets the last 1 pt. play

`[go]\$\$Wc Variation 1\$\$ ---------------------------\$\$ | X X X X X X X X X X X X . |\$\$ | . O . O . O . O . O . O X |\$\$ | . O . O . O . O . O . O X |\$\$ | . O . O . O . O . O . O X |\$\$ | . O . O . O . O O O O O X |\$\$ | . O . O . O O O X O X X X |\$\$ | . O . O . O X X X X 2 . . |\$\$ | . O . O X . . . . X 1 X . |\$\$ | . O X X X X X X X X O X 6 |\$\$ | X O . . . . . X O O O O 4 |\$\$ | X X X X X X X X O . . . 5 |\$\$ | . . . . . . . 8 X O . O . |\$\$ | . . . . . . . X 7 3 . . . |\$\$ ---------------------------[/go]`

After Black must play the hane-and-connect to get the last 1 pt. play.

`[go]\$\$Wc Variation 2\$\$ ---------------------------\$\$ | X X X X X X X X X X X X . |\$\$ | . O . O . O . O . O . O X |\$\$ | . O . O . O . O . O . O X |\$\$ | . O . O . O . O . O . O X |\$\$ | . O . O . O . O O O O O X |\$\$ | . O . O . O O O X O X X X |\$\$ | . O . O . O X X X X 2 . . |\$\$ | . O . O X . . . . X 1 X . |\$\$ | . O X X X X X X X X O X 4 |\$\$ | X O . . . . . X O O O O 3 |\$\$ | X X X X X X X X O . . . . |\$\$ | . . . . . . . . X O . O . |\$\$ | . . . . . . . X 6 5 . . . |\$\$ ---------------------------[/go]`

is a 2 pt. sente. White could also play the hane-and-connect at 4. It's ambiguous.

However, the hane-and-connect is technically inferior to the descent at 5.

Since Black gets the last play that gains 1 pt., White's job is to round the score to a 1 pt. win.

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Last edited by Bill Spight on Mon Nov 13, 2017 2:17 pm, edited 1 time in total.
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 Post subject: Re: This 'n' that #452 Posted: Mon Nov 13, 2017 1:58 pm
 Gosei

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Patience William, patience! I can win, but cannot yet say why with confidence. Therefore cannot yet be sure whether Black has additional resources. Annoyingly addictive problem though.

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

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 Post subject: Re: This 'n' that #453 Posted: Mon Nov 13, 2017 2:16 pm
 Judan

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ez4u wrote:

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 Post subject: Re: This 'n' that #454 Posted: Fri Nov 17, 2017 12:02 pm
 Judan

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I feel confident that Dave has found the solution. But, as he says, why it is right is not easy to explain. Anyway, it has been more than a week, so here goes.

`[go]\$\$Wc White to play\$\$ ---------------------------\$\$ | X X X X X X X X X X X X . |\$\$ | . O . O . O . O . O . O X |\$\$ | . O . O . O . O . O . O X |\$\$ | . O . O . O . O . O . O X |\$\$ | . O . O . O . O O O O O X |\$\$ | . O . O . O O O X O X X X |\$\$ | . O . O . O X X X X 2 . . |\$\$ | . O . O X . . . . X 1 X . |\$\$ | . O X X X X X X X X O X 4 |\$\$ | X O . . . . . X O O O O 3 |\$\$ | X X X X X X X X O . . . . |\$\$ | . . . . . . . . X O . O . |\$\$ | . . . . . . . X 6 5 . . . |\$\$ ---------------------------[/go]`

The first few moves occur at temperature 1, but Black gets the last play at that temperature. is sente, but White could also play it at 5.

`[go]\$\$Wc White wins\$\$ ---------------------------\$\$ | X X X X X X X X X X X X . |\$\$ | a O . O . O 7 O . O . O X |\$\$ | . O . O . O . O . O . O X |\$\$ | . O . O . O . O . O . O X |\$\$ | . O . O . O . O O O O O X |\$\$ | . O . O . O O O X O X X X |\$\$ | . O . O . O X X X X X . . |\$\$ | . O . O X . . . . X O X . |\$\$ | . O X X X X X X X X O X X |\$\$ | X O . . . . . X O O O O O |\$\$ | X X X X X X X X O . . . . |\$\$ | . . . . . . . . X O . O . |\$\$ | . . . . . . . X X O . . . |\$\$ ---------------------------[/go]`

The winning move is . Now the rest is miai, for a score of 1 pt. for White. That is far from obvious. Besides, the play at "a" looks bigger. Normally an open corridor of length 8 is equivalent to a closed corridor of length 6. How can the best play be on a closed corridor of length 4? The answer lies in the threatened atari against the Black stones on the top edge.

