// The constant base "a" that is being used to compute f_{ut}.
constexpr float A_CONST = 6.76;
// The max number of ratings by any given user on a given date. This
// was found by create_f_u_t.py.
constexpr int MAX_NUM_RAT_USER_DATE = 2651;
// The maximum possible value for f_{ut} is the floor of the log base
// "a" of the maximum number of ratings by any user on a given date.
auto BB = std::floor(std::log(MAX_NUM_RAT_USER_DATE)/std::log(A_CONST));
constexpr int MAX_F_U_T = BB;
It gives me error! When I compile, it
says: error: constexpr variable 'MAX_F_U_T' must be initialized by a constant expression constexpr int MAX_F_U_T = BB;