/usr/local/lib64/python3.6/site-packages/torch/include/ATen/native
Edit: /usr/local/lib64/python3.6/site-packages/torch/include/ATen/native/GridSampler.h (10525B)
#pragma once
#include
#include
namespace at { namespace native {
namespace detail {
enum class GridSamplerInterpolation {Bilinear, Nearest, Bicubic};
enum class GridSamplerPadding {Zeros, Border, Reflection};
} // namespace detail
using detail::GridSamplerInterpolation;
using detail::GridSamplerPadding;
// Unnormalizes a coordinate from the -1 to +1 scale to its pixel index value,
// where we view each pixel as an area between (idx - 0.5) and (idx + 0.5).
// if align_corners: -1 and +1 get sent to the centers of the corner pixels
// -1 --> 0
// +1 --> (size - 1)
// scale_factor = (size - 1) / 2
// if not align_corners: -1 and +1 get sent to the image edges
// -1 --> -0.5
// +1 --> (size - 1) + 0.5 == size - 0.5
// scale_factor = size / 2
template
static inline scalar_t grid_sampler_unnormalize(scalar_t coord, int64_t size,
bool align_corners) {
if (align_corners) {
// unnormalize coord from [-1, 1] to [0, size - 1]
return ((coord + 1) / 2) * (size - 1);
} else {
// unnormalize coord from [-1, 1] to [-0.5, size - 0.5]
return ((coord + 1) * size - 1) / 2;
}
}
// grid_sampler_unnormalize_set_grad works the same as grid_sampler_unnormalize
// except that it also returns the `d output / d input` via pointer argument
// `grad_in`.
// This is useful in the backward pass of grid_sampler.
template
static inline scalar_t grid_sampler_unnormalize_set_grad(scalar_t coord, int64_t size,
bool align_corners, scalar_t *grad_in) {
if (align_corners) {
// unnormalize coord from [-1, 1] to [0, size - 1]
*grad_in = static_cast(size - 1) / 2;
return ((coord + 1) / 2) * (size - 1);
} else {
// unnormalize coord from [-1, 1] to [-0.5, size - 0.5]
*grad_in = static_cast(size) / 2;
return ((coord + 1) * size - 1) / 2;
}
}
// Clips coordinates to between 0 and clip_limit - 1
template
static inline scalar_t clip_coordinates(scalar_t in, int64_t clip_limit) {
return std::min(static_cast(clip_limit - 1), std::max(in, static_cast(0)));
}
// clip_coordinates_set_grad works similarly to clip_coordinates except that
// it also returns the `d output / d input` via pointer argument `grad_in`.
// This is useful in the backward pass of grid_sampler.
template
static inline scalar_t clip_coordinates_set_grad(scalar_t in, int64_t clip_limit,
scalar_t *grad_in) {
// Note that it is important for the gradient calculation that borders
// are considered out of bounds.
if (in <= static_cast(0)) {
*grad_in = static_cast(0);
return static_cast(0);
} else {
scalar_t max = static_cast(clip_limit - 1);
if (in >= max) {
*grad_in = static_cast(0);
return max;
} else {
*grad_in = static_cast(1);
return in;
}
}
}
// Reflects coordinates until they fall between low and high (inclusive).
// The bounds are passed as twice their value so that half-integer values
// can be represented as ints.
template
static inline scalar_t reflect_coordinates(scalar_t in, int64_t twice_low,
int64_t twice_high) {
if (twice_low == twice_high) {
return static_cast(0);
}
scalar_t min = static_cast(twice_low) / 2;
scalar_t span = static_cast(twice_high - twice_low) / 2;
in = std::fabs(in - min);
// `fmod` returns same sign as `in`, which is positive after the `fabs` above.
scalar_t extra = std::fmod(in, span);
int flips = static_cast(std::floor(in / span));
if (flips % 2 == 0) {
return extra + min;
} else {
return span - extra + min;
}
}
// reflect_coordinates_set_grad works similarly to reflect_coordinates except
// that it also returns the `d output / d input` via pointer argument
// `grad_in`.
// This is useful in the backward pass of grid_sampler.
template
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(0);
return static_cast(0);
}
int grad_in_mult_;
scalar_t min = static_cast(twice_low) / 2;
scalar_t span = static_cast(twice_high - twice_low) / 2;
in = in - min;
if (in < static_cast(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(std::floor(in / span));
if (flips % 2 == 0) {
*grad_in = static_cast(grad_in_mult_);
return extra + min;
} else {
*grad_in = static_cast(-grad_in_mult_);
return span - extra + min;
}
}
// Mapping the out-of-boundary points back into boundary
// This would only affect padding_mode=border or reflection
template
static inline scalar_t compute_coordinates(scalar_t coord, int64_t size,
GridSamplerPadding padding_mode,
bool align_corners) {
if (padding_mode == GridSamplerPadding::Border) {
// clip coordinates to image borders
coord = clip_coordinates(coord, size);
} else if (padding_mode == GridSamplerPadding::Reflection) {
// reflect coordinates by image borders
if (align_corners) {
coord = reflect_coordinates(coord, 0, 2*(size - 1));
} else {
coord = reflect_coordinates(coord, -1, 2*size - 1);
}
// clip coordinates to image borders
coord = clip_coordinates(coord, size);
}
return coord;
}
// Computes the pixel source index value for a grid coordinate
template
static inline scalar_t grid_sampler_compute_source_index(
scalar_t coord,
int64_t size,
GridSamplerPadding padding_mode,
bool align_corners) {
coord = grid_sampler_unnormalize(coord, size, align_corners);
coord = compute_coordinates(coord, size, padding_mode, align_corners);
return coord;
}
// grid_sampler_compute_source_index_set_grad works similarly to
// grid_sampler_compute_source_index except that it also returns the
// `d output / d input` via pointer argument `grad_in`.
