AGA rules and cultural barriers

snorri · **#41**

xed_over wrote:

HermanHiddema wrote:

The point was that this is, IMO, a weakness of area scoring rules.

Sure, I don't disagree this point.

I do disagree. I think Herman's example is misleading people to think that inferior play is somehow allowed under this position under AGA rules but not under Japanese rules. In fact, with odd komi, as is appropriate for the comparison, inferior or superior play for black with respect to choosing to make a point or play a dame has the same effect in both AGA and Japanese rulesets.

If you want to play a Edo-era style jubango with your rival and use komi = 0, allowing jigo, by all means use Japanese rules. You should also set seiza style, etc. I intend to do this myself whenever I get a suitable opponent and someone to serve the tea.

AGA rules do have that weakness that Herman mentions for that situation.

But for situations where the goal is to determine the winner, the position posted is a red herring.

snorri · **#42**

mhlepore wrote:

Click Here To Show Diagram Code: [go]$$B white to play $$ +-----------+ $$ | . . X X X | $$ | O X X X . | $$ | O O O X . | $$ | . O O X . | $$ | O . O X . | $$ +-----------+[/go]

Suppose for the sake of argument:
1) there are no prisoners
2) komi in this game = 1.5.

My understanding is that White's ability to throw in at the 1-2 point is relevant in certain rulesets but not others.

The "elegance" of one ruleset over another in these situations is interesting only to rules buffs. Strong players from a variety of countries seem to just want to play Go.

I remember years ago the Seattle Go Center having monthly tournaments where we played rated games but we did not have the White passes last requirement. Everyone was always thankful to her that when it was announced, regardless of its impact on the territory vs. area scoring equivalence.

Thanks for using komi = 1.5. This example is a true difference. Under Japanese rules, white has no way to win this game. Under AGA rules, white can make the ko and win it, forcing black to either play in his own territory or pass one more stone than white, leading to W+0.5. White can win with the same strategy under Chinese rules. Anyone know how to post a 5x5 sgf, BTW?

Edit: fixed SGF

jts · **#43**

I suspect that it's a problem with our sgf tags rather than with Eidogo, since Eidogo is able to host 9x9 and 13x13 games.

ez4u · **#44**

I think eidogo can not handle a 5X5 game (SZ[5] tag). Cgoban chokes on the original file that I downloaded from post #42 since it contains two SZ tags (both SZ[5]). Removing either one with a text editor allowed Cgoban to handle it properly. Drago ignored the duplication and ran the original file correctly. Eidogo could not handle the file as a 5X5 game regardless of what I did with it.

RobertJasiek · **#45**

These late game ko examples are not specific to AGA Rules or culture, but a general feature of area scoring strategy:

http://home.snafu.de/jasiek/kodame.pdf

HermanHiddema · **#46**

snorri wrote:

You didn't state the komi.

Remember that when comparing area rules to territory rules, it's important to apply odd komi. With komi = -0.5 or 1.5, with either Japanese rules or AGA rules, either black wins or white wins. To be specific, if komi=-0.5, black wins even when playing the "inferior" move of a dame instead of making an eye in the corner in both rulesets, and when komi=1.5, white wins even if black plays the intuitively optimal move, in both rulesets.

snorri wrote:

I do disagree. I think Herman's example is misleading people to think that inferior play is somehow allowed under this position under AGA rules but not under Japanese rules. In fact, with odd komi, as is appropriate for the comparison, inferior or superior play for black with respect to choosing to make a point or play a dame has the same effect in both AGA and Japanese rulesets.

If you want to play a Edo-era style jubango with your rival and use komi = 0, allowing jigo, by all means use Japanese rules. You should also set seiza style, etc. I intend to do this myself whenever I get a suitable opponent and someone to serve the tea.

AGA rules do have that weakness that Herman mentions for that situation.

But for situations where the goal is to determine the winner, the position posted is a red herring.

I don't get what you are getting at here at all.

Sure I can define a komi where there is no difference in game outcome. If I define komi = 6.5 for black, black could pass and win, but what is the point of that?

