Where to play at the end of the Fuseki (practical example)?

[Kirby]

Kirby, your personal animus against me is becoming rather tiresome, for others as well as myself, I'm sure. Try and find some other way of masturbating in public.

As far as I am concerned it is not an argument. It is an attempt to learn something - a discussion. As a strong dan player myself I can contribute to the discussion at its present level. I also have insight into the pro literature, which I hope helps the discussion. I don't see any useful contributions from you.

I don't call you names, accuse you of trolling, or personally attack you. You do this to me sometimes, just as in this post.

I merely disagree with your view sometimes. My contribution to this thread is to argue about concrete reasons about why the group is thick or not thick. I didn't see how you couldn't see the group as thick, which is why I asked for clarification. Instead of giving clarification, you accused me of trolling.

I disagree with you sometimes in a direct way, but this is the nature of discussion.

Calling people trolls, referencing masturbation, and the like are not what I'd call discussion.

Yes, I disagree about your assessment of the group's thickness. And yes, I disagree that other pro examples are necessarily relevant. But that's why I drill down on the actual reasons that our opinions differ, rather than resorting to personal attacks and name calling.

[John Fairbairn]

Kirby

I merely disagree with your view sometimes

No. You are a stalker. Over a period of several years, you have gone for long periods latching on to almost every post I make, finding ways to disagree that no-one else does. The tone is invariably intended to denigrate either directly or by attrition, seeking responses to specious points that remain on the record because I do not have time to respond. You try to waste more of my time by asking me to repeat reasons I have already given. That is trolling. No-one else does this to me; you do it to no-one else. I certainly do not do this to you. In contrast, I very rarely comment on to your posts. It is one-sided behaviour.

I don't call you names, accuse you of trolling, or personally attack you.

So labelling me a racist just because I don't like Mickey Mouse games in Korea doesn't count? The constant denigration doesn't count?

Stalking, hounding, hectoring, badgering and being generally bumptious is not discussion. It is a form of abuse.

If you really are the intelligent goodie-goodie you think you are, you should ask yourself why someone you have never met or dealt with, and who does not intersect with any part of your life outside these threads, should feel so offended by your behaviour and by no-one else's.

So here's the deal. I am neither asking you to agree with me or to apologise. But I am asking you to stop commenting, directly or indirectly, on my contributions. The alternative is that I stop contributing altogether.

And because I have so little free time to keep responding myself, let's make it formal: I am hereby asking admins to give Kirby rigorous advice to curb his behaviour.

[Joaz Banbeck]

More fun with PON

The Chernobyl group

$$B
$$ +---------------------------------------+
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . O . . . . . . . . . . . . . . . |
$$ | . . . , . . . . . , . . . . . X . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . d . . . . |
$$ | . . . . . . . . . . . . . d c . . . . |
$$ | . . . , . . . . . , . . d c b B . . . |
$$ | . . . . . . . . . . . d c b a . X . . |
$$ | . . . . . . . . . . d c b a O O X . . |
$$ | . . . . . . . . . d c b a O a O X . . |
$$ | . . O . . . . . . . d c b a O X . O . |
$$ | . . . . . . . . . . d c b a O X . . . |
$$ | . . . O . . . . 1 , d c b a O O X . . |
$$ | . . . . . X . . . . . B b a O X X . . |
$$ | . . . . . . . . . . . . c b a . . . . |
$$ | . . . . . . . . . . . . d c b . . . . |
$$ +---------------------------------------+

Click Here To Show Diagram Code

[go]$$B
$$ +---------------------------------------+
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . O . . . . . . . . . . . . . . . |
$$ | . . . , . . . . . , . . . . . X . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . d . . . . |
$$ | . . . . . . . . . . . . . d c . . . . |
$$ | . . . , . . . . . , . . d c b B . . . |
$$ | . . . . . . . . . . . d c b a . X . . |
$$ | . . . . . . . . . . d c b a O O X . . |
$$ | . . . . . . . . . d c b a O a O X . . |
$$ | . . O . . . . . . . d c b a O X . O . |
$$ | . . . . . . . . . . d c b a O X . . . |
$$ | . . . O . . . . 1 , d c b a O O X . . |
$$ | . . . . . X . . . . . B b a O X X . . |
$$ | . . . . . . . . . . . . c b a . . . . |
$$ | . . . . . . . . . . . . d c b . . . . |
$$ +---------------------------------------+[/go]

PON = int(0.33(9 + 0.5(9) + 0.35(9) + 0.25(9)) - 1.96) = int(4.277) = 4.

