isaf27's blog

About the Codeforces Round #637
By isaf27, history, 5 years ago, In English

Hello Codeforces.

I'm writing this post to make comments about a situation on the last Codeforces Round and tell the bad news. We did many mistakes and due to them, the round caused much dissatisfaction from the Codeforces community.

Some of our mistakes:

  1. Some stupid mistakes in the statements.

  2. In the problem D2E/D1C the numbers $$$d_i$$$ were not necessarily sorted, but there were no pretests for that.

  3. The checker of the problem D2F/D1D didn't check one of the requirements and due to that $$$8$$$ solutions failed on pretests during the system testing.

  4. After the editorial was posted the mistake was found in the main solution of the problem D1E (more details here). Now we don't know the correct solution.

So, the round was very unsuccessful, I'm very sorry about this. I will make conclusions and will try to avoid such situations later. Please, treat with respect to the authors, even in such a bad situation, a big work was done and I hope you enjoyed the problems.

Now about the bad news: due to the wrong checker and the wrong solution, we decided to make Div1 round unrated, Div2 round is still rated, Sorry for all, who had a big positive rating change.

Also, we are making a D1E problem-solving challenge: if you have an algorithm, that can be proven, please share your approach.

So, that was all news, sorry again,

Ivan.

P.S.

If you are angry now, you can use this post to set a dislike, please don't dislike an announcement/editorial.

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

Comments Comments (121)
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5 years ago, # |
  Vote: I like it +454 Vote: I do not like it

RIP

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5 years ago, # |
  Vote: I like it +373 Vote: I do not like it

When arranging contests, there's a "strategic" point of view. There were many contests arranged on Codeforces, and hopefully many more will come.

Humans make mistakes, programmers make plenty of mistakes. Try as we might, we can't fix every single mistake, ever. What we can do, however, is to set up processes to minimize the chance of them happening during preparation, and processes to uncover them and minimize their impact when they happen during a contest. Polygon, Codeforces, their authors, and community as a whole have gone a long way in that regard. Here's a "thank you!" to the people involved, might sound trivial, but I mean it. And each new mistake is an opportunity to improve these processes for the future.

In short, ponder on how to avoid similar mistakes next time. Then cheer up, and move on.

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5 years ago, # |
  Vote: I like it +679 Vote: I do not like it

Sorry, Ivan Belonogov!

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5 years ago, # |
  Vote: I like it +63 Vote: I do not like it

Thanks for this write-up!

We all make mistakes (my contests haven't been flawless either). The best we can do is learn from them and try to find ways to prevent them from happening again in the future.

Side note: Event though div1E didn't work out, I still really liked the concept of the problem and it gave rise to some quite interesting discussions on whether this is possible at all ;)

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

Can't just fix the rating of those negatively affected? Me and many others didn't suffer from those mistakes...

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    5 years ago, # ^ |
      Vote: I like it -9 Vote: I do not like it

    Yes, it's the first time I see such an outcome to unrate the round after official results are final... I am ok with keeping accepted solutions to E. If you would like to remove this task, remove it and unrate for those who got this accepted and will have a negative change after the removal.

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      5 years ago, # ^ |
        Vote: I like it +84 Vote: I do not like it

      You don't know what you're talking about. Keeping the round rated without any kind of solution to one of the tasks is just unfair to those who tried to solve it (which there were many in Div. 1).

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        5 years ago, # ^ |
        ← Rev. 2   Vote: I like it -54 Vote: I do not like it

        You don't know what you're talking about. There were many contests where either the judging queue was extremely long or the checker to some task was incorrect, or the tests were wrong, yet the rounds were rated, even though the impact was obvious for the much bigger number of participants.

        There were not too many participants, who tried to solve it as it was one of the last tasks in D1 (it is a reasonable assumption, everyone could tell now that they always start solving from the last task :) ). I did not even read it.

        Edit. See some examples below, there were tons of such rounds. Cf should be consistent. Looks like it tries to care for the community instead. In this case, after the results are final and the expected number of affected participants is low, this is a bad decision.

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

          Well, I only saw wrong author's solution two times and both rounds were unrated. There is a huge difference between wrong checker or bad tests and wrong proof. As Xellos says below, D1E is the real reason, otherwise the round would probably be left rated. I'm sorry, I didn't mean to offend you in any way and I am sorry for your loss. But it's not the end of the world, so please accept it as it is.

