### LilyWhite's blog

By LilyWhite, history, 2 years ago,

I have a friend who is rated purple on CF but only 1700 on AtC.

So how do they really map?

• +14

 » 2 years ago, # | ← Rev. 2 →   +3 I'm 1500 there. But It's not good to scale I think because they have a different kind of rating system altogether. All I can say is that, it goes both ways with tourist being +600 there and me being -500.
•  » » 18 months ago, # ^ |   +14 I think the reason behind this is that in Codeforces, if two competitors with a rating difference of $400$ compete in a single contest, it is expected that one competitor is $10$ time more likely to win the contest; and with a rating difference of $800$, the ratio becomes $100$; with a rating difference of $1200$, the ratio becomes $1000$, and so on...... (it's actually not bad to think that the ratio between any master to tourist is no more than $13183$ LOL), but in Atcoder the $400$ becomes $600$, so lower-rated participants in Codeforces becomes even more lower-rated in Atcoder, while higher-rated participants in Codeforces becomes even more higher-rated in Atcoder......(the bound between is extremely high, namely $3169$ QWQ); additionally, I personally think that Atcoder choses a rating calculation method more optimistic and tends to give more importance into "good times" contests of a participant, while Codeforces is more pessimistic and and tends to give more importance into "bad times" contests of a participant. Maybe there's consideration behind this ^_^.
 » 2 years ago, # | ← Rev. 3 →   +3 They use very similar model (use different constants). But slightly different topics.P.S. Atcoder 1300
 » 2 years ago, # | ← Rev. 2 →   +11 I am red here but not even yellow at atcoder.Edit : now i am yellow
 » 2 years ago, # |   0 There's already a blog discussing this.
•  » » 2 months ago, # ^ |   0 Yeah, the same blog.
 » 2 years ago, # | ← Rev. 2 →   -10 [Deleted]
•  » » 2 years ago, # ^ |   +38 cool story