### 619's blog

By 619, history, 2 weeks ago,

After the temporary rollback of ratings to recalculate rating, My Δ in Educational Codeforces Round 161 (Rated for Div. 2) changed from +50 to +40. Is this normal? Every time recalculation has happened, My Δ has either remained same or increased by +1 or +2 in all of the contests except this one. If cheaters on average perform better than their current rating, Then according to the Elo system after removing cheaters everyone should get a net increase in Δ right?

• +19

 » 2 weeks ago, # |   +2 same problem(
 » 2 weeks ago, # |   +7 is something wrong with codeforces
 » 2 weeks ago, # |   +2 em... i think you might check your total rating ~ my recalculation contains 3 contests, after the 1st contest recalc, my total rating get extra Δand then during the 2nd recalc, although my rank is higher but my basic rate also increases since that extra Δso i think it is reasonable that the new Δ-2nd may decrease (compared with the original Δ-2nd) but overall, the total rating should increase (and my total score did increase)
•  » » 2 weeks ago, # ^ |   +1 My overall rating has decreased too From 1559 to 1556.
•  » » 2 weeks ago, # ^ |   +1 Overall rating too decreased by 10.
 » 2 weeks ago, # | ← Rev. 3 →   +8 My rating also decreased after recalculation. Especially, in Codeforces Round 921.Before: Rank = 2291 | Δ = -5 After   : Rank = 2184 | Δ = -11Personally, I think that rating change is calculated similar to percentile. For example, Before: Rank 20 out of 100 | Percentile = 20% After   : Rank 18 out of 80 | Percentile = 22.5%So even if my rank increased, my percentile got worse, hence negative Δ.
•  » » 2 weeks ago, # ^ |   0 Shouldn't rating be calculated using some metric like calculation equivalent points to a rating and then applying the change?what I mean is say on average people of rating 1180-1190 got 500 points and 1120-1210 got 525 points then map those points to the ratings and then calculate "equivalent rating of which each player performed" say someone is 1210 but only got 500 points then his performance rating would be 1180 and then he will get Δ according to difference of his current and his performance rating.I think this is how ELO should work because if it works the way you are claiming, Say in some div2 contest only experts participated and all the newbies,pupils,specialists refused to participate. Then will the worst performing expert (say he solved 2 problems) in that contest get rating equivalent to a person who generally comes last in a div2 contest?
•  » » » 2 weeks ago, # ^ | ← Rev. 2 →   0 Rating is calculated by comparing your expected rank with your actual rank using seedi. Learn more about it here.So when many newbies below your rank were eliminated, your seedi increased significantly, but your actual rank didn't increase that much. Hence your Δ changed from +50 to +40.The opposite is also true, which explains why your Δ increases when many non-deserving contestent above you are eliminated.
•  » » » » 2 weeks ago, # ^ |   0 Got it, Thanks.
 » 2 weeks ago, # |   0 It's quite strange. I think there is a bug. I got +500 in my second contest, which clearly shouldn't be that much.
•  » » 2 weeks ago, # ^ | ← Rev. 3 →   -16 Sorry to everyone who got offended, it was a light-hearted comment. 🥲
•  » » » 2 weeks ago, # ^ |   +20 No, he is from China.
•  » » 2 weeks ago, # ^ |   +6 How is it possible to have +500 while performing such poorly? There must be a bug, better let Mike know this.
•  » » » 2 weeks ago, # ^ | ← Rev. 2 →   +3 I remember I had 1448 before the ratings rolled back. Now I have 1630? I also see a lot of friends of mine get huge bonus points or their rating decreased quite much.
•  » » » 2 weeks ago, # ^ |   +3 There's an display offset for the rating before your 6th round
•  » » » » 2 weeks ago, # ^ |   0 Well, I feel it quiet strange. adiishot got the rank similar to me. His 2nd contest. And got +512 which seems same to me. But SummerFlower got +474 in his 1st contest. Why is this?
•  » » » 2 weeks ago, # ^ | ← Rev. 2 →   +1 Your "internal" rating used for delta calculation starts at 1400 instead of 0.int a[6] = {1400, 900, 550, 300, 150, 50};After $i$ contests, your displayed rating is internalRating - a[i] for $i\le5$, and after the 6th contest they are the same
•  » » » » 2 weeks ago, # ^ |   0 Thank you very much.
 » 2 weeks ago, # |   +3 well, my overall rating increased by +22. so not a problem for me... :D
 » 2 weeks ago, # |   0 Same happened for me. My rating got decreased by 5. Although, not much, but would love to get an explanation.
 » 2 weeks ago, # |   0 My rating has been decreased from 1555 to 1549... It wasn't a high deflection :) But the participants who got out of competition should also considered (must given some negative delta), since most of the people might get deflections due to change in participants count.
 » 2 weeks ago, # |   +4 maybe cheater/bot performed so poorly so that amount of removed contestants which had lower rank than you were greater than ranked higher then it's possible
 » 2 weeks ago, # |   0 i'm from 1612 to 1607
 » 2 weeks ago, # |   0 Ok so my happiness of becoming specialist haven’t lasted long .My overall rating decreased from 1409 to 1394 nice
•  » » 2 weeks ago, # ^ |   +4 Lol bro... Same happened with one of my friend. His rating decreased from 1601 to 1598. Now, he is specialist again. He even posted on Linkedin about becoming expert.
 » 2 weeks ago, # | ← Rev. 4 →   +3 I was surprised to gain $77$ rating from nowhere, the previous recalc just gave me $2$ ratingAnd I checked the contest history, my delta for Educational Codeforces Round 161 (Rated for Div. 2) increased from $+290$ to $+458$ giving me a true rating of $1838$ despite my perf being $1749$. I think this is weird. Is it because the recalculation causes history rating to be inconsistent for new accounts (first 6 contests)?
•  » » 2 weeks ago, # ^ | ← Rev. 2 →   0 How did you gain rating from a Div 3, while you are rated higher than 1600?
•  » » » 2 weeks ago, # ^ |   0 Rating was 1555 at registration and the recalc pushed up the history rating
•  » » » » 2 weeks ago, # ^ |   0 Ah, I see! Thanks for letting me know!
 » 2 weeks ago, # | ← Rev. 2 →   0 same , my rating also decreassed by 5 -7.
 » 2 weeks ago, # |   0 My rating changed from 1100 to 1252 I guess the change was due to Codeforces Round 921 (Div. 2)
 » 2 weeks ago, # |   +3 Yesterday, I was an Expert and today, I woke up to discover I am a Specialist. :)