MikeMirzayanov's blog

Codeforces: Updates in rating and rounds
By MikeMirzayanov, 7 years ago, translation, In English

Hello, Codeforces!

It's time for news. I hope you will enjoy!

  • We reduce the rating bound for the orange color. Thus, now the orange rating (and the Master title) will start from 2100 rating units.

  • The lower bound of the rating for legendary grandmasters is increased to 3000 rating units. Thus, right now in the community, 14 participants meet this requirement. Real legends!

  • For rounds like "Div. 2 Only" the upper bound of the rating for official participation is increased. Now everyone whose rating is less than 2100 (i.e., before masters) will be able to register for such rounds to participate officially, their rating will be updated based on the results of the round. We do not plan to increase the complexity of Div. 2 rounds. Practice shows that the problems of such rounds are interesting and useful for participants "below the orange".

  • For parallel Div. 1 and Div. 2 rounds we don’t change the rating bound between divisions. So Div. 1 edition of the round continue to include participants with the rating from 1900 and above.

  • As an experiment, we plan to host rounds of simplified complexity (Div. 3). In such rounds, the official results will include participants with ratings less than 1600. We plan to include in these rounds simple training problems that will help beginner participants to gain skills and to get new knowledge in a real contest. Since even in the Div. 2 rounds regularly some Div. 1 users register new account and take high place, we also expect such unsportsmanlike behavior in the Div. 3 rounds. We will exclude from the official standings of Div. 3 rounds and put in a separate rooms all those who can’t be reliably called to be a real participant. Accounts that materially participated in less than 2 rating rounds (materially means solved at least one problem there) before the start of the Div. 3 rounds, and those who have ever gained 1900 or more rating units will not get into the official standings and will be assigned to separate rooms. However, this does not mean that there is no rating recalculation for them. Thus, the rating will be updated for all users whose rating is strictly less than 1600 at the time of the start of a round. Perhaps we will experiment with the definition of who should be considered a reliable Div. 3 participant. And thanks to VLamarca for the post about idea of Div.3 rounds!

Updating the boundaries of ratings and changing colors is not an instantaneous process. For this reason, the website may still have outdated information for some time. We are working to apply the announced changes during the day.

I hope you enjoy this news.
— MikeMirzayanov

  • Vote: I like it
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  • Vote: I do not like it

Comments Comments (177)
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7 years ago, # |
  Vote: I like it +150 Vote: I do not like it

I am sure, the concept of Div. 3 round will definitely help many beginners.

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    7 years ago, # ^ |
      Vote: I like it +86 Vote: I do not like it

    Thanks, hope to see you on Codeforces Round 479 (Div. 3)!

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      7 years ago, # ^ |
        Vote: I like it +48 Vote: I do not like it

      It was a good decision (about DIV3)!

      It is very important for beginners (it's to hard for schoolboy from 5-7 forms to participate in DIV2)

      I want to help with problems for DIV3 rounds (without payments :) )

      Please tell me, what I need to do?

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        7 years ago, # ^ |
          Vote: I like it -16 Vote: I do not like it

        It is a down at the product. It will get more user from leetcode! Just run my codeforces!

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      7 years ago, # ^ |
        Vote: I like it 0 Vote: I do not like it

      I have some questions (and I think not only me):

      1) Will problems in Div. 2 and Div. 3 cross?

      1.1) Is that crossing going to be permanent?

      2) As I understand, rating system is something like that(answer if its not so):

      • Div. 3 (-INF; 1600)

      • Div. 2 [1600; 2100)

      • Div. 1 [2100; +INF)

      3) Problems for Div. 3 rounds will be made by 1600+ rate users, or other can make something too?

      Sorry for my poor English :D

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        7 years ago, # ^ |
        ← Rev. 2   Vote: I like it +18 Vote: I do not like it

        for point 2)

        as I understood, the rating system will be like this:

        • Div. 3 (-INF; 1600)
        • Div. 2 [1600; 1900)
        • Div. 1 [1900; +INF)

        but the "Div. 2 Only" rounds will now affect the rating of purple users as well (i.e., it will be official for all participants with less than 2100 rating)

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          7 years ago, # ^ |
            Vote: I like it +3 Vote: I do not like it

          Maybe is upper bound for Div. 2 to move to 2100? Than "Div. 2 Only" will be real "Div. 2 Only".

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          6 years ago, # ^ |
            Vote: I like it -22 Vote: I do not like it

          Hi my rating is 887. Can i participate in div2 and div3?

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        7 months ago, # ^ |
          Vote: I like it 0 Vote: I do not like it

        Div 4?

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      7 years ago, # ^ |
        Vote: I like it 0 Vote: I do not like it

      As a bonus, it will also encourage top to mid level users to give a try to peoblem setting. And writing problems for Div 3 contest can be a good way to start. This may increase the frequency of rounds to. So overall we are moving in the right direction. :)

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      7 years ago, # ^ |
        Vote: I like it 0 Vote: I do not like it

      It's a great Idea. Thanks MikeMirzayanov & CF team for your relentless efforts :)

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    7 years ago, # ^ |
      Vote: I like it -37 Vote: I do not like it

    It is a down at the product. It will get more user from leetcode! Just run my codeforces!

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7 years ago, # |
← Rev. 2   Vote: I like it +45 Vote: I do not like it

In my opinion, this is a terrible decision. Hello rating inflation!

