Since the two failures of the contests last weekend, a lot of people have expressed that they want to help Codeforces in some way, but there isn't much many of us can actually do about the system. At the same time, there have also been a lot of (reasonable) requests for a testing round before round 656. So let's put those two together. Why don't we set some potential testing rounds? Maybe they should be rated, maybe they shouldn't, but in any case, they should be interesting enough to draw in participants like normal rounds do. It's probably not a good idea to "sacrifice" rounds not rated for Div. 1, as some have suggested, because that still wastes the efforts of the setters. So what I'm suggesting is that we prepare rounds with the specific intent of them being testing rounds.

Some advantages of this system:

• If these rounds are unrated, there's much less pressure for original/novel problems (and probably fewer problems will be rejected), so more of these rounds will be able to be prepared
• On this same point, it's a great entry point for new problemsetters: rounds are easier to prepare and there will likely be fewer participants (meaning it's easier to manage during the contest)
• It reduces pressure on MikeMirzayanov and the Codeforces team
• You get more problems to solve!

Some potential disadvantages:

• If problems are of lower quality, then they might pollute CF! But there's a simple solution to this: if this becomes an issue, just don't add the problems to "Problemset"
• People would be preparing rounds with a larger chance of the whole round failing! While this is true, these rounds support CF in a different way: they test its infrastructure. And it's not like the whole round is wasted if something goes wrong — after all, that's what we possibly expect from a testing round.

I think it would help, and some testing round would especially be necessary before round 656. So... I'm not one to just throw around words. I have a few problems of my own prepared (not the most "novel", but they should be somewhat educational — I tried to include some common topics, as people have been wanting lately), and am willing to offer them to a testing round. I'll probably host it in the gym, unless it becomes an "official" testing round, and I've adjusted the constraints/time limits to take longer per test case to better simulate the judge pressure of an actual round, since there will likely be fewer people.

Tentatively (it's still in the testing phase, so things may change), there will be 5 problems and the round will last 2 hours. Expect the difficulty to be around Div. 3, maybe somewhat easier. When it's ready, I'll post it in the gym.

I think a good time to schedule it would be around a day before the upcoming round 656, perhaps at the time that Monogon's round was to be held before it was rescheduled. So for now, it will be held at this time (later changed to 1 hour earlier — ignore this link).

What do you think about this?

UPD: you can now view the contest in the gym. Registration opens 6 hours before it starts, which I don't think I have control over. It will start at Jul/16/2020 16:35 (Moscow time), which is 1 hour earlier than it was initially set to.

Thanks to 12tqian, meiron03, and Kaunta for testing. A special thanks to 12tqian for letting me theme the problems around him. And, of course, thanks to MikeMirzayanov for the awesome Polygon, the even more awesome Codeforces, and the platform issues so that this round can be possible :P

UPD 2: the scoring distribution is $$$(1 + 1) - 1 - 1 - 1 - 1$$$ (it's ICPC mode lol)

A is split into subtasks. A1 has a time limit of 15 seconds (maximum setting) with 20 tests, and I highly encourage submitting slow solutions that get close to TL. The rest of the problems have relatively normal constraints. If more people register than I expect, I'll lower these numbers.

If you really want to put load on the queue, you can stall your program until it gets close to 15 seconds. An example of this in C++:

// put this at the beginning of the code
auto begin = std::chrono::high_resolution_clock::now();

const double STOP_TIME = 14; // if your solution is fast, you can make this closer to 15
std::chrono::high_resolution_clock::time_point now;
do {
  // run the solution here, or something that the compiler won't optimize away
  
  now = std::chrono::high_resolution_clock::now();
} while (std::chrono::duration_cast<std::chrono::duration<double>>(now - begin).count() < STOP_TIME);

Other languages have stuff like this too, you can check the documentation for it.

UPD 3: Editorial is out. I hope you enjoyed the round! It seems like there were way too few participants for it to be effective, though. I hope the div. 3 tomorrow goes well.

Congrats to the winners!

$$$~$$$ 1. Geothermal
$$$~$$$ 2. Fanurie
$$$~$$$ 3. CV_Hasan_Fan
$$$~$$$ 3. NotGivingUp
$$$~$$$ 5. idk3910

And an honorable mention to h2o_ and erekle for full-solving.