Function DuplicateEdges

tensorflow/core/graph/graph_constructor.cc:1618–1661

typedef std::map<const Node*, Node*> map_node;

edge_list DuplicateEdges(Graph* dest, map_node_list& duplicated_nodes,
    map_node& margin_nodes) {
  edge_list edges;
  for (const Edge* e : dest->edges()) {
    auto src = e->src();
    auto dst = e->dst();

    auto src_dup_nodes = duplicated_nodes[src];
    auto dst_dup_nodes = duplicated_nodes[dst];

    //duplicate inner edges between duplicated nodes
    if (!src_dup_nodes.empty() && !dst_dup_nodes.empty()) {
      for (size_t i = 0; i < src_dup_nodes.size(); ++i) {
        edges.emplace_back(src_dup_nodes[i], e->src_output(),
            dst_dup_nodes[i], e->dst_input());
      }
      continue;
    }

    //duplicate edges from duplicated nodes to margin node
    if (!src_dup_nodes.empty()) {
      auto margin_node = margin_nodes[dst];
      if (margin_node != nullptr) {
        for (size_t i = 0; i < src_dup_nodes.size(); ++i) {
          edges.emplace_back(src_dup_nodes[i], e->src_output(),
              margin_node, e->dst_input());
        }
      }
      continue;
    }

    //duplicate edges from margin node to duplicated nodes
    if (!dst_dup_nodes.empty()) {
      auto margin_node = margin_nodes[src];
      if (margin_node != nullptr) {
        for (size_t i = 0; i < dst_dup_nodes.size(); ++i) {
          edges.emplace_back(margin_node, e->src_output(),
              dst_dup_nodes[i], e->dst_input());
        }
      }
    }
  }
  return edges;
}

void AggregateForApply(Graph* dest, Node* n,
    map_node_list& duplicated_nodes, int grad_input) {