This 'n' that

Bill Spight · Post by **Bill Spight** » Wed Nov 04, 2015 6:03 pm

A couple of bridge anecdotes

A brief snippet of a conversation that I overheard between two bridge partners after a tournament in Albuquerque:

Partner A: I got that bid from Marshall Miles. You know, the guy who wrote All 50 Cards.

Partner B: I always knew you weren't playing with a full deck.

----

It is not unusual in bridge for the declarer to show his hand and declare how many tricks he will make. But occasionally a defender can make a declaration. He cannot show his hand to his partner, but shows it to the declarer.

At a tournament in Arizona my partner and I were playing against a couple who had the classic farmers' look. The husband was tall and gaunt, with a prominent Adam's apple; the wife was a stocky 5' by 5'. The husband was declarer at a contract of Two Diamonds and at trick eight or nine my partner claimed to defeat the contract by two tricks. The declare agreed. At this point his wife piped up: "We'll play it out." Firmly.

I said to her, "He's the declarer." Meaning that it was his decision to make whether to agree with my partner's declaration. (As dummy she had no say in the matter -- although in rare cases she could appeal the result later.)

She replied, "He's my husband and he'll do what I say."

We played the hand out.

Bill Spight · Post by **Bill Spight** » Thu Nov 05, 2015 12:05 am

Territory in the Capture Game

I have mentioned a number of times how the concept of territory is implicit in the capture game. Once the dame are filled, the game can be scored in terms of territory and the winner determined without playing the game out. However, territory in the capture game is not exactly the same as territory in regular go.

Click Here To Show Diagram Code: [go]$$B Equal territory $$ ----------- $$ | . O . X . | $$ | . O . X . | $$ | . O . X . | $$ | . O . X . | $$ | . O . X . | $$ -----------[/go]

By symmetry it is plain that each player has the same amount of territory, but the dame are still unfilled.

Click Here To Show Diagram Code: [go]$$B Filling the dame $$ ----------- $$ | . O 3 X . | $$ | . O 2 X . | $$ | . O 1 X . | $$ | . O 4 X . | $$ | . O 5 X . | $$ -----------[/go]

After the dame are filled each player has three safe moves left. Each of those moves is a point of territory. That means that the group tax applies to territory in the capture game. Many people think that the group tax only applies to stone counting, but that is not so. The net score is 0, which means that the second player wins. Since it is White's turn, Black wins.

Click Here To Show Diagram Code: [go]$$Wm6 Playing out the game $$ ----------- $$ | 3 O X X 4 | $$ | . O O X . | $$ | 1 O X X 2 | $$ | . O O X . | $$ | 5 O X X 6 | $$ -----------[/go]

After

White can resign.

In the next example White has surrounded more empty points than Black, but neither player has any territory.

Click Here To Show Diagram Code: [go]$$B No territory $$ ----------- $$ | . O . O O | $$ | X X O . . | $$ | . X O . . | $$ | . X O O O | $$ | . X X X X | $$ -----------[/go]

Click Here To Show Diagram Code: [go]$$B Black wins $$ ----------- $$ | 1 O 2 O O | $$ | X X O . . | $$ | . X O . . | $$ | 3 X O O O | $$ | . X X X X | $$ -----------[/go]

is like a dame. Because of the group tax, Black has no territory. OTOH, if White played at 3 the result would be seki, with no territory for either player.

After :b3:

the net score is 0, as the White eye is seki, with no territory for either player. Since it is White's turn, Black wins.

Click Here To Show Diagram Code: [go]$$B Continuation $$ ----------- $$ | X O O O O | $$ | X X O . 4 | $$ | . X O 5 . | $$ | X X O O O | $$ | . X X X X | $$ -----------[/go]

If

,

maintains the seki. White can resign.

The fact that the White eye on the right is seki instead of dead is because Black cannot sacrifice enough stones to roll up the eye. In Capture 7 Black could possibly roll up the eye.

