Ratings and Rep points

Ratings and Rep points

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Representative points and ratings

About the Rating system

The ratings are calculated according to a slight variant of the European Go Federation’s GoR algorithm, which in turn is basically an Elo rating scheme: each player is assigned a numerical rating; the probability of a player winning any given game is assumed to depend only on the difference in the ratings of the two players (allowing for handicaps by changing rating by 100/stone; games on more than 6 stones are ignored). The ratings of the two players are adjusted slightly according to the outcome of each game in a tournament (the rating is assumed constant throughout a single tournament); the adjustment is larger for lower ranked players to allow for the greater variation of weaker players.

The player’s initial rating is determined by their initial claimed rank : 2100 for 1 dan, 2000 for 1 kyu etc.  The adjustments are set so that the each rank correspond to a range of +/- 50 points;  thus a 1 dan would expect to have a rating in the range 2050-2149.  However as a rank of 7 dan is special, and should be awarded only by the Ratings Committee, ratings of 2650 to 2699 are  assigned 6 dan only by AGATHA.

In order for the algorithm not to inflate ratings over time, and to prevent wild oscillations for kyu players, some ad hoc limitations on a single game rating change are imposed (see the EGF web page for a complete description of the statistical theory and the parameters used). To allow for the fact that a player’s strength may change radically between appearances at a tournament, the Tournament Director may register the player at another rank: if a player at a tournament claims a ranking difference of 2 stones or more (200 rating points) from their current rating, they are given a new rating based on their claim (which makes the mathematical theory behind the scheme dubious, but does make the final numbers seem more reasonable Ñ but note that it makes them reasonable in the sense of corresponding with Australian ratings, which for middle dan players seem to be about 1 stone stronger than Japanese rankings, 1 to 2 stones weaker than EGF, and about the same as American). If a TD changes the entered rank so as to give a new rank, that change will be flagged in AGATHA so that the Rating Committee may override; note the number of games rated column is reset to zero for that player (the Total # column reflects the total number of eligible games played throughout our history). Note also that a player entered at a rank of 5d or above starts with rating 2500 (and so will not be regraded unless the registered rank is 3d or less)

Because we have far fewer tournament, some other ad hoc variations have been introduced, the main one being that if the indicated change for one or more players as calculated over a tournament is larger than a threshold (50) then the ratings for that tournament are recalculated with the indicated players being assumed to have changed their ratings initially; this is actually done in a number of steps with the players with very large indicated changes being modified first. This is iterated until the maximum change is less than the threshhold (but in order to ensure convergence he maximum change for any individual player is decreased on each iteration). Secondly, a maximum initial rating of 2500 (5 dan) is assigned; stronger players must earn their higher ratings (ideally all players should start with the same initial rating, and allow the system to work out relative levels; but we do not have enough games for this).

Because of time lag, ratings will be conservative, particularly for kyu players. The Ratings columns adjusts all ratings so that one anchor player (Andrew Chi, a very strong player who tragically died) is set to 2700; this seems to give reasonable results. Note the T.Rk column is the rank as claimed at the most recent AGA tournament.

Ratings calculated over a small number of games are not meaningful.

Representative Points System Rules 2019

The AGA Representative points system is used to select Australian National Representatives at international tournaments where the organisers request a National representative at their event. The system is used to select the Australian representative at the World Amateur Go Championships and the Korean Prime Minister’s Cup[1] and may be extended to other events if the AGA Committee so decides.

Points are accrued in the following manner.

  1. Participants in the Australian Open Championship are assigned Representative points according to their placing, as determined by number of won games,

Placing:       1        2         3         4         5         6        7         8         9       10        11                    12   13 ≥14

Points: 2000  1700 1400 1200 1000  800    700     600     500     400      300                                                                    200 200 100

However only members of the AGA at the start of the Tournament may add these points to their Representative Point account.

In an Accelerated Swiss tournament, the Accelerated Score of a player (Wins+initial Acceleration) shall  be used in place of just Wins, to determine Representative Points earned.