In Lee's game Gu later attacked at a, and Lee tenukid and Gu later attacked again at b and Lee ended up making a small life in sente. Despite getting 2 tenukis from it Lee later said he should not have ignored the initial attack but jumped to c to preserve the power of the thickness.

$$B
$$ +---------------------------------------+
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . O . . . . . . . . . . . . . . . |
$$ | . . . , . . . . . , . . . . . X . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . , . . . . . , . . . . . X . . . |
$$ | . . . . . . . . . . . . . a . . X . . |
$$ | . . . . . . . . . . . . . . O O X . . |
$$ | . . . . . . . . . . . b . O . O X . . |
$$ | . . O . . . . . . . . . . . O X . O . |
$$ | . . . . . . . . . . . c . . O X . . . |
$$ | . . . O . . . . 1 , . . . . O O X . . |
$$ | . . . . . X . . . . . X . . O X X . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ +---------------------------------------+

Click Here To Show Diagram Code

[go]$$B
$$ +---------------------------------------+
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . O . . . . . . . . . . . . . . . |
$$ | . . . , . . . . . , . . . . . X . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . , . . . . . , . . . . . X . . . |
$$ | . . . . . . . . . . . . . a . . X . . |
$$ | . . . . . . . . . . . . . . O O X . . |
$$ | . . . . . . . . . . . b . O . O X . . |
$$ | . . O . . . . . . . . . . . O X . O . |
$$ | . . . . . . . . . . . c . . O X . . . |
$$ | . . . O . . . . 1 , . . . . O O X . . |
$$ | . . . . . X . . . . . X . . O X X . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ +---------------------------------------+[/go]

What does the PON estimate say?

$$B
$$ +---------------------------------------+
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . O . . . . . . . . . . . . . . . |
$$ | . . . , . . . . . , . . . . . X . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . , . . . . . , . . . . . X . . . |
$$ | . . . . . . . . . . . d . 1 a . X . . |
$$ | . . . . . . . . . . d c b a O O X . . |
$$ | . . . . . . . . . d c b a O a O X . . |
$$ | . . O . . . . . . . d c b a O X . O . |
$$ | . . . . . . . . . . d c b a O X . . . |
$$ | . . . O . . . . X , d c b a O O X . . |
$$ | . . . . . X . . . . . B b a O X X . . |
$$ | . . . . . . . . . . . . c b a . . . . |
$$ | . . . . . . . . . . . . d c b . . . . |
$$ +---------------------------------------+

Click Here To Show Diagram Code

[go]$$B
$$ +---------------------------------------+
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . O . . . . . . . . . . . . . . . |
$$ | . . . , . . . . . , . . . . . X . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . , . . . . . , . . . . . X . . . |
$$ | . . . . . . . . . . . d . 1 a . X . . |
$$ | . . . . . . . . . . d c b a O O X . . |
$$ | . . . . . . . . . d c b a O a O X . . |
$$ | . . O . . . . . . . d c b a O X . O . |
$$ | . . . . . . . . . . d c b a O X . . . |
$$ | . . . O . . . . X , d c b a O O X . . |
$$ | . . . . . X . . . . . B b a O X X . . |
$$ | . . . . . . . . . . . . c b a . . . . |
$$ | . . . . . . . . . . . . d c b . . . . |
$$ +---------------------------------------+[/go]

After we have

PON = int(0.33(7.4 + 0.5(7) + 0.35(6) + 0.25(5.2)) - 1.96) = int(2.759) = 2.

