Accumulate and For

#include <array>
#include <chrono>
#include <iostream>
#include <numeric>
#include <random>
#include <vector>
using namespace std;
using chrono::system_clock;
using chrono::high_resolution_clock;
using chrono::duration_cast;
using chrono::microseconds;
int main() {
  vector<int> v;
  unsigned seed = system_clock::now().time_since_epoch().count();
  mt19937_64 gen(seed);
  uniform_int_distribution<int> dist(0, 9);
  for (int i = 0; i < 300000; i++) v.push_back(dist(gen));
  auto t0 = high_resolution_clock::now();
  long acc = accumulate(v.begin(), v.end(), 0); cout << "acc(vec): " << acc << ", ";
  auto t1 = high_resolution_clock::now();
  cout << duration_cast<microseconds>(t1 - t0).count() << " ms" << endl;
  t0 = high_resolution_clock::now();
  acc = 0; for (auto& e: v) acc += e; cout << "for(vec): " << acc << ", ";
  t1 = high_resolution_clock::now();
  cout << duration_cast<microseconds>(t1 - t0).count() << " ms" << endl;
  array<int, 300000> a;
  for (auto& e: a) e = dist(gen);
  t0 = high_resolution_clock::now();
  acc = accumulate(a.begin(), a.end(), 0); cout << "acc(arr): " << acc << ", ";
  t1 = high_resolution_clock::now();
  cout << duration_cast<microseconds>(t1 - t0).count() << " ms" << endl;
  t0 = high_resolution_clock::now();
  acc = 0; for (auto& e: a) acc += e; cout << "for(arr): " << acc << ", ";
  t1 = high_resolution_clock::now();
  cout << duration_cast<microseconds>(t1 - t0).count() << " ms" << endl;
}