torch/include/ATen/native/AdaptivePooling.h

#pragma once

#include <ATen/native/DispatchStub.h>
#include <cmath>

namespace at {
class Tensor;

namespace native {

using adaptive_avg_pooling_fn = void(*)(Tensor& output, const Tensor& input, IntArrayRef output_size);
using adaptive_avg_pooling_backward_fn = void(*)(Tensor& grad_input, const Tensor& grad_output);
DECLARE_DISPATCH(adaptive_avg_pooling_fn, adaptive_avg_pool2d_kernel);
DECLARE_DISPATCH(adaptive_avg_pooling_backward_fn, adaptive_avg_pool2d_backward_kernel);

using adaptive_max_pooling_fn = void(*)(const Tensor& output, const Tensor& indices, const Tensor& input, IntArrayRef output_size);
using adaptive_max_pooling_backward_fn = void(*)(const Tensor& grad_input, const Tensor& grad_output, const Tensor& indices);
DECLARE_DISPATCH(adaptive_max_pooling_fn, adaptive_max_pool2d_kernel);
DECLARE_DISPATCH(adaptive_max_pooling_backward_fn, adaptive_max_pool2d_backward_kernel);

static inline int64_t start_index(int64_t a, int64_t b, int64_t c) {
  return (a / b) * c + ((a % b) * c) / b;
}

static inline int64_t end_index(int64_t a, int64_t b, int64_t c) {
  return 1 + ((a + 1) * c - 1) / b;
}

}} // namespace at::native