Life In 19x19

Life in 19x19. Go, Weiqi, Baduk... Thats the life.
https://lifein19x19.com/

Endgame proverbs

https://lifein19x19.com/viewtopic.php?t=622

Page 3 of 4

Re: Endgame proverbs

Posted: Tue May 25, 2010 1:02 pm
by topazg
Bill Spight wrote:
I know that the Davies / Ogawa book refers to that single atari as a 2 point gote move, so I suppose I'm biased as that's been my reference for endgame evaluation, but it feels more intuitive to evaluate the point value as the swing value.


For purposes of simple comparison, there is nothing wrong with swing values, along with the necessary multiplications and divisions. :) However, I have observed for many years that people assume that the swing value tells you how much a play gains. That is not so. Since questions that go beyond simple comparison, such as whether to play gote or reverse sente, pretty much require saying how much a play gains, I just talk about that. :)


Actually, even here that doesn't quite seem to add up. Assume the board is completely played out apart from that single stone atari. In territory scoring, the capture gains white one prisoner and one point of territory, which is two points. If Black saves it, there are no points there. Whether or not this is two points gained for White or one point gained for White and one point deprived from Black, the net gain is still two points for whoever plays it first. For example:

Click Here To Show Diagram Code
[go]$$Bcm1 Prisoners: B=0, W=0
$$ --------------------
$$ | . . . X . X O . . |
$$ | . . . X O O O . . |
$$ | . . . X O . . . . |
$$ | . . . X O . . . . |
$$ | . . . X O . . . . |
$$ | . . . X O . . . . |
$$ | . . . X O . . . . |
$$ | . . . X O . . . . |
$$ | . . . X O . . . . |
$$ --------------------[/go]


Here, Black has 27 points of territory, and White has 32, assuming no komi. If Black plays E9, that's the final score, W+5. If White plays E9, he has 33 territory and 1 prisoner, and the final score is W+7. I cannot see how this isn't a net gain of 2 points?

Re: Endgame proverbs

Posted: Tue May 25, 2010 1:33 pm
by John Fairbairn
I hope that count, move, point, and tally are not being used in confusing ways, at least in the literature. Charles Matthews introduced the term, tally, for the net number of plays between two positions. That is clear, I think. I hope that people are not confused. As for count, OC it is regular English, but Berlekamp introduced it as a technical term to refer to the assessed territory (along with dead and captured stones) in a local region. I am unfamiliar with its use to refer to the value of plays (which is what makes it a good term for something else ). I hope that people will not start using it that way.


Bill, Hope doesn't cut the mustard here, I'm afraid. We really need someone like yourself to write a definitive work - which I more than vaguely remember you promised us once.

Think about it. We are using words like score and count and value in both colloquial and technical senses as well as abbreviations for e.g. de-iri value. We have some people who would like to add things like count-1 and count-2. We borrow words like de-iri and miai which have no clear meaning for most people, and in the case of miai this is only clear to people like Japanese accountants - not to mention the confusion with miai points. We have people who think (and so use language) on the basis of a mathematical background and the rest. We have competing rule sets which can affect some counts. We have people who introduce new words or concepts, such as tally - which is actually far from clear even when defined, because you have to understand why it is defined - or CGT. We have subtle differences between British and American Englishes, and less subtle differences from people who don't use English as a mother tongue. We have people who use Japanese terms (e.g. moku) and we have people who misuse Japanese terms (e.g. moku).

Mud is much, much clearer. We need the Clarifier!

The outlook wasn't brilliant for the Mudville Gang that day;
The score stood one or jigo, with but few moves more to play,
And then when White's group died with ko, and Black's group did the same,
A sickly silence fell upon the patrons of the game.

A straggling few got up to go in deep despair. The rest
Clung to that hope which springs eternal in the human breast;
They thought, if only Bill would have but a whack at that -
We'd put up even money, now, just to know where we are at.

Re: Endgame proverbs

Posted: Tue May 25, 2010 1:56 pm
by HermanHiddema
topazg wrote:
Bill Spight wrote:
I know that the Davies / Ogawa book refers to that single atari as a 2 point gote move, so I suppose I'm biased as that's been my reference for endgame evaluation, but it feels more intuitive to evaluate the point value as the swing value.


