National Rating System: How it works?
9/2/2016 11:46 AM

Criteria of Rated tournament

Singapore Weiqi Assoication (SWA) recognizes the following tournament categories:

  • Class A
    National tournament or selection games that is endorsed by SWA; or overseas tournament that is recognized by SWA
  1. Time limit requirements: Basic time minimum 45 minutes per side; 
  2. Min. board size: 19x19
  3. Min. no of rounds: 6 (not applicable to selection games)
  4. Weight for inclusion to SWA ratings: 1.00
  • Class B
    National tournament, endorsed by SWA
  1. Time limit requirements: Basic time minimum 30 minutes per side; 
  2. Min. board size: 19x19
  3. Min. no of rounds: 6
  4. Weight for inclusion to SWA ratings: 0.75
  • Class C
    National tournament or selection games that is endorsed by SWA; or overseas tournament that is recognized by SWA
  1. Time limit requirements: Basic time minimum 15 minutes per side; 
  2. Min. board size: 13x13
  3. Min. no of rounds: 6 (not applicable to selection games)
  4. Weight for inclusion to SWA ratings: 0.50
  • Class D
    Private tournament played on Internet, endorsed by SWA
  1. Time limit requirements: Basic time minimum 30 minutes per side; 
  2. Min. board size: 19x19
  3. Min. no of rounds: 6
  4. Weight for inclusion to SWA ratings: 0.25
  • Class E
    Private games played face-to-face, endorsed by SWA
  1. Time limit requirements: Basic time minimum 15 minutes per side; 
  2. Min. board size: 13x13
  3. Min. no of rounds: 8
  4. Weight for inclusion to SWA ratings: 0.15

 

Requirement for endorsement

  • Tournament details must be submitted to SWA no later than 1 month before the event
  • Confirmation will be given by SWA 2 weeks after submission
  • Tournament details have to include the following:
    • Tournament class
    • Location of tournament
    • Time limit requirements 
    • Board size
    • No of rounds
    • Duration of the tournament
    • Estimated no. of participants
    • Format of the tournament (e.g. round robin)
  • Results of the tournament must be submitted no later than 1 week of the tournament
  • Results submitted must adhere to the standard excel format*; or OpenGotha tournament xml file and standings html file

*Standard excel format for download: Tournament Results Template_v1.0_160902.xlsx

Overseas tournament requirements for recognition

  • In addition to the Class A/C requirements, overseas tournament need to fulfill the following requirement to be recognized as a rated tournament:
    • Min. no. of participating countries: 3
  • If the Singapore representative is not sent by SWA, the results of the tournament must be submitted no later than 1 week of the tournament
  • Results submitted must adhere to the standard excel format*; or OpenGotha tournament xml file and standings html file

*Standard excel format for download: Tournament Results Template_v1.0_160902.xlsx

Initial rating point assignment

Rating point will be pre-assigned to the players prior the tournament based on the following Kyu/Dan rank mapping:

  Kyu/Dan Rank

  Initial Rating Point

  21 – 30 kyu

  1500

  11 – 20 kyu

  1700

  1- 10 kyu

  1900

  1 Dan

  2100

  2 Dan

  2200

  3 Dan

  2300

  4 Dan

  2400

  5 Dan

  2500

  6 Dan

  2600

Certified players will be assigned with the initial rating as their provisional rating based on the above table.

Non-certified players will be assigned with the initial rating based on the following tournament categories:

  • Primary 1 & 2: 1500
  • Primary 3 & 4: 1700
  • Primary 5 & 6: 1900
  • Secondary/Tertiary/Open: 1900

For tournament with more than 85% rated players, the initial rating of the non-rated player will be calculated based the rating of the opponents (average of the strongest win and weakest loss out of minimum of 5 games). This condition take priority over the provisional rating. 