Since Lee only tenukied once in this position, the PON estimate seems too high. (Not scientifically validated, as I said.) Note that Black's attack reduced the PON estimate by 2, not by 1, as we would expect from the algorithm.

$$B
$$ +---------------------------------------+
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . O . . . . . . . . . . . . . . . |
$$ | . . . , . . . . . , . . . . . X . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . , . . . . . , . . . . . X . . . |
$$ | . . . . . . . . . . . . . 1 . . X . . |
$$ | . . . . . . . . . . . . . . O O X . . |
$$ | . . . . . . . . . . . . . O . O X . . |
$$ | . . O . . . . . . . . . . . O X . O . |
$$ | . . . . . . . . . . . 2 . . O X . . . |
$$ | . . . O . . . . X , . . . . O O X . . |
$$ | . . . . . X . . . . . X . . O X X . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ +---------------------------------------+

Click Here To Show Diagram Code

[go]$$B
$$ +---------------------------------------+
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . O . . . . . . . . . . . . . . . |
$$ | . . . , . . . . . , . . . . . X . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . , . . . . . , . . . . . X . . . |
$$ | . . . . . . . . . . . . . 1 . . X . . |
$$ | . . . . . . . . . . . . . . O O X . . |
$$ | . . . . . . . . . . . . . O . O X . . |
$$ | . . O . . . . . . . . . . . O X . O . |
$$ | . . . . . . . . . . . 2 . . O X . . . |
$$ | . . . O . . . . X , . . . . O O X . . |
$$ | . . . . . X . . . . . X . . O X X . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ +---------------------------------------+[/go]

would have preserved an actual PON of at least 2, which pros generally do in the opening. Lee later said that he should have played there, but he did not, so it is a close call.

[admin]
In an attempt to get the discussion back on subject, I'm quoting the most recent on-topic post.
I ask that all participants please stick to the subject.
Thanks,
JB
[/admin]

[John Fairbairn]

The possible omission number (PON) is related to the strength or weakness of a group. A PON of 0 means that the group is unsettled; the attacker to play can kill, the defender to play can live. A PON of 1 means that the attacker to play can move to a position with a PON of 0. I have observed that in the opening pros generally try to make groups with a PON of at least 2.

Bill, I've heard of PON before, but have forgotten the background and certainly have no experience of it - which makes framing a sensible question about it a little difficult. But what caught my attention most was your feeling that the PON number may be coming out a bit high in the instances here, as well as your sense that pros don't like PONs below 2. My interest was because this chimed with an observation I made when looking at miai.

When I was coming up through the ranks years ago, the way the concept of miai that was used and taught among UK amateurs (the blind leading the blind, of course) was that it was OK to leave a group until it had exactly two options left. In those days virtually the only known pukka strategy was the one-weak-group strategy, and this idea of miai resonated with that. I absorbed all that and ended up with some bad habits. Talking about miai also went a bit out of fashion, so it was only relatively recently that I discovered that miai with just two options is quite rare in pro games. They seem to insist on three or more (which is similar to PON = 2+??). To give myself a crutch to think and take notes about this, I came up with the nonsense word tri-ai.

So, to come to my question, is it possible that PON is (or should be) based on measuring the safety of a group as opposed to its life? In other words, we should expect groups with high PONs because pros want to be able to respond before the group can be bullied, not just at the last possible moment to make two eyes.

[Kirby]

Kirby

I merely disagree with your view sometimes

No. You are a stalker.

More name calling. I am not a stalker. I disagree with you sometimes. That's not stalking. I disagree with others here, too. Do I have strong opinions? Yes. Am I somewhat stubborn? Yes (a lot of us are). Do I disagree with a variety of people on the forum, not including just you? Yes.

Over a period of several years, you have gone for long periods latching on to almost every post I make, finding ways to disagree that no-one else does.

I don't disagree with everything you say. I have sometimes liked your posts on L19 using the feature here. Often, when I agree, I don't elaborate on my agreement. Silence sometimes means that I agree, because I don't have anything to add.

You take it as disagreeing with everything that you say because I mostly comment at times that I disagree.

I don't call you names, accuse you of trolling, or personally attack you.

So labelling me a racist just because I don't like Mickey Mouse games in Korea doesn't count? The constant denigration doesn't count?

When did I label you as a racist? Yes, I don't like the term "Mickey Mouse" games, and you know that. Yet, you continue to use it. I don't make up terms like this. I don't talk about "public masturbation". I don't call you a troll. I don't do any of that.

