Endgame corner invasion examples
I am taking examples based on the lower left corner from this game of Fllecha's: viewtopic.php?f=4&t=13209
Area scoring. White komaster.
OC,
prevents an effective invasion.Evaluate the corner before
.Enjoy!
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| This 'n' that http://www.lifein19x19.com/viewtopic.php?f=12&t=12327 |
Page 13 of 53 |
| Author: | Bill Spight [ Wed May 25, 2016 9:54 pm ] |
| Post subject: | Re: This 'n' that |
Endgame corner invasion examples I am taking examples based on the lower left corner from this game of Fllecha's: viewtopic.php?f=4&t=13209 Area scoring. White komaster. OC, prevents an effective invasion.Evaluate the corner before .Enjoy!
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| Author: | Bill Spight [ Thu May 26, 2016 7:21 pm ] |
| Post subject: | Re: This 'n' that |
mongus asks how to play this kind of position. See viewtopic.php?f=11&t=13222 I have simplified it slightly. Experienced players don't often get into such positions, so this may be unfamiliar. Help mongus out. Evaluate the region inside the box. (Assume that all stones currently on the board are immortal.) Enjoy!
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| Author: | jeromie [ Thu May 26, 2016 8:58 pm ] |
| Post subject: | Re: This 'n' that |
Bill Spight wrote: Endgame corner invasion examples I am taking examples based on the lower left corner from this game of Fllecha's: http://www.lifein19x19.com/forum/viewto ... =4&t=13209 Area scoring. White komaster. OC, prevents an effective invasion.Evaluate the corner before .Enjoy! |
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| Author: | emeraldemon [ Wed Jun 01, 2016 2:45 pm ] |
| Post subject: | Re: This 'n' that |
| Author: | gamesorry [ Wed Jun 01, 2016 3:53 pm ] |
| Post subject: | Re: This 'n' that |
emeraldemon wrote: |
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| Author: | Bill Spight [ Thu Jun 23, 2016 3:26 pm ] |
| Post subject: | Re: This 'n' that |
I see that it has been almost one month since I last updated this thread. My apologies. Life happens.  I asked people to help out mongus with play in a Black box which White has penetrated. No guarantee that I have analyzed the position accurately, OC, but I'm pretty close, I think. Black to play makes the nose attachment, which was mongus's play, I believe. After  Black has 9.75 points of territory.Where is the 0.75 point? -  make one point of territory plus 0.5 point at "a". keeps Black from making any more territory here.Black has 9 pts. of territory plus half of 1.5, or 9.75 points. If the rest of the board is settled, leaving only this region for play, if Black plays first she gets 9 pts. Since there are no kos, we can take that as the maximum value for the Black territory before either side makes a play. Similarly, we can find the minimum value for the Black territory by finding the result of local play when White plays first. What is it? Enjoy!
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| Author: | mongus [ Tue Jul 19, 2016 5:54 am ] |
| Post subject: | Re: This 'n' that |
Sorry, only just noticed this. Many thanks for analysing this for me. So I think the general approach is to essentially realise that roughly half the territory has been lost and the play then focuses on building up a wall to preserve your half whilst white takes the other half. The problem with the way I was playing was that I refused to accept that I should lose any territory at all, and rather than building a barrier protecting my half, I built some swiss cheese that allowed my opponent to to infiltrate a very large majority of the space. Very enlightening, thank you. |
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| Author: | Bill Spight [ Tue Jul 19, 2016 7:29 am ] |
| Post subject: | Re: This 'n' that |
Hi, mongus. Sorry it took me so long to post that.  And I see that almost another month has gone by. {sigh} But I will revive this thread, and say a bit more about your position.
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| Author: | mongus [ Wed Jul 20, 2016 6:07 am ] |
| Post subject: | Re: This 'n' that |
Bill Spight wrote: Hi, mongus. Sorry it took me so long to post that. And I see that almost another month has gone by. {sigh} But I will revive this thread, and say a bit more about your position. No problem at all! My understanding of the game has progressed since I posted the initial thread. I don't seem to be falling into such situations quite as much as I used to. |
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| Author: | Bill Spight [ Sat Oct 22, 2016 12:28 am ] |
| Post subject: | Re: This 'n' that |
Another sporadic post, I am afraid. The logic of discovery Often a subject is taught in a "logical" manner, by starting with its elements and building up to more complex aspects. Go lends itself to such pedagogy, where beginners may learn about ladders and about living (or killing) by playing in the middle of a three point eye. But often you see learners making leaps of understanding (or sometimes misunderstanding) skipping over logical or pedagogical steps. Also, if you take a historical view of a subject, you can see ideas be discovered and usually tested against other ideas. Sometimes the new ideas prevail, sometimes they lose against traditional ideas, often they survive in modified form. This is a process of discovery and dialectic, in which the subject makes progress over time. This dialectical process is a way of learning at the level of the community of those who are interested in the subject. This history of discovery and dialectic can provide a good way for individuals to learn a subject, although it does not seem to be as popular among pedagogues as the analytical approach. |
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| Author: | globulon [ Sat Oct 22, 2016 3:59 am ] |
| Post subject: | Re: This 'n' that |
I heartily agree with you. I really like to learn about the history of ideas and I often feel I understand something much better when I can see the historical iterations it passed though. It's harder to learn this way though because as you noted it's much less popular as an approach so there doesn't tend to be books or stuff teaching in this manner. We tend to have a division between teaching and history. |
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| Author: | Bill Spight [ Sat Oct 22, 2016 8:24 am ] |
| Post subject: | Re: This 'n' that |
globulon wrote: I really like to learn about the history of ideas and I often feel I understand something much better when I can see the historical iterations it passed though. Yes, you get to see how the ideas are tested and refined, or even rejected.
