AIWCF ratings are calculated using the Glicko-2 rating system which is an impoved version of the Elo rating system. If you want to know more about the Glicko and Elo systems, you can see the following references: Glicko system explained on Wikpedia Site of Mark Gilckman (inventor of Glicko Syestem) Full details of Glicko system Full details of Glicko-2 system Elo system explained on Wikpedia
AIWCF Ratings are calculated on the 1st day of every month. The Rating Lists for each month can be seen by clicking Rating Lists on the Login page (also called the Server Home page).
The options bar at the top of the page allows you to select Engine Allowed or No Engine (the ratings for these two sections are entirely separate), the year and month of the rating period. You can also display the list in order of Highest to Lowest or by Serial Number. If you are interested to quickly locate your own rating you may prefer to display in terms of SrNo. Of course, you can also use search in page (Ctl+F on PCs) to locate your name. If you display in order of Highest and scroll down you will notice that that the list actually consists of two parts. The second half of the list shows players whose Rating Deviation (RD) is 250 and higher. The rating of these players is not considered to be accurate because they have either played very few games or have been inactive for a long time.
Deviation, Volatility, Games
The list also displays Rating Deviation and Volatility. These are indicators in the Glicko-2 rating system.
Ratings reported are always uncertain. Rating deviation (RD) is an indicator of the range within which a players playing strength might actually lie. One can consider a player's rating to be not the reported value but perhaps somewhere between two RDs less or more than the published value. For example, if a player’s rating is published as is 1850 and the RD is 50, the player's rating should be considered to be in the range 1750 to 1950.
Volatility is the degree of fluctuation in rating. If a player has erratic performances (e.g. suddenly losing to much lower rated players), the Volatility will be high.
The last column Games is the number of completed games during the 1 month period prior to the rating calculation. A zero in this column indicates that the player had no result in this period.
To see a graph of ratings of any player, please click Rating Profiles from Server Home page.
Type the player's Serial Number in the box provided, or the first few alphabets of the player's name. (For example, typing "Gau" is sufficient to access the rating profile of Gautam De). Then click Show rating data. The options box should be left as Glicko system. For other options, see below.
You will now see a graph of the complete rating history of the player from Septemner 2009 (when the server started) upto the present time. Below that you will see a table listing the complete rating history of the player.
When AIWCF started in 1993 games were played by post-card. We were using a point-difference method to calculate ratings 2 times a year. The same outdated rating system was continued when the server started in 2009. The old system ratings were not in the same scale as the more modern Elo or Glicko systems. For this reason, we are now showing the old ratings scaled by the formula 1.514*Value+288.8 for comparison purposes. To see the old ratings, please select Old system, then click Show rating data.
To compare the published ratings from the Old system and the present Glicko-2 system, please select the option Comparison, then click Show rating data.
Note: The old system ratings and comparison are shown here for historical purposes. Ratings from the old system should not be considered to have the same reliability as the new system and very big differences will be seen between the old and new systems.