This 'n' that
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moha
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Re: This 'n' that
I think what confused me is that you were talking about the whole position complex, while I'm only about the E15 area... But now I think that even if that area is double sente, that still not necessarily means that the best line always starts there (in other, different positions).
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Bill Spight
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Re: This 'n' that
Well, if we are only talking about the E-15 region, things are even more complex. Each player has both a sente option and a gote option. 
What do we call it? An ambiguous double sente/gote? 
What do we call it? An ambiguous double sente/gote? The Adkins Principle:
At some point, doesn't thinking have to go on?
— Winona Adkins
Visualize whirled peas.
Everything with love. Stay safe.
At some point, doesn't thinking have to go on?
— Winona Adkins
Visualize whirled peas.
Everything with love. Stay safe.
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moha
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Re: This 'n' that
Actually this may also be shown right here. Suppose B to play, and he takes top gote first. Then W's best line seems to also ignore the double sente at E15 area, and take the gote there instead.moha wrote:I think what confused me is that you were talking about the whole position complex, while I'm only about the E15 area... But now I think that even if that area is double sente, that still not necessarily means that the best line always starts there (in other, different positions).
So taking double sente CAN be a mistake (even at roughly correct temperatures, when the opponent actually responds, though this seems a special case here since W's sente forces B to take a valuable gote as well - BTW is white's sente in E15 area really a +1? Not a 0?)
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Bill Spight
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Re: This 'n' that
moha wrote:Actually this may also be shown right here. Suppose B to play, and he takes top gote first. Then W's best line seems to also ignore the double sente at E15 area, and take the gote there instead.moha wrote:I think what confused me is that you were talking about the whole position complex, while I'm only about the E15 area... But now I think that even if that area is double sente, that still not necessarily means that the best line always starts there (in other, different positions).
You mean this sequence, right?
OC, now both locally and globally Black needs to take her sente, nothing ambiguous about it.
So taking double sente CAN be a mistake
Absolutely.
(even at roughly correct temperatures, when the opponent actually responds, though this seems a special case here since W's sente forces B to take a valuable gote as well)
Well, once Black has taken the hane-and-connect, what is left is doubly ambiguous between sente and gote, so it's a very special case.
BTW is white's sente in E15 area really a +1? Not a 0?)
The size of the sente is determined by how much the reverse sente gains, and the reverse sente gains 1 pt.
If Black took her sente option instead, it would gain 0 pts. but that's normal. Sente gains nothing.The Adkins Principle:
At some point, doesn't thinking have to go on?
— Winona Adkins
Visualize whirled peas.
Everything with love. Stay safe.
At some point, doesn't thinking have to go on?
— Winona Adkins
Visualize whirled peas.
Everything with love. Stay safe.
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moha
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Re: This 'n' that
Hm. I guess you mean B's reverse sente sequence that gains 1pt in E15 area is C13 D13 D14 (since starting with atari would not really seem reverse sente, but a sente followed by an optional gote)?Bill Spight wrote:The size of the sente is determined by how much the reverse sente gains, and the reverse sente gains 1 pt.moha wrote:BTW is white's sente in E15 area really a +1? Not a 0?)
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Bill Spight
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Re: This 'n' that
moha wrote:Hm. I guess you mean B's reverse sente sequence that gains 1pt in E15 area is C13 D13 D14 (since starting with atari would not really seem reverse sente, but a sente followed by an optional gote)?Bill Spight wrote:The size of the sente is determined by how much the reverse sente gains, and the reverse sente gains 1 pt.moha wrote:BTW is white's sente in E15 area really a +1? Not a 0?)
These complicated positions strain the standard classifications. Indeed, sente followed by an optional gote is a kind of reverse sente in this position. Each player has the choice of playing sente or gote, and that is how Black makes the choice: sente and stop, or sente and continue.
I have more to say about this position, but let me make this observation. I have to use a game tree, because I don't know of any such actual position on the go board, but one probably exists.
