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#pragma once
#include <ATen/CollapseDims.h>
#include <ATen/Parallel.h>
#include <ATen/TensorUtils.h>
#include <c10/util/irange.h>
#include <cstring>
#include <limits>
namespace at {
/*
* The basic strategy for apply is as follows:
*
* 1. Starting with the outermost index, loop until we reach a dimension where
* the data is no longer contiguous, i.e. the stride at that dimension is not
* equal to the size of the tensor defined by the outer dimensions. Let's call
* this outer (contiguous) tensor A. Note that if the Tensor is contiguous, then
* A is equal to the entire Tensor. Let's call the inner tensor B.
*
* 2. We loop through the indices in B, starting at its outermost dimension. For
* example, if B is a 2x2 matrix, then we do:
*
* B[0][0]
* B[0][1]
* B[1][0]
* B[1][1]
*
* We set the offset into the underlying storage as (storageOffset + stride_B *
* index_B), i.e. basically we compute the offset into the storage as we would
* normally for a Tensor. But because we are guaranteed the subsequent data is
* contiguous in memory, we can simply loop for sizeof(A) iterations and perform
* the operation, without having to follow the order described by the strides of
* A.
*
* 3. As an optimization, we merge dimensions of A that are contiguous in
* memory. For example, if A is a 3x3x3x3 tensor narrowed from a 3x3x4x3 tensor,
* then the first two dimensions can be merged for the purposes of APPLY,
* reducing the number of nested loops.
*/
inline Tensor sort_strides(Tensor& tensor_) {
IntArrayRef strides = tensor_.strides();
std::vector<int64_t> indices;
indices.reserve(tensor_.ndimension());
for (const auto i : c10::irange(tensor_.ndimension())) {
indices.push_back(i);
}
std::sort(indices.begin(), indices.end(), [&strides](int64_t i1, int64_t i2) {
return strides[i1] > strides[i2];
});
Tensor tensor = tensor_.permute(indices);
return tensor;
}
template <typename T, int N>
struct strided_tensor_iter_fixed {
public:
T* data_ = NULL;
int64_t dim_ = 0;
int64_t counter_[N] = {0};
int64_t sizes_[N] = {0};
int64_t strides_[N] = {0};
strided_tensor_iter_fixed(strided_tensor_iter_fixed const&) = delete;
void operator=(strided_tensor_iter_fixed const& x) = delete;
strided_tensor_iter_fixed(strided_tensor_iter_fixed&&) = default;
strided_tensor_iter_fixed(
Tensor& tensor,
C10_UNUSED bool sort_strides = false)
: data_(tensor.data_ptr<T>()) {
std::memset(counter_, 0, sizeof(int64_t) * N);
if (tensor.dim() > 0) {
std::memcpy(
sizes_, tensor.sizes().data(), tensor.dim() * sizeof(int64_t));
std::memcpy(
strides_, tensor.strides().data(), tensor.dim() * sizeof(int64_t));
}
dim_ = std::get<1>(collapse_dims(sizes_, strides_, tensor.ndimension()));
}
};
template <typename T>
struct strided_tensor_iter {
private:
public:
T* data_ = NULL;
int64_t dim_;
std::vector<int64_t> counter_;
std::vector<int64_t> sizes_;
std::vector<int64_t> strides_;
strided_tensor_iter(strided_tensor_iter const&) = delete;
void operator=(strided_tensor_iter const& x) = delete;
strided_tensor_iter(strided_tensor_iter&&) = default;
strided_tensor_iter(Tensor& tensor)
: data_(tensor.data_ptr<T>()),
dim_(tensor.ndimension()),
counter_(dim_, 0),
sizes_(tensor.sizes().vec()),
strides_(tensor.strides().vec()) {
dim_ = std::get<1>(collapse_dims(sizes_.data(), strides_.data(), dim_));
}
};
inline bool _all_equal_numel(at::ArrayRef<Tensor> tensors) {
if (tensors.empty())
return true;
int64_t all_numel = tensors[0].numel();
for (const auto i : c10::irange(1, tensors.size())) {
if (tensors[i].numel() != all_numel)
return false;
}
return true;
}
inline std::string _all_equal_numel_error(at::ArrayRef<Tensor> tensors) {
std::ostringstream oss;
oss << "inconsistent tensor size, expected ";
for (size_t i = 0; i < tensors.size() - 1; i++) {
oss << tensors[i].sizes() << ", ";
}
oss << "and " << tensors[tensors.size() - 1].sizes()
<< " to have the same number of elements, but got ";
for (size_t i = 0; i < tensors.size() - 1; i++) {
oss << tensors[i].numel() << ", ";
}
oss << "and " << tensors[tensors.size() - 1].numel()
<< " elements respectively";
return oss.str();
}
inline bool _apply_preamble(ArrayRef<Tensor> tensors) {
checkDeviceType("CPU_tensor_apply", tensors, kCPU);
checkLayout("CPU_tensor_apply", tensors, kStrided);
if (!_all_equal_numel(tensors))
AT_ERROR(_all_equal_numel_error(tensors));
// An empty tensor has no elements
for (auto& t : tensors)
if (t.numel() == 0)
return false;
return true;
}
inline int64_t _max_dim_tensors(ArrayRef<Tensor> tensors) {
int64_t dim = 0;
for (auto& t : tensors)
dim = std::max(dim, t.ndimension());
return dim;
}
inline void iterate(int64_t /*size*/){};