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| Author: | Bill Spight [ Sun Oct 23, 2016 2:00 pm ] |
| Post subject: | Re: This 'n' that |
I thought it would be interesting to go back and look at ancient games, courtesy of GoGoD, and try to ascertain ancient ideas in the opening and see how they were modified or discarded. OC, this will involve some interpretation, and, hence, the possibility of error. Here is a partial game record dated 196 A.D. OC, it may be a later reconstruction or forgery. It illustrates some ideas that are still around.The game was played with setup stones, and White played first. It seems that the keima approach to the 4-4 stone has always been popular. And the ogeima response was popular well into the 20th century. We do not see it so much these days, but that does not mean that it is bad, or even inferior. It gives the opponent a lot of play, however.  is still joseki, albeit rarely seen. It is obviously not territorial, but aims at the bottom left corner. is a wedge, a play that is still with us, too. The wedge tells us that the ancients had the concepts of miai and of a base, as Black can form a base with a play at either "a" point. approaches , making a base at the same time. Then  makes a base. The kick,  , makes Black slightly overconcentrated, but we know that there was no concept of overconcentration until the 17th century. The kick offers some protection for the White corner.  is neither territorial nor moyo building, but takes aim at the White corner. We still have this kind of play, as well, and not just against the ogeima response, but against the one space jump and the keima, as well.  takes aim at the Black corner, and Black defends with sente. (The corner is still a bit thin, though.) Then  makes a base on the top side. approaches the top right corner. Then  is another wedge. That surprised me. Why not a pincer? gives White the opportunity to make a base with  , and with sente, as  makes a base, too. The miai seems to me to favor White. is a rather nice sacrifice, don't you think? As a result, White invades the corner and connects his stones with sente.With sente in hand, White plays the kick,  , and then plays the ogeima response.  is the last play of the opening, but I doubt if that concept had any significance to players of that time. OTOH, if White had made a base on the bottom side with , Black could have gotten the last big play of the opening with an extension on the right side. Looking at this game, and other ancient games, I think that the concept of the base had great importance then. It is still important, OC, but not so much, I think. In particular, the wedge, , is slack by today's standards, but guaranteed a base for Black on the right side. I have marked the bases made by each player in this opening. |
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| Author: | Bill Spight [ Mon Oct 24, 2016 10:13 am ] |
| Post subject: | Re: This 'n' that |
Another very old game record.  Dated 280 A.D.After the usual ogeima response, aims at the Black corner. Black does not reply passively, but plays a pincer with .White plays a counterpincer with , and after prevents the underneath connection and hems in  , White makes a base with . This maneuver looks questionable to me. If White already had the extension, , would the exchange, - , be worth it? Besides which, would White want to play as an extension after , anyway? But I think that at the time the base, - , was appealing. Gotta run. More on this game in the next note.
