# AGA Rules: Handicap and Komi calculations incorrect

Hallo together,

as announced already in the chat, I made a several-hours-effort today to find out how online-go server calculates handicap and komi for games running on AGA rules, and comparing this with how it should be (acc. to official AGA rules and other references). Here is the result:

# Analysis of Server Settings for Handicap and Komi with AGA Rules

Executive Summary on Analyisis of Handicap/Komi Calculation for AGA Rules by the Go Server at “online-go.com”:

• For 19x19 board,
• handicaps are calculated correctly (at least up to a rank difference of 9), but komi calculation does not follow AGA rules, because komi values are calculated for territory count whereas online-go server uses area count!
• For 13x13 board,
• The komi of 0.5 for even games is definitely too small.
• handicap and komi calculations are strange and do not follow AGA rules.
• handicap/komi pairs are identical for 3 successive rank differences, respectively, which is strange.
• For 9x9 board,
• The komi for even games could not yet be checked.
• handicap and komi calculations are strange and do not follow AGA rules.
• handicap/komi pairs are identical for 4 successive rank differences, respectively, which is strange.
• Generally, I found no difference whether the game is ranked or unranked.

Below are tables with the handicap/komi values as they should be, compared to what they are today on online-go.

##Expected settings acc. to Official AGA Rules:

• These tables seem to assume territory counting. For area counting (like in online-go.com) we need to increase komi by “n-1” when “n” is “2” or greater, where “n” is the number of handicap stones (compare “http://www.usgo.org/aga-concise-rules-go”, item 4).
• The table in the link above seems to omit the 0.5 komi for jigo altogether (which is mentioned in official AGA rules) to avoids a draw.

References:
[1] http://www.usgo.org/aga-concise-rules-go (the official AGA rules!)
[2] http://senseis.xmp.net/?AGAHandicaps
[3] http://senseis.xmp.net/?HandicapForSmallerBoardSizes

From the above, I conclude that the following should be implemented, when considering online-go’s
rating system and scoring method:

19x19 board, AGA Rules:

``````.                           How it should be acc. to [1]                                   How it is now
.                               __________________                                       ___________________
.                              /                  \                                     /                   \
. ----------------------------+--------------------------------------------------------+-------------------------------
.Rank             Rating     | Handicap  Komi                 (Komi)                  | Current "online-go" behaviour:
.difference       difference | Stones    (for area scoring)   (for territory scoring) | Handicap
.                            |           [like at online-go]  [just for information]  | Stones       Komi
.----------------------------+--------------------------------------------------------+-------------------------------
.    0          0.0 -   50.0 |     0       7.5                  (7.5)                 |   0           7.5
.    1         50.1 -  150.0 |     0       0.5                  (0.5)                 |   0           0.5
.    2        150.1 -  250.0 |     2       1.5                  (0.5)                 |   2           0.5
.    3        250.1 -  350.0 |     3       2.5                  (0.5)                 |   3           0.5
.    4        350.1 -  450.0 |     4       3.5                  (0.5)                 |   4           0.5
.    5        450.1 -  550.0 |     5       4.5                  (0.5)                 |   5           0.5
.    6        550.1 -  650.0 |     6       5.5                  (0.5)                 |   6           0.5
.    7        650.1 -  750.0 |     7       6.5                  (0.5)                 |   7           0.5
.    8        750.1 -  850.0 |     8       7.5                  (0.5)                 |   8           0.5
.    9        850.1 -  950.0 |     9       8.5                  (0.5)                 |   9           0.5
.   10        950.1 - 1050.9 |     9       8.5                  (0.5)                 |  ???          ???
.   11       1050.1 - 1150.9 |     9       8.5                  (0.5)                 |  ???          ???
.   12       1150.1 - 1250.9 |     9       8.5                  (0.5)                 |  ???          ???
.   13       1250.1 - 1350.9 |     9       8.5                  (0.5)                 |  ???          ???
.   14       1350.1 - 1450.9 |     9       8.5                  (0.5)                 |  ???          ???
.   15       1450.1 - 1550.9 |     9       8.5                  (0.5)                 |  ???          ???
.   16       1550.1 - 1650.9 |     9       8.5                  (0.5)                 |  ???          ???
.   17       1650.1 - 1750.9 |     9       8.5                  (0.5)                 |  ???          ???
.   18       1750.1 - 1850.9 |     9       8.5                  (0.5)                 |  ???          ???
.   19       1850.1 - 1950.9 |     9       8.5                  (0.5)                 |  ???          ???
.--------------------------------------------------------------------------------------------------------------
``````