template <typename Arg, typename... Args>
inline void iterate(int64_t size, Arg& iter, Args&... iter_tail) {
iter.counter_[iter.dim_ - 1] += size;
iter.data_ = iter.data_ + size * iter.strides_[iter.dim_ - 1];
iterate(size, iter_tail...);
}
inline bool iterate_continue() {
return true;
};
template <typename Arg, typename... Args>
inline bool iterate_continue(Arg& iter, Args&... iter_tail) {
return iter.counter_[iter.dim_ - 1] < iter.sizes_[iter.dim_ - 1] &&
iterate_continue(iter_tail...);
}
inline int64_t max_iterate_size() {
return std::numeric_limits<int64_t>::max();
};
template <typename Arg, typename... Args>
inline int64_t max_iterate_size(Arg& iter, Args&... iter_tail) {
return std::min(
(iter.sizes_[iter.dim_ - 1] - iter.counter_[iter.dim_ - 1]),
max_iterate_size(iter_tail...));
}
inline void iterate_overflow(){};
template <typename Arg, typename... Args>
inline void iterate_overflow(Arg& iter, Args&... iter_tail) {
if (iter.counter_[iter.dim_ - 1] == iter.sizes_[iter.dim_ - 1]) {
for (int64_t i = iter.dim_ - 1; i > 0; i--) {
if (iter.counter_[i] == iter.sizes_[i]) {
iter.counter_[i] = 0;
iter.counter_[i - 1]++;
iter.data_ = iter.data_ - (iter.sizes_[i] * iter.strides_[i]) +
iter.strides_[i - 1];
}
}
}
iterate_overflow(iter_tail...);
}
inline void forward(int64_t /*offset*/){};
template <typename Arg, typename... Args>
inline void forward(int64_t offset, Arg& iter, Args&... iter_tail) {
int64_t multi = offset;
for (int64_t i = iter.dim_ - 1; i >= 0; i--) {
int64_t inc = multi % iter.sizes_[i];
multi = multi / iter.sizes_[i];
iter.data_ = iter.data_ + inc * iter.strides_[i];
iter.counter_[i] += inc;
}
forward(offset, iter_tail...);
}
inline int64_t max_dim() {
return 0;
}
template <typename Arg, typename... Args>
inline int64_t max_dim(Arg& iter, Args&... iter_tail) {
return std::max(iter.dim_, max_dim(iter_tail...));
}
inline void apply_op(){};
template <typename Op, typename... Args>
inline void apply_op(
int64_t numel,
int64_t offset,
const Op& op,
Args... iters) {
// For 0-dim tensors
if (numel == 1 && max_dim(iters...) == 0) {
op(*iters.data_...);
return;
}
if (offset > 0)
forward(offset, iters...);
// Splitting this into chunks helps the compiler create faster assembly
for (int64_t i = 0; i < numel;) {
for (; iterate_continue(iters...) && i < numel;) {
op(*iters.data_...);
iterate(1, iters...);
i++;
}
iterate_overflow(iters...);
}
}
/*
Apply a pointwise operator to sequence of tensors
The calling convention for op is a function/functor that takes the same
number of pointers of type scalar as the number of given tensors. For example,
to compute a = b * c, op would be of the form:
[](scalar* a_val, const scalar* b_val, const scalar* c_val) { a_val[0] =
b_val[0] * c_val[0]; };
*/
template <typename scalar1, typename scalar2, typename Op>
inline void CPU_tensor_apply2(Tensor tensor1, Tensor tensor2, const Op op) {
if (!_apply_preamble({tensor1, tensor2}))
return;
if (_max_dim_tensors({tensor1, tensor2}) <= 8) {
apply_op(
tensor1.numel(),
0,
op,
strided_tensor_iter_fixed<scalar1, 8>(tensor1),
strided_tensor_iter_fixed<scalar2, 8>(tensor2));
} else {
apply_op(
tensor1.numel(),
0,
op,
strided_tensor_iter<scalar1>(tensor1),
strided_tensor_iter<scalar2>(tensor2));
}
}
template <typename scalar1, typename scalar2, typename scalar3, typename Op>
inline void CPU_tensor_apply3(
Tensor tensor1,
Tensor tensor2,
Tensor tensor3,
const Op op) {
if (!_apply_preamble({tensor1, tensor2, tensor3}))
return;
if (_max_dim_tensors({tensor1, tensor2, tensor3}) <= 8) {
apply_op(
tensor1.numel(),
0,
op,
strided_tensor_iter_fixed<scalar1, 8>(tensor1),
strided_tensor_iter_fixed<scalar2, 8>(tensor2),
strided_tensor_iter_fixed<scalar3, 8>(tensor3));
} else {
apply_op(
tensor1.numel(),
0,
op,
strided_tensor_iter<scalar1>(tensor1),
strided_tensor_iter<scalar2>(tensor2),
strided_tensor_iter<scalar3>(tensor3));
}
}
template <
typename scalar1,
typename scalar2,
typename scalar3,
typename scalar4,
typename Op>
inline void CPU_tensor_apply4(
Tensor tensor1,
Tensor tensor2,
Tensor tensor3,
Tensor tensor4,
const Op op) {
if (!_apply_preamble({tensor1, tensor2, tensor3, tensor4}))
return;
if (_max_dim_tensors({tensor1, tensor2, tensor3, tensor4}) <= 8) {
apply_op(
tensor1.numel(),
0,
op,
strided_tensor_iter_fixed<scalar1, 8>(tensor1),
strided_tensor_iter_fixed<scalar2, 8>(tensor2),
strided_tensor_iter_fixed<scalar3, 8>(tensor3),
strided_tensor_iter_fixed<scalar4, 8>(tensor4));
} else {
apply_op(
tensor1.numel(),
0,
op,
strided_tensor_iter<scalar1>(tensor1),
strided_tensor_iter<scalar2>(tensor2),
strided_tensor_iter<scalar3>(tensor3),
strided_tensor_iter<scalar4>(tensor4));
}
}
} // namespace at