I wrote a little more about it here.

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    7 years ago, # ^ |
      Vote: I like it +60 Vote: I do not like it

    Why do you think so? Current anti-inflation heuristics work rather well and I don't see reason why they will break after changes.

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      7 years ago, # ^ |
        Vote: I like it +32 Vote: I do not like it

      From my past experience, any time there is a combined div1 + 2 round, the div1 participants are cushioned by thousands of div2 users even if they perform terribly relative to div1 alone. Same thing would happen with these candidate masters in 1900-2100 range. clearly this would lead to devaluation of ratings!

      As for the anti-inflation practices, I recall that they only apply to div 1. I couldn't find it after a quick search, so if this is different, please send me the link.

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      7 years ago, # ^ |
      ← Rev. 2   Vote: I like it +35 Vote: I do not like it 
      If we assume that the rating was already calculated fair (i.e. everybody has perfect statistically based rating) then expected change of rating after a contest is equal to zero for any participant [...]

Choose a group of the most rated (before the round) participants and decide that their total rating shouldn’t change [...]

      Afaik I proved this is wrong and directly leads to rating inflation

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        7 years ago, # ^ |
          Vote: I like it +31 Vote: I do not like it

        Haha, nobody cares of your opinion, l o s e r

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    7 years ago, # ^ |
      Vote: I like it +133 Vote: I do not like it

    On another note, I really hope that div3 contest does not influence the frequency of div2 or div1 contests. They are already extremely infrequent and at inconvenient times for many players.

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7 years ago, # |
  Vote: I like it +268 Vote: I do not like it

I hope div2 contests don't become rare like div1(of course not as rare as div1) after this update..

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    7 years ago, # ^ |
      Vote: I like it +47 Vote: I do not like it

    Div 3 rounds will be prepared by separate people. They will not affect Div.1/Div.2 rounds.

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      7 years ago, # ^ |
        Vote: I like it 0 Vote: I do not like it

      Who can set div3 contests? blue as a lower bound or specific people like educational rounds ?

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        7 years ago, # ^ |
        ← Rev. 2   Vote: I like it +25 Vote: I do not like it

        Right now I'm planning to run them by my students in Saratov State U. We will ask help of community in case of luck lack of ideas or time to prepare such rounds.

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7 years ago, # |
  Vote: I like it +5 Vote: I do not like it

Nice improvement. Do we restrict new user to only join Div 3 contest?

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7 years ago, # |
  Vote: I like it 0 Vote: I do not like it

I like this decision personally, as it motivates more to be div1.

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7 years ago, # |
  Vote: I like it 0 Vote: I do not like it

Hmmm, so now some Div2 rounds are for people below 2100 and some for people below 1900 (based on whether or not there is a Div1 also)? Why the inconsecvence tho?

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7 years ago, # |
  Vote: I like it +20 Vote: I do not like it

Can't wait to see the changes in practice, but for my perspective this will another the transition between div 1 and 2, and will make div 2 rounds more competitive.

Thanks for the update Mike and CF team! It's nice to know that CF is always trying to improve and open to changes like this :)

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7 years ago, # |
  Vote: I like it +122 Vote: I do not like it

after 3 years of coding

i will fight in #Div_3 -_-

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7 years ago, # |
  Vote: I like it +21 Vote: I do not like it

So the problems in div 3 are easier than problems in div 2 and problems in div 2 are easier than problems in div 1,right?

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7 years ago, # |
  Vote: I like it +10 Vote: I do not like it

please don't reduce no. of DIV2 contest.

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    7 years ago, # ^ |
      Vote: I like it 0 Vote: I do not like it

    Yes,the number of DIV2 contests must remain the same.

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7 years ago, # |
  Vote: I like it +135 Vote: I do not like it

Mike, I truly appreciate how well you listen to the community! Those changes look good and are a great boost to those around purple.

I would suggest adding a new milestone to the rating of 2800, since the range of IGM is now huge. Perhaps borrowing the unofficial term "super grandmaster" from chess?

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    7 years ago, # ^ |
      Vote: I like it +29 Vote: I do not like it

    I am more for increasing Grandmaster from 2500 — 2750 (also that is increasing of both yellow zones for 50). So International Grandmaster could be from 2750-3000.

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      7 years ago, # ^ |
        Vote: I like it +14 Vote: I do not like it

      Why not keep the Grandmaster lower bound at 2400 but just increase the Grandmaster-International Grandmaster boundary to 2700?

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        7 years ago, # ^ |
          Vote: I like it +1 Vote: I do not like it

        You just don't want red to be further away from you

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      7 years ago, # ^ |
      ← Rev. 2   Vote: I like it +33 Vote: I do not like it

      Yeah, increasing the boundaries would be better and would even out the color band ranges.

      Currently: {200, 200, 100, 200, 400} are the range gaps starting from CM.

      With Grandmaster at 2500 and International Grandmaster at 2750, we would have {200, 200, 200, 250, 250}

      Can something be done about this before it's too late? MikeMirzayanov

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7 years ago, # |
  Vote: I like it +50 Vote: I do not like it

Is it rated for purple contestant in the education round?

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7 years ago, # |
  Vote: I like it +113 Vote: I do not like it

I think this will motivate people in rating 1900-2100 to participate in "Div2 only" contests and avoid giving Div1 contests. I think you should come up with a solution to tackle this scenario.

