=~=~=~=~=~=~=~=~=~=~=~= PuTTY log 2005.08.16 17:49:01 =~=~=~=~=~=~=~=~=~=~=~= _ __ __ __ | | / /__ / /________ ____ ___ ___ / /_____ | | /| / / _ \/ / ___/ __ \/ __ `__ \/ _ \ / __/ __ \ | |/ |/ / __/ / /__/ /_/ / / / / / / __/ / /_/ /_/ / |__/|__/\___/_/\___/\____/_/ /_/ /_/\___/ \__/\____/ ^^__ _____________________ _ _ _ / - \_ / ____/ _/ ____/ ___/ _ | || || | <| __< / /_ / // / \__ \ (_) |_______| <| \ / __/ _/ // /___ ___/ / _ \__ ___ / <| \ /_/ /___/\____//____/ (_) |___|_| <|______\ |_|___| _|____|_ ====================================== |___|_| (________) freechess.org ---- 69.36.243.188 (_______) /________\ ====================================== /_______\ (Login screen designed by Alefith) ****** Welcome to the Free Internet Chess Server at freechess.org ****** Webpage: http://www.freechess.org Head admin : Chessty Complaints to : complaints@freechess.org Server location: freechess.org Server version : 1.25.16 If you are not a registered player, enter guest or a unique ID. (If your return key does not work, use cntrl-J) login: DrDave "DrDave" is a registered name. If it is yours, type the password. If not, just hit return to try another name. password: **** Starting FICS session as DrDave **** ------------------------------------------------------------------ ------------ *** Message Of The Day *** fics% help ratings ratings Chess ratings serve two purposes: (a) they tell you your relative ability, and (b) are useful means for identifying and playing opponents of roughly your same ability. This server utilizes the Glicko rating system developed by Mark E. Glickman (with assistance and corrections by Dmitry Dakhnovsky and server implementation by Vek and Hawk). The full explanation of this system is given in the "glicko" help file. In general, your rating will be adjusted by several factors: (a) the result of your game (win, loss, draw), (b) your opponent's rating, (c) the stability of your rating, and (d) the stability of your opponent's rating. If you want to determine how your rating might change after a match with a given player, use the "assess" command. At present, there are separate ratings for these kinds of chess: Blitz, Bughouse, Lightning, Standard, Suicide Chess and Wild. Odds games and nonstandard games are unrated by default. Your current rating is available on your "finger" file. Ratings are given in "games", "history" and "journal" displays. Once you have an established rating (RD <80) in a given type, your highest established rating to date will also be displayed. Players with established ratings will also have their ratings listed on several ranking lists (see the "best", "hbest", "rank" and "hrank" help files). By default, the "who" command lists logged on users in order of their blitz ratings. This way, you can identify and match players of certain ratings. Ratings can be used in (a) your "formula" for filtering out match requests from other players, (b) "availmax" and "availmin" settings in order to modify which players you will be notified about, and (c) the "kiblevel" variable in order to filter out kibitzes and whispers. The "provshow" variable can be used to display a player's rating type (such as provisional or established); read "help v_provshow" for details. TRANSFERRING RATINGS FROM ANOTHER CHESS SERVER It is possible to transfer your rating from another chess server to this server. Contact an admin concerning which admin should process your request since different admins are on different chess servers. In general, you will need to email your request to that admin. Please use the subject line "Request for ratings transfer" and in the body of the email tell the admin your handle(s) on both chess servers. Also be sure to "message" the admin on the other server so the admin can verify that you are the person you claim to be. SPECIAL NOTES: (a) In the case of adjourned games that are resumed, ratings are adjusted by the users' ratings at the time the match is concluded rather than the ratings they had when the match was started. (b) Users who abuse the ratings system in one way or another will be penalized. Penalities may include being placed on the abuser list (see "help abuser"), being prevented from playing rated chess games, and/or being banned from the server. See Also: abuser assess blitz best bughouse finger formula games glicko hbest history hrank journal kiblevel lightning message rank standard suicide_chess v_provshow who wild [Last modified: July 9, 1997 -- Friar] fics% help glicko +-------------------------------------------------+ | Vek-splanation of the Glicko Ratings System | +-------------------------------------------------+ As you may have noticed, each FICS player now has a rating and an RD. RD stands for "ratings deviation". Why a new system ---------------- The new system with the RD improves upon the binary categorization that was used before on fics and elsewhere, where players with fewer than 20 games were labeled"provisional" and others were labeled "established". Instead of two separate ratings formulas for the two categories, there is now a single formula incorporating the two ratings and the two RD's to find the ratings changes for you and your opponent after a game. What RD represents ------------------ The Ratings Deviation is used to measure how much a player's current rating should be trusted. A high RD indicates that the player may not be competing frequently or that the player has not played very many games yet at the current rating level. A low RD indicates that the player's rating is fairly well established. This is described in more detail below under "RD Interpretation". How RD Affects Ratings Changes ------------------------------ In general, if your RD is high, then your rating will change a lot each time you play. As it gets smaller, the ratings change per game will go down. However, your opponent's RD will have the opposite effect, to a smaller extent: if his RD is high, then your ratings change will be somewhat smaller than it would be otherwise. A further use of RD's: ---------------------- Vek asked Mark Glickman the following: > Given player one with rating r1, error s1, > and player two with r2 and s2, do you have a formula for the probability > that player 1's "true" rating is greater than player 2's ? Mark said: Yes - it's: 1/(1 + 10^(-(r1-r2)f(sqrt(s1^2 + s2^2))/400) ) where f(s) is [the function applied to RD in Step 2 below]. How