Anyway, here is one way to play out the miai. Since the whole board is miai, there are several ways to play, OC.

`[go]\$\$Wc White wins, cont.\$\$ ---------------------------\$\$ | X X X X X X X X X X X X . |\$\$ | . O . O . O O O 8 O 9 O X |\$\$ | . O . O . O . O 0 O . O X |\$\$ | . O . O . O . O . O . O X |\$\$ | . O . O . O . O O O O O X |\$\$ | . O . O . O O O X O X X X |\$\$ | . O . O . O X X X X X . . |\$\$ | . O . O X . . . . X O X . |\$\$ | . O X X X X X X X X O X X |\$\$ | X O . . . . . X O O O O O |\$\$ | X X X X X X X X O . . . . |\$\$ | . . . . . . . . X O . O . |\$\$ | . . . . . . . X X O . . . |\$\$ ---------------------------[/go]`

and are obviously miai, even if they may not appear to be best. eliminates the atari before the dame stage, so the remaining plays continue as usual.

`[go]\$\$Wcm11 White wins (ii)\$\$ ---------------------------\$\$ | X X X X X X X X X X X X . |\$\$ | 1 O 5 O . O O O X O O O X |\$\$ | . O . O . O . O X O . O X |\$\$ | . O . O . O . O . O . O X |\$\$ | . O . O . O . O O O O O X |\$\$ | . O . O . O O O X O X X X |\$\$ | . O 7 O . O X X X X X . . |\$\$ | 3 O 6 O X . . . . X O X . |\$\$ | 2 O X X X X X X X X O X X |\$\$ | X O 4 . . . . X O O O O O |\$\$ | X X X X X X X X O . . . . |\$\$ | . . . . . . . . X O . O . |\$\$ | . . . . . . . X X O . . . |\$\$ ---------------------------[/go]`

- closes off the longest corridor. Then - are miai.

`[go]\$\$Bcm18 White wins (iii)\$\$ ---------------------------\$\$ | X X X X X X X X X X X X . |\$\$ | O O O O 2 O O O X O O O X |\$\$ | . O . O . O . O X O . O X |\$\$ | . O . O . O . O . O . O X |\$\$ | . O . O . O . O O O O O X |\$\$ | . O . O 4 O O O X O X X X |\$\$ | . O O O 3 O X X X X X . . |\$\$ | O O X O X 1 . . . X O X . |\$\$ | X O X X X X X X X X O X X |\$\$ | X O X . . . . X O O O O O |\$\$ | X X X X X X X X O . . . . |\$\$ | . . . . . . . . X O . O . |\$\$ | . . . . . . . X X O . . . |\$\$ ---------------------------[/go]`

Then - are miai. Black scores 25 pts., but White scores 26 pts. to win by 1 pt.

Let's try a variation for Black at move 10.

`[go]\$\$Bcm10 Variation\$\$ ---------------------------\$\$ | X X X X X X X X X X X X 9 |\$\$ | 6 O 4 O 8 O O O X O O O X |\$\$ | . O . O . O . O 2 O . O X |\$\$ | . O . O . O . O . O . O X |\$\$ | . O . O . O . O O O O O X |\$\$ | . O . O . O O O X O X X X |\$\$ | 7 O 0 O . O X X X X X . . |\$\$ | 3 O 5 O X . . . . X O X . |\$\$ | 1 O X X X X X X X X O X X |\$\$ | X O . . . . . X O O O O O |\$\$ | X X X X X X X X O . . . . |\$\$ | . . . . . . . . X O . O . |\$\$ | . . . . . . . X X O . . . |\$\$ ---------------------------[/go]`

enters the longest corridor, and closes off the shortest one. Then the two White corridors on the left are plainly miai. After - they still are. After gets in the sente and then comes back to .

`[go]\$\$Bcm20 Variation, cont.\$\$ ---------------------------\$\$ | X X X X X X X X X X X X X |\$\$ | O O O O O O O O X O O O X |\$\$ | . O . O . O . O O O . O X |\$\$ | . O . O . O . O . O . O X |\$\$ | . O . O . O . O O O O O X |\$\$ | 4 O . O . O O O X O X X X |\$\$ | X O O O 2 O X X X X X . . |\$\$ | X O X O X 3 . . . X O X . |\$\$ | X O X X X X X X X X O X X |\$\$ | X O 1 . . . . X O O O O O |\$\$ | X X X X X X X X O . . . . |\$\$ | . . . . . . . . X O . O . |\$\$ | . . . . . . . X X O . . . |\$\$ ---------------------------[/go]`

and are miai, as are and . Black gets 25 pts. and White gets 26 pts., as above.

