Function CrossGradKernel

paddle/phi/kernels/cpu/cross_grad_kernel.cc:27–134

template <typename T, typename Context>
void CrossGradKernel(const Context &dev_ctx,
                     const DenseTensor &x,
                     const DenseTensor &y,
                     const DenseTensor &out_grad,
                     int axis,
                     DenseTensor *x_grad,
                     DenseTensor *y_grad) {
  auto &input_x = x;
  auto &input_y = y;
  auto &input_out_grad = out_grad;
  auto *output_x_grad = x_grad;
  auto *output_y_grad = y_grad;
  int dim = axis;
  auto input_x_dims = input_x.dims();
  if (dim != DDim::kMaxRank) {
    PADDLE_ENFORCE_EQ(
        dim < input_x_dims.size() && dim >= (0 - input_x_dims.size()),
        true,
        errors::OutOfRange(
            "Attr(dim) is out of range, It's expected "
            "to be in range of [-%d, %d]. But received Attr(dim) = %d.",
            input_x_dims.size(),
            input_x_dims.size() - 1,
            dim));
    if (dim < 0) {
      dim += input_x_dims.size();
    }

    PADDLE_ENFORCE_EQ(
        input_x_dims[dim] == 3,
        true,
        errors::InvalidArgument(
            "Input(X/Y).dims[dim] must be equal to 3. But received: "
            "Input(X/Y).dims[dim] = [%d].",
            input_x_dims[dim]));
  } else {
    for (auto i = 0; i < input_x_dims.size(); i++) {
      if (input_x_dims[i] == 3) {
        dim = i;
        break;
      }
    }
    PADDLE_ENFORCE_EQ(
        dim == DDim::kMaxRank,
        false,
        errors::InvalidArgument("There must be at least one dimension 'd' "
                                "so that Input(X/Y).dims()[d] is equal to 3. "
                                "But received: Input(X/Y).dims() == [%s].",
                                input_x_dims));
  }
  int64_t outer_loops = 1;
  for (int i = 0; i < dim; i++) {
    outer_loops *= input_x_dims[i];
  }
  int64_t slice_size = 1;
  for (int i = dim + 1; i < input_x_dims.size(); i++) {
    slice_size *= input_x_dims[i];
  }