I am sick of crying and complaining of high elo players. According to the devs, elo system was broken really, really badly. In previous system a new very smart player with let's say 90% winrate who faces much stronger opponents (according to elo) was still losing elo in long-term. High elo players are all veterans. Im sure that there is no player who has more then 1.8k elo and is playing less then 6 months. This fix was really needed. Thank you!
About elo system, Im a bit worried that you still pasting this link:
https://en.wikipedia.org/wiki/Elo_rating_system The Elo Rating System assumes that if two opponents with equal strength face each other, the probability of winning of player/team A is 50%. It is not true in the Town of Salem. First of all there are more teams then 2. Secondly, you need to realize that Town of Salem is an asymetric game, so if Mafia and Town have both the same Elo, probability for Town to win the game is much more then 50%. The adjustment for this in needed.
Thankfully equation to calculate elo change depends only on difference in elo. I will present my proposition of elo calculation on an example:
Let's say we have
9 Town members:
Jailor, Spy, Sheriff, Medium, Escort, Doctor, Vigilante, Sheriff, Veteran with average elo
1600.
we have
3 Mafia members: Mafioso, Godfather, Consort with 1600 elo
and
NK Serial Killer also with 1600 elo
Survivor and
Jester (are not that important).
Now very important part. I hope that the BMG has some statistic winrate for this specific rolelist (more or less). Let's say that statistically Town wins 80% of games, Mafia - 15% of games and SK - 5%.
Let's split this to 3 sets of 2 teams:
Town (84%) vs Mafia (16%)
Town (94%) vs SK (6%)
Mafia (75%) vs SK (25%)
Equation for new ranking is:
R = CR + K * (E - WR)
where
CR - current ranking
K - constant coefficient
E - result, 1 for win, 0 for loss
WR - win rate (for 84% it i 0.84)
Let's check what will happen in the game if the Town wins when K is equal to 12 (this means that max elo change will be 24, for 4 teams should be 8):
Town ranking change:
Town vs Mafia change:Town Ranking = 1600 + 12 * (1 - 0.84) = 1602
Mafia Ranking = 1600 + 12 * (0 - 0.16) = 1598
Town vs SK change:Town Ranking = 1600 + 12 * (1 - 0.94) = 1601
SK Ranking = 1600 + 12 * (0 - 0.06) = 1599
Of course we should sum up it so Town is now 1603, Mafia 1598 and SK 1599.
Let's check what will happen when the Mafia wins:
Town vs Mafia change:Town Ranking = 1600 + 12 * (0 - 0.84) = 1590
Mafia Ranking = 1600 + 12 * (1 - 0.16) = 1610
Mafia vs SK change:Mafia Ranking = 1600 + 12 * (1 - 0.75) = 1603
SK Ranking = 1600 + 12 * (0 - 0.25) = 1597
After sum up Town is now 1590, Mafia 1613 and SK 1597.
And finally SK wins:
Town vs SK change:Town Ranking = 1600 + 12 * (0 - 0.94) = 1589
SK Ranking = 1600 + 12 * (1 - 0.06) = 1611
Mafia vs SK change:Mafia Ranking = 1600 + 12 * (0 - 0.75) = 1591
SK Ranking = 1600 + 12 * (0 - 0.25) = 1609
After sum up Town is now 1589, Mafia 1591 and SK 1620.
This happens when Town, Mafia and SK are equal strength. What if it's not true?
Let's see how approximately a function probability of win of elo difference looks like:
http://imgur.com/a/TZXqmAnd let's check the graph where for difference 0 we have 0.86 probability of win (Town vs Mafia):
http://imgur.com/a/TkoEMNow consider Town of elo 1200 winning against mafia of elo 1475:
Town vs Mafia change:Town Ranking = 1200 + 12 * (1 - 0.5) = 1206
Mafia Ranking = 1475 + 12 * (1 - 0.5) = 1469
This is an example how elo could be calculated. I believe we should have at least few win ratios for different Any role faction. Retributionist present/not present. NK is ww/arso/nk.
I am not saying this is ideal, but is at least a good point to start.
Also please devs don't listen to people who are saying that elo should depends on Town role (you play as a Team) or what is worse from executed evils as Jailor or shot evils as Vigilante. Why?
Example:
4 people left:Medium, Escort, Vigilante, Investigator
Role list:Random Town, Town Killing, Town Investigative, Random Mafia
Now, because of elo Vigilante refuses to vote up the Medium claim, because he wants to shoot it at night and gain more elo. At night Vigilante shoots the Medium and unexpectedly realizes that an Escort claim was Random Mafia. Town loses. If he voted up the Medium and lynched him, he would shoot an Escort claim at night. Town wins.