benchmarkXcwise.cpp

// g++ -O3 -DNDEBUG benchmarkX.cpp -o benchmarkX && time ./benchmarkX

#include <iostream>
#include <Eigen/Core>

using namespace std;
using namespace Eigen;

#ifndef VECTYPE
#define VECTYPE VectorXLd
#endif

#ifndef VECSIZE
#define VECSIZE 1000000
#endif

#ifndef REPEAT
#define REPEAT 1000
#endif

int main(int argc, char *argv[]) {
  VECTYPE I = VECTYPE::Ones(VECSIZE);
  VECTYPE m(VECSIZE, 1);
  for (int i = 0; i < VECSIZE; i++) {
    m[i] = 0.1 * i / VECSIZE;
  }
  for (int a = 0; a < REPEAT; a++) {
    m = VECTYPE::Ones(VECSIZE) + 0.00005 * (m.cwise().square() + m / 4);
  }
  cout << m[0] << endl;
  return 0;
}