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 Post subject: Re: This 'n' that #455 Posted: Fri Nov 17, 2017 12:59 pm
 Judan

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White failure.

`[go]\$\$Wc White failure, jigo\$\$ ---------------------------\$\$ | X X X X X X X X X X X X . |\$\$ | 7 O . O . O 8 O . O . O X |\$\$ | . O . O . O 0 O . O . O X |\$\$ | . O . O . O . O . O . O X |\$\$ | . O . O . O . O O O O O X |\$\$ | . O . O . O O O X O X X X |\$\$ | . O . O . O X X X X X . . |\$\$ | . O . O X . . . . X O X . |\$\$ | 9 O X X X X X X X X O X X |\$\$ | X O . . . . . X O O O O O |\$\$ | X X X X X X X X O . . . . |\$\$ | . . . . . . . . X O . O . |\$\$ | . . . . . . . X X O . . . |\$\$ ---------------------------[/go]`

looks correct, but it is a very small error. is correct, OC. Then is correct if was correct. (Edit: is actually correct now, but we don't have to show that. ) eliminates the sente against the Black stones on the top edge. The rest of the play is as usual.

`[go]\$\$Wcm11 White failure (ii)\$\$ ---------------------------\$\$ | X X X X X X X X X X X X . |\$\$ | O O 1 O 5 O X O . O . O X |\$\$ | . O . O . O X O . O . O X |\$\$ | . O . O . O . O . O . O X |\$\$ | . O . O . O . O O O O O X |\$\$ | . O . O 7 O O O X O X X X |\$\$ | . O 3 O 6 O X X X X X . . |\$\$ | . O 2 O X 8 . . . X O X . |\$\$ | O O X X X X X X X X O X X |\$\$ | X O 4 . . . . X O O O O O |\$\$ | X X X X X X X X O . . . . |\$\$ | . . . . . . . . X O . O . |\$\$ | . . . . . . . X X O . . . |\$\$ ---------------------------[/go]`

- are miai, as are - .

`[go]\$\$Wcm19 White failure (iii)\$\$ ---------------------------\$\$ | X X X X X X X X X X X X . |\$\$ | O O O O O O X O 1 O 2 O X |\$\$ | . O . O . O X O . O 4 O X |\$\$ | . O . O . O 3 O . O . O X |\$\$ | . O . O . O . O O O O O X |\$\$ | . O . O O O O O X O X X X |\$\$ | . O O O X O X X X X X . . |\$\$ | . O X O X X . . . X O X . |\$\$ | O O X X X X X X X X O X X |\$\$ | X O X . . . . X O O O O O |\$\$ | X X X X X X X X O . . . . |\$\$ | . . . . . . . . X O . O . |\$\$ | . . . . . . . X X O . . . |\$\$ ---------------------------[/go]`

Finally and are miai, as are and . Black gets 25 pts., as usual, and White also gets 25 pts., for jigo.

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 Post subject: Re: This 'n' that #456 Posted: Sat Nov 18, 2017 2:42 am
 Tengen

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`[go]\$\$Wc White wins\$\$ ---------------------------\$\$ | X X X X X X X X X X X X . |\$\$ | a O . O . O 7 O . O . O X |\$\$ | . O . O . O . O . O . O X |\$\$ | . O . O . O . O . O . O X |\$\$ | . O . O . O . O O O O O X |\$\$ | . O . O . O O O X O X X X |\$\$ | . O . O . O X X X X X . . |\$\$ | . O . O X . . . . X O X . |\$\$ | . O X X X X X X X X O X X |\$\$ | X O . . . . . X O O O O O |\$\$ | X X X X X X X X O . . . . |\$\$ | . . . . . . . . X O . O . |\$\$ | . . . . . . . X X O . . . |\$\$ ---------------------------[/go]`

"Now the rest is miai"

Once more I wonder: What IS 'miai'? (And, applied to this position, why do we have a miai here?)

`[go]\$\$Wc White wins, cont.\$\$ ---------------------------\$\$ | X X X X X X X X X X X X . |\$\$ | . O . O . O O O 8 O 9 O X |\$\$ | . O . O . O . O . O . O X |\$\$ | . O . O . O . O . O . O X |\$\$ | . O . O . O . O O O O O X |\$\$ | . O . O . O O O X O X X X |\$\$ | . O . O . O X X X X X . . |\$\$ | . O . O X . . . . X O X . |\$\$ | . O X X X X X X X X O X X |\$\$ | X O . . . . . X O O O O O |\$\$ | X X X X X X X X O . . . . |\$\$ | . . . . . . . . X O . O . |\$\$ | . . . . . . . X X O . . . |\$\$ ---------------------------[/go]`

":b8: and :w9: are obviously miai"

Why are they miai? What IS miai? It must be something more specific than 'same move value'.