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    7 years ago, # ^ |
      Vote: I like it +45 Vote: I do not like it

    Let's look how it will work in practice. If you are right we will adopt the rules.

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      7 years ago, # ^ |
        Vote: I like it +89 Vote: I do not like it

      Also, I have seen people getting more than +400(1500 -> 1900) rating changes by topping div2 contests.

      In such a case a person with 2100 rating can get +300, to go RED.

      This implies, a person can become RED without ever giving a div1 contest.

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        7 years ago, # ^ |
          Vote: I like it -13 Vote: I do not like it

        Yeah I agree but staying in red is the challenge. Moreover topping a div2 round isn't an easy task and now CM's are rated. So I don't think someone can jump to red without being actually that good.

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          7 years ago, # ^ |
            Vote: I like it +21 Vote: I do not like it

          Yeah, but for me, becoming Red is a coveted achievement.

          Plus in my opinion Div2 contests are based on solving tasks quickly, and Div1 tasks are based on solving tougher problems.

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          7 years ago, # ^ |
            Vote: I like it +1 Vote: I do not like it

          cool, so now any tom dick can get this red shit.

          you simply cannot compare a red user that had 2400 rating before this shit happened, and one (actually 100's) that are going to get red due to this shit

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            7 years ago, # ^ |
            ← Rev. 2   Vote: I like it +5 Vote: I do not like it

            Well, I have seen people giving only div1+div2 contests to become red :P

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        7 years ago, # ^ |
        ← Rev. 4   Vote: I like it +18 Vote: I do not like it

        I think so. I became purple in a DIV2 round (not "DIV2 only") with 11th place and got +200 rating long time ago. I think it is not good because those with 2000 rating could get red or orange in luck.

        I've been in 1900-2000 (maybe 1850~1950 lol) for a very long time and I think getting a high place in "DIV2 only" is much more easier than even getting +50 in a DIV1 round (and it is true for me in the past several rounds).

        I do think it is not a great idea to let purple to participate in "Div2 only" contests. I think 2A and 2B is a waste of time for me.

        upd: And now I get yellow in luck.

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7 years ago, # |
  Vote: I like it +79 Vote: I do not like it

Glad to see div.3, really nice for beginners support! Small idea to improve this even farther: why not set the division border to 1500? Just registered user goes to div.2 first and then falls to div.3 if he's really the person this type of contest is meant for. No need in all the heuristics about distinguishing between first and second accounts.

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7 years ago, # |
← Rev. 3   Vote: I like it +18 Vote: I do not like it

giphy

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7 years ago, # |
  Vote: I like it 0 Vote: I do not like it

Now, is the educational round rated for div3 only or div2 as well.

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7 years ago, # |
  Vote: I like it 0 Vote: I do not like it

Oh no, that means I am in div. 3 now and not in div. 2. Thats quite painful.

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    7 years ago, # ^ |
      Vote: I like it 0 Vote: I do not like it

    Work a bit hard and you will leave it soon .

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7 years ago, # |
  Vote: I like it +35 Vote: I do not like it

I really like div 3 rounds !

For my opinion combination of changing master to 2100 and rating increase for only div 2 rounds are not good! On this way you removed problem from rating 1950-2050 and moved to 2150-2200. Many coders will compete only in div 2 rounds and that is bad.

I think one of that two things would be enough and really will solve problem, combination is bad.

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7 years ago, # |
  Vote: I like it +211 Vote: I do not like it

I don't think this is a good idea.

Div 1 contests are already quite rare. Now that 2100 and below can participate in Div2-only rounds, there is even less pressure to make Div1 versions of rounds. Plus, with the new Div 3 (I'm not sure what the point is, Div1A and Div1B are good problems for 1600-rated contestants) there will be even less attention paid to Div1.

It is true that for 1900-2100 rated people, Div2 contests are still a good level. I remember when I made division 1, there was a huge jump in difficulty, which was a little disorienting. But I also think it is a good rite of passage, and forcing 1900s to do Div1 contests will make them better in the long run.

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    7 years ago, # ^ |
      Vote: I like it +14 Vote: I do not like it

    I think so too. It's true that something needed to be changed but this is too much. Changing div 1 and Candidate Master lower bound to 2000 might solve the problem already.

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7 years ago, # |
← Rev. 2   Vote: I like it +5 Vote: I do not like it

So what is the difficulty of div 3 contests? (when comparing to div 2 difficulty) 1.A- 2.A 3.B 4.C 5.D ?

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    7 years ago, # ^ |
      Vote: I like it +14 Vote: I do not like it

    I don't know any more than you do but seems to me like its going to be more like AABBC.

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7 years ago, # |
  Vote: I like it -16 Vote: I do not like it

I have an idea, we could change our rank from point to some kind of medal, and the rank would be reset per 6 months

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7 years ago, # |
  Vote: I like it +11 Vote: I do not like it

newbies like me are happy now thanks .

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7 years ago, # |
  Vote: I like it +13 Vote: I do not like it

Will it be easier to become over 2200 rating? I mean if I'm around 2180 and play within 100 rank. I think there's a challenge between 1900 to 2200 rating now. I don't know how much will it be after 2099 rating can take part in Div.2 Only.

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7 years ago, # |
  Vote: I like it +8 Vote: I do not like it

More chances to lose rating!