Bill Spight · Post by **Bill Spight** » Fri Nov 06, 2015 8:27 am

Cats and Dogs

On Monday I attended an interesting talk by Professor Jorge Nuno Silva of the University of Lisbon. He heads a program for the use of intellectual games in the Portuguese schools. One of the games he showed us is Cats and Dogs, in which one player's pieces are cats and the other player's pieces are dogs. In his video these were cartoon characters. The players start with an empty board and take turns placing pieces on the squares of the board. A player may not play a piece rookwise adjacent to an opponent's piece. The first player without a move loses.

OC, it is easy to play Cats and Dogs as a form of no pass go. And yes, it has a form of territory.

Click Here To Show Diagram Code: [go]$$B Equal territory $$ ----------- $$ | . O . X . | $$ | . O . X . | $$ | . O . X . | $$ | . O . X . | $$ | . O . X . | $$ -----------[/go]

In this diagram each player has 5 points of territory for a net score of 0. Neither player can play on the center line, so those points are not dame. Black to play must start filling in his own territory, so White wins.

Click Here To Show Diagram Code: [go]$$B Game 1 $$ ----------- $$ | . 2 . 1 . | $$ | . 8 a . . | $$ | 6 . 7 . 5 | $$ | . b 9 . . | $$ | . 4 . 3 . | $$ -----------[/go]

and "a" together may be said to form a dame, as do :b9:

and "b".

After :b9:

the players can stop the game and count the territory.

Click Here To Show Diagram Code: [go]$$B Black +3 $$ ----------- $$ | C 2 . 1 C | $$ | C 8 . C C | $$ | 6 . 7 C 5 | $$ | C . 9 C C | $$ | C 4 . 3 C | $$ -----------[/go]

Each player's territory consists of empty points upon which she can play but her opponent cannot. As indicated, Black has 7 points of territory and White has 4 points, for a net score of 3 points for Black.

This concept of territory is different from that of regular go, as territory does not have to be surrounded. Cats and Dogs uses a form of proximity scoring. See http://senseis.xmp.net/?ProximityScoring .

Click Here To Show Diagram Code: [go]$$B Game 2 $$ ----------- $$ | . 2 . 1 . | $$ | . . . . . | $$ | 7 . 6 . 5 | $$ | . . . . . | $$ | . 4 . 3 . | $$ -----------[/go]

In this game White tries :w6:

to prevent Black from playing there, but Black counters with :b7:

.

Click Here To Show Diagram Code: [go]$$Wm8 B +3 $$ ----------- $$ | C O . X C | $$ | . 1 . 4 C | $$ | X . O . X | $$ | 2 . 3 . C | $$ | . O . X C | $$ -----------[/go]

and

are miai, and then :w10:

and

are dame. I have marked the territory. Black still wins by 3.

Edit: Another variation.

Click Here To Show Diagram Code: [go]$$B Game 3 $$ ----------- $$ | . 2 . 1 . | $$ | 7 . 9 . . | $$ | . 6 . . 5 | $$ | . 8 0 . . | $$ | . 4 . 3 . | $$ -----------[/go]

This time White tries :w6:

, which also prevents Black from playing on tengen. :b7:

invades. Then :w8:

makes 2 points of territory, as does :b9:

. Black wins by 4 points, as the reader may verify.

gowan · Post by **gowan** » Fri Nov 06, 2015 8:31 am

Interesting game. Has it been analyzed combinatorially?

Bill Spight · Post by **Bill Spight** » Fri Nov 06, 2015 8:49 am

gowan wrote:Interesting game. Has it been analyzed combinatorially?

The video Dr. Silva showed just gave us a taste of the game. There are several games that students play during their education, and there is a rotation, so that not every game is taught each year. The dame correspond to STARS in CGT, and the scoring is surely as I have indicated, but they may not use the term, territory. In both games :b7:

has a temperature of 3, and I expect that the students learn about temperature.

I do not know if more complicated infinitesimals have been discovered.

BTW, I spoke briefly with Silva and asked about go. He said that they tried introducing go into the rotation, but the teachers did not understand ending the game with passes. They may try introducing the Capture Game in the near future.

I have edited the previous note to add a third variation.

vier · Post by **vier** » Fri Nov 06, 2015 4:40 pm

gowan wrote:Interesting game. Has it been analyzed combinatorially?

