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#pragma once
#include <ATen/Tensor.h>
namespace torch {
namespace autograd {
namespace utils {
// Helper functions to enforce the "Gradient Layout Contract" described in
// torch/csrc/autograd/AccumulateGrad.h.
// Checks if grad obeys the contract with variable.
inline bool obeys_layout_contract(const at::Tensor& grad, const at::Tensor& variable) {
TORCH_INTERNAL_ASSERT(!grad.is_sparse());
TORCH_INTERNAL_ASSERT(!variable.is_sparse());
return variable.is_non_overlapping_and_dense() ?
(grad.strides() == variable.strides()) :
grad.is_contiguous(at::MemoryFormat::Contiguous);
}
// Creates a clone of new_grad that obeys the contract with variable.
// The clone should attach to new_grad's history if GradMode::is_enabled().
inline at::Tensor clone_obey_contract(const at::Tensor& new_grad, const at::Tensor& variable) {
if (variable.is_non_overlapping_and_dense()) {
// (1)
// Does this dicey-looking sequence attach the result to new_grad's
// history if GradMode::is_enabled()? Yes, and @alband says it should.
return std::move(at::empty_strided(variable.sizes(), variable.strides(),
variable.options().memory_format(c10::nullopt))
.copy_(new_grad));
} else {
// (2)
return new_grad.clone(at::MemoryFormat::Contiguous);
}
}
} // namespace utils
} // namespace autograd
} // namespace torch
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