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 Post subject: Re: Values of moves
Post #161 Posted: Thu Sep 20, 2018 11:17 am 
Gosei
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I'm not of the gospel type, I like to understand things. I will neither worship Bill for saying things I don't understand, neither will I diabolize Robert for doing the same. I admire both for scanning the horizon and building theory. Bill has been more zealous in explaining things - I assume Robert keeps that for his book. I see mitsun and others as those who try to bridge those early developments with what is being traditionally understood - "barbarians" if you like. John, you never answered my question whether my attempt at building that bridge was even moderately successful, so I assume it wasn't.

I'll keep it here (but will continue studying modern endgame theory, now that my interest is raised)

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 Post subject: Re: Values of moves
Post #162 Posted: Thu Sep 20, 2018 12:57 pm 
Oza

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Quote:
Btw, Go4Go calls Takao's opponent in this game Sun Zhe.


The Nihon Ki-in normally gives Son Makoto but the web site (though never the yearbooks or other publications, in my experience) adds the Chinese as an alternative. He comes from in Yokohama (i.e. Japan) and was raised there. His surname is common in China as Sun, but even if it ultimately came from there it's also got a long standing in Japan (Son is the usual reading but Mago also occurs).

Makoto is unusual - Satoshi or Tetsu would be the more common readings.

I don't know whether he has any recent Chinese connections or not, but I usually stick with the readings of the organisation a player works for.

There have been a few cases of Taiwanese Chinese pros (both Nihon Ki-in and Kansai Ki-in) in Japan getting a bit uppity about their names being read as Japanese. Even Go Seigen went through a phase of this. Editors sporadically attempt to pacify them, but then tend to lapse back. And some editors jump before they are pushed - sometimes wrongly. I think some of the website entries may fall under this category.

Edit: I decided to do a bit of digging about his origins. I found many Japanese references to him and none give Sun Zhe as a reading. Some, of course, give no reading at all, but an unusually high proportion do, as it is obviously seen as an unusual name (but so is Ichiriki Ryo and many others). Then it is invariably Son Makoto. It is the "Makoto" part that is seen as unusual and for that reason this portion is often given in hiragana (i.e. 孫まこと rather than 孫喆). The unusualness is not so much the kanji but the reading, although the kanji itself is classed as uncommon (because it is more usually written as 哲). There is absolutely nothing "Chinese" about this. Indeed the what stands out is the pure Japanese word Makoto rather then the common Sino-Japanese Tetsu (Satoshi wuld also be pure Japanese).

I also found local newspaper references to when he was a child prodigy in Kanagawa. There was no mention there that places him or his family in Taiwan or China, as you would expect as part of the usual journalistic "colour."

The Nihon Ki-in site (and only in its recent version) therefore appears to be the only source of a Sun Zhe reading, and even then not as the main reading. Knowing, further, a little bit about how this site is put together, I'm prepared to postulate that there was some automatic translation involved, and as Sun Zhe does exist as a Chinese name it may have crept in via this route. I could find no Chinese site that laid claim to Son as one of their sons (pun half intended :), and in fact his nationality (if mentioned) was listed as Japanese there.

Negatives don't prove much, so I can't unequivocally say he does not have Chinese connections or a personal preference for a Chinese reading, but common usage very, very strongly favours Son Makoto, and there is absolutely nothing countervailing I can see so far that supports using Sun Zhe.

All of this must, of course, be seen in the context that Japanese name readings in general are a complete dog's breakfast.

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 Post subject: Re: Values of moves
Post #163 Posted: Sat Sep 22, 2018 10:02 am 
Honinbo

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mitsun wrote:
Here are the graphs for the two positions Bill provided as Go diagrams earlier. The node counts and branch move values are for the gote assumption, with probability 50% for every branch.
Code:
   
                o 5.25                  o 2.75? really 3       
               / \                     / \
              /   \ -2.75             /   \ gote -1.25,
             /     \                 /     \ really sente
            /       \               /       \
           8         o 2.5         4         o 1.5
                    / \                     / \
                   /   \ -2.5              /   \ -1.5
                  /     \                 /     \
                 5       0               3       0

Bill demonstrated that the W branch is local gote in the first graph and local sente in the second graph. Is there an easy way to see this from the graphs? I guess the contradiction in the second graph is that the gote count of the starting position (2.75) is less than a terminal position (3) which B can always guarantee reaching, by treating the W move as sente.


Is there an easy way to see this from the graphs? Yes, indeed, as you have actually shown. :) Let me repeat the graphs without the calculations.

Code:
   
                o A                     o C     
               / \                     / \
              /   \                   /   \
             /     \                 /     \
            /       \               /       \
           8         o B           4         o D
                    / \                     / \
                   /   \                   /   \
                  /     \                 /     \
                 5       0               3       0



When we play the gote strategy for A in the four copies, we get these four results: 2*8 + 5 + 0 = 21. The sente strategy for Black yields these four result: 4*5 = 20. Black does better with the gote strategy, so we can use those results to find its territorial count: 21/4 = 5¼.

Using the graph we would first find the count of B, which is (5+0)/2 = 2½, and then find the count of A, assuming it to be gote, which is (8+2½)/2 = 5¼. OC, we can see at a glance that the count of A, assuming it to be sente, is 5, which is less than 5¼, so we conclude that A is gote. Using the graph gives us more information, and may be quicker.

When we play the gote strategy for C in the four copies, we get these four results: 2*4 + 3 + 0 = 11. The sente strategy for Black yields these four result: 4*3 = 12. Black does better with the sente strategy, so we can use those results to find its territorial count: 3.