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7 years ago, # |
  Vote: I like it +7 Vote: I do not like it

Will the div3 rounds be rated for participants with rating between 1600 and 1900(Experts)?

By that logic participants with rating >= 1900 can participate in div2 and div1,

participants with rating < 1600 can participate in div2 and div3

and Experts only get to play div2 rounds. It seems a bit unfair for Experts.

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    7 years ago, # ^ |
    ← Rev. 2   Vote: I like it 0 Vote: I do not like it

    As is said before the rating will be updated for all users whose rating is strictly less than 1600 at the time of the start of a round. I think those rating >=1600 can participate in div3 round but will be unrated.

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7 years ago, # |
  Vote: I like it +115 Vote: I do not like it

One of my goals for 2018 was to reach Master and I was looking forward to celebrating the day I made it. Now that it's just going to be given to me... I feel unfulfilled.

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7 years ago, # |
  Vote: I like it +11 Vote: I do not like it

can i still compete in div 2??

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7 years ago, # |
  Vote: I like it +89 Vote: I do not like it

I wanna say I agree with this and this would definitely help many beginners blablabla. BUT I have to say that it is no good in doing this.never.nope. First I have to say that I don't agree div1+2 mode at all.Because it makes a huge gap between the two rounds.1850-2050 is a really huge gap.People with all levels can be stuck in this.And the worst thing is after training hard,they found that they can hardly improve there score.And then they get frustrated and quit.(or stay training and become masters) Actually Div2 is not needed.All people sit in a same room can be a better choise.I don't know the original idea about Div1+2 mode.If some of the div1 guys thinks 2A and 2B is a waste of time to them,then 1A and 1B might also be a waste of time for Petr and tourist. If there is no need to seperate them from div1 to hold a div0,then there is no need to seperate some people from div2 to hold a div1.Things shall be merged,all people play together and then newbees can grow up. And now I sadly see that you goes a totally wrong way. Now there is a new div,and you think that shall help the beginners?wrong. First,the old gap is still alive(1850-2050),and the new gap is comming(1550-1750).In short,there would be two gaps,and the beginners shall face the same frustrated situations,two times. Second,you put 20 children together and no adults,and they will never learn how to speak.And if children lives TOGETHER with adults,they will learn.Same question,isn't it. Finally,100 years later we would have div1-20,totally 20 divs in our codeforces.(ofcause ,with 200+ colors).

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    7 years ago, # ^ |
      Vote: I like it +18 Vote: I do not like it

    Regarding your question about why there should be more than one division, I would say it is a problem setting issue. It's pretty hard to come up with truly challenging problems to very good people while being fair. A lot of people can set up a good contest for Div 2, but it would be unfair to let a guy like yancouto compete in such contest. The idea of not allowing really good players on tournaments is true for most competitions, like chess, football, etc. It is possible to host a lot of Div 2 contests and frankly, they are good and challenging for thousands of people.

    But whenever you find someone to set up a Div 1 contest, I really like the merge idea. In fact, that's pretty much what CS Academy does. If you are a beginner, you are probably going to perform badly compared to the very good coders. But that is how it is, right? ICPC, Codejam, TCO, etc.

    However, considering the way things are now, I don't think purple is high enough to be forbidden in Div 2 contests. Most purples won't solve Div 1 D so these changes make sense for me. Let's see how they work.

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      7 years ago, # ^ |
        Vote: I like it 0 Vote: I do not like it

      Idea is that if there's a Div1, it's too hard for many participants (so not really interesting) but it's somewhat easy for problem setter to add div2 AB problems (comparing to setting all the problems for Div1) and make it more interesting for these participants.

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    5 years ago, # ^ |
      Vote: I like it 0 Vote: I do not like it

    My apopogize as I thought we must wait 100 years then we can enjoy div 20. I was naive. The time we must wait is far shorter.

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7 years ago, # |
← Rev. 2   Vote: I like it +3 Vote: I do not like it

division partition technique.. :D specially good for beginners level but crucial for div2 :p

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7 years ago, # |
← Rev. 2   Vote: I like it +3 Vote: I do not like it

Thanks mikeMirzayanov for Div 3.

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7 years ago, # |
  Vote: I like it 0 Vote: I do not like it

WoW finally div3 ,, i wanted this to happen the moment i joined codeforces (4 years) and surprisingly codeforces did it ,,thanks codeforces

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7 years ago, # |
  Vote: I like it +138 Vote: I do not like it

Poor my title... I lost legendary grandmaster in mere few days even I don't participate contest OAQ

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7 years ago, # |
  Vote: I like it 0 Vote: I do not like it

is div3 like a div2 educational round ?

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7 years ago, # |
  Vote: I like it 0 Vote: I do not like it

This is a appreciable move because it will increase more participation in DIV3 regardless of fear of ratings drop and increase competitive spirit :) .Thanks Mike!

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7 years ago, # |
  Vote: I like it +60 Vote: I do not like it

People between 1900 and 2100 are basically in div. 1.5 now.

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7 years ago, # |
  Vote: I like it +180 Vote: I do not like it

While updates are still rolling, maybe we should assign distinguishable colors to international masters and GMs? Just a matter of style. They seem a bit worthless if there is no difference between GM and IGM on the leaderboard. Maybe something like this:

  • tourist
  • tourist
  • tourist
  • tourist
  • tourist
  • tourist
  • tourist
  • tourist
  • tourist
  • tourist

I think that 1.5div-title and div3 update is great, by the way.