It is easy to analyze the 1 x n game. I think the scores of the n x n game are 1, 0, 2, 0, 2 for n = 1, 2, 3, 4, 5.

Bill Spight · Post by **Bill Spight** » Sat Nov 07, 2015 10:50 am

My early bridge career

I learned to play bridge when I was six years old, but did not play much until I was thirteen. That was because other kids did not know how to play bridge, and the local duplicate bridge club met on Thursday nights, a school night. But I played a lot of Oh Hell, which is similar to bridge and whist. I did not start studying bridge until I was twelve.

In those days contract bridge was in its infancy, and the general level of technique was not very high. The hallmark of an expert then was said to be the ability to run a squeeze play. I ran my first one at age thirteen. It was on defense. I put my partner in to run her suit, which squeezed the declarer. I was the only one at the table who understood what had happened. When I was fourteen the local life master said that I was the best player in the club at the play of the hand, but the worst bidder.

When I arrived in Japan I looked up the local duplicate club in Tokyo. The had a game on Tuesday night. I called them up and spoke to a guy named Joe Montalto, who was one of the top level players in Japan at that time, though I did not know that, of course. He said that he would play with me unless another walk-in arrived. We won, and I recall that we defeated a two diamond contract by six tricks for a top score on that hand. He criticized my play on that hand, which surprised me because 1) it worked, and 2) we got a very good result.

I started playing frequently at the club, which had a game every afternoon and some nights. I played to make the local life masters look foolish, which was not a very good attitude, I am afraid.

I played a lot with Yetta Graeler, who was the wife of the concert master of the NHK orchestra, Louis Graeler.

One day Joe asked me to play with him that coming Sunday afternoon. On one hand I played a trump squeeze, which I thought nothing about, but Joe was suitably impressed.

After the game he told me that he was thinking about asking me to join his team, and that if I was amenable, there was a tournament the next month that we could play in and he would decide after that. Of course I agreed, and we got together socially with the rest of his team that evening. BTW, Joe was very good at the play of the cards. It was said that he could play the hand one trick better than everybody else, but unfortunately, he overbid by two tricks.

One member of Joe’s team was Lou Schaefer, the Philippina wife of an American Colonel. There was another guy at the club, Kunio, who was a couple of years older than I. Lou used to tell people that we were her sons. She said, “I had Kuni when the Japanese invaded, and Bill when the Americans came back.”

After the initial team get together Lou took me aside and told me to ignore Joe’s criticisms. “He criticizes everybody,” she said. It soon became apparent that Joe was asking me to possibly join his team because his teammates were tired of his constant criticism, and no longer wanted to be his partner. On the team they would play at the other table.

Joe and I played often in the weeks before the tournament, and his constant criticism was wearing. The trouble is, he was often right, or his critiques fell into a gray area that you could argue with. I never did. Yetta was also hypercritical, but she was not in Joe’s league, and it was easy to sluff off her complaints. Later, in New Mexico I also played with a woman who was also hypercritical, but she never criticized me. One player dubbed us Spight and Malice.

(What is it with these hypercritical bridge partners? Bad karma?)

In those days Japanese tournaments were one day affairs, as the Japan Contract Bridge League did not have a whole lot of players. Early in the first session Joe criticized my play on the previous hand. But this time there was no gray area, his analysis was simply wrong. I saw my chance and I took it. I set my cards face down on the table and said, “Joe, you are wrong and you know it.” Then I got up and went to the men’s room. I waited around for a couple of minutes and then returned to the table. We finished the round in silence, except for the talk necessary to play the game. Later I told Lou and she said, “You said that to Joe Montalto?!” Joe never criticized me again.

A couple of months later he remarked to someone, “Bill is a fine young player, but temperamental.”

About six months after I arrived in Japan Yetta's son Johnny came back from Czechoslovakia. He is the 5 kyu who got me started playing go and was my first teacher. We played once a week, and sometimes more often, for about 11 months.