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| Author: | Bill Spight [ Mon Oct 24, 2016 11:58 pm ] |
| Post subject: | Re: This 'n' that |
Black now plays the pincer,  , and White plays  , a counterpincer which also makes a base. stakes a claim on the right side. It follows one heuristic for extensions that is still followed today, but violates another modern heuristic.Note that it leaves four spaces between it and the White corner. That is usual for extensions today. The reason is shown in the next diagram. The reason for leaving four spaces is that if White invades, either right away or in a fight, Black has room to make a base by extending to  .The problem is that, by leaving six spaces between and the  stone, Black leaves enough room for White to make a base, as well. Today Black would only extend as far as R-10.In the actual game White approached with  and Black made a base. This exchange is good for Black, OC, as White is overconcentrated in the bottom right corner. Note that the main consideration for seems to be that Black has miai for a base, and not that it sketches out a sphere of influence with the stone. approaches the top right corner. Black plays the kick and then . . . plays a wedge on the top side. White makes a base and Black does, too.  -  is one joseki, even today.This game, like the other one, illustrates the significance of the base in these ancient games. , like the wedge, was chosen so that Black had miai for a base.I want to present a bit more of the game record, to highlight the reading ability and fighting skill of these ancient players. Black is thin in the top right. How does White take advantage of that?  is a reducing play.  , a different kind of wedge, is quite nice, isn't it? Black has nothing better than the descent. White continues the reduction with  . takes ko ( ) is also quite good. Through  White forces Black into a low posture on the right side. Next, White solidifies his position in the top right. Black's play, starting with the kick, has been a failure. Later, Black shows his prowess by invading the White stronghold in the bottom right corner. |
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| Author: | globulon [ Tue Oct 25, 2016 9:43 pm ] |
| Post subject: | Re: This 'n' that |
I'm really enjoying your commentaries on these games. It's interesting that they are more concerned to make a base than today's players. |
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| Author: | Bill Spight [ Thu Oct 27, 2016 7:47 am ] |
| Post subject: | Re: This 'n' that |
globulon wrote: I'm really enjoying your commentaries on these games. It's interesting that they are more concerned to make a base than today's players. Well, I guess that's just the result of not having more advanced thinking about the opening. Making a base with miai was one of the best things they could see to do. In the second game White punished Black for playing a wedge on the top side instead of a pincer, but did either player see it that way? |
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| Author: | Bill Spight [ Thu Oct 27, 2016 8:57 am ] |
| Post subject: | Re: This 'n' that |
We have seen that the ancients understood the importance of making a base in the opening, although they gave it too much importance. By the logic of discovery, it should be one of the first things taught about the opening. The idea of a base is still quite important. When I was learning go, other amateurs explained the saying, Corners, sides, center, by pointing out it was easier to make territory in the corner than on the side, and easier to make territory on the side than in the center. However, Takagawa, in his Go Reader (IIRC), said that the reason was not so much about territory as that it is easiest to make a base in the corner and hardest to make one in the center. What is a base? Like a lot of go terms, it does not seem to have a precise, generally accepted definition. The prototypical base is the two space extension on the side. In Contemporary Go Terms Nam Chihyung says that a base can make two eyes if attacked. Obviously that is so for the two space extension on the side if the board is otherwise empty. And we would not call it a base if it were surrounded so that it was dead on arrival. I think that there are intermediate or unclear cases where we would still want to call it a base. Now, one of the Nihon Kiin booklets that I bought when I was 4 kyu said that a base could not be cut in two (otherwise empty board assumed). That is obviously true for the two space extension. I don't remember all the variations in the booklet, but Black can easily connect underneath, as this diagram shows. Here is another variation. However, the underneath connection may be too passive, and the booklet showed connecting over the top. is necessary if White is to cut Black in two.If Black plays at 17 she easily wins the semeai. There are other variations, OC, but the message is clear. On an otherwise empty board a base cannot be cut in two. Unfortunately, I assumed that, because a base could not be cut in two, I should never allow a base to be cut in two. That sometimes led to heavy play. The ancients knew better, as I will illustrate in the next post.
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| Author: | Bill Spight [ Sun Oct 30, 2016 1:48 pm ] |
| Post subject: | Re: This 'n' that |
This is the famous game played in the Tang dynasty for a pair of gold petaled bowls. is unusual these days, but I suppose that the sequence up to was joseki back then. makes a base. approaches it. Since White is so strong in the area, you or I might have jumped out, but Black did not. attacks the Black group.  at 21 would have been heavy. Instead, Black sacrificed the stones. Black uses the thickness built up by the sacrifice to invade White's base. White connects underneath while Black builds more thickness. The local skirmish continues.  plays kikashi, forcing Black to make an empty triangle. is tesuji, as well.White makes a base on the right side, but, since it is so close to Black's thickness, it is vulnerable to attack. The attack comes with  . White counters with  , allowing  .White plays a counterattack against the Black corner. Will we ever look at the stones the same way again?  is tesuji.Both sides run out into the center.  pushes out in a twining attack against both White groups.  is tesuji, an excellent sacrifice that allows the White corner group to escape.The battle finally ends at move 132. Then White opens a new front with an invasion of the left side. The ancients had excellent reading and fighting skills.
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| Author: | Bill Spight [ Mon Oct 31, 2016 2:13 pm ] |
| Post subject: | Re: This 'n' that |
A quick note today about my discovery of the theme of the base in ancient openings. Everyone these days knows about corners, sides, center, but it is really a modern idea, and one that was challenged by the New Fuseki. Also, it is plain that ancient players often valued sides more than corners at various points in the opening, although it has nearly always been rare to place the first stone on the side. In the games we have looked at (with the corners already occupied by setup stones) one of the first things players did was to make a base on the side. It has seemed to me that players today are stressing the sides more than they did when I was learning go. With that in the back of my mind I noticed that players in the early modern era (17th century) often made a specific base on the side, on the 3-8 and 3-11 points. I have not done a study of that base, but it still occurs today, although not very frequently. We have seen it in these very ancient games when a player played on the 3-11 point with the 3-8 point as a miai point to make a base. In the early modern era players often made the base with no provocation at all. OC, making this base would usually be slow by today's standards.
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