Using the graph we would first find the count of D, which is (3+0)/2 = 1½, and then find the count of C, assuming it to be gote, which is (4+1½)/2 = 2¾. OC, we can see at a glance that the count of C, assuming it to be sente, is 3, which is greater than 2¾, so we conclude that C is White sente. Using the graph gives us more information, and may be quicker. :)

----

Suppose we wish to find a general rule to find out whether such a position is sente or gote. Let's relabel the graph with letters.

Code:
   
                o A         
               / \           
              /   \         
             /     \         
            /       \       
           a         o B     
                    / \     
                   /   \     
                  /     \   
                 b       c   



The result with the gote strategy is

2*a + b + c

The result with the sente strategy is

4b

Taking gote as the default, we get this rule:

Code:
   
                o A         
               / \           
              /   \         
             /     \         
            /       \       
           a         o B     
                    / \     
                   /   \     
                  /     \   
                 b       c   

A is White sente if and only if 4*b > 2*a + b + c.


Noting that we can subtract b from both sides of the inequality, we get

Code:
   
                o A         
               / \           
              /   \         
             /     \         
            /       \       
           a         o B     
                    / \     
                   /   \     
                  /     \   
                 b       c   

A is White sente if and only if 3*b > 2*a + c.


Now tell that rule to a regular go player. :scratch: :scratch: :scratch:

Archibald MacLeish wrote:
A poem should be wordless
As the flight of birds. . . .

A poem should be motionless in time
As the moon climbs. . . .

A poem should not mean
But be.

:D

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— Winona Adkins

Everything with love.


Last edited by Bill Spight on Sat Sep 22, 2018 10:56 am, edited 2 times in total.
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 Post subject: Re: Values of moves
Post #164 Posted: Sat Sep 22, 2018 10:53 am 
Honinbo

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To be kind to regular go players, especially if they have learned to count in the usual way (deiri), we can make the rule slightly less poetic. ;)

Code:
   
                o A         
               / \           
              /   \         
             /     \         
            /       \       
           a         o B     
                    / \     
                   /   \     
                  /     \   
                 b       c   

A is White sente if and only if b-c > 2*(a-b).


b-c is the deiri value of B, and a-b is the reverse sente value of A (if it is a White sente). Regular go players have already learned to multiply reverse sente values by 2 to compare them with gote. What this says is that A is sente if and only if its threat is greater than its reverse sente value.

Converting to O Meien's values, we get

Code:
   
                o A         
               / \           
              /   \         
             /     \         
            /       \       
           a         o B     
                    / \     
                   /   \     
                  /     \   
                 b       c   

A is White sente if and only if (b-c)/2 > a-b.


And if we note that B need not be gote, we get this definition.

Given position P and players A and B:
Position P is sente for player A if player B's reply to player A's play from position P gains more than player B's play from position P.


That's the correct version of O Meien's definition. :)

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 Post subject: Re: Values of moves
Post #165 Posted: Sat Sep 22, 2018 9:44 pm 
Tengen

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Bill Spight wrote:
A is White sente if and only if (b-c)/2 > a-b.
[/code]

Given position P and players A and B:
Position P is sente for player A if player B's reply to player A's play from position P gains more than player B's play from position P.


That's the correct version of O Meien's definition.


What slightly wrong definition does O give?

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 Post subject: Re: Values of moves
Post #166 Posted: Sat Sep 22, 2018 10:12 pm 
Lives in gote

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Warning: Mathlish

In fabulously lazy fashion (and therefore potentially incorrect) I'll use a tool to create the thermographs for me.

Second position first:

If it looks like a sente, quacks like a sente, it's a sente:

Attachment:
Screen Shot 2018-09-22 at 9.30.21 PM.png
Screen Shot 2018-09-22 at 9.30.21 PM.png [ 44.86 KiB | Viewed 668 times ]


The first position is more complex. There is a small double gote region when the temperature is between 5/2 (2.5) and 11/4 (2.75).

Attachment:
Screen Shot 2018-09-22 at 9.25.28 PM.png
Screen Shot 2018-09-22 at 9.25.28 PM.png [ 44.93 KiB | Viewed 668 times ]


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 Post subject: Re: Values of moves
Post #167 Posted: Sat Sep 22, 2018 10:57 pm 
Honinbo

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RobertJasiek wrote:
Bill Spight wrote:
A is White sente if and only if (b-c)/2 > a-b.
[/code]

Given position P and players A and B:
Position P is sente for player A if player B's reply to player A's play from position P gains more than player B's play from position P.


That's the correct version of O Meien's definition.


What slightly wrong definition does O give?


O Meien defines sente in terms of what the Go Player's Almanac calls privilege, and John Fairbairn translates as right. The idea is that a play is (local) sente if one player has the right to make it. Here is O's definition of right.

O Meien wrote:
If we were to give a definition of “right” here, it would be: if the next move is bigger than the move just played, that move has been your right.
-- Translated by John Fairbairn

As stated, there is some ambiguity, but O clears that up in the ensuing discussion. He regards the size of "the move just played" as the same as the size of the reverse sente by the opponent. But the size of the next move is the size of the threat, not the size of the reply. In the example he gives, the threat is a gote, so the size of the reply is the same as the size of the threat. I expect that if O saw an example where the reply is a reverse sente, he would get it right, and his readers might, as well, I don't know. But his definition is in terms of the sizes of the sente and its threat, not the sizes of the reverse sente and the reply.

It may be counterintuitive to think of a sente play in terms of the opponent's plays, but that's what makes it sente. Yes, a sente raises the local temperature, but it is the opponent's plays that indicate the current temperature.

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