I just disagree with you sometimes, and sometimes passionately.

But I am asking you to stop commenting, directly or indirectly, on my contributions. The alternative is that I stop contributing altogether.

And because I have so little free time to keep responding myself, let's make it formal: I am hereby asking admins to give Kirby rigorous advice to curb his behaviour.

I will comment when I feel inclined, at times when I disagree. This is not a situation of me attacking you. It's disagreeing at times. Please don't take it as a personal attack.

I will agree that I am a "stalker" on the forums if that means that I post often, especially when I disagree. But that's in response to anybody - not just you.

The many individuals I've disagreed with over the years can attribute to that.

[Kirby]

I see we received a PM from admins about our conversation here, John. So let's continue privately in PM if you have further to discuss.

[John Fairbairn]

There is nothing to discuss. You either keep away from my posts or I leave.

[Joaz Banbeck]

The possible omission number (PON) is related to the strength or weakness of a group. A PON of 0 means that the group is unsettled; the attacker to play can kill, the defender to play can live. A PON of 1 means that the attacker to play can move to a position with a PON of 0. I have observed that in the opening pros generally try to make groups with a PON of at least 2.

Bill, I've heard of PON before, but have forgotten the background and certainly have no experience of it - which makes framing a sensible question about it a little difficult. But what caught my attention most was your feeling that the PON number may be coming out a bit high in the instances here, as well as your sense that pros don't like PONs below 2. My interest was because this chimed with an observation I made when looking at miai.

When I was coming up through the ranks years ago, the way the concept of miai that was used and taught among UK amateurs (the blind leading the blind, of course) was that it was OK to leave a group until it had exactly two options left. In those days virtually the only known pukka strategy was the one-weak-group strategy, and this idea of miai resonated with that. I absorbed all that and ended up with some bad habits. Talking about miai also went a bit out of fashion, so it was only relatively recently that I discovered that miai with just two options is quite rare in pro games. They seem to insist on three or more (which is similar to PON = 2+??). To give myself a crutch to think and take notes about this, I came up with the nonsense word tri-ai.

So, to come to my question, is it possible that PON is (or should be) based on measuring the safety of a group as opposed to its life? In other words, we should expect groups with high PONs because pros want to be able to respond before the group can be bullied, not just at the last possible moment to make two eyes.

[admin]
I'm quoting the most recent relevant post to get the discussion back on subject.
[/admin]

[DrStraw]

Can you not just remove the irrelevant posts to a side thread so that the continuity is not disrupted?

[Knotwilg]

No. Someone should tell the person who's misbehaving here to stop misbehaving. Preferably an admin indeed. Reread the thread, there is one side trying to argue about the content and there's another side making permanent personal attacks.

I for one cannot watch this horrible behavior continue and leave the poor guy under such personal attack all the time.

If that means I will have to leave too, I will.

[Bill Spight]

The possible omission number (PON) is related to the strength or weakness of a group. A PON of 0 means that the group is unsettled; the attacker to play can kill, the defender to play can live. A PON of 1 means that the attacker to play can move to a position with a PON of 0. I have observed that in the opening pros generally try to make groups with a PON of at least 2.

Bill, I've heard of PON before, but have forgotten the background and certainly have no experience of it - which makes framing a sensible question about it a little difficult.

At this point, John, I expect that you are as much of an expert about PON as I am. Which isn't saying much.

But what caught my attention most was your feeling that the PON number may be coming out a bit high in the instances here, as well as your sense that pros don't like PONs below 2. My interest was because this chimed with an observation I made when looking at miai.

When I was coming up through the ranks years ago, the way the concept of miai that was used and taught among UK amateurs (the blind leading the blind, of course) was that it was OK to leave a group until it had exactly two options left. In those days virtually the only known pukka strategy was the one-weak-group strategy, and this idea of miai resonated with that. I absorbed all that and ended up with some bad habits. Talking about miai also went a bit out of fashion, so it was only relatively recently that I discovered that miai with just two options is quite rare in pro games. They seem to insist on three or more (which is similar to PON = 2+??). To give myself a crutch to think and take notes about this, I came up with the nonsense word tri-ai.