In the tree / represents a move by Black and \ represents a move by White. Numbers are scores from Black's point of view. BIG stands for some big number or other.Code: Select all
A
/ \ \ (Black has one possible move, White has two) / \ \_____ -1
/ \
B C
/ \ / \
BIG 0 0 -BIG
This may look like a kind of ambiguous double sente, but, unless there is a ko fight, the White move from A to C is not good. How come? Because the result for White is a local score of 0. A is better for White than that because White has the option of playing from A to a local score of -1, while the best that Black can do is to play to B with sente, for a local score of 0. A can be classified as a Black sente.
Code: Select all
A
/ \ \
/ \ \_____ -1
/ \
B C
/ \ / \
BIG D 0 -BIG
/ \
1 -1
A is now like the position around E-15. The count of D is 0, but now the White move from A to C is a possibility. Why? Because Black has the move from D to a score of 1, to act as a reverse sente for C. Without that Black move, the White move from A to C has no value, outside of a ko fight.
Last edited by Bill Spight on Sat May 18, 2019 6:09 pm, edited 5 times in total.
The Adkins Principle:
At some point, doesn't thinking have to go on?
— Winona Adkins
Visualize whirled peas.
Everything with love. Stay safe.
At some point, doesn't thinking have to go on?
— Winona Adkins
Visualize whirled peas.
Everything with love. Stay safe.
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Bill Spight
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Re: This 'n' that
The Adkins Principle:
At some point, doesn't thinking have to go on?
— Winona Adkins
Visualize whirled peas.
Everything with love. Stay safe.
At some point, doesn't thinking have to go on?
— Winona Adkins
Visualize whirled peas.
Everything with love. Stay safe.
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Grin Weepa
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Bill Spight
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Re: This 'n' that
Grin Weepa wrote:Not sure if I'm right about this,
just thought I'd give it a go.
Close.
at 1.
kills.The Adkins Principle:
At some point, doesn't thinking have to go on?
— Winona Adkins
Visualize whirled peas.
Everything with love. Stay safe.
At some point, doesn't thinking have to go on?
— Winona Adkins
Visualize whirled peas.
Everything with love. Stay safe.
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Grin Weepa
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moha
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Re: This 'n' that
This seems to imply one follows the other. But even if C is not better than A in points (as far as EV is comparable to a collapsed result), W may still be interested (even outside ko fights), if it leaves better parity on board (parity of last big gote moves etc.). Or are these dynamics out of scope here?Bill Spight wrote:unless there is a ko fight, the White move from A to C is not good. ... A can be classified as a Black sente.
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Bill Spight
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Re: This 'n' that
The Adkins Principle:
At some point, doesn't thinking have to go on?
— Winona Adkins
Visualize whirled peas.
Everything with love. Stay safe.
At some point, doesn't thinking have to go on?
— Winona Adkins
Visualize whirled peas.
Everything with love. Stay safe.
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Joaz Banbeck
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Re: This 'n' that
defendsHelp make L19 more organized. Make an index: https://lifein19x19.com/viewtopic.php?f=14&t=5207
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Bill Spight
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Re: This 'n' that
Back to the game tree for E-15
Let's simplify it by removing White's sente option.
What is this? Another ambiguous sente/gote?
Not really, even though Black could play A'-> B -> D as a ko threat. Kos aside, A' = D. Maybe that is obvious to you, but let me show that.
Now, with no ko fight, games add and subtract. So A' = D means A' - D = 0. How do you subtract D? You form the negative of D and add it. So how do you form the negative of D? In go it's easy, you just reverse the color of the stones. For a game you flip the tree and reverse the signs of the scores.
Let's do that for D.
First, flip the tree:
Second, reverse the signs:
So the negative of D is D! How about that?
Now to find out if A' - D = 0. That is so if the result with best play, after each player has made the same number of moves, is 0, no matter who plays first. It is also the case with a seki, or standoff, where neither player wants to play or is able to play. For instance, D' above = 0. Black prefers a score of 0 to -1, and White prefers 0 to 1 (for Black), so neither play wants to play.