Bill Spight · Post by **Bill Spight** » Wed Nov 11, 2015 7:45 pm

Evaluation through (hypothetical) play in the environment

We have already seen how we might evaluate plays in special, ideal environments, such that each player is indifferent whether to make the play or to play in the environment. These environments are special only in the sense of being engineered to produce exact results. But they are meant to mimic normal conditions on the go board. A randomly chosen environment from real games would produce approximately the same results.

We have also seen how environments consisting only of duplicate positions can be used to evaluate them.

We have also seen how an environment of plays that lose one point by territory scoring can be used to score local positions. A key point is that each side must make the same number of plays; otherwise the first player loses one point — or more if free passes are allowed.

We can also evaluate non-terminal plays in a similar fashion. The logic is simple. If Player A makes a play that gains X points and then the other player, Player B, makes a play in another position that gains X points, the value of the combination of positions remains the same. Let’s use that idea to evaluate the following position.

Click Here To Show Diagram Code: [go]$$ Outer stones alive $$ . . . . . . . $$ . X X X X X . $$ . . O . O . . $$ . . O B O . . $$ . . O B O . . $$ . . O . O . . $$ . . O O O . . $$ . . . . . . .[/go]

Now, experienced players know that we evaluate this corridor as 2.5 points of territory for White. Let’s derive that from hypothetical play in an environment.

Click Here To Show Diagram Code: [go]$$W White first $$ . . . . . . . $$ . X X X X X . $$ . . O 1 O . . $$ . . O B O . . $$ . . O B O . . $$ . . O . O . . $$ . . O O O . . $$ . . . . . . .[/go]

elsewhere

Let us assume that the play elsewhere, in the environment, gains t points for either player and its local value is 0. (We use t for historical reasons.) Locally White gets 5 points and Black gets t, for a result of t - 5, from Black’s point of view. (By convention we take Black’s point of view.)

Click Here To Show Diagram Code: [go]$$B Black first $$ . . . . . . . $$ . X X X X X . $$ . . O 1 O . . $$ . . O B O . . $$ . . O B O . . $$ . . O . O . . $$ . . O O O . . $$ . . . . . . .[/go]

elsewhere

Now the result is 0 - t = -t.

If the result is the same regardless of who plays first, then we have the equation,

t - 5 = -t

and so

t = 2.5.

Each play gains 2.5 points.

Furthermore, the value of the local position is -2.5, as advertised.

Bill Spight · Post by **Bill Spight** » Thu Nov 12, 2015 11:58 am

Evaluation through (hypothetical) play in the environment, II

Now let’s evaluate a position with a follower.

Click Here To Show Diagram Code: [go]$$ Outer stones alive $$ . . . . . . . $$ . X X X X X . $$ . . O . O . . $$ . . O B O . . $$ . . O . O . . $$ . . O B O . . $$ . . O O O . . $$ . . . . . . .[/go]

Even experienced players might have to think a bit to evaluate this corridor.

Click Here To Show Diagram Code: [go]$$W White first $$ . . . . . . . $$ . X X X X X . $$ . . O 1 O . . $$ . . O B O . . $$ . . O . O . . $$ . . O B O . . $$ . . O O O . . $$ . . . . . . .[/go]

elsewhere

As before, White gets 5 points locally and Black gets t0, for a result of t0 - 5, from Black’s point of view. (I use t0 because we are going to find another environmental value for the follower.)

Click Here To Show Diagram Code: [go]$$B Black first $$ . . . . . . . $$ . X X X X X . $$ . . O 1 O . . $$ . . O X O . . $$ . . O . O . . $$ . . O B O . . $$ . . O O O . . $$ . . . . . . .[/go]

elsewhere

Now the result is v1 - t0, where v1 is the value of this follower.

Experienced players know that v1 = -1, and that t1 = 1. Black to play saves the :bc:

stone for a local score of 0, and White to play captures it for a local score of -2. Each play gains 1 point.

For the original position we have the equation,

t0 - 5 = —1 - t0

and so

t0 = 2.

Each play gains 2 points.

The value of the local position is -3.

Bill Spight · Post by **Bill Spight** » Fri Nov 13, 2015 7:59 am

Evaluation through (hypothetical) play in the environment, III

Now let’s evaluate a slightly different position.