2. Tie-breaking for earning of Points

All players on equal number of wins in a tournament shall receive an equal share of the available points (thus if 4 players are on equal number of wins after the top 3 placings, they share the Representative points for 4th, 5th, 6th and 7th placings).

Points will be recorded as whole integers, rounding to the nearest integer (10.4 becomes 10, 10.5 becomes 11).

3. Deduction of points for representation and depreciation of points

  1. The member who is the Australian citizen holding the highest total number of points at the end of the National Championships will be eligible for selection as the Australian representative, subject to rules 4 and 9 below; but a number of points is deducted from the representative’s Points, according to the number of times they have previously represented Australia at the WAGC:

No. of times:       0             1            2           3            4            5            6         7

Deduction:   5000        8000       12000 17000 23000      30000    38000 etc (triangular increase).

  1. The Committee may determine that representation at other international tournaments shall incur deduction of points, to a value set by the Committee.

[Example: the selected representative at the Korean Prime Minister’s Cup International Amateur Baduk Championships will have Representative Points deducted using the same scale as for the WAGC.]

  1. Immediately after the close of the Australian Open Championships, all accumulated Points for all players with a positive number of Points will be reduced by 20%; negative Points will appreciated by 20% (towards 0); the deduction of points from the Points of the selected representative, and any penalties accrued during the year (see Rule 8), will then be applied.

 Representative Points deducted from a player’s Points on account of selection for an international tournament shall be deducted at the time the Committee confirms the selection. In the event that the selected player cannot attend the tournament, the points will be restored when, and only if, a substitute player is confirmed.

4. Tie-breaking for selection of representative

Players having a Representative Point value within 50 of that of the leading player will be eligible for selection; if there are two or more players eligible for selection, a play-off shall be held. 

5. Other tournaments

Representative points may be earned also by players in tournaments other than the Australian Open Championship, provided the tournament has been so approved in advance by the AGA Committee.

To qualify for Representative Point awards, the tournament must:

(i) be advertised throughout Australia with reasonable advance notice       (ii) be played with a reasonable playing time

Representative points will be awarded in such tournaments according to a Representative points table to be decided and published by the AGA before the tournament, in the same proportions as the Australian Open Championship table above, but reduced by multiplication by a weighting factor to be determined by the Committee. For State tournaments, the Toyota-Denso Cup and the Korean Ambassador’s Cup this weighting factor will be calculated according to the following formula

  • for each section of the tournament, the number of players in the section (TN), and the total “Dan Strength”  (TD), that is, the number obtained by adding the dan ranking of all players of dan rank, are determined. For sections of a McMahon tournament, these numbers are calculated by including all players paired with players in that section.
  • For the National Championships tournament the weightings shall be
    • 100% for the top non-handicap section
    • 50% for other non-handicap sections if TN ≥ 6
    • 20% for other handicap sections if TN ≥ 6
  1. For other approved tournaments including, the Toyota-Denso Cup and the Korean Ambassador’s Cup the weighting shall be

(i) for non-handicap sections

30% if TD ≥ 48

20% if 32 ≤ TD ≤ 47

10% if 6 ≤ TD ≤ 31

(i) for handicap sections

10% if TN ≥ 12

5% if 6 ≤ TN ≤ 11

  1. otherwise no points shall be awarded

6. Inheritance of Credit Points

The Representative Points system replaces the Credit Points system; existing Credit Points in each player’s account shall be converted to Representative Points

7. Penalties

A player who forfeits a tournament game without giving the tournament director notice and reasonable cause may have up to 5000 points deducted from their accumulated Representative Points for each forfeited game or be banned from representing Australia for a period determined by the AGA committee; the player may appeal to the AGA Committee for consideration of mitigating circumstances. Other penalties may be applied by the Committee for offensive or inappropriate behaviour at tournaments including overseas tournaments in which the player represents the AGA.

8. Resolution  of disagreements

Disputes will be referred to the AGA Committee, if the dispute is not resolved there it will be managed through section 11.1 of the AGA Constitution.

The AGA Committee has sole responsibility for the selection of the WAGC representative not withstanding the claims of players as to their Representative Point standings.

[1] The representative for the KPC must have competed at the Korean Ambassador’s cup in the year of selection