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7 years ago, # |
  Vote: I like it -7 Vote: I do not like it

theenks mike.

mid expert so easy peasssyyy. 1550 rating, div 3 contest, top 50 -> easy 1750

master so easy peasyyyy. 2050 rating, div 2 contest, top 50 -> easy 2250 if you top 10, then enjoy international master easy peasy

predictions: we will see VLamarca or similar user complaining to allow [2100, 2300] users to participate in div2 contests in near future (at max 2 months) since entire [1900,2100] will eventually shift to that range.

i see almost everyone with rating [1500, 2100] will get +100 — +200 in its rating easy peasy.

E869120 you make great graphs, a request to please also compare number of huge increase in no of experts/masters in few div3/div2 contest

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    7 years ago, # ^ |
    ← Rev. 3   Vote: I like it +5 Vote: I do not like it

    "2050 rating, div 2 contest, top 50 -> easy 2250" When I had 1883 rating(about 150 less than your example) I got +100 for top 20. So for top 50, i think 2050 will probably become no more than 2125 and most likely will get about 2075-2100 rating if even that.

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      7 years ago, # ^ |
        Vote: I like it +6 Vote: I do not like it

      seeing how top 50 in div2 now gets +100, I think the new change would also makes it close to +100, as you have more 1900-2100 range participating. I really don't like how this is going. Feels like it's going to be a speed contest instead. Like if you solve 5 problems, you get increased rating, if you solve 4, then it's really a matter of who solve 4 faster.

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7 years ago, # |
  Vote: I like it +2 Vote: I do not like it

With this change expert users (1600-1900) lose really much. We can participate officially only on div2. Lots of people below 1600 will only participate in div3, while purple users will be able to come down to div2. So experts have to beat most of the purple users in order to improve to div1. I think this update will make a huge gap between purple and blue users.

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    7 years ago, # ^ |
    ← Rev. 2   Vote: I like it 0 Vote: I do not like it

    do not worry much :D all of them are going to gradually move to 2200+ easily and won't take part in next div2 and will never participate again in any div1

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7 years ago, # |
  Vote: I like it +4 Vote: I do not like it

So sometimes we will see that there are three types of rounds simultaneously?

Div.1, Div.2, Div.3 rounds or just as usual?

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7 years ago, # |
  Vote: I like it +5 Vote: I do not like it

How will Div. 1,2, and 3 share problems during contests?

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7 years ago, # |
  Vote: I like it +30 Vote: I do not like it

Me: How much divisions can be on cf?

Mike:

(Actually div3 is very good idea, thank you Mike)

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7 years ago, # |
  Vote: I like it +10 Vote: I do not like it

MikeMirzayanov, About the people making fake accounts, I have made a post about that some time ago, I wonder if you could take a look at it, but basically, in this post I ask why div2 contestants cannot choose to participate out of competition in div2 contests (and for div1 in div1 contests as well), I believe making this possible would make fewer people create fake accounts.

Here's the link to the post.

http://mirror.codeforces.com/blog/entry/57448

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    7 years ago, # ^ |
      Vote: I like it +17 Vote: I do not like it

    irrelevant the problem is div1 fake accounts who get top ranks in div2 contests, no problem with fake account of div2 members in div2 contest.

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7 years ago, # |
  Vote: I like it 0 Vote: I do not like it

I think making div2 contests rated for purple coders is not good because then they will have to solve easy problems first( around 20 minutes ) which will give them little less time on solving more difficult problems (d, e) and if it's unrated for them then they can directly start from c onwards and focus more on thinking about difficult problems which helps a lot.

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7 years ago, # |
  Vote: I like it +11 Vote: I do not like it

I cannot believe how fast this became true. Thanks a lot for giving us voice MikeMirzayanov. I wish all the success for you and your team at making competitive programming better and more popular :)

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7 years ago, # |
  Vote: I like it -22 Vote: I do not like it

I'm a beginner , How can I know my rating..? I haven't found yet.

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    7 years ago, # ^ |
      Vote: I like it 0 Vote: I do not like it

    You have never participated in a rated contest

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      7 years ago, # ^ |
        Vote: I like it -17 Vote: I do not like it

      I have participated in recent cf rounds and even solved level A problems completely .

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        7 years ago, # ^ |
          Vote: I like it +1 Vote: I do not like it

        You only participated in the April Fools contest. That one was was a joke contest and therefore not rated.

        Compete in a regular contest, and you will get a rating.

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          7 years ago, # ^ |
          ← Rev. 2   Vote: I like it +3 Vote: I do not like it

          but I had participated in rated contests too please see here

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            7 years ago, # ^ |
              Vote: I like it +6 Vote: I do not like it

            No, you didn't participate in those two contests. You solved some problems after the contest was over. That's not the same thing.

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7 years ago, # |
  Vote: I like it +27 Vote: I do not like it

So, I was hoping to reach Div1 now I'm down to Div3 :D

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7 years ago, # |
  Vote: I like it 0 Vote: I do not like it

Finally becomes div1 after last contest Purple is now div2

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7 years ago, # |
  Vote: I like it 0 Vote: I do not like it

It is good for me (Chinese) since I rarely found a div1 round at a suitable time. However, now there are some div2 round I can participate in and some I cannot, that is a little confusing. There must be a better solution because this one may lead to problems.

