Github user hakanmemisoglu commented on a diff in the pull request:
https://github.com/apache/incubator-quickstep/pull/233#discussion_r112067899
--- Diff: utility/DAG.hpp ---
@@ -489,6 +495,40 @@ bool DAG<T, LinkMetadataT>::hasCycleHelper(const
typename DAG<T, LinkMetadataT>:
return false;
}
+template <class T, class LinkMetadataT>
+std::vector<typename DAG<T, LinkMetadataT>::size_type_nodes> DAG<T,
LinkMetadataT>::getTopologicalSorting() const {
+ // We implement "Kahn's algorithm" for the sorting.
+ DCHECK(!hasCycle());
+ std::unique_ptr<std::vector<typename DAG<T,
LinkMetadataT>::size_type_nodes>>
+ sorted_list(new std::vector<size_type_nodes>());
+ sorted_list->reserve(this->size());
+ // Key = node ID, value = # incoming edges for this node.
+ // NOTE(harshad) - We modify the "values" in this map as we go along.
+ std::unordered_map<typename DAG<T, LinkMetadataT>::size_type_nodes,
std::size_t> num_incoming_edges;
+ std::queue<typename DAG<T, LinkMetadataT>::size_type_nodes>
nodes_with_no_children;
+ for (auto node_id = 0u; node_id < this->size(); ++node_id) {
+ if (nodes_[node_id].getDependencies().empty()) {
+ nodes_with_no_children.emplace(node_id);
+ }
+ num_incoming_edges[node_id] = nodes_[node_id].getDependencies().size();
+ }
+ while (!nodes_with_no_children.empty()) {
--- End diff --
I think this is the place where Kahn's algorithm starts to work. Can you
separate methods into logical pieces with comments or by refactoring?
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