Click Here To Show Diagram Code: [go]$$ Outer stones alive $$ . . . . . . . $$ . X X X X X . $$ . . O . O . . $$ . . O . O . . $$ . . O B O . . $$ . . O B O . . $$ . . O O O . . $$ . . . . . . .[/go]

This is obviously a sente, but let’s not start with that idea.

Click Here To Show Diagram Code: [go]$$W White first $$ . . . . . . . $$ . X X X X X . $$ . . O 1 O . . $$ . . O . O . . $$ . . O B O . . $$ . . O B O . . $$ . . O O O . . $$ . . . . . . .[/go]

elsewhere

As before, White gets 5 points locally and Black gets t0, for a result of t0 - 5.

Click Here To Show Diagram Code: [go]$$B Black first $$ . . . . . . . $$ . X X X X X . $$ . . O 1 O . . $$ . . O . O . . $$ . . O B O . . $$ . . O B O . . $$ . . O O O . . $$ . . . . . . .[/go]

elsewhere

Now the result is v1 - t0, where v1 is the value of this follower.

Experienced players know that v1 = -2, and that t1 = 2. Black to play saves the :bc:

stones for a local score of 0, and White to play captures them for a local score of -4.

For the original position we have the equation,

t0 - 5 = —2 - t0

and so

t0 = 1.5.

Wait! t1 > t0 (2 > 1.5). That means that White’s reply gains more than t0, so White will reply instead of playing elsewhere. :b1:

is sente.

Click Here To Show Diagram Code: [go]$$B Black sente $$ . . . . . . . $$ . X X X X X . $$ . . O 1 O . . $$ . . O 2 O . . $$ . . O B O . . $$ . . O B O . . $$ . . O O O . . $$ . . . . . . .[/go]

The result after :w2:

is -4. That gives us this equation.

t0 - 5 = -4

and so

t0 = 1.

The reverse sente play gains 1 points.

The value of the original position is -4.

Note that we could have started with the assumption that the play was sente and confirmed that by the fact that t1 > t0 (2 > 1).

There is another way that we could have figured out that this was a Black sente, one I often used way back before I found out about solving for t0 and t1. I calculated the value of the position after :b1:

, which is -2 and used that to calculate the value of the original position as if it were gote. That comes to -3.5. The value if it is a Black sente is -4. White would certainly prefer it to be -4, and therefore will make it sente by replying to :b1:

.

As simple as the material in this note may seem, it is very important for understanding local sente and gote. It illustrates why we call this a one point sente. Not because, as it sounds, the sente gains 1 point, but because it tells us when each player is indifferent between playing locally or playing in the environment. (OC, in a non-ideal environment that may not be the case.

) It is the reverse sente that gains 1 point.

It also illustrates why we say that the sente player has the privilege of playing the sente. When plays in the (ideal) environment gain less than 2 points and more than 1 point, Black may play locally with sente, while White has to wait until the plays in the environment gain 1 point or less.

It also illustrates why we say that sente gains nothing. The reverse sente gains 1 point with a play to a value of -5, which means that the original value is -4, the same as after Black’s sente and White’s reply.

The material in this note is also important because it shows us how to distinguish between local sente and gote. As I said, that was something that was never explained to me when I was learning. I had to figure it out for myself. Probably that was because there are other meanings of sente and gote, and so there was some confusion among the writers about their meaning. Before I figured out how to tell the difference, I did what I think most players do, I made an educated guess about whether a play was sente or gote and did the calculations accordingly. With some experience, that usually works, or the errors are small.

However, the calculated values in yose books are often wrong, and sometimes the lines of play are wrong, or if they are not wrong from the point of view of tesuji, they give the wrong impression of when to play elsewhere. I show an example on Sensei’s Library. here ( http://senseis.xmp.net/?YoseErrorsInMagicOfGo ) and here ( http://senseis.xmp.net/?TenukiIsAlwaysAnOption ). Very often the calculations are wrong because the play is misidentified as sente or gote. That suggests that the writer (often a strong amateur ghost writer) did not check, or did not know how to check. Now you do.

