Class VarNode

src/core/include/megbrain/graph/var_node.h:237–561

! * \brief Node for a variable. * * It must be the output of exactly one OperatorNode and may be input to other * OperatorNode. * * Each variable has an owner, the operator that generates this variable as one * of the output. * * VarNode class exposes most commonly used memory management interface */

 * VarNode class exposes most commonly used memory management interface
 */
class VarNode final : public GraphNodeBase {
public:
    /*!
     * \brief this constructor should only be called by
     *      OperatorNodeBase::add_output
     *
     * implemented in core/impl/graph/operator_node.cpp
     */
    inline VarNode(Maybe<std::string> name, OperatorNodeBase* owner);

    /* ===================== memory optimization ===================== */

    using LayoutConstraintCallback = thin_function<bool(const TensorLayout&)>;

    /*!
     * \brief add a callback function to check the validity of a particular
     *      tensor layout
     *
     * If callback returns true, it means that this VarNode's dev_tensor
     * with given layout may be forwarded to opr directly, otherwise it
     * will be implicitly rearranged to a contiguous one.
     */
    MGE_WIN_DECLSPEC_FUC VarNode& add_layout_constraint(
            LayoutConstraintCallback callback);

    /*!
     * \brief requires the layout to be contiguous
     *
     * Note: since many oprs require inputs to be contiguous, this is
     * implemented by marking a flag on the var rather than adding a
     * LayoutConstraintCallback to check whether it is contiguous. All the
     * existing callbacks would be cleared and new callbacks would be
     * ignored after add_layout_constraint_contiguous() is invoked.
     */
    MGE_WIN_DECLSPEC_FUC VarNode& add_layout_constraint_contiguous();

    /*!
     * \brief requires the layout to be monotone while allowing broadcast
     *
     * Note: similar to add_layout_constraint_contiguous() this is
     * implemented by marking a flag; however user-defined callbacks are
     * still invoked since they might impose stronger constraints.
     */
    MGE_WIN_DECLSPEC_FUC VarNode& add_layout_constraint_monotone();

    /*!
     * \brief request that memory should be readonly forwarded from other
     *      var
     *
     * Note that this function must be called from
     *      OperatorNodeBase::mem_plan_fwd_in2out_readonly.
     *
     * \return whether this request could be satisfied
     */
    MGB_WARN_UNUSED_RESULT MGE_WIN_DECLSPEC_FUC bool set_fwd_in2out_readonly(
            VarNode* input, const SubTensorSpec& sub);

    /*!