Hi, In an undirected graph, we create an undirected edge: add_edge(a, b, g); We get the reverse of that edge: edge(b, a, g); Now, are these two edges the same or different? vIf I compare them with the == operator, they are equal, but they have different source and target vertexes. Can I count on this behavior? Will it stick? I'm asking because I couldn't find it in the documentation. Please find attached my unit test. On Debian Jessie, I'm compiling it with: g++ test.cc -l boost_test_exec_monitor -l boost_unit_test_framework -o test Thanks & best, Irek