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 Post subject: This 'n' that
Post #1 Posted: Mon Oct 05, 2015 4:11 pm 
Judan

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Many people have their study journals here. You might think of this as a retrospective study journal, where I mostly talk about things I have learned. Or more or less random musings. Or whatever. :)

Here is a problem I just composed. It is easy, but there are a couple of quirks. It is based on some things I discovered long ago. Enjoy! :D

Click Here To Show Diagram Code
[go]$$B AGA rules. No komi. Black to play and win.
$$ -------------------
$$ | . X O . . . O O O |
$$ | X O O . O O O X X |
$$ | X X O . O X X X . |
$$ | . X O O . . . X . |
$$ | . X . . X X X X . |
$$ | . X O O O O O X . |
$$ | X O O X X O X O . |
$$ | X X O . O O X X X |
$$ | . X . . . O O O . |
$$ -------------------[/go]

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 Post subject: Re: This 'n' that
Post #2 Posted: Mon Oct 05, 2015 5:01 pm 
Judan

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Click Here To Show Diagram Code
[go]$$B AGA rules. No komi. Black to play and win.
$$ -------------------
$$ | 4 C O . . . O O O |
$$ | X O O . O O O X X |
$$ | X X O . O X X X . |
$$ | . X O O 3 . . X . |
$$ | . X . . X X X X . |
$$ | . X O O O O O X . |
$$ | X O O X X O X C 5 |
$$ | X X O . O O X X X |
$$ | . X 1 2 . O O O . |
$$ -------------------[/go]


Click Here To Show Diagram Code
[go]$$B
$$ -------------------
$$ | O 6 O . . . O O O |
$$ | X O O . O O O X X |
$$ | X X O . O X X X . |
$$ | . X O O X . . X . |
$$ | . X 7 8 X X X X . |
$$ | . X O O O O O X . |
$$ | X O O X X O X . X |
$$ | X X O . O O X X X |
$$ | . X X O . O O O 9 |
$$ -------------------[/go]


And then white gives black a pass stone.

So black has 2 prisoners + 11 = 13 points.
White has 1 prisoner + 11 = 12 points.

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 Post subject: Re: This 'n' that
Post #3 Posted: Mon Oct 05, 2015 5:05 pm 
Oza

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Once you say contrived (oops! AGA) rules I lose interest.

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 Post subject: Re: This 'n' that
Post #4 Posted: Mon Oct 05, 2015 6:27 pm 
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Kirby wrote:
Click Here To Show Diagram Code
[go]$$B AGA rules. No komi. Black to play and win.
$$ -------------------
$$ | 4 C O . . . O O O |
$$ | X O O . O O O X X |
$$ | X X O . O X X X . |
$$ | . X O O 3 . . X . |
$$ | . X . . X X X X . |
$$ | . X O O O O O X . |
$$ | X O O X X O X C 5 |
$$ | X X O . O O X X X |
$$ | . X 1 2 . O O O . |
$$ -------------------[/go]


Click Here To Show Diagram Code
[go]$$B
$$ -------------------
$$ | O 6 O . . . O O O |
$$ | X O O . O O O X X |
$$ | X X O . O X X X . |
$$ | . X O O X . . X . |
$$ | . X 7 8 X X X X . |
$$ | . X O O O O O X . |
$$ | X O O X X O X . X |
$$ | X X O . O O X X X |
$$ | . X X O . O O O 9 |
$$ -------------------[/go]


And then white gives black a pass stone.

So black has 2 prisoners + 11 = 13 points.
White has 1 prisoner + 11 = 12 points.


I counted using Chinese and Japanese scoring and there is a difference here so maybe that's why he says AGA? Did I count wrong?

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 Post subject: Re: This 'n' that
Post #5 Posted: Mon Oct 05, 2015 6:51 pm 
Judan

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Kirby wrote:
Click Here To Show Diagram Code
[go]$$B AGA rules. No komi. Black to play and win.
$$ -------------------
$$ | 4 C O . . . O O O |
$$ | X O O . O O O X X |
$$ | X X O . O X X X . |
$$ | . X O O 3 . . X . |
$$ | . X . . X X X X . |
$$ | . X O O O O O X . |
$$ | X O O X X O X C 5 |
$$ | X X O . O O X X X |
$$ | . X 1 2 . O O O . |
$$ -------------------[/go]


Click Here To Show Diagram Code
[go]$$B
$$ -------------------
$$ | O 6 O . . . O O O |
$$ | X O O . O O O X X |
$$ | X X O . O X X X . |
$$ | . X O O X . . X . |
$$ | . X 7 8 X X X X . |
$$ | . X O O O O O X . |
$$ | X O O X X O X . X |
$$ | X X O . O O X X X |
$$ | . X X O . O O O 9 |
$$ -------------------[/go]


And then white gives black a pass stone.

