为什么 vs2015/2019 中相同的 C++ 代码比 vs2013 慢 [关闭]

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This is my code. The copy or move operation is performed in a loop.

In vs2013 , one time is 3000+ms in my pc. vs2015 is 5000+ms and vs2019 is 4000+ms .I try it many times.

#include <iostream>
#include <chrono>
#include <sstream>
int main()
{ 
    for (int count = 0; count < 10; count++)
    {
        {
            char ch[50];
            auto pretime = std::chrono::steady_clock::now();
            for (int i = 0; i < 500000; i++)
            {
                std::stringstream ss;
                ss << 123 << "654";
                auto&& str = std::move(ss.str());
                sprintf_s(ch, "%s", str.c_str());
            }
            auto curtime = std::chrono::steady_clock::now();
            auto duration = std::chrono::duration_cast<std::chrono::milliseconds>(curtime - pretime);
            std::cout << "move time= " << duration.count() << "ms" << std::endl;
        }
    
        {
            char ch[50];
            auto pretime = std::chrono::steady_clock::now();
            for (int i = 0; i < 500000; i++)
            {
                std::stringstream ss;
                ss << 123 << "654";
                auto str = ss.str();
                sprintf_s(ch, "%s", str.c_str());
            }
            auto curtime = std::chrono::steady_clock::now();
            auto duration = std::chrono::duration_cast<std::chrono::milliseconds>(curtime - pretime);
            std::cout << "copy time= " << duration.count() << "ms" << std::endl;
        }
    }
}

vs2013

vs2015

Who can tell me the reason? Thanks.