Hi,
I have another tsumego from 321go:
"What is the value of playing at A?" (not saying for which colour)
(Then it gives a "3" as answer.)
The general chapter seems to be about counting, the exercises before that were about either counting territory after finding 1 move, or making territory plus capturing 1 stone.
They were NOT about living.
But I see no advantage for black or white taking "A".
If black takes A, white can connect.
If white takes A, she reduces her liberties while winning nothing.
So, why does it make points for anyone to play at "A", and why 3??
3 can't mean capturing the whole white group.
Please help with this exercise III
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Jika
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Please help with this exercise III
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EdLee
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Bill Spight
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Re: Please help with this exercise III
Please, Ed. A play at "a" only gains 1½ pts.
Jika, by value of a move they mean the difference between the territorial value when Black plays first and the territorial value when White plays first. As Ed shows, that difference is 3 points. The differerence is also called the swing value.
A related question is what is the territorial value of the original local position? Since the local position is a gote, it is the average of the value after Black plays first (0) and the value after White plays first (-3, from Black's perspective), or -1½ pts. When Black plays first, she gains 1½ pts. (on average), moving from a position worth -1½ to a position worth 0. Likewise, when White plays first he also gains 1½ pts., moving from a position worth -1½ to a position worth -3.
Jika, by value of a move they mean the difference between the territorial value when Black plays first and the territorial value when White plays first. As Ed shows, that difference is 3 points. The differerence is also called the swing value.
A related question is what is the territorial value of the original local position? Since the local position is a gote, it is the average of the value after Black plays first (0) and the value after White plays first (-3, from Black's perspective), or -1½ pts. When Black plays first, she gains 1½ pts. (on average), moving from a position worth -1½ to a position worth 0. Likewise, when White plays first he also gains 1½ pts., moving from a position worth -1½ to a position worth -3.
Last edited by Bill Spight on Thu Jul 25, 2019 8:16 am, 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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EdLee
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Re: Please help with this exercise III
I agree with the posts that have been written, but I want to try to say things in an easier way. Not sure if it'll help, but I'll try.
So let's simplify things, and finish the borders on the rest of the board:
To see in practical terms how much 'a' is worth, above, compare the difference in score if white plays:
to if black plays:
The black territory in both cases is identical. But the white territory is different: In Diagram A, white has 17 points on the board (surrounding 17 empty intersections). In Diagram B, white has 14 points on the board (surrounding 14 empty intersections).
17 - 14 is 3, so that's where the 3 points comes from.
In a real game, the borders aren't finished off like they are right before you score the game. So people usually look at just that local area and count the point difference.
So let's simplify things, and finish the borders on the rest of the board:
To see in practical terms how much 'a' is worth, above, compare the difference in score if white plays:
to if black plays:
The black territory in both cases is identical. But the white territory is different: In Diagram A, white has 17 points on the board (surrounding 17 empty intersections). In Diagram B, white has 14 points on the board (surrounding 14 empty intersections).
17 - 14 is 3, so that's where the 3 points comes from.
In a real game, the borders aren't finished off like they are right before you score the game. So people usually look at just that local area and count the point difference.
be immersed
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Bill Spight
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Re:
EdLee wrote:Hi Bill,
Sorry if any of the following is already covered in your This 'n That thread on endgame studies.
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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Jika
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Re: Please help with this exercise III
First, thank you all!
Sometimes I get the feeling that my beginner's questions trigger a much more high level discussion, which is good, because it would mean that you find benefits for your own play.
But, hm, these calculations seem quite advanced for me...
@Ed: I did not count the F1 point. I overlooked that it is protected, so I did not count it as white's territory, and even thought black could take it to prevent white from connecting!
@Bill: Is it important to learn these calculations at my stage (given the above mistakes)?
@Kirby: This is helpful. In addition to not seeing F1, I also did not realize how strong white is to the right.
Excuse: the original diagram is on the corner of a bigger board, so the H-stones are towards the middle of the board, not towards the border.