So black has 2 prisoners + 11 = 13 points.
White has 1 prisoner + 11 = 12 points.


Click Here To Show Diagram Code
[go]$$B AGA rules. No komi. Black to play and win.
$$ -------------------
$$ | 4 B O . . . O O O |
$$ | X O O . O O O X X |
$$ | X X O . O X X X . |
$$ | . X O O 3 . . X . |
$$ | . X . . X X X X . |
$$ | . X O O O O O X . |
$$ | X O O X X O X W 5 |
$$ | X X O . O O X X X |
$$ | . X 1 2 . O O O 6 |
$$ -------------------[/go]

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 Post subject: Re: This 'n' that
Post #6 Posted: Mon Oct 05, 2015 6:51 pm 
Judan

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DrStraw wrote:
Once you say contrived (oops! AGA) rules I lose interest.


OK. Chinese rules. :)

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 Post subject: Re: This 'n' that
Post #7 Posted: Mon Oct 05, 2015 6:52 pm 
Judan

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Abyssinica wrote:
I counted using Chinese and Japanese scoring and there is a difference here so maybe that's why he says AGA? Did I count wrong?


AGA scoring is not Japanese scoring. :)

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 Post subject: Re: This 'n' that
Post #8 Posted: Mon Oct 05, 2015 7:02 pm 
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Bill Spight wrote:
Abyssinica wrote:
I counted using Chinese and Japanese scoring and there is a difference here so maybe that's why he says AGA? Did I count wrong?


AGA scoring is not Japanese scoring. :)


I know this - I used it to confirm the fact that AGA was supposed to let you count in Japanese but still coincide with Chinese scoring.

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 Post subject: Re: This 'n' that
Post #9 Posted: Mon Oct 05, 2015 8:19 pm 
Judan

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Okay, I'll try again.

Click Here To Show Diagram Code
[go]$$B AGA rules. No komi. Black to play and win.
$$ -------------------
$$ | 1 X O . . . O O O |
$$ | X O O . O O O X X |
$$ | X X O . O X X X . |
$$ | . X O O 3 . . X . |
$$ | . X 7 6 X X X X . |
$$ | . X O O O O O X . |
$$ | X O O X X O X O 5 |
$$ | X X O . O O X X X |
$$ | . X 2 . . O O O 4 |
$$ -------------------[/go]


Black gets pass stone, so 13 points.
White has 12.

I don't really know why to do this order except that I can't see a winning counter by white.

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 Post subject: Re: This 'n' that
Post #10 Posted: Mon Oct 05, 2015 8:24 pm 
Judan

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Kirby wrote:
Okay, I'll try again.

Click Here To Show Diagram Code
[go]$$B AGA rules. No komi. Black to play and win.
$$ -------------------
$$ | 1 X O . . . O O O |
$$ | X O O . O O O X X |
$$ | X X O . O X X X . |
$$ | . X O O 3 . . X . |
$$ | . X 7 6 X X X X . |
$$ | . X O O O O O X . |
$$ | X O O X X O X O 5 |
$$ | X X O . O O X X X |
$$ | . X 2 . . O O O 4 |
$$ -------------------[/go]


Black gets pass stone, so 13 points.
White has 12.

I don't really know why to do this order except that I can't see a winning counter by white.


Interesting. I did not examine that line. More about the reasons later. :)

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 Post subject: Re: This 'n' that
Post #11 Posted: Tue Oct 06, 2015 9:13 am 
Oza

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Abyssinica wrote:
Bill Spight wrote:
Abyssinica wrote:
I counted using Chinese and Japanese scoring and there is a difference here so maybe that's why he says AGA? Did I count wrong?


AGA scoring is not Japanese scoring. :)


I know this - I used it to confirm the fact that AGA was supposed to let you count in Japanese but still coincide with Chinese scoring.

its the pass stones and white plays last rule that allows that to happen.

