from Class — pytorch Architecture

Source Code

aten/src/ATen/templates/TensorBody.h lines 662–703

template <>
struct MaybeOwnedTraits<at::Tensor> {
  using owned_type = at::Tensor;
  using borrow_type = at::Tensor;

  static borrow_type createBorrow(const owned_type& from) {
    // NOTE: this can be implemented without the special
    // unsafe_borrow_t Tensor constructor as
    //
    // return borrow_type(c10::intrusive_ptr<at::TensorImpl, at::UndefinedTensorImpl>::reclaim(from.unsafeGetTensorImpl()));
    //
    // but that hurts inlining due to the nullptr check in the
    // Tensor(c10::intrusive_ptr<...>) constructor. We already know
    // that from.impl_ isn't null because from is a valid Tensor, so
    // we needn't do the check again. (using __builtin_assume can
    // avoid this, but wouldn't be portable to MSVC.)
    return borrow_type(borrow_type::unsafe_borrow_t{}, from);
  }

  static void assignBorrow(borrow_type& lhs, const borrow_type& rhs) {
    lhs.unsafeReleaseTensorImpl();
    // See above note: this can be implemented with public API
    // similarly to createBorrow(), but that would hurt inlining.
    lhs = borrow_type(borrow_type::unsafe_borrow_t{}, rhs);
  }

  static void destroyBorrow(borrow_type& toDestroy) {
    toDestroy.unsafeReleaseTensorImpl(); // "leak" it, but it was already +0.
  }

  static const owned_type& referenceFromBorrow(const borrow_type& borrow) {
    return borrow;
  }

  static const owned_type* pointerFromBorrow(const borrow_type& borrow) {
    return &borrow;
  }

  static bool debugBorrowIsValid(const borrow_type& /*borrow*/) {
    return true;
  }
};