For purposes of simple comparison, there is nothing wrong with swing values, along with the necessary multiplications and divisions. :) However, I have observed for many years that people assume that the swing value tells you how much a play gains. That is not so. Since questions that go beyond simple comparison, such as whether to play gote or reverse sente, pretty much require saying how much a play gains, I just talk about that. :)


Actually, even here that doesn't quite seem to add up. Assume the board is completely played out apart from that single stone atari. In territory scoring, the capture gains white one prisoner and one point of territory, which is two points. If Black saves it, there are no points there. Whether or not this is two points gained for White or one point gained for White and one point deprived from Black, the net gain is still two points for whoever plays it first. For example:

Click Here To Show Diagram Code
[go]$$Bcm1 Prisoners: B=0, W=0
$$ --------------------
$$ | . . . X . X O . . |
$$ | . . . X O O O . . |
$$ | . . . X O . . . . |
$$ | . . . X O . . . . |
$$ | . . . X O . . . . |
$$ | . . . X O . . . . |
$$ | . . . X O . . . . |
$$ | . . . X O . . . . |
$$ | . . . X O . . . . |
$$ --------------------[/go]


Here, Black has 27 points of territory, and White has 32, assuming no komi. If Black plays E9, that's the final score, W+5. If White plays E9, he has 33 territory and 1 prisoner, and the final score is W+7. I cannot see how this isn't a net gain of 2 points?


In endgame terms, this position can currently be considered as W+6. Black can play, and gain one point, for a final result of W+5. White can play, for a gain of one point, for a final result of W+7.

The 2 points here is the swing value, which is the difference between those two scores, the one where black plays first and the one where white plays first.

For many endgame purposes, swing values are not very useful. so Bill is using average gain values.

Example:

Click Here To Show Diagram Code
[go]$$Bc
$$ --------------------
$$ | . . . X . X O . . |
$$ | . . . X O O O . . |
$$ | . . . X . X O . . |
$$ | . . . X O O O . . |
$$ | . . . X . X O . . |
$$ | . . . X O O O . . |
$$ | . . . X . X O . . |
$$ | . . . X O O O . . |
$$ | . . . X O . . . . |
$$ --------------------[/go]


Here we have the same endgame play four times. White can expect to capture twice, while Black will connect twice. In total, White can thus expect to score 4 points in the center (two captures, two points), so on average, white has scored 4 point on 4 identical positions, so each of them gained 1 point on average.

Re: Endgame proverbs

Posted: Tue May 25, 2010 2:01 pm
by topazg
In endgame terms, this position can currently be considered as W+6


Sure, but that's only one way of considering it, which I really find incredibly unintuitive, even though I understand the reasoning. In reality, I see the position as W+5 with 2 points up for stakes. Seeing half of those belonging to each player already just feels weird :P

Re: Endgame proverbs

Posted: Tue May 25, 2010 2:05 pm
by Bill Spight
topazg wrote:
Bill Spight wrote:For purposes of simple comparison, there is nothing wrong with swing values, along with the necessary multiplications and divisions. :) However, I have observed for many years that people assume that the swing value tells you how much a play gains. That is not so. Since questions that go beyond simple comparison, such as whether to play gote or reverse sente, pretty much require saying how much a play gains, I just talk about that. :)


Actually, even here that doesn't quite seem to add up. Assume the board is completely played out apart from that single stone atari. In territory scoring, the capture gains white one prisoner and one point of territory, which is two points. If Black saves it, there are no points there. Whether or not this is two points gained for White or one point gained for White and one point deprived from Black, the net gain is still two points for whoever plays it first. For example:

Click Here To Show Diagram Code
[go]$$Bcm1 Prisoners: B=0, W=0
$$ --------------------
$$ | . . . X . X O . . |
$$ | . . . X O O O . . |
$$ | . . . X O . . . . |
$$ | . . . X O . . . . |
$$ | . . . X O . . . . |
$$ | . . . X O . . . . |
$$ | . . . X O . . . . |
$$ | . . . X O . . . . |
$$ | . . . X O . . . . |
$$ --------------------[/go]


Here, Black has 27 points of territory, and White has 32, assuming no komi. If Black plays E9, that's the final score, W+5. If White plays E9, he has 33 territory and 1 prisoner, and the final score is W+7. I cannot see how this isn't a net gain of 2 points?