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    5 years ago, # ^ |
      Vote: I like it +95 Vote: I do not like it

    If there wasn't that div1E, I'd expect that to happen, but "wrong problem" is the reason to unrate. You can't check who was affected by trying to solve it and it should serve as a warning to contest organisers everywhere to really make sure it doesn't happen.

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      5 years ago, # ^ |
        Vote: I like it +83 Vote: I do not like it

      This. Unrating the round is the only right thing to do when a problem is just outright wrong, but people with positive deltas are (predictably) going to complain about it.

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5 years ago, # |
  Vote: I like it +87 Vote: I do not like it

This should probably be linked on the official announcement, too.

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5 years ago, # |
  Vote: I like it +51 Vote: I do not like it

In div1C, there was no maxtest in pretests, not even something stupid like islands at 0,1,...,10000 with $$$G=R=1000$$$. I got completely unnecessary MLE because I allocated 2e7 vectors worst-case. There's a simple workaround in implementation with which it passes — use an initially empty vector<vector<int>> V and allocate 2e7 ints where the $$$i$$$-th of them is:

  • $$$0$$$ if the $$$i$$$-th vector is empty
  • $$$4k+1$$$ if the $$$i$$$-th vector contains only $$$k$$$
  • $$$4k+2$$$ if the $$$i$$$-th vector is stored as V[k]

Since the solution is just Dijkstra on small distances and the $$$i$$$-th vector contains states which had distance $$$i$$$, we're only appending, which is easy and fast. If the answer is small, few vectors are used, and if it's large, it's very likely that most vectors are 1-element vectors with no overhead. The same argument works for efficiency since there's one less memory access for vectors with size at most 1 and if there are few vectors to access, it's more cache-efficient, but that's probably not important, I expect the number of distance updates (costly due to push_back) to be much smaller than the number of states.

Still, this is unnecessarily convoluted, implementation tricks to remove a constant factor from time/memory shouldn't be the main point of failure in this problem, which they definitely were regardless of the intended solution.

Also, we are making a D1E problem-solving challenge: if you have an algorithm, that can be proven, please share your approach.

Even if you can't prove it — maybe someone else will.

If you are angry now, you can use this post to set a dislike, please don't dislike an announcement/editorial.

Tbh it makes more sense to downvote a mistake and then upvote effort to admit/fix it. Sure you can ask people to downvote you instead, but most downvotes from non-smurfs have been cast on the announcement already...

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    5 years ago, # ^ |
      Vote: I like it +33 Vote: I do not like it

    I had the same problem with ML in div1C. The easiest way to fix this is use vector<forward_list<int>>. Empty forward list uses three times less memory than empty vector.

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    5 years ago, # ^ |
      Vote: I like it +23 Vote: I do not like it

    I have a better workaround for this problem, since R,G≤1000 the maximum edge weight can't exceed 2000 and at any time the maximum and minimum distance in the priority queue won't differ more than 2000 (easy to prove it by mathematical induction).

    Now we don't 2e7 vectors,we just need 2005 vectors. push_back in v[d%2005] and clear the vector when you visit it.

    Here's my accepted solution: https://codeforces.me/contest/1340/submission/77908138

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

      Yeah, good idea, although a lot harder to realise. It also avoids push_back reallocation overhead since clear keeps the allocated space. I just did the first quick dumb thing that came to mind.

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

        After doing this I thought I had invented a way to implement Dijkstra in linear time for small weights, but then a friend told me it's called Dial's algorithm and it's pretty famous :(

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5 years ago, # |
  Vote: I like it +26 Vote: I do not like it

But still the problems are fairly nice.

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

NOOOOO, RIP GM(((((((((((((

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5 years ago, # |
  Vote: I like it +101 Vote: I do not like it

Why not make it semi-rated? I remember a similar situation happened in round 611 and problem Friends and Gifts had something wrong in the checker source after that round became semi-rated as the number of affected participants was small.

so If the number of participants that got affected in this round small, I think it should be semi-rated

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    5 years ago, # ^ |
      Vote: I like it -29 Vote: I do not like it

    Semi-rating or rejudging after taking out who had something wrong sounds like a better ideia than rooling back all the ratings. Only a small amount got stuck in div1E I suppose.