The situation simply shows a position where a set of moves result in the same score for area rules, but in different scores for territory rules. You can construct such a position for any komi, odd or even, whole or fractional, in such a way that it makes a difference.

hyperpape · **#47**

I think the point is that area scoring only works properly with certain values of komi, and that under those values of komi, there are fewer differences between it and territory scoring.

RobertJasiek · **#48**

hyperpape wrote:

area scoring only works properly with certain values of komi,

Area scoring works properly under each komi value, but the relation between area scoring and territory scoring works better under standard area komi than under other komi values.

Quote:

and that under those values of komi, there are fewer differences between it and territory scoring.

Do you mean that more often the winner is the same (area scoring with standard area komi versus territory scoring with standard area komi) or do you mean something else?

HermanHiddema · **#49**

hyperpape wrote:

I think the point is that area scoring only works properly with certain values of komi, and that under those values of komi, there are fewer differences between it and territory scoring.

Well that is just not true. :scratch:

hyperpape · **#50**

RobertJasiek wrote:

hyperpape wrote:

area scoring only works properly with certain values of komi,

Area scoring works properly under each komi value, but the relation between area scoring and territory scoring works better under standard area komi than under other komi values.

Quote:

and that under those values of komi, there are fewer differences between it and territory scoring.

Do you mean that more often the winner is the same (area scoring with standard area komi versus territory scoring with standard area komi) or do you mean something else?

Yes.

Herman: does that suffice to clarify the point?

Bill Spight · **#51**

Under button go with area scoring, on his move a player may take the button, which is worth 1/2 pt.

Click Here To Show Diagram Code: [go]$$B Button go, komi = 1 $$ +-----------+ $$ | . . O O . | $$ | X X X O . | $$ | . . X O O | $$ | X . X O . | $$ | . X . O . | $$ +-----------+[/go]

Black's turn.

Click Here To Show Diagram Code: [go]$$W Button go, komi = 2 $$ +-----------+ $$ | . . X X X | $$ | O X X X . | $$ | O O O X . | $$ | . O O X . | $$ | O . O X . | $$ +-----------+[/go]

White's turn.

Button go gives us the best of both worlds.

Button go, the wave of the future!

HermanHiddema · **#52**

hyperpape wrote:

Herman: does that suffice to clarify the point?

Well, not really. If I understand correctly, the claim is that an area scoring game with a komi of 7.5 is more likely to have the same result as a territory scoring game with 6.5 than it would have if the area scoring game had komi 6.5?

If we ignore special situations like seki, then for any area scoring game with score X, the territory score is either also X (if white had the last move), or it is X-1 (if black had the last move). AFAIK, it is not statistically significantly more likely for the last move in pro games (with area scoring) to be black, so I don't see any reason for the claim to be correct.

RobertJasiek · **#53**

Here is a citation of my proofs of 1997:

https://groups.google.com/forum/?hl=de# ... _Pri3bdzsJ

Code:

From: Robert Jasiek <jas...@berlin.snafu.de>

Subject: Re: Changing Komi to 6.5 Points

Date: 1997/07/10

Message-ID: <33C4B819.2DD@berlin.snafu.de>

X-Deja-AN: 255931142

References: <OcXWZHA5VLwzEwkg@jklmn.demon.co.uk> <5q0b2u$qc3$1@news.cc.ucf.edu>

To: "Dr. Kuo-Chi Lin" <kl...@pegasus.cc.ucf.edu>

Organization: Unlimited Surprise Systems, Berlin

Reply-To: jas...@berlin.snafu.de

Newsgroups: rec.games.go

Dr. Kuo-Chi Lin wrote:
> 
> Matthew Macfadyen (Mat...@jklmn.demon.co.uk) wrote:
> 
>[...]
> : But there are an odd number of points on the board, so a simple parity
> : argument says that when this occurs the margin will be an odd number, so
> : the game might be moved from a 4 point Black win to 5, but not from 5 to
> : 6, thus with 5.5 points komi a player used to Japanese counting does not
> : have to worry about losing due to the number of dame points being odd.
> 
> Can someone confirm this theory?  Personally, I do not think it is
> correct.
> 
> Kurt

I am also surprised about this, but I am guilty of having supplied the
mathematical background for this as included at the end of the message.