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 Post subject: Re: This 'n' that #457 Posted: Sat Nov 18, 2017 8:28 am
 Judan

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RobertJasiek wrote:
`[go]\$\$Wc White wins, cont.\$\$ ---------------------------\$\$ | X X X X X X X X X X X X . |\$\$ | . O . O . O O O 8 O 9 O X |\$\$ | . O . O . O . O . O . O X |\$\$ | . O . O . O . O . O . O X |\$\$ | . O . O . O . O O O O O X |\$\$ | . O . O . O O O X O X X X |\$\$ | . O . O . O X X X X X . . |\$\$ | . O . O X . . . . X O X . |\$\$ | . O X X X X X X X X O X X |\$\$ | X O . . . . . X O O O O O |\$\$ | X X X X X X X X O . . . . |\$\$ | . . . . . . . . X O . O . |\$\$ | . . . . . . . X X O . . . |\$\$ ---------------------------[/go]`

":b8: and are obviously miai"

Why are they miai? What IS miai? It must be something more specific than 'same move value'.

These corridors are obviously miai because, sans ko, we may consider that if one player plays in one the other player will play in the other. There are only two of these, so that is obvious. Now suppose that there are more than two of them. In actual play we do not know which one our opponent may play in, but we can decide which pair or pairs to regard as miai.

Quote:
`[go]\$\$Wc White wins\$\$ ---------------------------\$\$ | X X X X X X X X X X X X . |\$\$ | a O . O . O 7 O . O . O X |\$\$ | . O . O . O . O . O . O X |\$\$ | . O . O . O . O . O . O X |\$\$ | . O . O . O . O O O O O X |\$\$ | . O . O . O O O X O X X X |\$\$ | . O . O . O X X X X X . . |\$\$ | . O . O X . . . . X O X . |\$\$ | . O X X X X X X X X O X X |\$\$ | X O . . . . . X O O O O O |\$\$ | X X X X X X X X O . . . . |\$\$ | . . . . . . . . X O . O . |\$\$ | . . . . . . . X X O . . . |\$\$ ---------------------------[/go]`

"Now the rest is miai"

Once more I wonder: What IS 'miai'? (And, applied to this position, why do we have a miai here?)

Like most words, miai has more than one meaning. The basic one is that there is a pair of local positions such that we may assume, in correct alternating play sans ko, that one player will play in one and the other player will play in the other. We may also have a pair of plays in a single local position where the plays are not independent, such that we may assume that one player will make one play and the other player will make the other. Sometimes we know which player will make which play. It does not matter which player plays in a miai first, and, as I have indicated above, we may regard a pair of plays or positions as miai without consulting the other player.

Suppose that we have two independent, mirror positions on the board. Sans ko, they are miai. They are miai, no matter how complex they are, because if one player plays in one, the other player may make the corresponding opposite and equal play in the other, to produce another pair of mirror positions.

In this case, although it is complicated, play proceeds through a number of miai sequences. It does not matter who plays first, the result will be the same. Let White play first, and the result will still be a one point win for White.

`[go]\$\$Wc White wins by one point\$\$ ---------------------------\$\$ | X X X X X X X X X X X X . |\$\$ | 3 O . O . O W O 1 O 2 O X |\$\$ | . O . O . O . O . O 6 O X |\$\$ | . O . O . O . O . O . O X |\$\$ | . O . O . O . O O O O O X |\$\$ | . O . O . O O O X O X X X |\$\$ | . O . O . O X X X X X . . |\$\$ | 5 O . O X . . . . X O X . |\$\$ | 4 O X X X X X X X X O X X |\$\$ | X O . . . . . X O O O O O |\$\$ | X X X X X X X X O . . . . |\$\$ | . . . . . . . . X O . O . |\$\$ | . . . . . . . X X O . . . |\$\$ ---------------------------[/go]`

and are miai. - is a miai sequence.

`[go]\$\$Wcm7 White wins by one point\$\$ ---------------------------\$\$ | X X X X X X X X X X X X . |\$\$ | O O 1 O 5 O W O O O X O X |\$\$ | . O . O . O . O . O X O X |\$\$ | . O . O . O . O . O . O X |\$\$ | . O . O . O . O O O O O X |\$\$ | . O . O 7 O O O X O X X X |\$\$ | . O 3 O 6 O X X X X X . . |\$\$ | O O 2 O X 8 . . . X O X . |\$\$ | X O X X X X X X X X O X X |\$\$ | X O 4 . . . . X O O O O O |\$\$ | X X X X X X X X O . . . . |\$\$ | . . . . . . . . X O . O . |\$\$ | . . . . . . . X X O . . . |\$\$ ---------------------------[/go]`

- and - are miai sequences. Black gets 25 pts. but White gets 26 pts. to win by 1 pt.