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    5 years ago, # ^ |
      Vote: I like it +54 Vote: I do not like it

    Username checks out

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    5 years ago, # ^ |
      Vote: I like it +34 Vote: I do not like it

    I remember also, on round 601, they had an appeal form for people who were affected by an issue with Div. 2 B (which thousands of people would have attempted!), but left it rated. Maybe this could be reproduced here?

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      5 years ago, # ^ |
        Vote: I like it -63 Vote: I do not like it

      I don't like Mike (or some other coordinators?) trying their best to make rounds with wrong model solutions to be rated.

      For that particular round 601, there indeed was a correct solution, so it should have been:

      • make the round unrated because it had wrong protests,
      • or fix the model solution, change the tests, and rejudge all solutions

      But absurdly someone just decided to add a constraint $$$m \le n$$$ (meh, seriously), and give participants with wrong solutions a REWARD of 1000 points JUST BECAUSE THEY WERE CARELESS AS THE AUTHORS WERE.

      This could give participants a negative signal: if a problem is on the easy side but you don't know the solution, just submit a stupidly simple solution. Either it is actually correct, or authors will add additional constraints to make my solution correct. lol

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5 years ago, # |
  Vote: I like it +161 Vote: I do not like it

Irrespective of all the other issues involved, deciding to undo rating changes over a full day after the contest is honestly a disgrace to the platform. There was no advance warning that the round might be unrated, and rating changes were rolled out over a day ago. If there was any consideration at all of unrating the round, rating updates should have been postponed until a final decision was made. Moreover, most of the issues in this round, most notably the grammar errors and the weak pre-tests, should have been very easy to identify and fix. From a coordinator’s perspective, this round never should have been approved in its current state, and after the round, the numerous issues should have received a much quicker response.

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

    The linked comment about div1E was posted 13 hours ago, long after rating changes. Then it definitely took some time to come to the conclusion that it really is wrong.

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    5 years ago, # ^ |
      Vote: I like it +92 Vote: I do not like it

    I guess it's just because D1E's jury solution has just been hacked which is a must-fix to me. The other issues are there but probably not enough to get the round unrated.

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

    For what it’s worth, I’d support a solution along the lines of what some others have suggested so far—allow participants to submit a form if the issues with the round, possibly excluding the weak pre-tests on C (as weak pre-tests are unfortunately not overly uncommon), affected their performance. This has been implemented in the past on a much larger scale than would be required here. Moreover, since the biggest issue with this set was the incorrect solution to E, this would allow for the preservation of rating changes for the vast majority of participants, which seems preferable at this point for a number of reasons.

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    5 years ago, # ^ |
      Vote: I like it +270 Vote: I do not like it

    Why is reverting rating changes a disgrace? I think an actual disgrace would be to call a round with wrong author's solution rated.

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

      To be clear, my problem is not (strictly) with unrating the round. My problem is with the way the situation was handled--all but one of the issues with the round were clear well before rating changes were applied (it was also known that most solutions that passed E were not fully correct, I believe, though the error in the author's solution was not yet discovered), but rating changes went through and we never heard anything about the possibility of unrating the round until a sudden announcement a day longer.

      In general, once ratings update (and certainly after ratings have updated and a brief time to check for errors in the calculation has passed), they should be final. If this means that rating updates need to take longer so that an informed decision about whether to keep each contest rated can be made, then so be it. (This also would not be difficult to implement or create significant delays if editorials were released immediately after each round, which doesn't seem implausible--in fact, creating the infrastructure to automatically publish editorials after the round seems quite plausible. This round's problems could have been dealt with far more efficiently if the editorial was published when the contest ended, rather than 12 hours after the fact.)

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        5 years ago, # ^ |
          Vote: I like it +90 Vote: I do not like it

        Why are you so attached to these ratings? It's a very rare case that model solution gets hacked, you can't predict that and you can't measure how much it affected contestant who have tried it and it is a disgrace to keep a round with unsolvable problem rated.

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        5 years ago, # ^ |
          Vote: I like it +49 Vote: I do not like it

        In general, once ratings update (and certainly after ratings have updated and a brief time to check for errors in the calculation has passed), they should be final.

        Again, I don't understand why. I'd rather have my rating recalculated or reverted once in a few months, than wait for a whole day or more for it to change after each contest.

