闲:测试memcpy和std::copy vector之间拷贝

预测:底层C函数肯定比stl算法快

结果:少量数据底层快,大数据以上则stl对vector的处理可能更好

C/C++:

 #include <iostream>
 #include <vector>
 #include <functional>
 #include <algorithm>
 #include <string>

 template<typename T>
 void Display(const T &rhs)
 {
     for (auto iter = rhs.begin(); iter != rhs.end();)
     {
         printf("%c\n", *iter++);
     }
 }

 int main()
 {
     std::vector<char> vec1_;
     char ch = 'a';
     ; i < ; i++)
     {
         vec1_.push_back(ch);
     }

     std::clock_t start, end;

     start = std::clock();
     std::vector<char> vec2_(vec1_.begin(), vec1_.end());
     end = std::clock();

     std::cout << "迭代器范围初始化: " << ((double)(end-start)/CLOCKS_PER_SEC) << std::endl;
    // Display(vec2_);

     start = std::clock();
     std::vector<char> vec3_;
     vec3_.resize(vec1_.size());
     std::copy(vec1_.begin(), vec1_.end(), vec3_.begin());
     end = std::clock();

     std::cout << "std::copy: " << ((double)(end-start)/CLOCKS_PER_SEC) << std::endl;
    // Display(vec3_);

     start = std::clock();
     std::vector<char> vec4_;
     vec4_.resize(vec1_.size());
     std::memcpy(&vec4_[], &vec1_[], vec1_.size());
     end = std::clock();
     std::cout << "memcpy: " << ((double)(end-start)/CLOCKS_PER_SEC) << std::endl;
     //Display(vec4_);

     ;
 }

注意点:memcpy 只能按字节拷贝,所以选择char进行，实际意义不明显...