Since White has played more stones, let's assume that it is Black's play. Any Japanese or Korean pro will count 27 points for Black and 33 points for White, for a net count of -6 (for Black). A Black play gains 1 point, for a score of -5. :)

You compare two different lines of play and note that the swing value tells you the difference. :)

But what about a bit more complicated example? :)

Click Here To Show Diagram Code
[go]$$Bcm1 Prisoners: B=0, W=0
$$ --------------------
$$ | . . X . X X O . . |
$$ | . X . X O O O . . |
$$ | . . . X O . . . . |
$$ | . . . X O . . . . |
$$ | . . . X O . . . . |
$$ | . . . X O . . . . |
$$ | . . . X O . O . . |
$$ | . . . X X O . . . |
$$ | . . . . . . . . . |
$$ --------------------[/go]


White to play.

Re: Endgame proverbs

Posted: Tue May 25, 2010 2:10 pm
by HermanHiddema
topazg wrote:
In endgame terms, this position can currently be considered as W+6


Sure, but that's only one way of considering it, which I really find incredibly unintuitive, even though I understand the reasoning. In reality, I see the position as W+5 with 2 points up for stakes. Seeing half of those belonging to each player already just feels weird :P



Yes, but by that reasoning, these two positions:

Click Here To Show Diagram Code
[go]$$Bc
$$ --------------------
$$ | . . . X . X O . . |
$$ | . . . X O O O . . |
$$ | . . . X . X O . . |
$$ | . . . X O O O . . |
$$ | . . . X . X O . . |
$$ | . . . X O O O . . |
$$ | . . . X . X O . . |
$$ | . . . X O O O . . |
$$ | . . . X O . . . . |
$$ --------------------[/go]


Click Here To Show Diagram Code
[go]$$Bc
$$ --------------------
$$ | . . . X . X O . . |
$$ | . . . X O X O . . |
$$ | . . . X O X O . . |
$$ | . . . X O X O . . |
$$ | . . . X O O O . . |
$$ | . . . X X X O . . |
$$ | . . . X O X O . . |
$$ | . . . X O O O . . |
$$ | . . . X O . . . . |
$$ --------------------[/go]


are both B+7 with 8 points up for grabs.

In evaluating endgame, it is much more useful to consider the average for each possible endgame play to get a realistic idea of how the game is going.

It is even more useful to simply read out the entire endgame and determine the exact score the game will have, BTW, But we'll assume that that is not possible :)

Re: Endgame proverbs

Posted: Tue May 25, 2010 2:16 pm
by Chew Terr
So Topazg's way (also the only way I know how to use) seems the simplest way of comparing two possible moves, and Bill's way seems designed to show who is currently ahead, by how much? Sorry, doing the best I can to keep up and understand this discussion, because it's interesting.

Re: Endgame proverbs

Posted: Tue May 25, 2010 2:18 pm
by Bill Spight
kokomi wrote:
karaklis wrote:If the opponent has no gain from a sente move, was it really sente then?


A sente move that does no good to yourself, or even benefits your opponent is called 'Su Shou'.


Thanks. :) Is that Chinese?

There are losing sente and there are aji keshi. But in general we assume that the player whose sente a play is will get to play it (with sente, of course). Therefore, we evaluate positions as though they were already played. So actually playing the sente does not change that assessment, and so we say that sente gains nothing. :)

Re: Endgame proverbs

Posted: Tue May 25, 2010 2:29 pm
by topazg
Bill Spight wrote:But what about a bit more complicated example? :)

Click Here To Show Diagram Code
[go]$$Bcm1 Prisoners: B=0, W=0
$$ --------------------
$$ | . . X a X X O . . |
$$ | . X . X O O O . . |
$$ | . . . X O . . . . |
$$ | . . . X O . . . . |
$$ | . . . X O . . . . |
$$ | . . . X O . . . . |
$$ | . . . X O . O . . |
$$ | . . . X X O . . . |
$$ | . . . . b c . . . |
$$ --------------------[/go]


White to play.


Keep bearing with me Bill, this is fabulous stuff, I'm just slow!

I consider "a" a 3 point gote move, because it's 2 initial points and 2 for a followup gote move, whereas "b" I consider a 2 point gote move.