Even if the textbooks often get it wrong, that does not mean that strong players do. I remember once figuring out that a play that the textbooks said was sente was actually gote, and the next day I was playing over one of Sakata’s games, I think with Fujisawa Hideyuki, and the play came up. They played it as gote.

Bill Spight · Post by **Bill Spight** » Sat Nov 14, 2015 11:30 am

Sente or gote?

Click Here To Show Diagram Code: [go]$$ Outer stones alive $$ . . . . . . . $$ . . X X X . . $$ . . X . X . . $$ . . O X O . . $$ . . O X O . . $$ . . O O O . . $$ . . . . . . .[/go]

This kind of play has been described in the literature in two ways, as either a 1 point sente or a 2 point gote (by swing values). Let’s analyze it in terms of play in an environment with temperature 1, which fits either case.

Click Here To Show Diagram Code: [go]$$B Black first $$ . . . . . . . $$ . . X X X . . $$ . . X 1 X . . $$ . . O X O . . $$ . . O X O . . $$ . . O O O . . $$ . . . . . . .[/go]

elsewhere

The local result is 0, and the net result after :w2:

is -1, as advertised.

Next let’s look at it as a White sente.

Click Here To Show Diagram Code: [go]$$W White sente $$ . . . . . . . $$ . . X X X . . $$ . . X 1 X . . $$ . . O B O . . $$ . . O X O . . $$ . . O O O . . $$ . . . . . . .[/go]

takes back at :bc:

The result is -1. Sente gains nothing.

Click Here To Show Diagram Code: [go]$$W White gote $$ . . . . . . . $$ . . X X X . . $$ . . X 1 X . . $$ . . O B O . . $$ . . O B O . . $$ . . O O O . . $$ . . . . . . .[/go]

takes the

stones, leaving

Click Here To Show Diagram Code: [go]$$W White gote, ii $$ . . . . . . . $$ . . X X X . . $$ . . X W X . . $$ . . O . O . . $$ . . O . O . . $$ . . O O O . . $$ . . . . . . .[/go]

The

stone is en prise. Now we know already that this position is gote with a play gaining 1 point. Let’s continue play at temperature 1.

Click Here To Show Diagram Code: [go]$$W White gote, iii $$ . . . . . . . $$ . . X X X . . $$ . . X O X . . $$ . . O 3 O . . $$ . . O C O . . $$ . . O O O . . $$ . . . . . . .[/go]

,

elsewhere

After :b2:

, unlike with prototypical gote, the play at temperature 1 is not over. So White connects at 3.

White has two points for the captured stones plus one point of territory (marked), and Black has two points elsewhere, for a net result of -1.

White does not have the privilege of playing :w1:

with sente. OTOH, Black may will reply to :w1:

as it does not lower the local temperature, so it will often be played with sente. Sente or gote?

For a long time I did not care.

Then for a while I leaned towards sente. But without privilege, Black could often get the reverse sente in normal play. Finally I admitted that it lies on the cusp of sente and gote, and introduced the new classification of ambiguous. Also, I realized that other kinds of plays could be ambiguous, those in which a player had the privilege of playing one option with sente or playing another with gote, leading to the same evaluation. See http://senseis.xmp.net/?AmbiguousPosition on Sensei’s Library.

Bill Spight · Post by **Bill Spight** » Sun Nov 15, 2015 9:26 pm

The reverse

Click Here To Show Diagram Code: [go]$$ Outer stones alive $$ . . . . . . . $$ . . X X X . . $$ . . X . X . . $$ . . O . O . . $$ . . O B O . . $$ . . O O O . . $$ . . . . . . .[/go]

I’m getting a lot of mileage out of these short corridors, aren’t I?

I suppose that an inexperienced player might look at this position and just see a dead Black stone. Let’s look more closely.

Click Here To Show Diagram Code: [go]$$W White first $$ . . . . . . . $$ . . X X X . . $$ . . X . X . . $$ . . O 1 O . . $$ . . O X O . . $$ . . O O O . . $$ . . . . . . .[/go]

elsewhere

Result: t0 - 2

Click Here To Show Diagram Code: [go]$$B Black first $$ . . . . . . . $$ . . X X X . . $$ . . X . X . . $$ . . O 1 O . . $$ . . O B O . . $$ . . O O O . . $$ . . . . . . .[/go]

moves to the position in the previous note. We already know that

v1 = -1 and

t1 = 1.

