C++ 11 缓冲区

#include 
#include 

template
void log_progress(Diff d)
{
    std::cout << "..("<< std::chrono::duration_cast(d).count()<< " ms)..";
}

int main()
{
    volatile int sink = 0;
    std::cout << std::unitbuf; // enable automatic flushing

    auto t1 = std::chrono::high_resolution_clock::now();
    for (int j = 0; j < 5; ++j)
    {
        for (int n = 0; n < 10000; ++n)
            for (int m = 0; m < 20000; ++m)
                sink += m * n; // do some work
        auto now = std::chrono::high_resolution_clock::now();
        log_progress(now - t1);
    }
    std::cout << 'n';
}