So here is a sketch of a proof for the above:

Presumptions are OddBoardSize and EvenSekiParity and standard area komi
s(t) = 2t - 0.5; t positive natural numbers; e.g. 5.5 komi.

We are interested in smallest possible winning margins:
For Japanese rules: B+0.5 or W+0.5.
For area rules (like AGA): B+1.5 or W+0.5.
(Proof see inclusions.)

Now we want to observe the consequences of a last neutral point
possibly changing the Japanese result into another win under area
rules. A last neutral point conforms to 1 point, thus only 
smallest Japanese winning margins are of interest. Theoretically
4 cases occur: Each possible smallest Japanese winning margin
combined with each possible colour for the last neutral point to
be got. Details:

(1) Japanese B+0.5, B last neutral point:
With area rules this gives B+1.5. Hence B remains the winner.

(2) Japanese B+0.5, W last neutral point:
This is not possible, proof see inclusions.

(3) Japanese W+0.5, B last neutral point:
This is not possible, proof see inclusions.

(4) Japanese W+0.5, W last neutral point:
With area rules this would be W+1.5. However, this is not
possible, proof see inclusions.

Hence the only possible case is (1). There the winner is the same.
So indeed in the most frequently occuring parity case players
used to Japanese scoring need not worry about last neutral points
with area rules.

-:)]

Further reasons to use standard area komi only are contained in the
inclusions below. Especially this means that 7.5 komi are much more
preferable than 6.5.

-- 
robert jasiek
http://www.inx.de/~jasiek/

Subject: Re: Why 5.5 komi???
Date: Fri, 23 May 1997 15:31:59 +0200
From: Robert Jasiek <jas...@berlin.snafu.de>
Organization: Unlimited Surprise Systems, Berlin
Newsgroups: rec.games.go

> As I know, in chinese counting system, giving 6 or 6.5 has the same
> effect
> as giving 5.5. Am I right?
> Xin Kang

No, you are wrong. Proof:

Let n be the number of board points. It is sufficient to consider
n being odd. For even n things are inverted.
For simplicity two representative types of area rule sets shall be
considered: that of AGA 1991 and that of Ing 1991.
Komi for AGA type use half points: k = 0.5, 1.5, 2.5,...
Komi for Ing type use natural numbers with black winning ties:
k = 0, 1, 2,...
Let a be the area winning margin on the board for black. (Negative
values are a win for white.)
Let w be the winning margin for black. By definition: w = a - k.

It is necessary to consider cases depending on BoardSizeParity,
SekiParity, Winner. The board can have an even or an odd number
of empty grid points that are not monochromely surrounded. (They
occur in odd "sekis".)

n odd, SekiParity even, black win:
----------------------------------

a = 1, 3, 5, 7,... is possible.
The interesting value for a is the smallest with a black win.
Then w is the smallest possible winning margin.

AGA: a = k + 0.5 + (k - 0.5) mod 2
Ing: a = k + (k + 1) mod 2

Example:

R     k     a     w

AGA   5.5   7     1.5
AGA   6.5   7     0.5
Ing   6     7     1
Ing   7     7     0

n odd, SekiParity even, white win:
----------------------------------

a = 1, 3, 5, 7,... is possible.
The interesting value for a is the greatest with a black loss.
Then w is the smallest possible winning margin.

AGA: a = k - 0.5 - (k + 0.5) mod 2
Ing: a = k - 1 - k mod 2

Example:

R     k     a     w

AGA   5.5   5     -0.5
AGA   6.5   5     -1.5
Ing   6     5     -1
Ing   7     5     -2

n odd, SekiParity odd, black win:
----------------------------------

a = 0, 2, 4,... is possible.
The interesting value for a is the smallest with a black win.
Then w is the smallest possible winning margin.