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 Post subject: Re: This 'n' that
Post #12 Posted: Tue Oct 06, 2015 9:33 am 
Judan

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Abyssinica wrote:
I counted using Chinese and Japanese scoring and there is a difference here so maybe that's why he says AGA? Did I count wrong?


Bill Spight wrote:
AGA scoring is not Japanese scoring. :)


Abyssinica wrote:
I know this - I used it to confirm the fact that AGA was supposed to let you count in Japanese but still coincide with Chinese scoring.


xed_over wrote:
its the pass stones and white plays last rule that allows that to happen.


You're welcome. :)

Or my apologies, depending upon how you feel about that. ;)

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 Post subject: Re: This 'n' that
Post #13 Posted: Tue Oct 06, 2015 10:03 am 
Judan

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I begin to study ko fights.

When I became shodan I realized, to my surprise and dismay, that I knew next to nothing about go. Oh, I had a pretty good intuition about the game ;), but I was playing by the seat of my pants.

One thing I decided to research was ko fights. Kos are not independent plays, but involve plays elsewhere, in what I call the ko ensemble. One of the first things that I studied was the relationship between kos and the environment (other plays on the board besides ko threats), although I did not use the term at that time. This led me to the idea of komonster -- again, a term I did not use until much later, after learning about Professor Berlekamp's idea of komaster. A komonster is not only able to win a ko, but to reduce the size of plays that the koloser is able to get in exchange for the ko (the ko exchange). Nowadays we say that the komonster is able to reduce the temperature of the environment (or ambient temperature) before winning the ko.

The "half point ko" at the end of the game illustrates komonster effects, even though it is usually played at a lower ambient temperature than the size of the ko to begin with. Now I knew that, in theory, the size of each play in such a ko is 1/3 point (by territory scoring), not 1/2 point, but on the other hand, if you don't know who will win the ko fight, it's a 50-50 chance, and a half point makes sense. But my study of the komonster gave me a different understanding of the half point ko.

Suppose that we do know who will win the final ko. Then the koloser gets zero in the ko exchange. That means that taking the ko is enough for the komaster to win it. So instead of there being three moves between winning and losing the ko, there would be only two moves, in practice. Each move would gain 1/2 point, making for a half point ko. :)

Later on I learned about Chinese (area) scoring, in which each stone gains one point, so that each play in the final ko gains 4/3 points, not 1/3 point. Each dame gains 1 point, as well. But suppose that the komonster can reduce the ambient temperature from 1 point (dame) to 0 (no dame). Then the value of each move in the ko would become 4/2 = 2 points. That is the basis for my little problem. :)

I have to go now. More about that problem later. :)

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 Post subject: Re: This 'n' that
Post #14 Posted: Tue Oct 06, 2015 10:57 am 
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I don't know about this particular problem, but with Chinese scoring, there are certainly cases where it is better to fill a mutual dame than to fill the last half-point ko. If you have enough threats to win the ko anyway, then playing dame first can be worth two points extra.

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 Post subject: Re: This 'n' that
Post #15 Posted: Tue Oct 06, 2015 11:21 am 
Judan

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mitsun wrote:
I don't know about this particular problem, but with Chinese scoring, there are certainly cases where it is better to fill a mutual dame than to fill the last half-point ko. If you have enough threats to win the ko anyway, then playing dame first can be worth two points extra.


Oh, yes. :) That is implied in the idea of komonster. The komonster does not win the ko right away, but makes another play.

I'll also get around to virtual ko threats (now called tertiary ko threats). A pair of dame can act as a ko threat for the koloser. :)

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Post #16 Posted: Wed Oct 07, 2015 7:31 am 
Judan

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OK, here is one answer to my little problem. Kirby gave another. :)

Click Here To Show Diagram Code
[go]$$B
$$ -------------------
$$ | 3 X O 0 . . O O O |
$$ | X O O . O O O X X |
$$ | X X O . O X X X . |
$$ | . X O O 4 5 . X . |
$$ | . X 8 9 X X X X . |
$$ | . X O O O O O X . |
$$ | X O O X X O X O 7 |
$$ | X X O . O O X X X |
$$ | . X 1 2 . O O O 6 |
$$ -------------------[/go]


:b1: is a 2 point sente (1 pt. under territory scoring). :b3: gains 2 points, because White is komonster, as explained earlier. :w4: gains 1.75 points and then :b5: gains 1.5 points. Then the players share the dame and protective play. :w10: could be a pass, but it costs nothing and allows us to count territory. White has 10 points of territory and Black has 11, to win by 1 point. (The original position is worth 0.75 for White; Black gained 1.75 in the play.)

