c++ 計時 chrono

#ifdef COMPILEDWITHC11
        std::chrono::steady_clock::time_point t1 = std::chrono::steady_clock::now();
#else
        std::chrono::monotonic_clock::time_point t1 = std::chrono::monotonic_clock::now();
#endif


double tick= std::chrono::duration_cast<std::chrono::duration<double> >(t2 - t1).count();

reference:      C++11 std::chrono庫詳解-mjwk-博客園