#pragma omp parallel for schedule(static, 1) reduction(+:num_lines)
for (int i = 0; i < nfiles; ++i) {
   vec_str_int_type locvec;
   num_lines += get_properties(fname[i], locvec);
   #pragma omp critical
   {
      // Append local vector to propvec (consumes more memory)
      // propvec.insert(
      //    propvec.end(),
      //    std::make_move_iterator(locvec.begin()),
      //    std::make_move_iterator(locvec.end())
      // );

      // Append local vector to propvec (faster)
      auto it  = locvec.begin();
      auto it2 = locvec.end();
      for (; it != it2; ++it)
         propvec.emplace_back(std::move(*it));
   }
}