On the assumption that :b1:

is gote, we have

t0 - 2 = -1 - t0

and so

t0 = 0.5

In that case, t1 > t0, so play continues at temperature 1.

Click Here To Show Diagram Code: [go]$$B Black first $$ . . . . . . . $$ . . X X X . . $$ . . X 2 X . . $$ . . O 1 O . . $$ . . O B O . . $$ . . O O O . . $$ . . . . . . .[/go]

takes back at 1, :w4:

elsewhere

The local score is -1, so we still have t0 = 0.5, and the original count is -1.5. The play by White gains 0.5, and the sequence, :b1:

-

,

, also gains 0.5. We consider that sequence as a unit.

Experienced players are familiar with sequences of play that end in gote that are played as a unit. However, there is not yet a generally accepted term for those sequences. Combinatorial game theory calls :b1:

in this position a reversible play, so I propose to call the gote sequence a reverse.

Here are a couple of other examples.

Click Here To Show Diagram Code: [go]$$B Honinbo Shusai Meijin (w) vs. Go Seigen (3 stones) $$ --------------------------------------- $$ | . . . . . . . 3 1 2 . O O X . . . X . | $$ | . X X . . . X X O O O O X X . X X O . | $$ | . O X . X X X O O X X . X . . X O O O | $$ | . . O X . O O X O , . . X . . X X X O | $$ | . . O X . X . X O X X O O X X . . O . | $$ | X X X . O . X . O . X O O O O . O . . | $$ | X O X . O X X X O O X X O X X O . O . | $$ | O O X X X O X O O X X O O X . X O . O | $$ | . O X . O O O O . O O X X X X X X O . | $$ | . O X , O X O X O , X O O O X X X X O | $$ | . . O X O X O X O . . O . O X . . X . | $$ | . . O X X X O . . . . . O O O X X . X | $$ | . O X X O O O O . . . O X X O X X X . | $$ | . . O X X X O . O . . O X O . O O X . | $$ | . O O X . X O O X O O X X O . . O X . | $$ | . O X X . O X X X , O . X X X X X . . | $$ | . . O X . O X . X O . O X O O O X . . | $$ | . . O O X O X . X O O . O . . O O X X | $$ | . . . O X X . 5 4 6 . . . . . . . O . | $$ ---------------------------------------[/go]

Here are the final plays from a three stone game between Shusai and Go Seigen in 1929. :b1:

-

and

-

are both reverses called hane-and-connect. Each reverse gains 1 point.

Click Here To Show Diagram Code: [go]$$B Honinbo Retsugen (W) vs. Yasui Chitoku $$ --------------------------------------- $$ | . . . . . . X O O O . . . . O X . . . | $$ | . . . . . . X X O . O . . . O X X . . | $$ | . . . X X X . X X O O . . . O X . X . | $$ | . X X O X O O X X X O . . O O X X . . | $$ | . X O O O . O X . O O . O . O X . . X | $$ | X O O X X . O O X O X . O . O X X X O | $$ | X . O . . O . . X X O . O O . O O O O | $$ | X O O X X X O . X O O O X O O . . X O | $$ | . X X X O . O . . O X X X X X X X X O | $$ | . . X X O . O X X X O . . X O O O O . | $$ | X X O X X O X O . X X X . X X O O . . | $$ | X O O O O O X X X . . X X O O X X O . | $$ | X X O . O X X O . . O X O X O . . . . | $$ | X O O . O O O X X X X O O X . . O O . | $$ | O . . O X X X X X O . O O O O O O X O | $$ | . . . O X X O O X O . O X X X X O X . | $$ | . O . O X O . O X O . X . . . X X . X | $$ | . . O . X O O O O O X X X . . . . X . | $$ | . 2 1 3 X X O . . O O O X . . . . . . | $$ ---------------------------------------[/go]

Here are the final three moves from a castle game between Honinbo Retsugen and Yasui Chitoku in 1802. This is a common reverse to gain 0.5 point.

