So, I've noticed that sometimes the rating of a contest's problems is updated within a few hours, but sometimes it takes days. For example of it taking a long time, it's been 9 (!) days from the last Edu round, and still no ratings. Obviously given the current condition I can't give a proof that sometimes it takes a few hours or <= 1 day, but you all know that's the case.
Sometimes (I guess like now), after a few contests, all the recent contest's problems' ratings are updated at once.
Why do these things happen? Is it hard to calculate the ratings? Isn't it simply running a short script that calculates the formula that was mentioned a few times before?
I like knowing the ratings because I can infer from them a lot about how I did in a contest.
Does anybody know?