        I agree with you regarding editorials. In a perfect world editorials should not only be finished before the round but also early enough for testers to read and check them.

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        5 years ago, # ^ |
          Vote: I like it +92 Vote: I do not like it

        all but one of the issues with the round were clear well before rating changes were applied

        ... and none of them could be a reason to make the round unrated.

        Imagine that John is accused of insulting his neighbor multiple times. There is a case and a judge just gives John a warning but basically John is decided innocent (no penalty). A few hours later it turns out that John actually killed his neighbor a day before. Will you say that the verdict should hold and John is still innocent?

        all but one of the issues with John were clear well before the verdict was announced

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        5 years ago, # ^ |
          Vote: I like it +44 Vote: I do not like it

        'In general, once ratings update, they should be final'

        Yep, and generally they are. This is a rare exception to the rule, which doesn't 'disgrace' this platform at all.

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

Hmmm, goodbye, IGM.

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5 years ago, # |
  Vote: I like it +129 Vote: I do not like it

RIP, ratings :(

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    5 years ago, # ^ |
      Vote: I like it +236 Vote: I do not like it

    I get to be 10th again! :D

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5 years ago, # |
  Vote: I like it +386 Vote: I do not like it

I really hope Belonogov will get another round in his name.

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    5 years ago, # ^ |
      Vote: I like it +350 Vote: I do not like it

    Codeforces Round #XYZ — Sorry, Ivan Belonogov!

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5 years ago, # |
  Vote: I like it +71 Vote: I do not like it

If the current rating must be rolled back, can you just keep the max-ever? I don't know if I'll be able to reach that high in future :(

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    5 years ago, # ^ |
      Vote: I like it +59 Vote: I do not like it

    I also thought that when I reached 2580

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

      Thanks for your encouragement, but I'm afraid that there's no time for me after August this year…… If I don't perform well in the CNOI, I'll have to say goodbye to programming and of course, Codeforces, for years. Well, thanks anyway.

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      5 years ago, # ^ |
        Vote: I like it -63 Vote: I do not like it

      How was your stay in India?

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5 years ago, # |
  Vote: I like it -146 Vote: I do not like it

Div2 should be unrated also

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5 years ago, # |
  Vote: I like it +72 Vote: I do not like it

Keep positive deltas and undo for the rest. Seems good to everyone xD

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5 years ago, # |
  Vote: I like it +23 Vote: I do not like it

good bye, orange!

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

Good news for me!!!!!!!!

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

N.O!

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5 years ago, # |
  Vote: I like it -25 Vote: I do not like it

I think you can solve this problem by the same way as this: https://codeforces.ml/blog/entry/71534

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

Revive

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5 years ago, # |
  Vote: I like it +1107 Vote: I do not like it

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

    lose rating, get contribution on making a meme about your loss of rating.
    I think life is fair(at least for you)

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      5 years ago, # ^ |
        Vote: I like it -20 Vote: I do not like it

      Rating over contribution any day.

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        5 years ago, # ^ |
          Vote: I like it +143 Vote: I do not like it

        Internet points over internet points any day.

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

          internet points

          The usual term is e-penis length.

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

Lol even the title of this blog has a grammatical mistake.

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5 years ago, # |
  Vote: I like it +58 Vote: I do not like it

For my opinion it's not correct make Div1 round unrated. For example there are contestants, who did not read the problem div1E (for example me). You can make round unrated for people, whose rating was downed.))

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    5 years ago, # ^ |
      Vote: I like it +52 Vote: I do not like it

    Ever heard of inflation?

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      5 years ago, # ^ |
        Vote: I like it +25 Vote: I do not like it

      Yes, but I remember round, in which codeforces used this method).

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        5 years ago, # ^ |
        ← Rev. 3   Vote: I like it 0 Vote: I do not like it

        A round where every rating change was maximized with 0? Show me.

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

          inbound4806319471649067210

          Read the last sentences.

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            5 years ago, # ^ |
              Vote: I like it -38 Vote: I do not like it

            Nope, your argument isn't valid, at all.

            In that educational round, it was absolutely possible to identify "the participants affected by it", by rejudging all previously accepted solutions and see which becomes WA. Also, that problem had a provable 100% correct solution.

