reflect_coordinates_set_grad Class — pytorch Architecture

Source Code

aten/src/ATen/native/GridSampler.h lines 110–137

template<typename scalar_t>
static inline scalar_t reflect_coordinates_set_grad(scalar_t in, int64_t twice_low,
                                                    int64_t twice_high, scalar_t *grad_in) {
  if (twice_low == twice_high) {
    *grad_in = static_cast<scalar_t>(0);
    return static_cast<scalar_t>(0);
  }
  int grad_in_mult_;
  scalar_t min = static_cast<scalar_t>(twice_low) / 2;
  scalar_t span = static_cast<scalar_t>(twice_high - twice_low) / 2;
  in = in - min;
  if (in < static_cast<scalar_t>(0)) {
    grad_in_mult_ = -1;
    in = -in;
  } else {
    grad_in_mult_ = 1;
  }
  // `fmod` returns same sign as `in`, which is positive after the `if` above.
  scalar_t extra = std::fmod(in, span);
  int flips = static_cast<int>(std::floor(in / span));
  if (flips % 2 == 0) {
    *grad_in = static_cast<scalar_t>(grad_in_mult_);
    return extra + min;
  } else {
    *grad_in = static_cast<scalar_t>(-grad_in_mult_);
    return span - extra + min;
  }
}