13x13 board, AGA Rules:

``````.                 How it should be acc. to [2] and extra 0.5 komi acc. to [1]              How it is now
.                               __________________                                       ___________________
.                              /                  \                                     /                   \
.----------------------------+--------------------------------------------------------+-------------------------------
.Rank             Rating     | Handicap  Komi                 (Komi)                  | Current "online-go" behaviour:
.difference       difference | Stones    (for area scoring)   (for territory scoring) | Handicap
.                            |           [like at online-go]  [just for information]  | Stones       Komi
.----------------------------+--------------------------------------------------------+-------------------------------
.    0          0.0 -   50.0 |     0       5.5                  (5.5)                 |   0           0.5
.    1         50.1 -  150.0 |     0       0.5                  (0.5)                 |   0           0.5
.    2        150.1 -  250.0 |     0      -5.5                 (-5.5)                 |   0           0.5
.    3        250.1 -  350.0 |     2       1.5                  (0.5)                 |   2          -4.5
.    4        350.1 -  450.0 |     2      -4.5                 (-5.5)                 |   2          -4.5
.    5        450.1 -  550.0 |     3       2.5                  (0.5)                 |   2          -4.5
.    6        550.1 -  650.0 |     3      -3.5                 (-5.5)                 |   3           5.5
.    7        650.1 -  750.0 |     4       3.5                  (0.5)                 |   3           5.5
.    8        750.1 -  850.0 |     4      -2.5                 (-5.5)                 |   3           5.5
.    9        850.1 -  950.0 |     5       4.5                  (0.5)                 |   4           0.5
.   10        950.1 - 1050.0 |     5       4.5                  (0.5)                 |   4           0.5
.   11       1050.1 - 1150.0 |     5       4.5                  (0.5)                 |   4           0.5
.   12       1150.1 - 1250.0 |     5       4.5                  (0.5)                 |   5          -4.5
.   13       1250.1 - 1350.0 |     5       4.5                  (0.5)                 |   5          -4.5
.   14       1350.1 - 1450.0 |     5       4.5                  (0.5)                 |   5          -4.5
.   15       1450.1 - 1550.0 |     5       4.5                  (0.5)                 |  ???         ????
.   16       1550.1 - 1650.0 |     5       4.5                  (0.5)                 |  ???         ????
.   17       1650.1 - 1750.0 |     5       4.5                  (0.5)                 |  ???         ????
.   18       1750.1 - 1850.0 |     5       4.5                  (0.5)                 |  ???         ????
.   19       1850.1 - 1950.0 |     5       4.5                  (0.5)                 |  ???         ????
.   ...                      |                                                        |
.--------------------------------------------------------------------------------------------------------------
``````

9x9 board, AGA Rules:

``````.                          How it should be acc. to [2]                                    How it is now
.                               __________________                                       ___________________
.                              /                  \                                     /                   \
.----------------------------+--------------------------------------------------------+-------------------------------
.Rank             Rating     | Handicap  Komi                 (Komi)                  | Current "online-go" behaviour:
.difference       difference | Stones    (for area scoring)   (for territory scoring) | Handicap
.                            |           [like at online-go]  [just for information]  | Stones       Komi
.----------------------------+--------------------------------------------------------+-------------------------------
.    0          0.0 -   50.0 |     0       5.5                  (5.5)                 |  ???          ???
.    1         50.1 -  150.0 |     0       2.5                  (2.5)                 |   0           3.5
.    2        150.1 -  250.0 |     0      -0.5                 (-0.5)                 |   0           3.5
.    3        250.1 -  350.0 |     0      -3.5                 (-3.5)                 |   0           3.5
.    4        350.1 -  450.0 |     0      -6.5                 (-6.5)                 |  ???         ????
.    5        450.1 -  550.0 |     0      -9.5                 (-9.5)                 |   2           0.5
.    6        550.1 -  650.0 |     0     -12.5                (-12.5)                 |   2           0.5
.    7        650.1 -  750.0 |     0     -15.5                (-15.5)                 |   2           0.5
.    8        750.1 -  850.0 |     0     -18.5                (-18.5)                 |   2           0.5
.    9        850.1 -  950.0 |     0     -21.5                (-21.5)                 |  ???         ????
.   10        950.1 - 1050.0 |     0     -21.5                (-21.5)                 |  ???         ????
.   11       1050.1 - 1150.0 |     0     -21.5                (-21.5)                 |  ???         ????
.   12       1150.1 - 1250.0 |     0     -21.5                (-21.5)                 |  ???         ????
.   13       1250.1 - 1350.0 |     0     -21.5                (-21.5)                 |  ???         ????
.   14       1350.1 - 1450.0 |     0     -21.5                (-21.5)                 |  ???         ????
.   15       1450.1 - 1550.0 |     0     -21.5                (-21.5)                 |  ???         ????
.   16       1550.1 - 1650.0 |     0     -21.5                (-21.5)                 |  ???         ????
.   17       1650.1 - 1750.0 |     0     -21.5                (-21.5)                 |  ???         ????
.   18       1750.1 - 1850.0 |     0     -21.5                (-21.5)                 |  ???         ????
.   19       1850.1 - 1950.0 |     0     -21.5                (-21.5)                 |  ???         ????
.   ...                      |                                                        |
.--------------------------------------------------------------------------------------------------------------
``````

