lanczos_sum_expg_scaled Class — pytorch Architecture

Source Code

aten/src/ATen/native/Math.h lines 581–618

template <typename scalar_t>
static scalar_t lanczos_sum_expg_scaled(scalar_t x) {
  // lanczos approximation
  static constexpr scalar_t lanczos_sum_expg_scaled_num[13] = {
    0.006061842346248906525783753964555936883222,
    0.5098416655656676188125178644804694509993,
    19.51992788247617482847860966235652136208,
    449.9445569063168119446858607650988409623,
    6955.999602515376140356310115515198987526,
    75999.29304014542649875303443598909137092,
    601859.6171681098786670226533699352302507,
    3481712.15498064590882071018964774556468,
    14605578.08768506808414169982791359218571,
    43338889.32467613834773723740590533316085,
    86363131.28813859145546927288977868422342,
    103794043.1163445451906271053616070238554,
    56906521.91347156388090791033559122686859
  };
  static constexpr scalar_t lanczos_sum_expg_scaled_denom[13] = {
    1.,
    66.,
    1925.,
    32670.,
    357423.,
    2637558.,
    13339535.,
    45995730.,
    105258076.,
    150917976.,
    120543840.,
    39916800.,
    0.
  };
  return ratevl(x, lanczos_sum_expg_scaled_num,
      sizeof(lanczos_sum_expg_scaled_num) / sizeof(lanczos_sum_expg_scaled_num[0]) - 1,
      lanczos_sum_expg_scaled_denom,
      sizeof(lanczos_sum_expg_scaled_denom) / sizeof(lanczos_sum_expg_scaled_denom[0]) - 1);
}