Method init

src/opr/impl/loop/grad.cpp:393–410

! * \brief initialize for given output vars * \param dest_vars vars in fwd graph needed to give grad */

     * \param dest_vars vars in fwd graph needed to give grad
     */
    void init(const VarNodeArray& dest_vars) {
        mgb_assert(m_var_fwd2grad.empty() && !dest_vars.empty());
        SubgraphDepIter iter;
        for (auto i : dest_vars)
            iter.add(i);

        for (auto i : iter.oprs()) {
            process_opr(i);
        }

        for (auto i : iter.input_makers()) {
            process_input_maker(i);
        }

        for (auto&& i : m_var_fwd2grad) {
            mgb_assert(i.second->owner_graph() == m_grad_desc->sub_graph());
        }
    }

    //! get var in grad graph corresponding to given var in fwd graph
    VarNode* map_var(VarNode* fwd_var) const { return m_var_fwd2grad.at(fwd_var); }