However, I'm aware that "a" is in reality also a 1 point sente move move if Black _does_ respond, and that's the tricky point for me intuitively. So, if White captures, it feels necessary to consider the recapture against "c" for Black. "c" is obviously 2 points gote, and the recapture is 2 points gote, so it doesn't make much odds for Black which he takes. To assume Black treats it as gote (may as well under the circumstances), we have White gaining 2 points at the top, Black gaining two points at the bottom, and White gaining another point at the top (net gain of 1 point), against White gaining two points at the bottom and Black gaining 2 points at the top (net gain of 0 points). So capturing the two stones is worth one more point.

Re: Endgame proverbs

Posted: Tue May 25, 2010 2:34 pm
by topazg
HermanHiddema wrote:In evaluating endgame, it is much more useful to consider the average for each possible endgame play to get a realistic idea of how the game is going.


See, I'd read "Four 2 point gote moves, each as big as the other, doesn't matter which one to play" and just play them out :P

Re: Endgame proverbs

Posted: Tue May 25, 2010 2:47 pm
by kokomi
Bill Spight wrote:
kokomi wrote:why gote is preferred to reverse sente?


In general, to get the last play at the level of the plays,

For instance, suppose that the last two plays are a gote that gains 1 point and a reverses sente that gains 1 point. If you take the reverse sente, you gain 1 point, but then the opponent takes the gote to gain 1 point, as well. Net result: 0. But if you take the gote, you gain 1 point, and then the opponent takes his sente, for no gain. Net result: 1 point for you. Note that in the second line of play you get the last play (the reply to the sente). :)


ok, this sounds reasonable. When i have a rs of 2pts and a gote of 1pt, so i should go rs first. Then it's like when the pts of rs=gote, gote is preferred to rs?

Re: Endgame proverbs

Posted: Tue May 25, 2010 2:48 pm
by HermanHiddema
topazg wrote:
HermanHiddema wrote:In evaluating endgame, it is much more useful to consider the average for each possible endgame play to get a realistic idea of how the game is going.


See, I'd read "Four 2 point gote moves, each as big as the other, doesn't matter which one to play" and just play them out :P


Yes, but what do you do when there are still 10, 9, 8, etc point plays on the board? Do you think "I don't know how that will go, I'll count it as no points", or do you think "Oh those are equivalent, white will get 4 points there, probably" and use those 4 points in your estimate of the score?

If you do the second one, then extending that thinking to "oh, one of those, it's worth 1 point to white on average" will get you to average gain counting.

Re: Endgame proverbs

Posted: Tue May 25, 2010 3:01 pm
by RedStick
John Fairbairn wrote:
Does "endgame" always have to wait until the "middle game" in over?


No-one has answered this part of the OP's question, but it represents the real problem succinctly. The real problem is one of terminology, and even the Basic Endgame Theory page on SL manages to start off on entirely the wrong foot.

The first point is that it is more correct to talk about "boundary plays" (= yose) and these can occur even in the opening. They are common in the middle game. Conversely, the endgame can include plays (e.g. ko fights) that are not boundary plays.

The second point is that discussion of the topic is riddled with confusing usages of terms such as count, size, move, point, tally, etc. It is usually futile to start reading anything, even by an expert, about counting boundary plays unless you know for certain how these various terms are being used. It is not just that writer A may use one term and writer B another. It is that writer A may use the same term in two ways even in the same sentence. For example, with count you need to know whether the de-iri count or the miai count is being referred to. Context can help, but as the earlier posts in this thread show, it is unsafe to make assumptions about the context.

Even if you do come to terms, so to speak, with counting you need to remember that this is just one part of boundary play study. For instance, you need to be familiar with the many tesujis for this aspect of the game - not so very different from middle-game or life-and-death tesujis, but instead of good shape or life the goal is to gain extra points.

A further aspect of study is really for dan players, and that is thickness (i.e. solidity). Often you will want to play the most secure move rather than the one that looks biggest. This applies usually to boundary plays in the middle game (and ability here is one of the markers for very strong players), but it can occur quite late in the game, too, for example when there are still ko fights lurking.

There are also other kinds of boundary play strategy. One centres round the tedomari - getting the last move of a certain level. Just as in the opening where, say, there are three big 20-point big points you will usually try to improvise a plan to get two out of three of these, so with boundary plays: if there are three 2-point gote plays you will want to ensure you get two of them (this is often where thickness comes in). Timing is general is an important element of boundary play strategies.