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7 years ago, # |
  Vote: I like it -56 Vote: I do not like it

Is It Rated?

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7 years ago, # |
  Vote: I like it +10 Vote: I do not like it

Soo, what about contest frequency? Seems that there will be even less div. 1 contests now...

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    7 years ago, # ^ |
      Vote: I like it +11 Vote: I do not like it

    I'm afraid that there will really be less div. 1 contests because the purples can compete in "div. 2 only" contests.

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    7 years ago, # ^ |
      Vote: I like it -27 Vote: I do not like it

    I believe you should be more optimistic. More frequent participation from purples in CF + smother transition into div. 1 -> less people leaving the plataform after reaching candidate master -> more coders engaged in CF and more people motivating each other -> more potencial div. 1 authors in the future

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      7 years ago, # ^ |
        Vote: I like it +18 Vote: I do not like it

      I think the main problem is lack of time of coordinators raither than lack of author since suggested contests can wait for really long after being submitted. And it will escalate now..

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7 years ago, # |
  Vote: I like it +48 Vote: I do not like it

Finally I became orange, but I feel like I'm cheating something.. :)

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7 years ago, # |
  Vote: I like it +5 Vote: I do not like it

For this update, CMs have found their true role: the interlude between Div1 and Div2...

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7 years ago, # |
  Vote: I like it +10 Vote: I do not like it

I just got 2200+ rating then...

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7 years ago, # |
  Vote: I like it +8 Vote: I do not like it

Legends say that dreamoon_love_AA wants the div2 bound to raise higher to get div2 rank 1.

Jokes aside, that means I can go for div2 top 5 again? Free rating let's go!

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    7 years ago, # ^ |
      Vote: I like it +107 Vote: I do not like it

    Everyone now thinks that every single purple will get easily into top 5. What you all did not see coming is that there can only be 5 in top 5.

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7 years ago, # |
← Rev. 2   Vote: I like it +1 Vote: I do not like it

Are Div. 2 rounds rated for Div.3 participants ?

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7 years ago, # |
← Rev. 2   Vote: I like it +1 Vote: I do not like it

The international master band looks a bit thin. Maybe IM should be 2300-2500, and GM 2500-2700. Btw, I had the idea of div3 before vlamarca: http://mirror.codeforces.com/blog/entry/57783?#comment-414511 :)

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    7 years ago, # ^ |
      Vote: I like it +12 Vote: I do not like it

    Have you made millions with the idea though?

    Me neither

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7 years ago, # |
← Rev. 2   Vote: I like it +8 Vote: I do not like it

Will problem setters be able to propose div3 contest in the future? I hope not — So problem setters are not driven away from setting hard questions instead of trivial ones that are easy to come up with.

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    7 years ago, # ^ |
      Vote: I like it +19 Vote: I do not like it

    If only trivial problems were easy to come up with :D We often struggle more to find a nice A/B than F/G for Educational rounds.

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7 years ago, # |
  Vote: I like it 0 Vote: I do not like it

I think that when a user is registered for the first time, he should start from div3. In this way it will be harder for div1 users to ruin a div2 contest because they will need to take part in two contests. Of course that means that it will be easier to ruin a div3 contest, but as I understand div3 is just for educational purposes and not so much for competitive.

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7 years ago, # |
  Vote: I like it +2 Vote: I do not like it

Very good update. I want to see the problems of Div 3

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7 years ago, # |
  Vote: I like it +17 Vote: I do not like it

Can't wait to find out the problems in div 3.

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7 years ago, # |
  Vote: I like it +5 Vote: I do not like it

What will be the relation between Div-2 and Div-3? Previously we saw that there were some overlap problems between Div-1 and Div-2.

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7 years ago, # |
  Vote: I like it -16 Vote: I do not like it

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7 years ago, # |
  Vote: I like it -13 Vote: I do not like it

This means I'll be in Div.3 now? -_-

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7 years ago, # |
← Rev. 5   Vote: I like it -34 Vote: I do not like it

The concept of div.3 is really great and problemset should be standard.In my point of view it could have been better if only Newbies and Pupils ( <1400 ) was eligible for this type of contest.Although Div.2 problemset is perfect for both Pupils and Specialists.
Candidate Masters participating in Div.2 is not a good decision at all.( I see!!I made lots of candidate masters angry.It was just my point of view . Div.2 A,B,C are wasteful for them)

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    7 years ago, # ^ |
      Vote: I like it +15 Vote: I do not like it

    Candidate masters participating in div2 is a good decision

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    7 years ago, # ^ |
      Vote: I like it -31 Vote: I do not like it

    I don't think candidate masters solve div1 D,E regularly, so what's the issue?

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    7 years ago, # ^ |
      Vote: I like it 0 Vote: I do not like it

    No clue why you get downvotes, this is 100% correct

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7 years ago, # |
  Vote: I like it +9 Vote: I do not like it

Atcoder.jp V 2.0

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7 years ago, # |
  Vote: I like it +14 Vote: I do not like it

I'm not a fan of this update because of decreasing the lower bound of master rating :(

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7 years ago, # |
  Vote: I like it 0 Vote: I do not like it

Does this mean that participants with less than 1600 rating can still participate in Div. 2 rounds and get rating recalculations after the contest ?

