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Judging/Rejudging challenge problem in long contests

In the problem statement of DIVLAND in APRIL15, it says

Your solution will be tested against only on 20% of the test files during the contest and will be rejudged against 100% after the end of competition.

From my understanding this means a submission will potentially receive changed verdict due to the new tests (e.g. from AC to WA). However, I originally thought (from my previous experience in long contests) that a submission will be run against all test cases during the contest, but only showing a partial scores. Therefore I made a clarification request to the problem author of DIVLAND and received a reply saying that

It's running against all test cases, but revealing score only to 20%.

However I found one of my APRIL15 AC submissions received TLE after rejudging. This is probably due to my program trying to run up to the TL with slight tolerance :). This indicates that all submissions were indeed re-run during rejudging, making solutions running up to TL more risky.

So I was kind of confused by how the challenge problem is judged and rejudged. I tried but didn't find a clear explanation on the site regarding this. I believe the better way is to run against all tests (otherwise you could get WA after rejudging :|). But I think re-running solutions is not necessary for rejudging purpose, which could undesirably change AC to TLE. We can preserve the full scores without showing them during the contest, and just update the scores after the contest.

asked 15 Apr '15, 03:13

yubowenok's gravatar image

6★yubowenok
465
accept rate: 50%

edited 15 Apr '15, 13:56

admin's gravatar image

0★admin ♦♦
19.8k350498541


Yes, it played a bad joke with me during January challenge - it seems that number of TL's during that rejudge is much higher than during contest :)

I also can't understand reasons for such rejudge - korean teams are hardcoding testcases anyway, and for other people it brings only bad news in most cases, because of those TL's.

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answered 15 Apr '15, 03:20

lebron's gravatar image

7★lebron
3.3k317
accept rate: 24%

"It's running against all test cases, but revealing score only to 20%." - This is true.

However, at present we do not have a provision of storing the full score in the first run. Hence we do a rejudge after the contest. We try and make sure that the TLE's solutions are rejudged again so that the newly added TLE's disappear. Sometimes, in exceptional cases, it does not happen. In case your solution is a victim, you can get back to us and we will try and rejudge it again.

This will change in near future. We are working on storing the full score in the first run.

link

answered 16 Apr '15, 21:36

admin's gravatar image

0★admin ♦♦
19.8k350498541
accept rate: 36%

I had experienced the same in September... feels bad.. :(

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answered 17 Apr '15, 01:45

rohanagarwal's gravatar image

5★rohanagarwal
1009
accept rate: 5%

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question asked: 15 Apr '15, 03:13

question was seen: 1,236 times

last updated: 17 Apr '15, 01:45