AGA: a = k + 0.5 + (k + 0.5) mod 2
Ing: a = k + k mod 2

Example:

R     k     a     w

AGA   5.5   6     0.5
AGA   4.5   6     1.5
Ing   6     6     0
Ing   5     6     1

n odd, SekiParity odd, white win:
---------------------------------

a = 0, 2, 4,... is possible.
The interesting value for a is the greatest with a black loss.
Then w is the smallest possible winning margin.

AGA: a = k - 0.5 - (k - 0.5) mod 2
Ing: a = k - 1 - (k + 1) mod 2

Example:

R     k     a     w

AGA   5.5   4     -1.5
AGA   4.5   4     -0.5
Ing   6     4     -2
Ing   5     4     -1

---------------------------------

Results:
- For each case and each area rule set two komi values are
  equivalent.
- Consistency independent of SekiParity is only given with
  standard komi s:

AGA: s(t) = 2t - 0.5; t positive natural numbers
Ing: s(t) = 2t; t natural numbers

- For AGA s = 1.5, 3.5, 5.5, 7.5, 9.5,..., for Ing s = 0, 2, 4,...
- Inconsistent komi change the smallest winning margins to a win
  of the other player in case of odd SekiParity.
- With area rules the nearest a values for constant SekiParity
  have a difference of 2. Thus with properly chosen k as to the
  rule set the value of a is constant for all k with |a-k| <= 2.

--robert jasiek
http://www.inx.de/~jasiek/endrules.html

Subject: 
           Re: Use for dame
      Date: 
           Sat, 21 Jun 1997 19:25:48 +0200
      From: 
           Robert Jasiek <jas...@berlin.snafu.de>
        To: 
           ML go-rules <go-r...@lists.io.com>
References: 
           1

>      But alternate filling is starting to catch on in the domestic
> Japanese professional tournaments too. One reason may be the discovery
> that it provides a check on the result. With 5.5-point compensation,
> if the margin of victory is half a point, and if the neutral points
> have been filled alternately, then the winner is (almost always) the
> player who got the last neutral point.

Here a sketch for a proof is given.

def) Definitions:

n: # board points
k: komi
wt: winning margin for territory score
tB: # B points for score
tW: # W points for score
e: # empty board points
eB: # empty board points surrounded by B
eW: # empty board points surrounded by W
eN: # empty board points that are not surrounded
fB: # surrounded empty board points in B seki
fW: # surrounded empty board points in W seki
cB: # prisoners of B color
cW: # prisoners of W color
ms: # stones played during game
mp: # passes during game
sB: # B stones played during game
sW: # W stones played during game
pB: # B passes during game
pW: # W passes during game

D := eB - eW + cW - cB

Presuppositions:

0) Rules: Japanese 1989
1) n = 361 : ODD
2) k = 5.5
3) wt = 0.5
4) eN : EVEN at game end
5) fB = fW
6) pB = 1
7) pW = 1

Implications:

10) def => wt = | tB - tW |
11) def => tB = eB - fB + cW
12) def => tW = eW - fW + cB + k
13) def => e = eB + eW + eN
15) def => ms = sB + sW
16) def => mp = pB + pW
17) setup with empty board => eN : ODD at game start
18) (1) and setup with empty board => e = n = 361 : ODD at game start
19) (6), (7), (16) => mp = 1 + 1 = 2 : EVEN. This also means: no move
after any pass.

Now we show:

A) D is even in case of a B win.
B) D is odd in case of a W win.
C) D is even in case of the last played stone being B.
D) D is odd in case of the last played stone being W.

Then it follows: A <=> C AND B <=> D.

The details:

(A)

30) (3), (10) => wt = 0.5 = | tB - tW |
31) (30) and B win => 0.5 = tB - tW
32) (30) and W win => 0.5 = tW - tB
33) (11), (12), (30) =>
0.5 = | tB - tW | = | eB - fB + cW - eW + fW - cB - k |
34) (5), (33) => 0.5 = | tB - tW | = | eB - eW + cW - cB - k |
35) (31), (34) => 0.5 = eB - eW + cW - cB - k in case of B win
36) def, (2), (35) => 6 = eB - eW + cW - cB = D is EVEN in 
case of B win.