 

System Description

The rating system is derived from ELO rating system used by International Chess Federation (FIDE). It is based on the idea that one can define a probability of winning a game (so called winning expectancy SE) depending on the difference of opponents ratings D=RB-RA. For the player with lower rating (let us call him "player A") the quantity is given by 

(1)      SE(A) = 1 / [eD/a + 1] - ε/2 

The winning expectancy of his higher (or evenly) ranked opponent ("player B") is obtained from the equation 

(2)      SE(A) + SE(B) = 1 - ε 

If ε=0, Eq.(2) simply states that the sum of both winning expectancies should be normalized to one. However, such setting suffers from long term deflation as the new improving players take points from already established players. This is countered by various instruments like an existence of rating bottom, winning expectancy setting, rating resets in some specific cases and finally by introduction of a small parameter ε > 0.
At the moment, we use ε=0.016, a value fitted to balance rating variations in dan region. Although such small value has negligible effect on variation of player's rating at one tournament, the parameter ε allows to tune the long term system behaviour in a desired way.

A typical behaviour of SE is shown in Table I where the quantity was calculated with the parameters fixed at the values: a=115ε=0. This setting gives about 30% probability for beating a 1 grade stronger opponent. Since stronger players play more consistently than the weaker ones, the probability of beating a 1 grade weaker opponent tends to rise with player's grade. This fact is reflected in our system by an appropriate dependence of parameter a on the rating value of player A. The complete setting is shown in Table II where the corresponding probabilities of beating a 1 grade stronger opponent are given as well. As one can see, 20 kyu is expected to win about 40% games with one grade stronger opponent while the top amateur players should win only 20% of their games with 100 rating points stronger opponents.

Table I: Winning expectancies SE for some selected rating differences D calculated with a=115ε=0
D 20 40 60 80 100 120 140 160 180 200 300 400
SE(D) 0.457 0.414 0.372 0.333 0.295 0.260 0.228 0.199 0.173 0.149 0.069 0.030


 

In a single even game the rating of a player changes by 

(3)      Rnew - Rold = con * [ SA - SE(D)] 

where SA is the achieved result (SA = 1, 0 or 0.5 in case of jigo) and the factor con characterizes the magnitude of the change. In our system the parameter con is a decreasing function of player's rating specified in Table II.

Table II: The dependence of parameters con and a on the rating. For convenience the winning expectancies (in percents) for beating 100 points stronger opponent are shown as well. We use linear extrapolation between the points given in the table and con=10, and a=70 for GoR > 2700. 
GoR con a SE(100)   GoR con a SE(100)
100 116 200 37.8   1500 47 130 31.7
200 110 195 37.5   1600 43 125 31.0
300 105 190 37.1   1700 39 120 30.3
400 100 185 36.8   1800 35 115 29.5
500 95 180 36.5   1900 31 110 28.7
600 90 175 36.1   2000 27 105 27.8
700 85 170 35.7   2100 24 100 26.9
800 80 165 35.3   2200 21 95 25.9
900 75 160 34.9   2300 18 90 24.8
1000 70 155 34.4   2400 15 85 23.6
1100 65 150 33.9   2500 13 80 22.3
1200 60 145 33.4   2600 11 75 20.9
1300 55 140 32.9   2700 10 70 19.3
1400 51 135 32.3          

 

All the following examples are computed with ε set at zero:

 

Example 3: Both opponents have the same rating RA=RB=2400. This gives D=0 and SE=0.5 for both players. If player A wins, his new rating will be 

  Rnew(A) = 2400 + 15 (1-0.5) = 2407.5 

At the same time, the rating of player B drops by 7.5, i.e. Rnew(B)=2392.5

Example 4:   RA=320RB=400 and player A wins: 

  a=189,    SE(80)=0.396 

  Rnew(A) = 320 + 104 (1-0.396) = 383 

  Rnew(B) = 400 + 100 (0-0.604) = 340 

 

The system also allows to include handicap games assuming that the rating difference D is reduced by 100(H-0.5), where H is the number of given handicaps. Note, that it can happen that the winning expectancy of a weaker player is larger than SE of the stronger player (i.e. the weaker player is expected to win the game) if the number of given handicaps (reduced by 0.5) is larger than the absolute value of (RA-RB)/100.

 

Example 5:   RA=1850RB=2400, player A takes 5 handicaps and wins: 

  D=100,    a=90,    SE(100)=0.248 

  Rnew(A) = 1850 + 33 (1-0.248) = 1875 

  Rnew(B) = 2400 + 15 (0-0.752) = 2389 

(The above system description has been adopted from European Go Federation, http://www.europeangodatabase.eu/EGD/EGF_rating_system.php)