[eigen] Matrix2i mean

[Petr Kubánek <pkubanek@xxxxxxxxx>]

Hi,

calculating mean on int matrix fails to produce expected results - see
below. I noticed 
https://eigen.tuxfamily.org/bz/show_bug.cgi?id=426
which is a bit similar, but different.

Obviously all similar reduxes (sum, prod) fails as well. Is there a way
how to change type used as the internal storage and result for sum.
mean calculations?

Thanks

-- 
Petr Kubánek
Software Engineer - Telescope Control System
Large Binocular Telescope Observatory
580D Steward Observatory
933 N Cherry Avenue
Tucson, AZ 85721

This results in:

-4095 12288.6
12288.5 12288.6


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

int main(int, char **)
{
  Eigen::Matrix<int16_t, 2, 2> m;
  m <<
    INT16_MAX / 2.0, INT16_MAX,
    2, 2;

  double mean = (INT16_MAX / 2.0 + INT16_MAX + 2 + 2) / 4.0;
  std::cout << m.mean() << " " << mean << std::endl;

  Eigen::Matrix<double, 2, 2> md = m.cast<double>();
  std::cout << md.mean() << " " << mean << std::endl;
}