Notes:

• Who makes the first active move - Black or White?
• In games with 0 handicap stones, Black moves first
• In games with n=2 or more handicap stones, the system places the n handicap stones on predefined points acc. to AGA rules, and then White makes the first move.
• By definition, games with one handicap stone do not exist.
• Shall handicap/komi be calculateted based on rank difference or based on rating difference?
• Currently online-go uses the rank as the basis for handicap/komi calculation.
• Mathematically, it is more precise to use the rating value, and this is also acc. to the philosophy of AGA, see “http://senseis.xmp.net/?AGAHandicaps” (those ratings times 100 are the ratings at “online-go”).
• After all, both methods are ok. The method using the rank might be easier to understand by the human players who think in ranks rather then ratings, so online-go’s method is also well justifiable.

##ANNEX: Test Results

Common settings:

• Time Control: Live, Byo-Yomi 3m+5x30s
• [x] Disable Analysis
• In case of uneven games, the weaker player is always black (this is correctly chosen by the Go server because setting of color is set to “automatic”)

RESULTS:

19x19 games, AGA rules:

``````.19x19 games, AGA rules:
.=======================
.-----------+-----------------------------+-----+-------------+---------------------+------------------------------------
.           | Black's Live   White's Live |Delta| Game &      | Chosen by system:   |
.Date       | Rating/Rank    Rating/Rank  |Rank | Rules *     | Handic.stones  Komi | Notes:
.-----------+-----------------------------+-----+-------------+---------------------+------------------------------------
.2015-12-20 |  59/21k(me)        21k      |   0 | 19x19 AGA(u)|      0         +7.5 | Game information says handicap=0 (opponent: disc)
.2015-12-20 |  59/21k(me)    195/20k      |   1 | 19x19 AGA(u)|      0         +0.5 | Game information says handicap=1 (opponent: Pisdemono)
.2015-12-20 |  59/21k(me)    205/19k      |   2 | 19x19 AGA(u)|      2         +0.5 | Game information says handicap=2 (opponent: Sophin)
.2015-12-20 |  59/21k(me)        18k      |   3 | 19x19 AGA(u)|      3         +0.5 | Game information says handicap=3 (opponent: Icho8)
.2015-12-20 |     25k         59/21k(me)  |   4 | 19x19 AGA(u)|      4         +0.5 | Game information says handicap=4 (opponent: dlited)
.2015-12-20 |  59/21k(me)    599/16k      |   5 | 19x19 AGA(u)|      5         +0.5 | Game information says handicap=5 (opponent: totrov.ov)
.2015-12-20 |  59/21k(me)    600/15k      |   6 | 19x19 AGA(r)|      6         +0.5 | Game information says handicap=6 (opponent: Ericd)
.
.
.2015-12-20 |  59/21k(me)        12k      |   9 | 19x19 AGA(u)|      9         +0.5 | Game information says handicap=9 (opponent: chupp)
.-----------+-----------------------------+-----+-------------+---------------------+------------------------------------
.                                                 * (u) = unranked
.                                                   (r) = ranked
``````

Conclusion on 19x19 AGA games:

• The handicap is calculated correctly (at least until rank difference=9).
• The komi is not calculated correctly in accordance with AGA rules. Note that AGA rules are specified for territory count when specifying that komi=0.5 for handicap games. However, the online-go server uses area counting. For area counting, when the number of handicap stones “n” is equal to “2” or greater, we need to increase the default “0.5” komi by “n-1”. This is explained in “http://www.usgo.org/aga-concise-rules-go”, point 4: Quote: “If the players have agreed to use area counting to score the game (Rule 12), White receives an additional point of compensation for each Black handicap stone after the first.”

