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 Post subject: Re: Some endgame fun
Post #21 Posted: Fri Jan 28, 2011 7:28 pm 
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Sorry, I guess I sort of derailed the thread :(

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 Post subject: Re: Some endgame fun
Post #22 Posted: Fri Jan 28, 2011 8:12 pm 
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Numsgil wrote:
Like is there ever a time where responding to a "sente" play with a threat larger than the current temperature is suboptimal?


Yes. You may be interested in Berlekamp's "Economist's view" chapter in Games of No Chance, in which he explains Sentestrat and a lot of other things. :)

Quote:
It just gives us a hard and fast rule for which plays are actually sente.


It is a specialized meaning of sente. Go players in general will not understand it. ;)

Moi wrote:
Do you mean score or count?


Numsgil wrote:
Bleh, I can never remember which is which, so for the record I have and probably will butcher these terms, and even use them interchangeably.


You meant score. To call it gain implies that you are starting from zero. Since I use gain starting from any position, we could have a language problem if you mean something else. :)

Quote:
All are correct, but for C, it should be:
Code:
                    C
                   / \
                  C1  0
                 / \
                C2  4
               / \
              C3  7
             / \
           Big  13



Please note that C1 is a 3 point sente, not gote. And that the count at C1 is 7, the same as the count at B1.

With the correction to C, there are two orthodox lines of play:

1) Black plays to C1 in C, White plays to 0 in B, then Black plays the sente to 7 in C, and then to 4 in A, as though it were sente. Result: 11.

2) Black plays to B1 in B, White plays to 0 in C, then Black plays the sente to 7 in B, and then to 4 in A, as though it were sente. Result: 11.


Quote:

Code:
       A
      / \
A1   0  -3

       B
      / \
B1   0  -4

        C
       / \
C1    2   0
        /  \ (sente for white)
C2     0   -3



Note that C is gote. :)

Quote:
But are there endgame sequences where other issues than tedomari prevent the biggest-move-on-the-board-first from reaching the optimal solution (still not counting kos)?


Yes. I used to compose problems where the key was what plays were left at the end, before I realized how stupid that was. ;)

Still, tedomari helps humans recognize such sequences.

Quote:
Is the loss in points always no more than 1?


No, but I like problems where the incorrect play loses only 1 point. :)

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 Post subject: Re: Some endgame fun
Post #23 Posted: Sun Jan 30, 2011 6:14 pm 
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Bah, I'm feeling a bit pessimistic about the endgame, then.

Is there anything between the normally espoused endgame counting and just enumerating over every possible move order to arrive at a "perfect" endgame play? I don't even really mind if it's unwieldy to do in your head at this point, I just want to feel like it's possible to stare at a go board with a well defined endgame and figure out the perfect play.

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 Post subject: Re: Some endgame fun
Post #24 Posted: Sun Jan 30, 2011 6:53 pm 
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Numsgil wrote:
Bah, I'm feeling a bit pessimistic about the endgame, then.


Courage, mon vieux! :)

Quote:
Is there anything between the normally espoused endgame counting and just enumerating over every possible move order to arrive at a "perfect" endgame play? I don't even really mind if it's unwieldy to do in your head at this point, I just want to feel like it's possible to stare at a go board with a well defined endgame and figure out the perfect play.


Well, top players in the late 19th century played nearly perfect endgames. :)

Click Here To Show Diagram Code
[go]$$W Shusai clinches the game
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . X . . . . . |
$$ | . . O . X . . X . . . O . O . . X . . |
$$ | . . . O X . 1 O . O . O X . O O X . . |
$$ | . . O , X . X X O , . X O O O X . . X |
$$ | . . . . . . X O O . . X X . O X X . O |
$$ | . O O O O . . X O . . . . X O O X . . |
$$ | O X X X X X . . . . . . X O X O . . . |
$$ | . O O X . . . X . . . . . . X . O O . |
$$ | . . O X . . . . . . . X . . . . O X . |
$$ | . X X X O . . O . , . . . X . , . X . |
$$ | . O X X . O . . . . . O . . X . . . . |
$$ | O . O X . . . . . O . . O . . X . X . |
$$ | . . O O O . . O O . . . . O O X . . . |
$$ | . . O X . . . X . . X . . . X O X X . |
$$ | . . O X O O . X O O X . . X . O O O . |
$$ | . O X X X . X . . O X . . . . O . . . |
$$ | . O X . . . . X . O . . . X O . . . . |
$$ | O X X . . X . X O . X . X . X O O . . |
$$ | . . . . . . X O O . . . . . X X O . . |
$$ ---------------------------------------[/go]


In 1907, Tamura Yasuhisa, who later became Shusai Meijin, spent 8 hours gazing at the board, verifying that this move, W148, secured a 2 point victory.

Here is the whole game. :)



When composing problems I used to define each play precisely, so that I could guarantee a certain result. Now I find that it is easier and more realistic to create more or less random plays within my parameters, because the largest play is nearly always the right play, and a large enough number of random plays will almost always wash out anomalies. :)

Nearly perfect endgames are humanly possible, and amateurs can, with persistence and hardly any talent achieve a high level of endgame play. :)

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Last edited by Bill Spight on Thu Aug 02, 2012 9:31 pm, edited 1 time in total.
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 Post subject: Re: Some endgame fun
Post #25 Posted: Sun Jan 30, 2011 7:18 pm 
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Okay, so certainly normal counting is the start, since it is usually the right move. What then? Especially in something like the game you showed, where a lot is on the line and you have nothing but time, what do you do once you've figured out the count of the endgame moves remaining, and decide it's a really close game. Or let's say it's an important game, and you have nothing but time, and the normal counting method puts you half a point behind. Is there a systematic way to approach the board and see if there's a clever sequence that can net you another point?

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 Post subject: Re: Some endgame fun
Post #26 Posted: Sun Jan 30, 2011 7:26 pm 
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Numsgil wrote:
Is there a systematic way to approach the board and see if there's a clever sequence that can net you another point?


Yes. If there is a significant drop in the size of plays, you may be able to engineer getting the last play before the drop. My problem that you referred to is an example. :)

Also, you may be able to make a ko such that you can take and win the ko while your opponent makes smaller plays. :)

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Visualize whirled peas.

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