in src/c_interface.cpp [268:277]
bool get_shared_limits(char precision, bool a_t, bool b_t, unsigned int grid, unsigned int *shared) {
std::string prec_string(1, precision);
if (grid >= selections[prec_string][get_op_string(a_t, b_t)].size())
return false;
*shared = selections[prec_string][get_op_string(a_t, b_t)][grid].shared_sizes.size();
return true;
}