            In this round, both of the points above are not true.

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              5 years ago, # ^ |
                Vote: I like it -29 Vote: I do not like it

              Hello guys, mind if you could share why you gave downvotes in this comment?

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                5 years ago, # ^ |
                  Vote: I like it +34 Vote: I do not like it

                Cuz most people don't care about what a fake account says

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

            A round where every rating changed was maximized with 0? Show me.

            You just showed a round where some people were affected and they could appeal. It's completely different from maximizing rating change with 0 for everybody. And how do you want to check if somebody was affected by an unsolvable problem? I can find an example of such issue making a round unrated.

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

            Some people are removed and rating recalculated for the rest.

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5 years ago, # |
  Vote: I like it +195 Vote: I do not like it

Grandmaster Hyperbolic (04.24.2020 ~ 04.25.2020)

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

It happens sometimes, no problem, and we hope for the best in the next rounds

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

Was this the reason that codeforces.com was down after the contest?

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    5 years ago, # ^ |
      Vote: I like it +163 Vote: I do not like it

    I decided to backup all the submissions from the contest in the state they were before system testing. Currently, it is a manual operation: just one SQL-statement to be executed. I executed something like CREATE TABLE Submission_1340_1341 SELECT * FROM Submission WHERE NOT contestId IN (1340, 1341);. And I don't know why, but I added NOT into it. It starts process to backup all the submissions EXCEPT the current contest. Unfortunately for MariaDB/MySQL it is difficult to abort/rollback such statements because of ACID. TLDR; the database hangs in the state of rolling the transaction, blocked the table with submissions, and so on. After some time I decided to kill the database process and re-run it (it is a little bit dangerous, but it seemed that rollback could take hours). After restarting the database again tried to rollback it. So I restarted it again with a special option to disable incomplete transactions recovery. That's the whole story. I think I turned a little gray in the process of all this.

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

      Is there also some reason why http://codeforces.me/ is unavailable for several days?

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

        codeforces.ru is not supported, please always use codeforces.com There was a permanent redirect from codeforces.ru to codeforces.com for years.

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5 years ago, # |
  Vote: I like it +46 Vote: I do not like it

Oh No, my +1 is gone!

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5 years ago, # |
  Vote: I like it +148 Vote: I do not like it

People who demand the round to be rated just because they had positive change — are you insane? People who are doing it while have solved E — I don't know what is wrong with you.

If the only way for you to get high rating is to get wrong solution accepted — you don't deserve that rating.

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    5 years ago, # ^ |
      Vote: I like it +40 Vote: I do not like it

    But why are those people insane? Isn't it natural to feel pity when you even didn't touch that problem and you lose your positive change because of an issue with that problem?

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      5 years ago, # ^ |
      ← Rev. 2   Vote: I like it +16 Vote: I do not like it

      Well, I think it's at least selfish to demand a round to be rated because it is convenient to you, despite there being a serious problem.

      It may feel like the problem does not affect you because you didn't touch it, but indirectly it does. For example, maybe someone below you wasted a lot of time on E and such people are partly the reason you have positive rating delta.

      About rating — I try to not think about it that way. It's supposed to be an estimate of skill. Yeah, it's really shaky at times but I think if you deserved that positive delta, you'll get that positive delta in the next few rounds. If you did not deserve that positive delta, then you'd likely lose it soon in the future anyway. I can sorta understand that if your rating is far below your real skill then such rounds will slow "progress". But then again probably a lot of people just trick themselves into thinking that their rating is far below their real skill.

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

        Regarding the last part, I totally agree.
        What about demand, well , let's be realistic. Assume we somehow have all the participants who struggled on E. Let's remove them from rankings. Will the rating changes of remaining participants have massive changes? I don't think so.

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

          let's be realistic

          Assume we somehow have all the participants who struggled on E

          That's not very realistic.

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

          I don't think so either (and since it was on a hard problem anyway, my opinion is maybe not so strong). Still, the fact that a problem is wrong is serious enough for me to unrate the round on principle.

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

    Bruh you haven't seen insane until you read some forums with discussions that go in circles for tens of pages.

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    5 years ago, # ^ |
      Vote: I like it -97 Vote: I do not like it

    Why didn't you submit the counterexample during the contest if that issue affected you so badly?

