is std::copy faster than std::cout for output?

问题

std::vector<int> v{2,4,6,8,10,12,14,16,18,20};

// print the numbers
    std::copy(v.cbegin(), v.cend(), std::ostream_iterator<int>(std::cout, " "));
    std::cout << '\n';

here std::copy is used to write to std out. Is this faster than using std::cout for the vector elements in a for loop like

for(auto element: v) std::cout << element << " ";

I could't find much information about how they would write to output buffers for both.

回答1:

To give an rough idea on the relative performance of the two, see the benchmark results here: http://quick-bench.com/wGYYPBXEgvLrkyp5gpJOnIpt7A4

I had to output to a std::stringstream instead of std::cout to keep quick-bench happy. It gives some insight on the raw performance of the underlying implementations, but not on how they crossplay with a highly OS dependent output stream like std::cout.

So it is hard to come to any definitive conclusions based on such a simple benchmark alone. I would take from this that in reality there is most likely not enough difference between the two approaches to prefer one over the other from a performance perspective.

来源：https://stackoverflow.com/questions/58621314/is-stdcopy-faster-than-stdcout-for-output