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7 years ago, # |
← Rev. 2   Vote: I like it -20 Vote: I do not like it

What is Round #48x? Is it a typo?

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    7 years ago, # ^ |
      Vote: I like it +3 Vote: I do not like it

    No. Right now I'm not sure about exact round number. I'll negotiate it with KAN. Hope there will be Div.1 or Div.2 round before the May, 13th.

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      7 years ago, # ^ |
      ← Rev. 2   Vote: I like it -7 Vote: I do not like it

      Thanks. Hope yet another round, too. (better if time is proper for me)

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7 years ago, # |
  Vote: I like it -42 Vote: I do not like it

Is it possible to make the Div.2 Only rated for ALL people but calculate the rating for Div.1 and Div.2 seperately?

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7 years ago, # |
  Vote: I like it -34 Vote: I do not like it

Sorry for my stupidity. But when we have two parralel rounds Div1 and Div2 which one should I register to if i have rating 1900? to Div1 or Div2 or I can register to any of them as official participant now.

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7 years ago, # |
  Vote: I like it -44 Vote: I do not like it

What a great update to raring system!!

So now people whose rating between 1900 -> 2100; are they considered div.1 or div.2? Because they participate officially in both contests.

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7 years ago, # |
  Vote: I like it +28 Vote: I do not like it

+1900 is candidate master or 2100 ????

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7 years ago, # |
← Rev. 8   Vote: I like it +117 Vote: I do not like it

For me, the only changing is "the Surface of the Water"...

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7 years ago, # |
  Vote: I like it +30 Vote: I do not like it

Shouldn't there be some limit on how high one's rating can go by participating in a div.3/div.2 contest? A 1550-1599 rated user could become 1st in a div.3 contest and become a candidate master without ever participating in a div.2 contest. Similarly, a 2050-2099 rated user could become a grandmaster without ever participating in a div.1 contest.

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7 years ago, # |
  Vote: I like it +35 Vote: I do not like it

Why isn't there an unrated participation for >1600 users?

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7 years ago, # |
← Rev. 3   Vote: I like it +71 Vote: I do not like it

Why I cannot register for the contest Codeforces Round 479 (Div. 3) as an unofficial participant ?

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7 years ago, # |
  Vote: I like it -148 Vote: I do not like it

I am happy that Codeforces team is constantly working on improving the platform, however, I have a serious concern about the new Div.3.

Given that the only difference between Div3 contests and usual contests is the low skill of participants, I suspect that very soon they will become uninteresting to spectators, problemsetters and sponsors.

To fix this, I suggest a new contest format for fresh coders, which has basically the following rules:

  • First, participants submit no more then 100 lines long solution to some particular problem. Then MikeMirzayanov selects some number (say 100) of solutions, which he considers the most elegant (preferably, some of them should be in Java, you will see later why).

  • He then gives the solutions for review to tourist and Petr and they choose ~20 participants who will compete in the main series of the contests.

  • Throughout the main contests participants will be regularly guided by tourist (C++ coders) and Petr (Java coders), constantly improving their CP skills.

  • The winner of such season will get an opportunity to participate in Div.1 contests regardless of his rating.

I suggest that the new format can be called "War of codes/styles" or something in that manner. I believe that such contests will make Div.3 far more spectacular as well as promote the educational spirit of the platform.

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    7 years ago, # ^ |
      Vote: I like it +89 Vote: I do not like it

    would probably work if mike tourist and petr were jobless and had nothing else to do.

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      7 years ago, # ^ |
        Vote: I like it -65 Vote: I do not like it

      That's the moment, were sponsors should take their chance

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    7 years ago, # ^ |
    ← Rev. 2   Vote: I like it +115 Vote: I do not like it

    Lol, this is the most fucked up and meaningless suggestion I've ever seen on codeforces

    P.S> Dude, you've placed fake support badge in your profile image, like, for real? :D

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      7 years ago, # ^ |
        Vote: I like it -66 Vote: I do not like it

      I once went on a date with a girl. I did not pay for her, and later when she asked I said I donated all my money to codeforces and showed her the badge. She said that I'm a real man and we had a great time.

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    7 years ago, # ^ |
      Vote: I like it 0 Vote: I do not like it

    Проорал в голосину

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7 years ago, # |
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Wish everyone can have your best time in the updated Codeforces !

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7 years ago, # |
  Vote: I like it 0 Vote: I do not like it

And with this update i lost my motivation to get into div1

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7 years ago, # |
  Vote: I like it +65 Vote: I do not like it

The problem with rating and multiple divisions is more fundamental than just inflation, and it gets worse the more divisions are there. ELO-like ratings (including the Codeforces one) have many assumptions, it is unclear how it would work with non-uniform sampling because of division boundaries, which might skew the resulting ratings.

I quickly tried to estimate the effect, and performed the following experiment. Suppose we have ELO ratings (for simplicity, pure ones, where games are for pairs of players). Let's generate player strengths with normal distribution (10k players, mean 1600, stdev 400), and use these as hidden values to determine game outcomes (i.e. probability of player 1 winning over player 2 is Sigmoid((strength1 - strength2) / 400.0)). Let's simulate the rating system, i.e. sample many pairs of players (5M in my experiment), flip a coin with the corresponding probability, and update ratings by ELO rules.