(From here on out we are talking about the actual PON, not the estimate.) A group with miai to live has a PON of 1, right? Adding another option to live yields a PON of 2, unless the opponent can destroy two options with a single play, which might be possible in some relatively undefined regions. It looks like your observation about pro games agrees with mine.

So, to come to my question, is it possible that PON is (or should be) based on measuring the safety of a group as opposed to its life? In other words, we should expect groups with high PONs because pros want to be able to respond before the group can be bullied, not just at the last possible moment to make two eyes.

IIUC, since in practice the pros rarely tenuki when the PON for the life of a group is 1, redefine the PON to make it 0 for such groups? We could do that by subtracting 1 from the PON as currently defined. That's an interesting idea, one that makes the PON a better guide to play.

----

At the time when I began studying pro games, I gave a lot of importance to sente, in the sense of the initiative. So I was quite surprised to observe the pros play reverse sente to bolster groups that could live in gote if attacked. I started doing so myself, without really understanding why. As you point out, a group with a PON of 1 can be bullied. And, as you suggest in this thread, having two groups with low PONs can be dangerous. For instance, in an attack against two groups, each with a PON of 1, the attacker might well be able to make a play that reduces the PON of each group to 0, killing one or the other. That's a good reason not to leave a group with a PON of 1 early in the game.

An exception to that rule occurs when a group is isolated, so that a double attack is unlikely to develop. Here is an illustrative game.

$$Bcm10 Increase the PON
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . , . . . . . , . . . . . X . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . 1 , . . . . . , . . . . . , . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . X . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . X X . . . . . , . . . . . , . . . |
$$ | . X O X . O . . . . . . . . . . . . . |
$$ | . O O O . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------

Click Here To Show Diagram Code

[go]$$Bcm10 Increase the PON
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . , . . . . . , . . . . . X . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . 1 , . . . . . , . . . . . , . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . X . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . X X . . . . . , . . . . . , . . . |
$$ | . X O X . O . . . . . . . . . . . . . |
$$ | . O O O . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------[/go]

Black, Yasui Chitetsu, extends to to prevent bullying, as well as to make territory.

$$Bcm22 Dosaku (W) - Chitetsu, 1674
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . X . . . . O . . . O X . . . . |
$$ | . . 9 , . . . . . , . . . O . X . . . |
$$ | . . . . . . . . . . . . . . . . X . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . 0 . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . X , . . . . . , . . . . . , X . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . 8 . . |
$$ | . . X . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . X X . . . . . , . . . O . 2 O 6 . |
$$ | . X O X . O . . . . . . O . X 3 1 4 . |
$$ | . O O O . . . . . . . . . . . . . 5 7 |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------

Click Here To Show Diagram Code

[go]$$Bcm22 Dosaku (W) - Chitetsu, 1674
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . X . . . . O . . . O X . . . . |
$$ | . . 9 , . . . . . , . . . O . X . . . |
$$ | . . . . . . . . . . . . . . . . X . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . 0 . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . X , . . . . . , . . . . . , X . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . 8 . . |
$$ | . . X . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . X X . . . . . , . . . O . 2 O 6 . |
$$ | . X O X . O . . . . . . O . X 3 1 4 . |
$$ | . O O O . . . . . . . . . . . . . 5 7 |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------[/go]

- lives in the corner. bolsters the White group and threatens the invasion at . Note that Yasui leaves his corner group with a PON of 1, as it is relatively isolated.

Later in the game, at , Dosaku uses the PON of 1 of that Black group to save his own group.

