Talk:Glicko rating system

If you are developing code based on this...
Base it off of the glicko-2 paper that is linked in the references. I was attempting to do it off of the algo specified in the wiki article, but a lot of important details are left out. Also glicko two has lots of improvements. — Preceding unsigned comment added by 134.134.137.71 (talk) 18:55, 11 April 2012 (UTC) More detail would be appreciated, about these important details left out, and the improvements contained in Glicko 2. How much is "a lot" ?? Why is Glicko 2 worth the extra effort? Thanks for your input. --Twixter (talk) 18:58, 25 April 2019 (UTC)


 * Yes, thanks for mentioning this. the article is very brief and has left important parts out. i personally also struggeled with this until i found the paper 240F:79:57A:1:582F:1D39:8023:2850 (talk) 06:22, 30 July 2023 (UTC)
 * Good message. I do t know why this wasn’t highlighted in the article Fewcada (talk) 11:58, 30 July 2023 (UTC)

Additional sources
Some relevant links  SunCreator (talk) 23:40, 22 December 2009 (UTC)

Public domain
The article states that "Both Glicko and Glicko-2 rating systems are under public domain". Is this a meaningful statement? Glicko is just a series of mathematical formulas, and mathematical formulas are not subject to copyright. JakubMarian (talk) 21:39, 23 September 2014 (UTC)


 * Dr. Mark Glickman patented Glicko-2 and attempted to license its use. After that did not work out he moved it to the public domain. Source: Dr Mark Glickman on the Perpetual Chess Podcast, EP 249, ~minute 34. https://www.perpetualchesspod.com/new-blog/2021/10/26/episode-249-dr-mark-glickman 4.31.102.58 (talk) 22:20, 7 June 2022 (UTC)

About the value of t
In the first step, if a player played in the previous rating period, should t be 0 or should it be 1? --Twixter (talk) 18:58, 25 April 2019 (UTC)


 * Evidently it's 1 because if it were zero, RD would not change and "If several games have occurred within one rating period, the method treats them as having happened simultaneously." Earnstein (talk) 19:30, 17 March 2022 (UTC)

Introducing a lower limit for RD in step 3?
Quoting from Glickman's pdf, "One practical problem with the Glicko system is that when a player competes very frequently,his/her rating stops changing appreciably which reflects that the RD is very small. This may sometimes  prevent  a  player’s  rating  from  changing  substantially  when  the  player  is  truly improving.  I would therefore recommend that an RD never drop below a threshold value,such as 30, so that ratings can change appreciably even in a relatively short time."

This being the case, perhaps the formula in step 3 should be

$$RD'=\max\left(30,\sqrt{\left(\frac{1}{RD^2}+\frac{1}{d^2}\right)^{-1}}\right)$$

--Twixter (talk) 21:46, 25 April 2019 (UTC)


 * thanks for shedding light on this!!! 240F:79:57A:1:582F:1D39:8023:2850 (talk) 06:23, 30 July 2023 (UTC)

Why is it d² written as 1/some values but only used as 1/d? that seems to be just doubling the work
its just doubling the required work 240F:79:57A:1:E022:A35A:5F86:5653 (talk) 05:05, 6 August 2023 (UTC)