These exercises from 321go seem to be very heterogeneous:
Most are simply "close a gap or kill stones so you win the territory.
Then it is quite obvious what to do.
And they only want me to count the points the winner gets there.
The other kind of exercises, like this one, are "open", and I seem to miss important points (like F1) or I do not understand how long I have to play out the situation to "see" the result.
Now I'm going back to those exercises I was not able to solve.
PS: What are the conventions of "he" or "she"?
I've seen "she" used for white, or is it interchangeable?
And is it important (will people jump down my throat if I forget to name both genders? And, going into political correctness, what about the usage of the third gender?)
Sometimes I get the feeling that my beginner's questions trigger a much more high level discussion, which is good, because it would mean that you find benefits for your own play.
But, hm, these calculations seem quite advanced for me...
@Ed: I did not count the F1 point. I overlooked that it is protected, so I did not count it as white's territory, and even thought black could take it to prevent white from connecting!
@Bill: Is it important to learn these calculations at my stage (given the above mistakes)?
@Kirby: This is helpful. In addition to not seeing F1, I also did not realize how strong white is to the right.
Excuse: the original diagram is on the corner of a bigger board, so the H-stones are towards the middle of the board, not towards the border.
These exercises from 321go seem to be very heterogeneous:
Most are simply "close a gap or kill stones so you win the territory.
Then it is quite obvious what to do.
And they only want me to count the points the winner gets there.
The other kind of exercises, like this one, are "open", and I seem to miss important points (like F1) or I do not understand how long I have to play out the situation to "see" the result.
Now I'm going back to those exercises I was not able to solve.
PS: What are the conventions of "he" or "she"?
I've seen "she" used for white, or is it interchangeable?
And is it important (will people jump down my throat if I forget to name both genders? And, going into political correctness, what about the usage of the third gender?)
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EdLee
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jlt
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Re:
Something like "White wants to defend W's corner"?EdLee wrote:One option: use Black/B, White/W, Black's/B's, White's/W's, etc.
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EdLee
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Hi Bill,
's local points) - ( 
's local points) = 2 - 3 = -1's local points) - ( 's local points) = 2 - 2 = 0.
How to calculate Swing_value = 0 ?
Thanks.
(C): Territorial value = (Territorial value = 2 - 3 = -1
's local points) - ( 's local points) = 2 - 3 = -1(B): Territorial value = (Territorial value = 2 - 2 = 0
Swing value = 0
's local points) - ( 's local points) = 2 - 2 = 0.How to calculate Swing_value = 0 ?
(A): confused: what are the 2 and 2½ in "Territorial value = 2 - 2½" ?Territorial value = 2 - 2½ = -½
Swing value = 0 - (-1) = 1
Gain = 0 - (-½) = -½ - (-1) = ½
Gain = Swing_value/2
Thanks.
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Bill Spight
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Re: Please help with this exercise III
Not to worry.Jika wrote:First, thank you all!
Sometimes I get the feeling that my beginner's questions trigger a much more high level discussion, which is good, because it would mean that you find benefits for your own play.
But, hm, these calculations seem quite advanced for me...
I knew nothing about them until I was 2 kyu. 
No.@Bill: Is it important to learn these calculations at my stage (given the above mistakes)?
There is no overall standard. I go by yin and yang. Yin = feminine = black; yang = masculine = white. Others do the reverse. Others use only one pronoun.PS: What are the conventions of "he" or "she"?
I've seen "she" used for white, or is it interchangeable?
Just be consistent.And is it important (will people jump down my throat if I forget to name both genders?
As you wish.And, going into political correctness, what about the usage of the third gender?)
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:
No matter who fills the dame the result is the same.EdLee wrote:Hi Bill,(C): Territorial value = (Territorial value = 2 - 3 = -1(B): Territorial value = (Territorial value = 2 - 2 = 0
Swing value = 0
How to calculate Swing_value = 0 ?