(B) 

40) (32), (34) => 0.5 = eW - eB + cB - cW + k in case of W win
41) (2), (40) => -5 = eW - eB + cB - cW is ODD in case of W win.
42) (41) => 5 = eB - eW + cW - cB = D is ODD in case of W win.

(C)

Presupposition:

50) The last stone of the game is played by B.

Implications:

51) (50) => sB = sW + 1.
52) (15), (51) => ms = 2*sW + 1
53) (52) => ms is ODD.

Now the parity changes during the game are analysed:

60) (17), (18) => At the game start eB = eW = cB = cW = 0, 
so D is EVEN. Besides e = eN = 361 are ODD.
61) After the first move eB = 360 is EVEN, eW = cB = cW = 0.
So D is still EVEN.
62) Changes due to a B move: placing the stone: e -> e - 1;
then if capture of i W stones: eB -> eB + i for the i board 
points of capture AND cW -> cW + i.
63) Net effect of (62) capture: D -> D + 2*i keeps its parity.
64) Changes due to a W move: placing the stone: e -> e - 1;
then if capture of j B stones: eW -> eW + j for the j board
points of capture AND cB -> cB + j.
65) Net effect of (64) capture: D -> D + 2*j keeps its parity.
66) (62), (64) => each succession of a B and a W move changes
without consideration of captures e -> e - 2 keeping parity.
67) (53), (60), (66) => e EVEN at game end
68) (4), (13), (67) => eB, eW either both EVEN or both ODD
at game end
69) (68) => The parity of eB - eW is EVEN and independent of 
eN value at game end.
70) (53), (61), (63), (65), (69) => D EVEN at game end.
71) Removals after the game end behave like captures during
the game and do not affect the parity of D.

(D)

Prove as in (C) but now

72) last stone by W => ms EVEN => e ODD at game end =>
eB - eW ODD at game end => D odd at game end

-:)]

Feel free to present a generalisation for aribitrary komi, scoring
systems, board sizes, winning margins, SekiParities, single pass
occurances, monochromely surrounded empty points in sekis, 
handicaps...

--robert jasiek
http://www.inx.de/~jasiek/rules.html

xed_over · **#54**

holy smokes.. eye glaze over with math proofs..

maybe a simple chart would help

5x5 board (25 points) - assuming most common endgame result, no special seki or other strange situations - there will always be a 2 point swing in result.

Code:

  5x5              komi (even or odd)
 B - W     even 0.5     odd 1.5    even 2.5    odd 3.5
- 10      B+4.5       B+3.5      B+2.5       B+1.5
- 11      B+2.5       B+1.5      B+0.5       W+0.5
- 12      B+0.5       W+0.5      W+1.5       W+2.5
- 13      W+1.5       W+2.5      W+3.5       W+4.5
- 14      W+3.5       W+4.5      W+5.5       W+6.5

So under these conditions, only with odd komi, can you hand over a pass stone to score with Territory counting and not change the result from the default Area based score.

snorri · **#55**

ez4u wrote:

I think eidogo can not handle a 5X5 game (SZ[5] tag). Cgoban chokes on the original file that I downloaded from post #42 since it contains two SZ tags (both SZ[5]). Removing either one with a text editor allowed Cgoban to handle it properly.

Thanks. I edited the original post so that it will work for CGoban users. The duplicate tag was just me trying in vain to manually fool eidogo.

HermanHiddema · **#56**

Ah, I see. The proof is older and concerns 5.5 komi, but would apply for 7.5 as well. So what you are saying is that 7.5 komi for area scoring is likely to have the same game outcome (but not necessarily score) as a territory scoring game with 7.5 (but not 6.5). The likelihood being high because it is rare for games to end with an odd number of points in seki.

Still, more likely does not mean it is certain, so snorri's claim that "In fact, with odd komi, as is appropriate for the comparison, inferior or superior play for black with respect to choosing to make a point or play a dame has the same effect in both AGA and Japanese rulesets." is not true in general.