(;SZ[19]FF[3]
PW[Honinbo Dosaku]
PB[Yasui Chitetsu]
DT[1674-12-06 (Enpo 2 XI 9)]
PC[Residence of Popular Affairs Minister Matsudaira Daisuke]
OH[2]
HA[2]
RE[W+1]
US[GoGoD95]
AB[dp][pd]
;W[fq];B[cm];W[cq];B[dq];W[dr];B[cp];W[br];B[bq];W[cr];B[cj];W[qp];B[oq]
;W[mq];B[ec];W[np];B[qj];W[nc];B[oc];W[nd];B[qe];W[jc];B[qq];W[pp];B[pq]
;W[rq];B[rr];W[rp];B[sr];W[ql];B[cd];W[qh];B[oj];W[oh];B[ol];W[rj];B[qm]
;W[qk];B[pm];W[op];B[ll];W[nk];B[nl];W[mk];B[ml];W[kn];B[gp];W[jl];B[lk]
;W[fp];B[gn];W[fo];B[in];W[dm];B[dl];W[el];B[km];W[jm];B[jn];W[ko];B[hl]
;W[jj];B[jp];W[li];B[lp];W[ps];B[nr];W[mr];B[ns];W[kp];B[kq];W[mo];B[lq]
;W[kl];B[lm];W[mn];B[nh];W[jo];B[ip];W[io];B[ho];W[nq];B[pr];W[ms];B[qs]
;W[jq];B[iq];W[jr];B[ir];W[im];B[hn];W[kr];B[em];W[fm];B[dn];W[ni];B[oi]
;W[mi];B[ph];W[og];B[kj];W[ki];B[ji];W[ij];B[jh];W[hi];B[pg];W[ok];B[lr]
;W[ls];B[is];W[ks];B[bp];W[en];B[dm];W[ng];B[of];W[pf];B[qg];W[qi];B[nf]
;W[mg];B[gq];W[gr];B[fs];W[eq];B[ar];W[fk];B[gl];W[fl];B[fn];W[ei];B[eo]
;W[pi];B[qf];W[mf];B[hc];W[fd];B[fc];W[ce];B[de];W[df];B[ee];W[bd];B[cc]
;W[cf];B[di];W[eh];B[ef];W[dh];B[ch];W[bc];B[bb];W[dd];B[dc];W[hd];B[ic]
;W[id];B[jb];W[ge];B[fe];W[ib];B[hb];W[kb];B[gf];W[hf];B[hg];W[gg];B[gh]
;W[fg];B[eg];W[fh];B[dg];W[ff];B[ed];W[dj];B[ci];W[nb];B[ob];W[ja];B[ik]
;W[jk];B[rh];W[ri];B[rg];W[oa];B[pa];W[na];B[qb];W[dk];B[ck];W[gk];B[hk]
;W[hj];B[gc];W[oe];B[pe];W[ne];B[ha];W[gd];B[sq];W[sp];B[si];W[sj];B[sh]
;W[pf];B[of];W[ia]
)

[dfan]

The possible omission number (PON) is related to the strength or weakness of a group. A PON of 0 means that the group is unsettled; the attacker to play can kill, the defender to play can live. A PON of 1 means that the attacker to play can move to a position with a PON of 0. I have observed that in the opening pros generally try to make groups with a PON of at least 2.

Robert Jasiek goes into this concept in some detail in his Joseki vol. 2, though the numbers are off by one; his "0-alive" groups have a PON of 1 and his "-1-alive" groups have a PON of 0. I thought his indexing was a little funny (by symmetry you'd think you'd want the unsettled state to be represented by 0) and am glad to see that someone else counts the way I do.

[Kirby]

The PON estimate is an interesting concept. This thread is the first I had heard of it. The weighted sun is also fascinating, though, it's not immediately clear to me how the calculation related to the number of times you can tenuki and still live.

Anyway, being able to tenuki and still live is a valuable metric, but it would also be useful to quantify how much the opponent can profit by attacking you. In an extreme example, straight-4 is totally alive, but if the opponent threatens to play in the center and reduce to one eye, response is necessary (e.g. If the group is otherwise surrounded). But it's not useful for the opponent to do that outside of a Ko threat.

So I wonder if it is straightforward to include value opponent gets in attacking the group in a PON estimate.

[DrStraw]

Every time I read this thread about PON I find myself wonder what the ponic value (or is it pony) of a ponnuki at tengen would be.

[Bill Spight]

Every time I read this thread about PON I find myself wonder what the ponic value (or is it pony) of a ponnuki at tengen would be.

PON estimate = int(0.33(9 + 0.5(12) + 0.35(16) + 0.25(20)) - 1.96) = int(6.488) = 6