The next diagram shows correct play by territory scoring.

Click Here To Show Diagram Code
[go]$$B Territory scoring
$$ -------------------
$$ | 4 X O . . . O O O |
$$ | X O O . O O O X X |
$$ | X X O . O X X X . |
$$ | . X O O 3 . . X . |
$$ | . X . . X X X X . |
$$ | . X O O O O O X . |
$$ | X O O X X O X O . |
$$ | X X O . O O X X X |
$$ | . X 1 2 . O O O . |
$$ -------------------[/go]


White wins the ko.

:b1: is a 1 point sente. :b3: gains 0.75 point. :w4: gains 0.5 point, because White is komonster. Each player has 12 points, for jigo. (The original position is worth 0.25 for White. Black gained 0.25 in the play.)

:b3: would be a mistake under area scoring. The next diagram shows best play after that.

Click Here To Show Diagram Code
[go]$$B AGA rules. No komi. Black to play and win.
$$ -------------------
$$ | 6 X O . . . O O O |
$$ | X O O . O O O X X |
$$ | X X O . O X X X . |
$$ | . X O O 3 . . X . |
$$ | . X 7 8 X X X X . |
$$ | . X O O O O O X . |
$$ | X O O X X O X O 5 |
$$ | X X O . O O X X X |
$$ | . X 1 2 . O O O 4 |
$$ -------------------[/go]

:b9: takes ko.

Click Here To Show Diagram Code
[go]$$Wm10 AGA rules. No komi. Black to play and win.
$$ -------------------
$$ | 3 X O . . . O O O |
$$ | X O O . O O O X X |
$$ | X X O . O X X X . |
$$ | . X O O X . . X . |
$$ | . X X O X X X X 2 |
$$ | 4 X O O O O O X 1 |
$$ | X O O X X O X . X |
$$ | X X O . O O X X X |
$$ | . X X O . O O O O |
$$ -------------------[/go]

:w14: fills the ko.

:b13: costs nothing. Result: White wins by 1.

:b1: is a 2 point sente. :b3: gains 1.75 point. :w6: gains 2 points. The original position is worth 0.75 for White. Black lost 0.25 in the play.

:b7: and :w8: are a miai pair of dame, which act as a tertiary ko threat. A tertiary threat is a defense against komonster. If :w8: filled the ko, Black would get a dame in the ko exchange.

In this position it did not matter because White had another ko threat, but :w4: was a sente to eliminate Black's tertiary threat at 5.

Kim Yonghoan also discovered komonster and tertiary threats. When we were getting to know each other around 20 years ago, we had a strange exchange of emails. Each of us thought that we knew something the other didn't, and we were a bit coy about our "secret". :)

Why "tertiary" threats? When I was learning go, the beginner literature said that a ko threat was something played to win the ko. OC, the opponent might not answer it. As I began to study ko, I realized that you might play a ko threat in order to make a gain if it were not answered. So a primary threat is one played to win the ko and a secondary threat is one made to gain something in the ko exchange. A tertiary threat is played to prevent a loss to the komonster.

Edit: Kirby's answer.

Kirby wrote:
Click Here To Show Diagram Code
[go]$$B AGA rules. No komi. Black to play and win.
$$ -------------------
$$ | 1 X O . . . O O O |
$$ | X O O . O O O X X |
$$ | X X O . O X X X . |
$$ | . X O O 3 . . X . |
$$ | . X 7 6 X X X X . |
$$ | . X O O O O O X . |
$$ | X O O X X O X O 5 |
$$ | X X O . O O X X X |
$$ | . X 2 . . O O O 4 |
$$ -------------------[/go]


Black gets pass stone, so 13 points.
White has 12.


OK. Now that we know that White is komonster, we can say that :b1: gains 2 points by area scoring. :w2: gains 2 points in reverse sente. :b3: gains 1.75 points. Then the dame and protective play are shared equally. In the play Black gains 1.75 points to win by 1. :)

In the sequence I gave Black got the last 2 point play, but White got the 1.75 point play. All same same. :)

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 Post subject: Re: This 'n' that
Post #17 Posted: Thu Oct 08, 2015 10:59 am 
Judan

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I develop my own theory of ko evaluation.

