eigen/bench/bench_sum.cpp

#include <iostream>
#include <Eigen/Core>
using namespace Eigen;
using namespace std;

int main() {
  typedef Matrix<SCALAR, Eigen::Dynamic, 1> Vec;
  Vec v(SIZE);
  v.setZero();
  v[0] = 1;
  v[1] = 2;
  for (int i = 0; i < 1000000; i++) {
    v.coeffRef(0) += v.sum() * SCALAR(1e-20);
  }
  cout << v.sum() << endl;
}