Black has 2 pts. White has 2½ pts.(A): confused: what are the 2 and 2½ in "Territorial value = 2 - 2½" ?Territorial value = 2 - 2½ = -½
Swing value = 0 - (-1) = 1
Gain = 0 - (-½) = -½ - (-1) = ½
Gain = Swing_value/2
Thanks.
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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EdLee
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Hi Bill,
Thanks for being patient with these 30k questions.
How to derive the ½ for white?
B has exactly 2 points (clear).
W has at least 2 points (clear); 3 max (also clear).
I can see one can argue there's a 50% chance W will get the extra 1 point.
But how to derive the (magical?) 50% odds?
Say the probability lies between 0.0 and 1.0;
how to derive exactly ½, and not any other value between 0 and 1?
Is it from the average of:
((B var): territorial value if first; -1)
-- and --
((C var): territorial value if first; 0);
thus (-1 + 0)/2 ? ( for this double-gote situation ).
Thanks for being patient with these 30k questions.
The whole number 2 is clear (for both B and W).Black has 2 pts. White has 2½ pts.
How to derive the ½ for white?
B has exactly 2 points (clear).
W has at least 2 points (clear); 3 max (also clear).
I can see one can argue there's a 50% chance W will get the extra 1 point.
But how to derive the (magical?) 50% odds?
Say the probability lies between 0.0 and 1.0;
how to derive exactly ½, and not any other value between 0 and 1?
Is it from the average of:
((B var): territorial value if
first; -1)-- and --
((C var): territorial value if
first; 0);thus (-1 + 0)/2 ? ( for this double-gote situation ).
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Jika
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Re: Please help with this exercise III
Just to confuse the discussion further (from a 50 k's perspective):
Maybe the situation in the first diagram is that B has taken the point where W could make an eye, so who gets the left over dame point does not matter, so it does not matter who's move it is?
But if white's possible eye-point is not taken yet, whoever's move it is will (considering the local situation only) take it with his/her next move; therefore there is a 50% chance for white taking it and getting an additional point, while black taking it would get him no points? (It would just create the situation of the first diagram, 2-2, plus 1 dame??)
This would explain the 50%, because considering a local move only, the likelihood of having the next move is 50%?
Please ignore if nonsense.
)No matter who fills the dame the result is the same. :
Maybe the situation in the first diagram is that B has taken the point where W could make an eye, so who gets the left over dame point does not matter, so it does not matter who's move it is?
But if white's possible eye-point is not taken yet, whoever's move it is will (considering the local situation only) take it with his/her next move; therefore there is a 50% chance for white taking it and getting an additional point, while black taking it would get him no points? (It would just create the situation of the first diagram, 2-2, plus 1 dame??)
This would explain the 50%, because considering a local move only, the likelihood of having the next move is 50%?
Please ignore if nonsense.
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Jika
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Re: Please help with this exercise III
I managed to solve 3 exercises on this basis, but now I'm stuck with another one (sigh):
I thought the solution would be 7 (the max points for B):
white taking A creates 1 point (A1).
black taking A kills the three stones (3x2=6) plus takes A1 (6+1=7).
They can't have the same territorial value both at the same time, so 7-1 does not work either?!
So, why 8?
Or maybe it is 3?!
(50% chance that W gets A, giving him 0+1/2 on A1;
50% chance that B gets A, getting the three stones+1 point, so 0+1/2x7 (in my calculation, see above)=3 1/2)
I like maths, but right now I'm feeling totally confused.
- Bildschirmfoto vom 2019-07-26 06-48-22.png (4.65 KiB) Viewed 16496 times
white taking A creates 1 point (A1).
black taking A kills the three stones (3x2=6) plus takes A1 (6+1=7).
They can't have the same territorial value both at the same time, so 7-1 does not work either?!
So, why 8?
Or maybe it is 3?!
(50% chance that W gets A, giving him 0+1/2 on A1;
50% chance that B gets A, getting the three stones+1 point, so 0+1/2x7 (in my calculation, see above)=3 1/2)
I like maths, but right now I'm feeling totally confused.