move semantics issue

result.txt

# for i in `seq 1 5`; do ./a.out>/dev/null;echo;done

### using std::vector<int>
7995
9732
8003
7981

7982
9833
8124
8070

8137
10157
8075
7987

8032
9821
8046
8040

8071
9782
8211
8064

### using MyVector
8327
10450
8250
8706

8120
9988
8309
8102

8466
10372
8772
8453

8589
10348
8386
8134

8301
10779
8121
8681

src.cc

#include <iostream>
#include <vector>
#include <chrono>

#define DurationTy std::chrono::duration_cast<std::chrono::milliseconds>
size_t const MAX = 100000u;
size_t const NUM = MAX / 100;

template <class T>
class MyVector {
 private:
  std::vector<T> _vec;

 public:
  MyVector() : _vec() {}

  MyVector(const MyVector& other) : _vec(other._vec) {}

  // MyVector& operator=(const MyVector& other) {
  //   if (this != &other) this->_vec = other._vec;
  //   return *this;
  // }

  typename std::vector<T>::const_iterator begin() { return _vec.begin(); }
  typename std::vector<T>::const_iterator end() { return _vec.end(); }

  void push_back(T t) { this->_vec.push_back(t); }
};

// typedef MyVector<int> VectTy;
typedef std::vector<int> VectTy;

int randomize(int mod) { return std::rand() % mod; }

VectTy factory(size_t size, bool pos) {
  VectTy vect;
  if (pos) {
    for (size_t i = 0u; i < size; i++) {
      // vect.push_back(i);
      vect.push_back(randomize(size));
    }
  } else {
    for (size_t i = 0u; i < size * 2; i++) {
      // vect.push_back(i);
      vect.push_back(randomize(size));
    }
  }
  return vect;
}

long d1(VectTy vect) {
  long sum = 0;
  for (auto& v : vect) sum += v;
  return sum;
}

long d2(VectTy& vect) {
  long sum = 0;
  for (auto& v : vect) sum += v;
  return sum;
}

long d3(VectTy&& vect) {
  long sum = 0;
  for (auto& v : vect) sum += v;
  return sum;
}

int main(void) {
  {
    auto start = std::chrono::steady_clock::now();
    long total = 0;
    for (size_t i = 0u; i < NUM; ++i) {
      total += d1(factory(MAX, i % 2));  // T1
    }
    auto end = std::chrono::steady_clock::now();
    std::cout << total << std::endl;
    auto elapsed = DurationTy(end - start);
    std::cerr << elapsed.count() << std::endl;
  }
  {
    auto start = std::chrono::steady_clock::now();
    long total = 0;
    for (size_t i = 0u; i < NUM; ++i) {
      VectTy vect = factory(MAX, i % 2);  // T2
      total += d1(vect);
    }
    auto end = std::chrono::steady_clock::now();
    std::cout << total << std::endl;
    auto elapsed = DurationTy(end - start);
    std::cerr << elapsed.count() << std::endl;
  }
  {
    auto start = std::chrono::steady_clock::now();
    long total = 0;
    for (size_t i = 0u; i < NUM; ++i) {
      VectTy vect = factory(MAX, i % 2);  // T3
      total += d2(vect);
    }
    auto end = std::chrono::steady_clock::now();
    std::cout << total << std::endl;
    auto elapsed = DurationTy(end - start);
    std::cerr << elapsed.count() << std::endl;
  }
  {
    auto start = std::chrono::steady_clock::now();
    long total = 0;
    for (size_t i = 0u; i < NUM; ++i) {
      total += d3(factory(MAX, i % 2));  // T3
    }
    auto end = std::chrono::steady_clock::now();
    std::cout << total << std::endl;
    auto elapsed = DurationTy(end - start);
    std::cerr << elapsed.count() << std::endl;
  }
  return 0;
}