RV/V Move ctors

gistfile1.cpp

#include <cstddef>
#include <cstdlib>
#include <ctime>
#include <iostream>
#include <vector>

struct ByValue {
  ByValue(std::vector<int> a, std::vector<int> b)
      : a_{std::move(a)}, b_{std::move(b)} {}

  std::vector<int> a_;
  std::vector<int> b_;
};

struct ByRValue {
  ByRValue(std::vector<int> &&a, std::vector<int> &&b) : a_{a}, b_{b} {}

  std::vector<int> a_;
  std::vector<int> b_;
};

template<class T>
void bench(size_t n) {
  std::vector<int> a, b;
  int sum = 0;
  for (size_t i = 0; i < n; ++i) {
    a.clear();
    b.clear();
    for (int j = 0; j < 2048; ++j) {
      a.push_back(j);
      b.push_back(j);
    }

    auto z = T{std::move(a), std::move(b)};
    for (int i : z.a_) sum += i;
    for (int i : z.b_) sum += i;
  }

  std::cout << "Sum: " << sum << std::endl;
}

int main(int argc, char *argv[]) {
  constexpr size_t B = 10000;
  constexpr size_t N = 10000000;
  std::cout << "ByRValue: Burn in..." << std::endl;
  bench<ByRValue>(B);
  std::cout << "ByRValue: Measuring..." << std::endl;
  auto t0 = clock();
  bench<ByRValue>(N);
  auto dt = static_cast<double>(clock() - t0) / CLOCKS_PER_SEC;
  std::cout << "ByRValue: " << (dt / N * 1e9) << "ns per iteration." << std::endl;

  std::cout << "ByValue: Burn in..." << std::endl;
  bench<ByValue>(B);
  std::cout << "ByValue: Measuring..." << std::endl;
  t0 = clock();
  bench<ByValue>(N);
  dt = static_cast<double>(clock() - t0) / CLOCKS_PER_SEC;
  std::cout << "ByValue: " << (dt / N * 1e9) << "ns per iteration." << std::endl;

}