Life In 19x19
http://www.lifein19x19.com/

Sente move in endgame
http://www.lifein19x19.com/viewtopic.php?f=15&t=3891		 Page 1 of 1
Author:  Toge [ Sun May 22, 2011 5:37 am ]
Post subject:  Sente move in endgame
If sente by definition is a move you're compelled to answer, how does it translate to endgame decision making? For example, let's say there is a 10 point move that is gote and a 4 point move that is sente. It's often said that sente's value is double, so let's value that sente to 8 points.

Which would you play? Do the values even matter, if not responding sente is game-losing decision?

..and then there's cases where 'sente' move ends up looking like two gotes.
Author:  SoDesuNe [ Sun May 22, 2011 6:30 am ]
Post subject:  Re: Sente move in endgame
I guess it translates as always.
Sente in the middlegame or opening means - in my opinion - also a move, which would be too big (e.g. local loss, death of a group etc.) if you would not answer.
That's why a Hane on the second line can easily be ignored in the middlegame because it's just too small, even when a monkey jump follows. In the endgame where only a "few" points are left, Sente is still decided by what is bigger. If you play a move which threatens to monkey jump, one is inclined to answer, but if I would play a move which threatens to kill a group of yours instead, than my move would be even more Sente ("Zwischenzug"?), I assume, just because you'll lose more points by not answering.

So I guess, it comes down to the follow-up, what the actual moves threatens. That's why you can sometimes mirror a "Sente" endgame move (e.g. Hane on the first line), threatening the same as your opponent.

To your question: If the "Sente"-play is really just 8 points big and has no severe follow-up (which would make it more than 10 points), than I'd play the Gote-move because chances are, my opponent ignores the "Sente" move and plays the big point himself.
If the "Sente"-play is somewhat game-deciding, it will be bigger than ten points, so in your example, the biggest point on the board and therefor has to be answered.
Author:  jts [ Sun May 22, 2011 7:06 am ]
Post subject:  Re: Sente move in endgame
Are we assuming that both the sente and the gote are also gote for your opponent?
Author:  Toge [ Sun May 22, 2011 7:29 am ]
Post subject:  Re: Sente move in endgame
SoDesuNe wrote:
So I guess, it comes down to the follow-up, what the actual moves threatens. That's why you can sometimes mirror a "Sente" endgame move (e.g. Hane on the first line), threatening the same as your opponent.


- Yes. In that case it would be better to make another hane that threatens to spoil more territory than the first one. Counter sente with another.

jts wrote:
Are we assuming that both the sente and the gote are also gote for your opponent?


- Yes. In my opinion it's better to think in sequences. If the sente sequence would end in gote, it wouldn't be so much sente. Those sente sequences that end in gote tend to be either players "privilege" and the other wouldn't be in a hurry to prevent it.

Example: Playing 3 is sente to threaten further intrusion. White responds with 4 and the spot 'a' in now white's rightful sente.

Click Here To Show Diagram Code
[go]$$
$$ | . . . . . . . . O X . . . . . , . . . |
$$ | . . . . . . . . O X . . . . . . . . . |
$$ | . . . . . . . 2 1 . . . . . . . . . . |
$$ | . . . . . . . 4 a 3 . . . . . . . . . |
$$ ---------------------------------------[/go]
Author:  jts [ Sun May 22, 2011 7:58 am ]
Post subject:  Re: Sente move in endgame
But the sente sequences which end in gote for your opponent (reverse sente, for him) are the sequences about which we say "sente is worth double". The reason the sequence is only worth double is, because it's your privilege to play it later. The sente-sente plays you have in mind are worth a kajillion points.
Author:  SoDesuNe [ Sun May 22, 2011 9:01 am ]
Post subject:  Re: Sente move in endgame
Toge wrote:
Click Here To Show Diagram Code
[go]$$
$$ | . . . . . . . . O X . . . . . , . . . |
$$ | . . . . . . . . O X . . . . . . . . . |
$$ | . . . . . . . 2 1 . . . . . . . . . . |
$$ | . . . . . . . 4 a 3 . . . . . . . . . |
$$ ---------------------------------------[/go]


Maybe off, but I think, if you want to end in Sente you play like this:

Click Here To Show Diagram Code
[go]$$
$$ | . . . . . . . . O X . . . . . , . . . |
$$ | . . . . . . . . O X . . . . . . . . . |
$$ | . . . . . . . 6 2 1 . . . . . . . . . |
$$ | . . . . . . . 4 3 5 . . . . . . . . . |
$$ ---------------------------------------[/go]
Author:  Bill Spight [ Sun May 22, 2011 9:24 am ]
Post subject:  Re: Sente move in endgame
Toge wrote:
If sente by definition is a move you're compelled to answer, how does it translate to endgame decision making?


That is only one meaning of sente. There are others.


Quote:
For example, let's say there is a 10 point move that is gote and a 4 point move that is sente.