Let's look at A' - D = A' + D.
First, suppose that Black plays first.
1) Let Black play from A' to B; then White will reply from B to D. As we now know, D + D = 0.
2) Let Black play from D to 1. Then White will play from A' to -1. 1 - 1 = 0.
Next, suppose that White plays first.
1) Let White play from A' to -1. Then Black will play from D to 1. 1 - 1 = 0.
2) Let White play from D to -1. Then Black will play A' -> B -> D -> 1. 1 - 1 = 0.
So A' = D. It's just a gote, except in ko fights.
In summary, in A, D is necessary to retain the option, C, by providing a possible reverse sente for it; and C is necessary to keep A from reducing to D.
Code: Select all
A
/ \ \
/ \ \_____ -1
/ \
B C
/ \ / \
BIG D 0 -BIG
/ \
1 -1
Let's simplify it by removing White's sente option.
Code: Select all
A'
/ \
B -1
/ \
BIG D
/ \
1 -1
What is this? Another ambiguous sente/gote?
Not really, even though Black could play A'-> B -> D as a ko threat. Kos aside, A' = D. Maybe that is obvious to you, but let me show that.
Now, with no ko fight, games add and subtract. So A' = D means A' - D = 0. How do you subtract D? You form the negative of D and add it. So how do you form the negative of D? In go it's easy, you just reverse the color of the stones. For a game you flip the tree and reverse the signs of the scores.
Let's do that for D.
First, flip the tree:
Code: Select all
D'
/ \
-1 1
Second, reverse the signs:
Code: Select all
D''
/ \
1 -1
So the negative of D is D! How about that?
Now to find out if A' - D = 0. That is so if the result with best play, after each player has made the same number of moves, is 0, no matter who plays first. It is also the case with a seki, or standoff, where neither player wants to play or is able to play. For instance, D' above = 0. Black prefers a score of 0 to -1, and White prefers 0 to 1 (for Black), so neither play wants to play.
Let's look at A' - D = A' + D.
Code: Select all
A' + D
/ \ / \
B -1 1 -1
/ \
BIG D
/ \
1 -1
First, suppose that Black plays first.
1) Let Black play from A' to B; then White will reply from B to D. As we now know, D + D = 0.
2) Let Black play from D to 1. Then White will play from A' to -1. 1 - 1 = 0.
Next, suppose that White plays first.
1) Let White play from A' to -1. Then Black will play from D to 1. 1 - 1 = 0.
2) Let White play from D to -1. Then Black will play A' -> B -> D -> 1. 1 - 1 = 0.
So A' = D. It's just a gote, except in ko fights.
In summary, in A, D is necessary to retain the option, C, by providing a possible reverse sente for it; and C is necessary to keep A from reducing to D.
Last edited by Bill Spight on Sun Oct 01, 2017 12:57 pm, edited 1 time in total.
The Adkins Principle:
At some point, doesn't thinking have to go on?
— Winona Adkins
Visualize whirled peas.
Everything with love. Stay safe.
At some point, doesn't thinking have to go on?
— Winona Adkins
Visualize whirled peas.
Everything with love. Stay safe.
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Bill Spight
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Re: This 'n' that
moha wrote:This seems to imply one follows the other. But even if C is not better than A in points (as far as EV is comparable to a collapsed result), W may still be interested (even outside ko fights), if it leaves better parity on board (parity of last big gote moves etc.). Or are these dynamics out of scope here?Bill Spight wrote:unless there is a ko fight, the White move from A to C is not good. ... A can be classified as a Black sente.
Why would White want to remove his option to play reverse sente? Maybe Black will play the sente and it will come to the same thing, but for White to play sente (except possibly in case of a ko fight) simply does Black's job for her. It is never better than doing nothing.
The Adkins Principle:
At some point, doesn't thinking have to go on?
— Winona Adkins
Visualize whirled peas.
Everything with love. Stay safe.
At some point, doesn't thinking have to go on?
— Winona Adkins
Visualize whirled peas.
Everything with love. Stay safe.