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 Post subject: Re: This 'n' that #458 Posted: Sat Nov 18, 2017 9:47 am
 Lives with ko

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Question for Bill - assuming no ko is involved anywhere, if you have two copies of a subgame G such that the temperature never increases as you descend any branch of the game tree of G (for example, pushing down a corridor that terminates in nothing or that terminates in only saving a single stone at the end satisfies this condition), is it always the case that you can treat the first move in the two copies of G as "miai" when determining what best play is?

And if so, is there a more general condition than this?

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 Post subject: Re: This 'n' that #459 Posted: Sat Nov 18, 2017 10:47 am
 Judan

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lightvector wrote:
Question for Bill - assuming no ko is involved anywhere, if you have two copies of a subgame G such that the temperature never increases as you descend any branch of the game tree of G (for example, pushing down a corridor that terminates in nothing or that terminates in only saving a single stone at the end satisfies this condition), is it always the case that you can treat the first move in the two copies of G as "miai" when determining what best play is?

And if so, is there a more general condition than this?

With no kos, if the temperature of G is less than 1, you can treat two copies of G as miai. Otherwise, maybe.

In the following position, consider play only in the corridors.

`[go]\$\$ Miai, but . . .\$\$ -------------------\$\$ | O X . . X . . X O |\$\$ | O O O O X O O O O |\$\$ | . . . . X . . . . |\$\$ | . . . . . . . . . |\$\$ | . . . O . . . . . |\$\$ | . . . O X X X . . |\$\$ | . . . O . O X . . |\$\$ | . . . O X X X X X |\$\$ | . . . O . . . O X |\$\$ -------------------[/go]`

Here the top two corridors are not miai.

`[go]\$\$ Black wins\$\$ -------------------\$\$ | O X . 1 X 2 . X O |\$\$ | O O O O X O O O O |\$\$ | . . . . X . . . . |\$\$ | . . . . . . . . . |\$\$ | . . . O . . . . . |\$\$ | . . . O X X X . . |\$\$ | . . . O . O X . . |\$\$ | . . . O X X X X X |\$\$ | . . . O 3 . . O X |\$\$ -------------------[/go]`

is a mistake. In the corridors Black wins by 1 pt.

`[go]\$\$ Miai play\$\$ -------------------\$\$ | O X . 1 X . . X O |\$\$ | O O O O X O O O O |\$\$ | . . . . X . . . . |\$\$ | . . . . . . . . . |\$\$ | . . . O . . . . . |\$\$ | . . . O X X X . . |\$\$ | . . . O . O X . . |\$\$ | . . . O X X X X X |\$\$ | . . . O 2 . . O X |\$\$ -------------------[/go]`

and are miai. The rest is a mirror position, for jigo.

Edit: Note that and are not interchangeable. We expect White to play will play at 2, and then Black will reply at 1. If instead White to play plays at 1, Black will not reply at 2.

`[go]\$\$W Miai play\$\$ -------------------\$\$ | O X . 1 X 4 5 X O |\$\$ | O O O O X O O O O |\$\$ | . . . . X . . . . |\$\$ | . . . . . . . . . |\$\$ | . . . O . . . . . |\$\$ | . . . O X X X . . |\$\$ | . . . O 3 O X . . |\$\$ | . . . O X X X X X |\$\$ | . . . O 2 . . O X |\$\$ -------------------[/go]`

White wins one point in the corridors.

`[go]\$\$W Miai play\$\$ -------------------\$\$ | O X . 1 X 2 . X O |\$\$ | O O O O X O O O O |\$\$ | . . . . X . . . . |\$\$ | . . . . . . . . . |\$\$ | . . . O . . . . . |\$\$ | . . . O X X X . . |\$\$ | . . . O . O X . . |\$\$ | . . . O X X X X X |\$\$ | . . . O 3 4 . O X |\$\$ -------------------[/go]`

Jigo.

_________________
Don't cry for me, Sergeant Tina.

Last edited by Bill Spight on Sat Dec 02, 2017 6:44 am, edited 2 times in total.
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 Post subject: Re: This 'n' that #460 Posted: Sun Nov 19, 2017 7:52 am
 Lives with ko

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Hmmm, I'll need to think about that a bit. Thanks.

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