    There is inconsistency in cf making the rounds rated or unrated. I would understand that every time some shit happens (long judging queue, unresponsive server, wrong pretests, etc.), the round gets unrated. This is fair. For some strange reason, cf tries to determine the impact on the community before making the round unrated. In this particular case, the impact was negligible. The fact that the ratings were final and nobody noticed the issue just confirms that. Yet, they decided that the final results will be reverted — which I haven't seen since the beginning of this platform.

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

      It's not like everybody who can't solve a problem during a round already has a counterexample to an unknown to him faulty model solution xD

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        5 years ago, # ^ |
          Vote: I like it +91 Vote: I do not like it

        I actually had a counterexample to this particular solution during the round, but I didn't know that it was model :)

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

      The impact of problem E's model solution being incorrect is absolutely unquantifiable. Do you think people begin ascertaining the correctness of the model solution if they're unable to solve a problem ?

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      5 years ago, # ^ |
        Vote: I like it +81 Vote: I do not like it

      "Hey, I can't solve a problem, the only solution I have came up with is wrong, here is countertest to this solution. Isn't it the model solution by any chance?" — great clarification, I would kill a person who sent it to me if I were the authors.

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

        Hey I have a counterexample to outputting 15 on every testcase. Why would you set a problem with a wrong model solution?!?

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

        As an author, I would definitely give attention to such clarification if it came from a veteran like you. When such concerns are indeed voiced by very experienced contestants, they have a chance to be right. But still, much more often it's not the right use of the contestant's time.

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5 years ago, # |
  Vote: I like it -97 Vote: I do not like it

what is that error? :))))

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

    Isn't that the ArnoldC language? It represents a parse error

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5 years ago, # |
← Rev. 2   Vote: I like it +59 Vote: I do not like it

I feel only those people should conduct Div1 Rounds who have conducted few Div2 Rounds earlier. Div 1 Rounds require more effort and more experienced problem setters. I know anybody can make a mistake but the chances of such errors will be less in case of an experienced problem setter.

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

It is the first time that I solved div1D in one contest... RIP IM

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5 years ago, # |
  Vote: I like it +40 Vote: I do not like it

Nice to see my -136 is gone xD (but tbh I did deserve some rating loss since my poor performance had nothing to do with those inadequacies)

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5 years ago, # |
  Vote: I like it -20 Vote: I do not like it

Why keep Div2 rated but not Div1?

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    5 years ago, # ^ |
      Vote: I like it -33 Vote: I do not like it

    Yes, I had a big negative rating change(-49) after this Div.2 contest as my programme to problem C failed when system testing. The pretests are't strong!

    If anyone is angry about this contest, let your friends on codeforces downvote this blog!!!!!!!!!!

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5 years ago, # |
  Vote: I like it -10 Vote: I do not like it

Everyone makes mistakes, don't care)))

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

jenish9599 Lucky XD

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

Codeforces Round #637 — Sorry, Ivan Belonogov!

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5 years ago, # |
  Vote: I like it +16 Vote: I do not like it

Also, there are weak tests on problem D2D/D1B (you can see a lot of uphacks).

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5 years ago, # |
  Vote: I like it +63 Vote: I do not like it

about

annoucement

editorial

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

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

Participants just move their up-votes from the announcement to this blog:|

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5 years ago, # |
  Vote: I like it -26 Vote: I do not like it

The most terrible way to thank Ivan Belonogov!

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

Good that they came to know this was the worst way to thank Ivan Belonogov! as they are no longer using it in the title.

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5 years ago, # |
  Vote: I like it -67 Vote: I do not like it

What would happen if an onsite ICPC contest has a problem with no solution? I suppose they would not make another contest, just remove all wrong ACs and move on. I guess the same could be done here, whoever wasted the time in the problem with no solution is kind of their fault too (but of course its not ideal situation).

I dont really care that much honestly, but in my opinion the correct thing to do would Be to keep this round rated. Keeping this an official thing would be cool. If one problem has no solution the round is still rated, 2 or more unrated.

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5 years ago, # |
  Vote: I like it -48 Vote: I do not like it

Why is only Div.2 rated? I had a big negative rating change. Can anyone help me downvote this blog?

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

So what's gonna happen to this div1E? Is there still no solution? Can the problem be modified to something easier that allows the old solution? Or will it be deleted?

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