You mean like this, I take it:

Code:
               A               B
              / \             / \
             5  -5           C  -4
                            / \
                          BIG  0

          BIG > 8


/ indicates a Black play, \ indicates a White play.

Quote:
It's often said that sente's value is double, so let's value that sente to 8 points.


That is informal talk, and can be misleading. The "value" of a sente is actually how much the reverse sente gains.

Quote:
Which would you play? Do the values even matter, if not responding sente is game-losing decision?


You are asking what is technically correct, even if it does not matter towards winning or losing the game? I will proceed on that basis.

Case 1. BIG >= 10

You should play B unless you need it as a ko threat.

Case 2. 10 > BIG > 8

Which to play depends on the rest of the board. Typically you should play A.

Quote:
..and then there's cases where 'sente' move ends up looking like two gotes.


That's a special case. :)
Author:  Toge [ Sun May 22, 2011 10:58 am ]
Post subject:  Re: Sente move in endgame
SoDesuNe wrote:
Toge wrote:
Click Here To Show Diagram Code
[go]$$
$$ | . . . . . . . . O X . . . . . , . . . |
$$ | . . . . . . . . O X . . . . . . . . . |
$$ | . . . . . . . 2 1 . . . . . . . . . . |
$$ | . . . . . . . 4 a 3 . . . . . . . . . |
$$ ---------------------------------------[/go]


Maybe off, but I think, if you want to end in Sente you play like this:

Click Here To Show Diagram Code
[go]$$
$$ | . . . . . . . . O X . . . . . , . . . |
$$ | . . . . . . . . O X . . . . . . . . . |
$$ | . . . . . . . 6 2 1 . . . . . . . . . |
$$ | . . . . . . . 4 3 5 . . . . . . . . . |
$$ ---------------------------------------[/go]


- This is an important observation! Correcting small habitual plays like this has big impact on playing skill. The diagram below has same result as white playing 'a' on diagram above, but the below diagram is much more solid. White has serious ko threat but black has possibility to gain one more point. Is there difference in black playing twice in either diagram? Has it been established that one way of playing is generally better than the other?

Bill Spight wrote:
The "value" of a sente is actually how much the reverse sente gains.


- This one is new information for me. I remember reading that in the opening shimari is just the reverse sente of kakari. If the whole game can be understood based on this duality, this is pretty enlightening. If one can't find a good move to play against opponent, play a move that would be good for the opponent. Tesuji is the only case that breaks the mirror?
Author:  Bill Spight [ Sun May 22, 2011 11:32 am ]
Post subject:  Re: Sente move in endgame
Toge wrote:
SoDesuNe wrote:
Toge wrote:
Click Here To Show Diagram Code
[go]$$
$$ | . . . . . . . . O X . . . . . , . . . |
$$ | . . . . . . . . O X . . . . . . . . . |
$$ | . . . . . . . 2 1 . . . . . . . . . . |
$$ | . . . . . . . 4 a 3 . . . . . . . . . |
$$ ---------------------------------------[/go]


Maybe off, but I think, if you want to end in Sente you play like this:

Click Here To Show Diagram Code
[go]$$
$$ | . . . . . . . . O X . . . . . , . . . |
$$ | . . . . . . . . O X . . . . . . . . . |
$$ | . . . . . . . 6 2 1 . . . . . . . . . |
$$ | . . . . . . . 4 3 5 . . . . . . . . . |
$$ ---------------------------------------[/go]


- This is an important observation! Correcting small habitual plays like this has big impact on playing skill. The diagram below has same result as white playing 'a' on diagram above, but the below diagram is much more solid. White has serious ko threat but black has possibility to gain one more point. Is there difference in black playing twice in either diagram? Has it been established that one way of playing is generally better than the other?


Well, you have not shown enough of the board to give a definitive answer, but if the existing stones of both players are strong, so that the only question is points on the bottom side, then the descent is normally better. The key is to realize that the descent is gote, not sente. If Black started with the descent, would the next play be a crawl? Of course not, but that, in effect, is more or less the result of playing the hane-and-connect.

BTW, in real games, more is normally at stake than mere points. Also, playing the hane but not connecting is sometimes right, a sente to prevent the opponent from playing the descent.

Quote:
Bill Spight wrote:
The "value" of a sente is actually how much the reverse sente gains.


- This one is new information for me.


You learn something every day. :)

Quote:
I remember reading that in the opening shimari is just the reverse sente of kakari.


That is BS.

Quote:
If the whole game can be understood based on this duality, this is pretty enlightening. If one can't find a good move to play against opponent, play a move that would be good for the opponent. Tesuji is the only case that breaks the mirror?


So much for enlightenment. ;)

Yes, The opponent's play is my play, is a good proverb, but, like almost all go proverbs, it has exceptions.