RD is Updated ----------------- In this system, the RD will decrease somewhat each time you play a game, because when you play more games there is a stronger basis for concluding what your rating should be. However, if you go for a long time without playing any games, your RD will increase to reflect the increased uncertainty in your rating due to the passage of time. Also, your RD will decrease more if your opponent's rating is similar to yours, and decrease less your opponent's rating is much different. Why Ratings Changes Aren't Balanced ----------------------------------- In the other system, except for provisional games, the ratings changes for the two players in a game would balance each other out - if A wins 16 points, B loses 16 points. That is not the case with this system. Here is the explanation I received from Mark Glickman: The system does not conserve rating points - and with good reason! Suppose two players both have ratings of 1700, except one has not played in awhile and the other playing constantly. In the former case, the player's rating is not a reliable measure while in the latter case the rating is a fairly reliable measure. Let's say the player with the uncertain rating defeats the player with the precisely measured rating. Then I would claim that the player with the imprecisely measured rating should have his rating increase a fair amount (because we have learned something informative from defeating a player with a precisely measured ability) and the player with the precise rating should have his rating decrease by a very small amount (because losing to a player with an imprecise rating contains little information). That's the intuitive gist of my extension to the Elo system. On average, the system will stay roughly constant (by the law of large numbers). In other words, the above scenario in the long run should occur just as often with the imprecisely rated player losing. Mathematical Interpretation of RD --------------------------------- Direct from Mark Glickman: Each player can be characterized as having a true (but unknown) rating that may be thought of as the player's average ability. We never get to know that value, partly because we only observe a finite number of games, but also because that true rating changes over time as a player's ability changes. But we can *estimate* the unknown rating. Rather than restrict oneself to a single estimate of the true rating, we can describe our estimate as an *interval* of plausible values. The interval is wider if we are less sure about the player's unknown true rating, and the interval is narrower if we are more sure about the unknown rating. The RD quantifies the uncertainty in terms of probability: The interval formed by Current rating +/- RD contains your true rating with probability of about 0.67. The interval formed by Current rating +/- 2 * RD contains your true rating with probability of about 0.95. The interval formed by Current rating +/- 3 * RD contains your true rating Type [next] to see next page. fics% fics% n with probability of about 0.997. For those of you who know something about statistics, these are not confidence intervals, but are called "central posterior intervals" because the derivation came from a "Bayesian" analysis of the problem. These numbers are found from the cumulative distribution function of the normal distribution with mean = current rating, and standard deviation = RD. For example, CDF[ N[1600,50], 1550 ] = .159 approximately (that's shorthand Mathematica notation.) The Formulas ------------ Algorithm to calculate ratings change for a game against a given opponent: Step 1. Before a game, calculate initial rating and RD for each player. a) If no games yet, initial rating assumed to be 1720. Otherwise, use existing rating. (The 1720 is not printed out, however.) b) If no RD yet, initial RD assumed to be 350 if you have no games, or 70 if your rating is carried over from ICC. Otherwise, calculate new RD, based on the RD that was obtained after the most recent game played, and on the amount of time (t) that has passed since that game, as follows: RD' = Sqrt(RD^2 + ct) where c is a numerical constant chosen so that predictions made according to the ratings from this system will be approximately optimal. Step 2. Calculate the "attenuating factor" for use in later steps. For normal chess, this is given by f = 1/Sqrt(1 + p RD^2) Here, RD is your opponent's RD, and p is the constant 3 (ln 10)^2 p = ------------- Pi^2 400^2 . For bughouse, we use f = 1/Sqrt(1 + p (RD1^2 + RD2^2 + RD3^2)) where RD1, RD2 and RD3 are the RD's of the other three players involved in the game, and p is given by 3 (ln 10)^2 p = ------------- Pi^2 800^2 . Note that this is between 0 and 1 - if RD is very big, then f will be closer to 0. Step 3. r1 <- your rating, r2 <- opponent's rating, (in bughouse, r1 is the average of your rating and your partner's rating, and r2 is the average of your opponents' ratings) 1 E <- ---------------------- -(r1-r2)*f/400 <- it has f(RD) in it! 1 + 10 This quantity E seems to be treated kind of like a probability. Step 4. K = q*f -------------------------------------- 1/(RD)^2 + q^2 * f^2 * E * (1-E) where q is a mathematical constant: q = (ln 10)/400 (normal chess), q = (ln 10)/800 (bughouse). NOTE: if K is less than 16, we use 16 instead. Step 5. This is the K factor for the game, so Your new rating = (pregame rating) + K * (w - E) where w is 1 for a win, 0.5 for a draw, and 0 for a loss. Step 6. Your new RD is calculated as RD' = 1 ------------------------------------------------- Sqrt( 1/(RD)^2 + q^2 * f^2 * E * (1-E) ) . The same steps are done for your opponent. Further information ------------------- A PostScript file containing Mark Glickman's paper discussing this ratings system may be obtained via ftp. The ftp site is hustat.harvard.edu, the directory is /pub/glickman, and the file is called "glicko.ps". It is available at http://hustat.harvard.edu/pub/glickman/glicko.ps. Credits ------- The Glicko Ratings System was invented by Mark Glickman, Ph.D. who is currently at Boston University. Vek and Hawk programmed and debugged the new ratings calculations (we may still be debugging it). Helpful assistance was given by Surf, and Shane fixed a heinous bug that Vek invented. Vek wrote this helpfile and Mark Glickman made some essential corrections and additions. Last major update: January 24, 1996 by hersco