Because of komonster effects, winning (or taking) the ko in my little problem gains 2 points by area scoring, 0.5 point by territory scoring. Neither of these is the "theoretical" value of 4/3 or 1/3. Because the value of plays usually drops over time, kos typically have some komonster effects, although normally not as big as the difference between the dame vs. no dame conditions in area scoring.

Let's look at these effects a little more closely. :)

Aside from dame, the two plays shown are the last on the board. (Just the top few lines of the board are shown.)

Click Here To Show Diagram Code
[go]$$B No ko threats, territory scoring
$$ -------------------
$$ | . X O . . . O . . |
$$ | X O O . O O O X X |
$$ | X X O . O X X X . |[/go]


Under Japanese/Korean (territory) scoring, the no ko threat condition makes the player who does not take the gote komonster. So it does not matter which play is made first, regardless of who has sente. As you may verify. :)

However, in a real game in which the outcome of the ko is uncertain, as a practical matter it is better to take the gote and gain 0.5 point for sure. In this position for Black to fill the ko may gain nothing. She might win it, anyway. :)

Click Here To Show Diagram Code
[go]$$B No ko threats, area scoring
$$ -------------------
$$ | . X O . . . O . O |
$$ | X O O . O O O X X |
$$ | X X O . O X X X . |[/go]


Under Chinese/AGA (area) scoring komonster effects could make these plays miai. But we need to consider the dame situation to tell.

If there are no dame, then the two plays are miai.

If there is one dame, then they are miai for Black, because Black gets the dame regardless. For example,

Click Here To Show Diagram Code
[go]$$B No ko threats, area scoring
$$ -------------------
$$ | 2 X O . . . O 1 O |
$$ | X O O . O O O X X |
$$ | X X O . O X X X . |[/go]


:b3: takes dame. :w4: fills ko.

But with one dame they are not miai for White. White should take the gote for a sure 2 point gain plus the dame. If he takes the ko instead:

Click Here To Show Diagram Code
[go]$$W No ko threats, area scoring
$$ -------------------
$$ | 1 X O . . . O 2 O |
$$ | X O O . O O O X X |
$$ | X X O . O X X X . |[/go]


:w3: fills ko. :b4: takes dame.

When there are two dame Black should take the gote.

Click Here To Show Diagram Code
[go]$$B No ko threats, area scoring
$$ -------------------
$$ | 2 X O . . . O 1 O |
$$ | X O O . O O O X X |
$$ | X X O . O X X X . |[/go]


:b3: takes dame. :w4: fills ko. :b5: takes dame.

That way she gets both dame, instead of sharing them with White.

And White can take the ko.

Click Here To Show Diagram Code
[go]$$W No ko threats, area scoring
$$ -------------------
$$ | 1 X O . . . O 2 O |
$$ | X O O . O O O X X |
$$ | X X O . O X X X . |[/go]


:w3: fills ko. :b4: takes dame. :w5: takes dame.

Because either way the dame are shared.

OC, as a practical matter either player should take the gote. :)

But what does this example say about evaluating plays in the ko? Let us take the value of a play in the gote as given. Either player gains 2 points, for a swing of 4 points. Then we may evaluate the ko ensemble, including any dame. We use swing values to compare different lines of play, as their difference produces swing values.

Code:
If there are no dame, then either winning or taking the ko swings 4 points.

If there is at least one dame, then

     1) with an odd number of dame

          a) winning the ko swings 4 points,

          b) taking the ko swings 2 points;

     2) with an even number of dame

          a) winning the ko swings 2 points,

          b) taking the ko swings 4 points.


If we do not know the number of dame, then the average swing for winning or taking the ko is 3 points, corresponding to the komonster value for territory scoring. :)

Now, I did not work this out when I started, because I was unaware of area scoring. ;) But I did work out a general way to evaluate prototypical ko ensembles. I have not run across anything like this way of evaluating kos in the go literature, despite its practical value, as evidenced by my little problem. I started writing a book about it in 1989, but that was before finding out about combinatorial game theory and Professor Berlekamp's work on kos. :D

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Post #18 Posted: Fri Oct 09, 2015 9:05 am 
Judan

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A bit more on the value of the "half point ko" under area scoring. Also some discussion of komonster.