13x13 games, AGA rules:

``````.-----------+-----------------------------+-----+-------------+---------------------+------------------------------------
.           | Black's Live   White's Live |Delta| Game &      | Chosen by system:   |
.Date       | Rating/Rank    Rating/Rank  |Rank | Rules *     | Handic.stones  Komi | Notes:
.-----------+-----------------------------+-----+-------------+---------------------+------------------------------------
.2015-12-20 |  59/21k(me)     73/21k      |   0 | 13x13 AGA(u)|      0         +0.5 | Game information says handicap=0 (opponent: World)
.2015-12-17 | -27/22k(me)     11/21k      |   1 | 13x13 AGA(r)|      0         +0.5 | (I did not check game information)
.2015-12-20 |  59/21k(me)    250/19k      |   2 | 13x13 AGA(u)|      0         +0.5 | Game information says handicap=1 (opponent: cheesyhelmet)
.2015-12-20 |  59/21k(me)    323/18k      |   3 | 13x13 AGA(u)|      2         -4.5 | Game information says handicap=2 (opponent: Miguel.12)
.2015-12-20 |  59/21k(me)    469/17k      |   4 | 13x13 AGA(u)|      2         -4.5 | Game information says handicap=2 (opponent: silverears)
.2015-12-20 |  59/21k(me)    580/16k      |   5 | 13x13 AGA(r)|      2         -4.5 | Game information says handicap=2 (oppenent: .Rev)
.2015-12-20 |  59/21k(me)    632/15k      |   6 | 13x13 AGA(u)|      3         +5.5 | Game information says handicap=3 (opponent: Rychey)
.2015-12-20 |  59/21k(me)    732/14k      |   7 | 13x13 AGA(u)|      3         +5.5 | Game information says handicap=3 (opponent: devikingerik)
.2015-12-20 |  59/21k(me)    850/13k      |   8 | 13x13 AGA(u)|      3         +5.5 | Game information says handicap=3 (opponent: kaiplaysgromp)
.2015-12-20 |  59/21k(me)    957/12k      |   9 | 13x13 AGA(u)|      4         +0.5 | Game information says handicap=5 (opponent: nghtstalker)
.                                         |  10 | 13x13 AGA   |      4         +0.5 | ("interpolated" from other data)
.                                         |  11 | 13x13 AGA   |      4         +0.5 | ("interpolated" from other data)
.                                         |  12 | 13x13 AGA   |      5         -4.5 | ("interpolated" from other data)
.                                         |  13 | 13x13 AGA   |      5         -4.5 | ("interpolated" from other data)
.2015-12-20 |  59/21k(me)    1442/7k      |  14 | 13x13 AGA(u)|      5         -4.5 | Game information says handicap=x (opponent: apple123)
.-----------+-----------------------------+-----+-------------+---------------------+------------------------------------
.                                                 * (u) = unranked
.                                                   (r) = ranked
``````

9x9 games, AGA rules:

``````.-----------+-----------------------------+-----+-------------+---------------------+------------------------------------
.| Black's Live   White's Live |Delta| Game &      | Chosen by system:   |
.Date       | Rating/Rank    Rating/Rank  |Rank | Rules *     | Handic.stones  Komi | Notes:
.-----------+-----------------------------+-----+-------------+---------------------+------------------------------------
.
.2015-12-20 |  59/21k(me)        20k      |   1 |  9x9  AGA(u)|      0         +3.5 | Game information says handicap=1 (opponent: Yuzuki)
.2015-12-20 |  59/21k(me)        19k      |   2 |  9x9  AGA(u)|      0         +3.5 | Game information says handicap=1 (opponent: Pisdemono)
.2015-12-20 |     24k         59/21k(me)  |   3 |  9x9  AGA(u)|      0         +3.5 | Game information says handicap=1 (opponent: j3bennett)
.                                             4
.2015-12-20 |  59/21k(me)        16k      |   5 |  9x9  AGA(r)|      2         +0.5 | Game information says handicap=2 (opponent: .Rev)
.2015-12-20 |  59/21k(me)    659/15k      |   6 |  9x9  AGA(r)|      2         +0.5 | Game information says handicap=2 (opponent: ham1988)
.2015-12-20 |  59/21k(me)        14k      |   7 |  9x9  AGA(u)|      2         +0.5 | Game information says handicap=2 (opponent: arthurtuco)
.2015-12-20 |  59/21k            13k      |   8 |  9x9  AGA(r)|      2         +0.5 | Game information says handicap=2 (opponent: xfmvx)
.2015-12-20 |  59/21k            12k      |   9 |  9x9  AGA(r)|      2         +0.5 | Game information says handicap=2 (opponent: TristamWolf)
.-----------+-----------------------------+-----+-------------+---------------------+------------------------------------
.                                                 * (u) = unranked
.                                                   (r) = ranked``````
5 Likes

Nice summary there, thanks!

FYI we do account for this, it’s just listed as a separate score line item (as opposed to just lumping it up into Komi) - if you hover over the score you’ll see a breakdown and under there you’ll see that white receives n-1 points from the handicap. So for 19x19 I believe we are compliant with AGA rules as far as scoring is concerned.

As for handicaps / komi for smaller boards, we are most definitely not compliant - during initial implementation 3+ years ago now we just went with the “Old Japanese Recommendation” for smaller boards for all rulesets since it was nice and concise, could be formulated easily, and because with 100 different options, why not With your nice breakout here though I think I’ll go back through and switch over to using the AGA values you’ve linked here (for AGA games at anyrate). So thanks for your work, it helps a lot!

3 Likes

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