Anyway, I agree with Bill that button go is superior in this respect. Button go adds the property that it is always better to keep sente, even when there are no more points on the board.

RobertJasiek · **#57**

Concerning the seki parity, it is an open problem with unclaimed prize to determine the relative frequencies of even / odd scores under area scoring. Only the overwhelming practical experience is known.

Regardless, and if we ignore ko and dame fights, it appears to be equally difficult to win a game under traditional territory scoring vs. area scoring, because the choices between branches representing Black's vs. White's wins are equally difficult regardless of whether - in a subtree near a game end - nearest scores differ by 1 or 2 points. (Assuming non-integer komi, so that choosing jigo is not an option.)

snorri · **#58**

HermanHiddema wrote:

Still, more likely does not mean it is certain, so snorri's claim that "In fact, with odd komi, as is appropriate for the comparison, inferior or superior play for black with respect to choosing to make a point or play a dame has the same effect in both AGA and Japanese rulesets." is not true in general.

In that context, I was referring to that specific example, not trying to make general statement. It's possible that a more general statement can be made for a broad class of games, but I'm not in that business.

HermanHiddema · **#59**

snorri wrote:

HermanHiddema wrote:

Still, more likely does not mean it is certain, so snorri's claim that "In fact, with odd komi, as is appropriate for the comparison, inferior or superior play for black with respect to choosing to make a point or play a dame has the same effect in both AGA and Japanese rulesets." is not true in general.

In that context, I was referring to that specific example, not trying to make general statement. It's possible that a more general statement can be made for a broad class of games, but I'm not in that business.

So if you are not referring to any general rule or principle, what is it about my comment that makes it misleading? Why is the example a red herring?

snorri · **#60**

IMHO, and this really is just my personal list.

Reasons to like AGA rules:

Because it is an area scoring ruleset, playout of life&death positions is allowed, which is good for beginners and also for resolving disputes.¹
It is possible to use either territory or area scoring. The game does not have to be stopped just because a player accustomed to Chinese rules accidentally throws a stone back in the opponent's bowl. It may be rude for a player to deliberately do that without agreeing with the opponent ahead of time that area scoring is okay, but that's a communication issue, not a technically blocking one.³
Because of the previous point, it is possible to count with territory first, then verify with area in close games.³

Reasons to dislike AGA rules:

Playing dame on the clock can be seen as a burden.²
You can play your own territory incessantly after the dame are filled instead of your opponent's territory, in theory providing another way of being a jerk. I've never seen anyone actually do this, though, so maybe I shouldn't include this on my personal list.¹
There is often a need to explain the rules to those unfamiliar with them, which is what motivated this thread to begin with. But this limitation is not unique to AGA rules. In the U.S., the same thing can be said of Ing rules. Also, if a TD were to decide to run a tournament via Chinese rules, like Craig Hutchinson used to do when he ran the Die Hard tournament at the U.S. Go Congress, those would have to be explained in detail as well to most players. IHMO, he did an excellent job of explaining them, and I miss him.¹
It's related to the above, but because in tournaments players see others counting via territory, it is easy to mistakenly assume that a territory ruleset like Japanese rules is being used. But that is not the case, and in some cases optimal play in the endgame with respect to kos and dames differs from territory rules, such as the example in mhlepore's earlier post. I am aware of at least one high-level game (both professional players) where this mattered, and I've never been a TD so I'm sure TDs can cite more. Robert Jasiek correctly states that the difference is a general property of area rulesets, but my point is that for AGA the illusion that the game might be played by territory rules makes the situation a little worse.³

So I can take it or leave it, but I think we should keep it. The real headache is Ing hardware regardless of whether Ing rules are being used. That stuff is just poorly designed and dangerous.

--
[1] Applies to all area scoring rulesets.
[2] I'm not sure in real Chinese tournaments in China if dame need to be filled in on the clock. Maybe someone with knowledge of that can comment.
[3] Applies to AGA rules, and likely to others with equivalence scoring, though it's hard for me to be complete about that.

AGA rules and cultural barriers

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