Click Here To Show Diagram Code
[go]$$B No ko threats
$$ -------------------
$$ | C B O . O C C X . |
$$ | X O O . O O O X . |
$$ | X X O . O X X X . |[/go]


Here we have the ko with the theoretically hotter gote in which whoever plays gains 1.5 points. At the dame stage or with no dame elsewhere they are miai, with a local net score of 0. (The local region is marked.)

Click Here To Show Diagram Code
[go]$$W No ko threats
$$ -------------------
$$ | 2 X O . O . 1 X . |
$$ | X O O . O O O X . |
$$ | X X O . O X X X . |[/go]


If :w1: takes the gote, :b2: wins the ko; each player gets two points.

Click Here To Show Diagram Code
[go]$$W No ko threats
$$ -------------------
$$ | 1 B O . O 4 2 X . |
$$ | X O O . O O O X . |
$$ | X X O . O X X X . |[/go]

:w3: wins ko.

Since White is komonster White may take the ko first. However, Black gets the dame at 4 to stay even.

They are also miai when Black plays first, as you may verify. :)

Click Here To Show Diagram Code
[go]$$B No ko threats
$$ -------------------
$$ | C B O . O C C X . |
$$ | X O O . O X X X . |
$$ | X X O . O X X X . |[/go]


In this case the two plays are not strict miai. In fact, at the dame stage they act like a dame.

Click Here To Show Diagram Code
[go]$$W No ko threats
$$ -------------------
$$ | 2 X O . O 1 3 X . |
$$ | X O O . O X X X . |
$$ | X X O . O X X X . |[/go]


White to play takes the gote to get the dame.

Local net result: 0.

Click Here To Show Diagram Code
[go]$$B No ko threats
$$ -------------------
$$ | 1 X O . O 2 3 X . |
$$ | X O O . O X X X . |
$$ | X X O . O X X X . |[/go]


Black to play wins the ko to get the dame.

Local net result: 2 points for Black.

Neither player can do better at the dame stage, as you may verify.

----

What is the takeaway from all this?

My impression is that most go tournaments in the West use area scoring, and most tournament players are aware that eliminating dame before winning a ko is advantageous. But how many are also aware that the ability to do that means that moves in the ko are worth more than their normal value? As my little problem illustrates. :)

Now, that specific knowledge may not make the difference between winning and losing in many games. OTOH, when it does matter, it is handy to know about, and at the end of the game the reading problems may not be very difficult. IMO, even when komonster effects do not matter to winning or losing the game, there is no reason not to play komonster positions correctly. :)

Besides, komonster effects are not restricted to these positions. They are present any time kos are won at a lower ambient temperature than the theoretical size of ko moves. It is easy, for instance, to replicate area scoring situations for territory scoring. Also, consider the extreme case where one player has an infinite supply of ko threats, having a dead group in double ko. Unless the opponent captures the dead group at the cost of one move and one point, the player with the dead group always has a ko threat. Then the value of moves in other simple kos increases by 50% on average in either area or territory scoring. That can substantially affect correct play.

Most kos have small komonster effects, and it may be best to save ko threats for possible future kos rather than to spend them to pick up 0.5 point or 1 point or so. But be aware of the possibility that correct play may mean playing kos earlier than their theoretical value might indicate.

Playing komonster positions

If you are komonster, you may gain by not winning the ko until it is necessary to do so. If your opponent is komonster, you may gain by winning the ko before its theoretical value indicates. If either player is komonster, it may be correct for each player to take the ko before its theoretical value indicates.

I have spoken. :D

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This post by Bill Spight was liked by: bayu
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 Post subject: Re: This 'n' that
Post #19 Posted: Fri Oct 09, 2015 1:49 pm 
Dies with sente

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Bill Spight wrote:
My impression is that most go tournaments in the West use area scoring, and most tournament players are aware that eliminating dame before winning a ko is advantageous.

As far as I know, with the exception of Britain, France and the Congress, Europe still uses territory scoring for the majority of tournaments. This does create areas where half the tournaments around are area scored and half are territory scored. Poor people living there have to learn the endgame twice :cry: .

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 Post subject: Re: This 'n' that
Post #20 Posted: Fri Oct 09, 2015 2:01 pm 
Oza
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Bill Spight wrote:
My impression is that most go tournaments in the West use area scoring


At least Seattle uses territory. I am curious what tournaments besides the US Open use AGA on a regular basis.

What does Cotsen use?

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