Optional return function

ROOT
2

In your “covariance_lib.cc”, at least:

  for(int i = 0; i < size_USER; i++) {
    boo = true;
    for (int j = 0; j < size_EVAL; j++) {

BTW. “Invalid read of size 4/8”, when related to a “float” or “int” or “double” or “long int” array, usually means that you are trying to access array’s element with an improper index (e.g. beyond the end of the array).