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Comment by _a_a_a_ | Hacker News Reader

"The solution presented here is ~550x faster than the following naive program."

   ... std::cin >> v; ...

Oh come on! That's I/O for every item, I'm surprised it's not even slower.

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Cin is buffered, do it is not technically doing I/O for every time. It is still dog slow of course.

Oops, buffered of course, you're right.

Yeah, how does the proposed solution solve the problem as stated: "Print the number of bytes whose value equals 127 in a 250MB stream of bytes uniformly sampled from [0, 255] sent to standard input."

When stdin is a file, as it is in this case, you can mmap it.

technically not an equivalent problem - you can't map a stream

The whole problem statement isn't equivalent to the substring of the problem statement that GP quoted? I agree. For example, the whole problem statement includes a part that specifies that stdin is a file stored in hugetlbfs.

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