// This is useful in the backward pass of grid_sampler.
template
static inline scalar_t grid_sampler_compute_source_index_set_grad(
scalar_t coord,
int64_t size,
GridSamplerPadding padding_mode,
bool align_corners,
scalar_t *grad_in) {
scalar_t grad_clip, grad_refl;
coord = grid_sampler_unnormalize_set_grad(coord, size, align_corners, grad_in);
if (padding_mode == GridSamplerPadding::Border) {
// clip coordinates to image borders
coord = clip_coordinates_set_grad(coord, size, &grad_clip);
*grad_in = (*grad_in) * grad_clip;
} else if (padding_mode == GridSamplerPadding::Reflection) {
// reflect coordinates by image borders
if (align_corners) {
coord = reflect_coordinates_set_grad(coord, 0, 2*(size - 1), &grad_refl);
} else {
coord = reflect_coordinates_set_grad(coord, -1, 2*size - 1, &grad_refl);
}
// clip coordinates to image borders
coord = clip_coordinates_set_grad(coord, size, &grad_clip);
*grad_in = (*grad_in) * grad_refl * grad_clip;
}
return coord;
}
static inline bool within_bounds_2d(int64_t h, int64_t w, int64_t H, int64_t W) {
return h >= 0 && h < H && w >= 0 && w < W;
}
static inline bool within_bounds_3d(int64_t d, int64_t h, int64_t w, int64_t D, int64_t H, int64_t W) {
return d >= 0 && d < D && h >= 0 && h < H && w >= 0 && w < W;
}
template
static inline scalar_t get_value_bounded(
scalar_t* data,
scalar_t x,
scalar_t y,
int64_t W,
int64_t H,
int64_t sW,
int64_t sH,
GridSamplerPadding padding_mode,
bool align_corners) {
x = compute_coordinates(x, W, padding_mode, align_corners);
y = compute_coordinates(y, H, padding_mode, align_corners);
int64_t ix = static_cast(x);
int64_t iy = static_cast(y);
if (within_bounds_2d(iy, ix, H, W)) {
return data[iy * sH + ix * sW];
}
return static_cast(0);
}
template
static inline void safe_add_2d(scalar_t *data, int64_t h, int64_t w,
int64_t sH, int64_t sW, int64_t H, int64_t W,
scalar_t delta) {
if (within_bounds_2d(h, w, H, W)) {
data[h * sH + w * sW] += delta;
}
}
template
static inline void safe_add_3d(scalar_t *data, int64_t d, int64_t h, int64_t w,
int64_t sD, int64_t sH, int64_t sW,
int64_t D, int64_t H, int64_t W,
scalar_t delta) {
if (within_bounds_3d(d, h, w, D, H, W)) {
data[d * sD + h * sH + w * sW] += delta;
}
}
template
static inline void add_value_bounded(
scalar_t* data,
scalar_t x,
scalar_t y,
int64_t W,
int64_t H,
int64_t sW,
int64_t sH,
scalar_t delta,
GridSamplerPadding padding_mode,
bool align_corners) {
x = compute_coordinates(x, W, padding_mode, align_corners);
y = compute_coordinates(y, H, padding_mode, align_corners);
int64_t ix = static_cast(x);
int64_t iy = static_cast(y);
safe_add_2d(data, iy, ix, sH, sW, H, W, delta);
}
// Calculate the differential of the cubic convolution, i.e. `d coeff / d x`
template
static inline void get_cubic_coefficients_grad(
scalar_t coeffs[4],
scalar_t t) {
// Must be the same as forward calculation in
// aten/src/ATen/native/UpSample.h:get_cubic_upsample_coefficients
scalar_t A = -0.75;
scalar_t x;
x = -1 - t; // 1 < x = |-1 - tx| < 2
coeffs[0] = (-3 * A * x - 10 * A ) * x - 8 * A;
x = -t; // x = |0 - tx| <= 1
coeffs[1] = (-3 * (A + 2) * x - 2 * (A + 3)) * x;
x = 1 - t; // x = |1 - tx| <= 1
coeffs[2] = (3 * (A + 2) * x - 2 * (A + 3)) * x;
x = 2 - t; // 1 < x = |2 - tx| < 2
coeffs[3] = (3 * A * x - 10 * A) * x + 8 * A;
}
}} // namespace at::native