Click Here To Show Diagram Code: [go]$$W Honinbo Genjo (W) vs. Yasui Chitoku $$ --------------------------------------- $$ | . . X O . . . . . . . . . X . . . . . | $$ | . X X O . . . . . . . O X . X . . . . | $$ | . X O O . O O O . O O O O X X . . . . | $$ | . X O , O X X O . , X X X . . , X . . | $$ | X X X . X X O X X X . . . X . . . . . | $$ | . O X X X O O O X O O . O . . X . . . | $$ | . O O O O . . X . X O . O X X O X . . | $$ | . . . . . . O X X X O . . O O O X . . | $$ | . O O . O . O O . O . . . O O X X . . | $$ | . O X O . X O X O , . . O X O , X . . | $$ | O O X . O O X X X O . X O X O X . X . | $$ | O X X . O X X X X . O O O X X . X O . | $$ | X . X O . O X . X O . . X X X X X O . | $$ | . X . X O . O X . X O O X O . X O . . | $$ | . . . X O O . . X X O X O O 5 X O . . | $$ | . . X , O X O . X O X X 4 2 1 X O . . | $$ | . . . X O . O . X . X O O 3 X O X O . | $$ | . . X X O . . O X X X X O . O O . . . | $$ | . . X O O . . . . . . O . . . . . . . | $$ ---------------------------------------[/go]

From another Chitoku game in 1802. :w1:

-

is a 5 move reverse that gains 1.5 points.

Here is Black's play.

Click Here To Show Diagram Code: [go]$$B Black's gote $$ --------------------------------------- $$ | . . X O . . . . . . . . . X . . . . . | $$ | . X X O . . . . . . . O X . X . . . . | $$ | . X O O . O O O . O O O O X X . . . . | $$ | . X O , O X X O . , X X X . . , X . . | $$ | X X X . X X O X X X . . . X . . . . . | $$ | . O X X X O O O X O O . O . . X . . . | $$ | . O O O O . . X . X O . O X X O X . . | $$ | . . . . . . O X X X O . . O O O X . . | $$ | . O O . O . O O . O . . . O O X X . . | $$ | . O X O . X O X O , . . O X O , X . . | $$ | O O X . O O X X X O . X O X O X . X . | $$ | O X X . O X X X X . O O O X X . X O . | $$ | X . X O . O X . X O . . X X X X X O . | $$ | . X . X O . O X . X O O X O . X O . . | $$ | . . . X O O . . X X O X O O 5 X O . . | $$ | . . X , O X O . X O X X 4 3 2 X O . . | $$ | . . . X O . O . X . X O O 1 X O X O . | $$ | . . X X O . . O X X X X O 6 O O . . . | $$ | . . X O O . . . . . . O . . . . . . . | $$ ---------------------------------------[/go]

at 2.

Note that this is also a reverse.

Reverses are fairly common, and recognizable. But sometimes they can fool even an experienced calculator. I have seen it happen. I do not recall ever getting caught, myself, but way back when I paid more attention to the count than the local temperature, and I probably did goof once or twice.

Bill Spight · Post by **Bill Spight** » Wed Nov 18, 2015 4:39 pm

Here is a study based on my research way back when.

Black to play. 6.5 komi.

Comments?

Enjoy!

Shaddy · Post by **Shaddy** » Wed Nov 18, 2015 5:08 pm

What's the ruleset?

Bill Spight · Post by **Bill Spight** » Wed Nov 18, 2015 5:17 pm

Shaddy wrote:What's the ruleset?

Territory.

Life In 19x19

This 'n' that

Re: This 'n' that

Re: This 'n' that

Re: This 'n' that

Re: This 'n' that

Re: This 'n' that

Re: This 'n' that

Re: This 'n' that

Re: This 'n' that

Re: This 'n' that

Re: This 'n' that

Re: This 'n' that

Re: This 'n' that

Re: This 'n' that

Re: This 'n' that

Re: This 'n' that