BTW, there was a time, a few centuries ago, when a kakari was played as sente, because the opponent replied with a pincer. That was at the dawn of the modern understanding of the opening. The next step was the realization that the kakari was not sente, and that playing in an open corner was better than the pincer. The next step was the realization that playing in an open corner was typically better than the approach. (But even today, Go Seigen recommends a two space high approach for White if Black's first move is on a 3-4 point.)
Author:  Toge [ Sun May 22, 2011 11:46 am ]
Post subject:  Re: Sente move in endgame
Oh the actual quote is from the book Elementary Go Series Vol 1. In The Beginning, page 11:

Quote:
These plays, which are known as kakari, are just as valuable as the
shimari they prevent, but they are not as simple.
Author:  Shaddy [ Sun May 22, 2011 12:18 pm ]
Post subject:  Re: Sente move in endgame
Sente moves in endgame are to be treated as your right. They should be played as soon as possible, because they're sente, right? If your opponent takes the reverse sente they have deprived you of your rights and that sometimes means you've made a mistake.
Author:  Toge [ Sun May 22, 2011 1:14 pm ]
Post subject:  Re: Sente move in endgame
Shaddy wrote:
Sente moves in endgame are to be treated as your right. They should be played as soon as possible, because they're sente, right? If your opponent takes the reverse sente they have deprived you of your rights and that sometimes means you've made a mistake.


- Like 'a' in post #4? Isn't there still the order ranking from biggest reverse sente to smallest? To become any good endgame player, one must be able to challenge opponent's false sentes. This is an interesting problem related to sente and tedomari in endgame.
Author:  Shaddy [ Sun May 22, 2011 1:26 pm ]
Post subject:  Re: Sente move in endgame
Sente means that the opponent must answer, in perfect play. a in post 4 might be sente- it depends on the rest of the board. A false sente is just gote that maybe looks like sente, right?- ignoring these is important in the entire game, not just endgame. There is the order from biggest reverse sente to smallest- I think you should take the sente moves that threaten the most first in order to avoid mutual damage. I don't know anything about tedomari.
Author:  Bill Spight [ Sun May 22, 2011 1:38 pm ]
Post subject:  Re: Sente move in endgame
Toge wrote:
Oh the actual quote is from the book Elementary Go Series Vol 1. In The Beginning, page 11:

Quote:
These plays, which are known as kakari, are just as valuable as the
shimari they prevent, but they are not as simple.


Right. Nothing there about shimari being reverse sente. :)
Author:  Dusk Eagle [ Sun May 22, 2011 7:59 pm ]
Post subject:  Re: Sente move in endgame
Shaddy wrote:
Sente moves in endgame are to be treated as your right. They should be played as soon as possible, because they're sente, right? If your opponent takes the reverse sente they have deprived you of your rights and that sometimes means you've made a mistake.


I'm not sure, but I think this is wrong, and could lead to aji-keshi (or at the very least, loss of ko threats) in some situations. Your sente should normally be played before your opponent's reverse sente becomes the biggest move on the board (I believe), but playing a 1-point first-line hane when there are still 4-point gote moves seems unnecessary.

Toge wrote:
Example: Playing 3 is sente to threaten further intrusion. White responds with 4 and the spot 'a' in now white's rightful sente.

Click Here To Show Diagram Code
[go]$$
$$ | . . . . . . . . O X . . . . . , . . . |
$$ | . . . . . . . . O X . . . . . . . . . |
$$ | . . . . . . a 2 1 . . . . . . . . . . |
$$ | . . . . . . b 4 . 3 . . . . . . . . . |
$$ ---------------------------------------[/go]

I don't think :b3: is actually sente. If white tenukis and black plays at :w4:, then depending on the ko threat situation, the size of the relative territories, and the current leader in the game, white can choose to either fall back to ''a'' or start the ko with ''b''. However, even if he does have to fall back to ''a'', I think in most situations the tenuki will still be correct.
Author:  Shaddy [ Mon May 23, 2011 9:00 am ]
Post subject:  Re: Sente move in endgame
You're right, it loses ko threats. Endgame kos don't ever seem to come up in my games so I'd forgotten that detail- thanks. Also, in that example, I don't think 3 is sente, or even that good. If black hanes to start a ko, and I were white and not sure about who is leading, I'd happily fight the ko, because both players stand to lose just as much.
Author:  mitsun [ Mon May 23, 2011 11:28 am ]
Post subject:  Re: Sente move in endgame
Shaddy wrote:
Sente moves in endgame are to be treated as your right. They should be played as soon as possible, because they're sente, right? If your opponent takes the reverse sente they have deprived you of your rights and that sometimes means you've made a mistake.
It's not nearly that simple. First, there is no need to take a sente move as long as it is a mistake (too small) for your opponent to play the corresponding reverse sente. Second, there are times when a move does not become sente (big enough that your opponent would have to answer in gote) when it is your turn to play, so it becomes correct for your opponent to make the reverse sente play. If this were not the case, a reverse sente play would always imply a mistake, by one player or the other :)
Page 1 of 1 All times are UTC - 8 hours [ DST ]
Powered by phpBB © 2000, 2002, 2005, 2007 phpBB Group
http://www.phpbb.com/