Proverbs don't really cope with such a wide range of requirements, although sayings such "the monkey jump is worth 7 (or 8) points" are useful in various ways. I think the most unuseful advice is to stress the importance of sente. It is often plain wrong - usually the biggest move is best, often the thickest move is best, and often the tedomari is your goal. Sente is just a means. The end (or boundary ;-) ) matters more than the means.

When you see a pro described as "good at the endgame", remember that this should be "good at boundary plays". In fact it really means he is good at the middle game. It does not mean he is good at counting local positions - all pros can do that and they have very many standard counts stored in their heads. It means rather that he is good at evaluating boundary plays, potential as well as actual, at an early stage and so can make the right decisions as regards timing or thickness.


Thanks John, this helps. I'm curious about how moves for thickness should be assessed but seeing as I'm several stones away from dan I suppose I can focus on more easily accessible ways to improve my game.

Bill and Topaz, you guys make my head hurt.

Re: Endgame proverbs

Posted: Tue May 25, 2010 3:13 pm
by Bill Spight
topazg wrote:
Bill Spight wrote:But what about a bit more complicated example? :)

Click Here To Show Diagram Code
[go]$$Bcm1 Prisoners: B=0, W=0
$$ --------------------
$$ | . . X a X X O . . |
$$ | . X . X O O O . . |
$$ | . . . X O . . . . |
$$ | . . . X O . . . . |
$$ | . . . X O . . . . |
$$ | . . . X O . . . . |
$$ | . . . X O . O . . |
$$ | . . . X X O . . . |
$$ | . . . . b c . . . |
$$ --------------------[/go]


White to play.


Keep bearing with me Bill, this is fabulous stuff, I'm just slow!

I consider "a" a 3 point gote move, because it's 2 initial points and 2 for a followup gote move, whereas "b" I consider a 2 point gote move.

However, I'm aware that "a" is in reality also a 1 point sente move move if Black _does_ respond, and that's the tricky point for me intuitively.


"a" confuses the textbook writers. ;) I have seen it called both a 2 point gote and a 1 point sente. I call it ambiguous. Dr. Berlekamp calls it an up in chilled go. :)

I can see how it looks like a 3 point move, but here is the game tree.

Code: Select all

                Z
               / 
              0   Y
                 / 
               -1  -3


The local count of Y is -2, an the local count of Z is -1. The swing between 0 and Y is 2, if it is a gote, but the swing between Z and 0 is 1 if it is sente. ;)

So, if White captures, it feels necessary to consider the recapture against "c" for Black. "c" is obviously 2 points gote, and the recapture is 2 points gote, so it doesn't make much odds for Black which he takes. To assume Black treats it as gote (may as well under the circumstances), we have White gaining 2 points at the top, Black gaining two points at the bottom, and White gaining another point at the top (net gain of 1 point), against White gaining two points at the bottom and Black gaining 2 points at the top (net gain of 0 points). So capturing the two stones is worth one more point.


Let me quote an interesting part: "we have White gaining 2 points at the top, Black gaining two points at the bottom, and White gaining another point at the top (net gain of 1 point)"

You have the order wrong. If White plays at "a" first, the remaining plays are miai, so if Black gains two points at the bottom White gains two points at the top. That means that White's first play gained 1 point, not the second one. (OC, as I see it each of the plays gains 1 point.) We both agree that if White plays at "b" first and then Black plays at "a", the net result of the play is 0. :)


Edit: Because it was confusing, I re-lettered the tree. Z indicates the region in the vicinity of "a" on the board. Y indicates the same region after White plays at "a" and captures 2 stones.

Re: Endgame proverbs

Posted: Tue May 25, 2010 3:20 pm
by topazg
Bill Spight wrote:You have the order wrong. If White plays at "a" first, the remaining plays are miai, so if Black gains two points at the bottom White gains two points at the top. That means that White's first play gained 1 point, not the second one. (OC, as I see it each of the plays gains 1 point.) We both agree that if White plays at "b" first and then Black plays at "a", the net result of the play is 0. :)


You are quite right, I worked that out in my shower in the intervening time ;)

I'm going to get there, I really will!
All times are UTC-07:00
Page 3 of 4

Powered by phpBB® Forum Software © phpBB Limited