Namnamseo's blog

By Namnamseo, history, 5 years ago, In English

ITC has a CMS but Russia has its own for IOI 2016. (from Minutes of IC February meeting)

Thought of nothing but a private fork of CMS...

Hi everyone! IOI 2016 is just a few days left, hope everyone's working out all right.

IOI 2016 is going to use PCMS2, and I have no idea about it.

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By Namnamseo, history, 5 years ago, In English

Yesterday I had to monitor the memory usage, and I googled to come up with a tool named Valgrind.

It contains many interesting tools, such as Memcheck(monitors memory access and reports on invalid memory access), Massif(monitors memory usage, such as peak or average usage), and Callgrind(monitors function call and records usage). I think it'd be useful for some situations. I always used GDB to debug segmentation faults, but Valgrind looks better somehow.

IOI's contest environment has Valgrind (and GDB), but no one around me seems to have experience with Valgrind. What are the pros and cons of Valgrind you know?

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By Namnamseo, history, 5 years ago, In English

Everyday, problems (for competitive programming) are made — and so are the datas.

I've seen tons of problems involvig a graph, directed or undirected, cyclic or acyclic, weighted or unweighted, dense or sparse, random or having some special requirements (i.e. perfect, cactus, scorpion, etc.). And preparing testcases for such problems inevitably involve building such graph. Also, there are so many problems involving trees, strings, arrays, and points on 2D or 3D space.

I learned a few tricks for making such datas, including making a connected graph by first building its spanning tree, putting a few special trees(all points lying on a line, 'sea urchin' trees, sqrt(N) vertices having sqrt(N) neighbors) to cut out some suboptimal solutions, and such. (Put it the other way, take a look at APIO 2013, the third task.)

But somehow, it feels tedious to code the same things every time(yes, I'm being lazy here), and I believe there are many ideas we can share to make the testcases better (and harder). I googled a little bit, but it seems there aren't one that's well-maintained.

I think it'd be good to have one that:

  • can be run directly as a tool, or can be used as a library;
  • provides templates for common structures and constraints;
  • its outputs should be easily formattable;
  • custom constraints can be easily added;
  • is open-source and well-maintained

Is there any?

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By Namnamseo, history, 6 years ago, In English

Posts in 'Recent actions' continuously go down and eventually disappear. How can I read old posts?

Personally I'd like to read a post about FFT. I think there were some links for FFT problems.

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By Namnamseo, history, 6 years ago, In English

What are the differences between submissions that show the test cases and output(even for the wrong submission) and those that don't?

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