If there are no division boundaries, after many games we get the following, as expected (x axis is rating, y — actual strength):

Let's add a division boundary at 1900 (i.e. when sampling pairs, only sample the ones from the same division):

OK, we have a small artifact around 1900 — ratings for "div1" players underestimate their actual strength. Let's try to make our "div1" smaller — move the border to 2100:

The effect becomes much more visible. "Div1" ratings are heavily squashed, and difference in strength between 2100 and 2500 is much bigger than between 1500 and 2100 (btw, I've always felt that smth like this is happening with the current CF rating). Finally, what happens with 3 divisions? Let's add boundaries at 1800 and 2100:

We see that "div1" range became almost vertical on the graph! The whole 2100+ strength range is squashed to a tiny ratings range. Of course, it won't happen on CF right away (because div1 ratings are inherited from the previous system), but eventually, it might converge to something like this.

I also tried to run 10x more games, and the picture became much better:

Which makes me think that division boundaries make ratings converge much slower for higher divisions, which for short-term means squashed rating in these ranges. This also explains why div1 ratings are growing so much in div1+div2 contests — we get "free" comparisons of unconverged div1 players and converged div2 players, making div1 ratings closer to their correct values.

It would be nice to understand this effect mathematically, and adjust rating formulas to make convergence equally fast in all divisions.

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    7 years ago, # ^ |
      Vote: I like it +2 Vote: I do not like it

    You suggest that the problem involves only the velocity of convergence, but isnt it more serious than that? In your simulation you considered that div. 2 players would opt to play both div. 1 and 2 right? But if one wants to maximize his rating, isnt it better to opt to play just on div. 2?

    I know that codeforces is or will be running a heuristic correction to this, but maybe a solution is to treat purples separately in div. 2 only rounds, that is, the realative position of a purple to a blue has no (or very little) effect.

    Or maybe my favourite solution is to always run a compound round of div. 1 + 2 + 3 (when there is a div. 1 round of course)

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7 years ago, # |
  Vote: I like it +15 Vote: I do not like it

The biggest problem of Codeforces is its ... ... ... slow loading, usual downs during contests. Other improvements, like Div.3, are some kind of procrastination, while not solving more serious issues.

Upd. I'm sending this message second time because after 1st time it disconnected.

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7 years ago, # |
← Rev. 3   Vote: I like it -10 Vote: I do not like it

I do not think there will be any inflation or deflation of ratings.

I have observed that just like fake accounts abuse the system to get more ratings, real accounts can abuse the system too. Just like tourist can gain ratings just by maintaining his predicted rank which would be 1, any coder with a rating of 2100 or below can only participate in "Div 2" Only Contests and easily get over 2100 rating. Since everyone between 1900 & 2100 will do this, there will literally be a GAP formed between 1900 to 2100 rating.

It will be much much harder for a below 1900 rated contestant to get above 1900 rating as his rating would not increase as much because of a contestant rated 2100 beat him.

Rich get richer. Poor get poorer. There will be a larger barrier now.

Some of my friends used to get insane rating increases in Div1 + Div2 while I always lost ratings. But I loved and anticipated for every educational rounds as it was always an easy ratings increase for me. Same would apply for Div3 as well as merged Div2.

Fake accounts may make it even more harder for Div3 contestants to get out of 1600.

While the previous concern was rapid fluctuation above and below 1900 rating & inconsistency of being able to participate in Div1 & enthusiasm for Div2, It makes it easier now to consistently be able to give both Div1 & 2 but very very hard for under 1900 contestants to move beyond 1900 due to bad rankings due to 1900-2100 band.

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    6 years ago, # ^ |
      Vote: I like it 0 Vote: I do not like it

    1st tourist doesn't gain rating by maintaing his predicted rank 1. His predicted rank is 1.7 or something so getting rank 1 will increase his rating. In fact predicted rank will be 1 only for a user with infinite rating.

    2nd someone below 1900 wouldn't lose much rating becuase of 2100 because it's expected that most probably 2100 guy would beat him on the other hand 1900 guy would have a much higher gain by beatiing 2100 guy.

    Yes fake accounts is terrible problem but that's an entirely different issue.

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7 years ago, # |
  Vote: I like it +5 Vote: I do not like it

I think the last column (the one about title/color changes) in the "Contest" section of the user profile is broken after the update. You should notice it if you see the profile of anyone who is at least orange. Maybe you should try to fix it. @MikeMirzayanov

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7 years ago, # |
  Vote: I like it +5 Vote: I do not like it

Now everyone whose rating is less than 2100 (i.e., before candidate masters) will be able to register for such rounds to participate officially

Shouldn't "before candidate masters" be "before masters"? MikeMirzayanov

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6 years ago, # |
  Vote: I like it +3 Vote: I do not like it

Thanks a lot

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6 years ago, # |
  Vote: I like it 0 Vote: I do not like it

I know this is super late but I just want to express my appreciation. I participated in my first div 3 contest and felt it was just right for my level. Thank you so much!

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6 years ago, # |
  Vote: I like it 0 Vote: I do not like it

So, problems for DIV3 is tend to be easier than them of DIV2?

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5 years ago, # |
  Vote: I like it -6 Vote: I do not like it

As an experiment, we plan to host rounds of simplified complexity (Div. 3).

ETA of outcomes of this experiment?

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5 years ago, # |
  Vote: I like it 0 Vote: I do not like it

Why can't I have gained 1900 points or higher in my rating to be a trusted participant in Div.3 rounds?

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