Dear all, I am implementing my custom algorithm for path discovery (as in a recent post), and I'd like to know one simple thing. My graph is a bidirectional sparse compressed row graph, and I need to represent a *directed* graph with that (I need in and out edges). So, is the order of nodes in an edge guaranteed to generate the correct in/out adjacent nodes? I do not care about ordering of nodes, just distinguishing nodes that belong to in and out edges. For instance, given a directed graph that has node 4 with two out edges to 5 and 6, and 4 in edges from 1, 2, and 3, am I guaranteed that, even if the graph is bidirectional, the in and out edges will be unaffected and won't be swapped? Moreover, when I dump the indices of out edges, the results seem to be right, but when I dump the in edges, results are erroneous. I must be doing something really wrong... And one more thing: I have tried my code with just using the stream output as in http://programmingexamples.net/wiki/CPP/Boost/BGL/DirectedGraph, just using std::cout << neighbors_out.first << std::endl; clang complains: main.cpp:165:19: error: invalid operands to binary expression ('ostream' (aka 'basic_ostream<char>') and 'boost::detail::csr_out_edge_iterator<boost::compressed_sparse_row_graph<boost::bidirectionalS, boost::no_property, boost::no_property, boost::no_property, unsigned long, unsigned long> >') std::cout << neighbors_out.first << std::endl; ~~~~~~~~~ ^ ~~~~~~~~~~~~~~~~~~~ while if I use the following, it compiles just fine (but as I said, the output is wrong): std::cout << neighbors_out.first->idx << std::endl; See the snippet for an example. Thanks & Cheers! typedef boost::compressed_sparse_row_graph<boost::bidirectionalS> boost_graph; typedef boost::graph_traits<boost_graph>::vertex_iterator vertex_iterator; typedef boost::graph_traits<boost_graph>::adjacency_iterator adjacency_iterator; typedef boost::graph_traits<boost_graph>::out_edge_iterator outward_iterator; typedef boost::graph_traits<boost_graph>::in_edge_iterator inward_iterator; // ... std::vector<std::pair<std::size_t, std::size_t>> results; results.push_back(std::make_pair( 0, 1)); results.push_back(std::make_pair( 0, 3)); results.push_back(std::make_pair( 1, 4)); results.push_back(std::make_pair( 2, 4)); results.push_back(std::make_pair( 3, 4)); results.push_back(std::make_pair( 4, 5)); results.push_back(std::make_pair( 4, 6)); results.push_back(std::make_pair( 5, 7)); results.push_back(std::make_pair( 7, 8)); results.push_back(std::make_pair( 8, 9)); results.push_back(std::make_pair( 8, 11)); results.push_back(std::make_pair( 8, 12)); results.push_back(std::make_pair( 9, 10)); results.push_back(std::make_pair(12, 10)); // Create the graph boost_graph graph(boost::edges_are_unsorted_multi_pass, results.begin(), results.end(), 13); std::cout << "Outward adjacents" << std::endl; std::pair<outward_iterator, outward_iterator> neighbors_out; neighbors_out = boost::out_edges(boost::vertex(4, graph), graph); for(; neighbors_out.first != neighbors_out.second; ++neighbors_out.first) { std::cout << neighbors_out.first->idx << std::endl; } std::cout << "Inward adjacents" << std::endl; std::pair<inward_iterator, inward_iterator> neighbors_in; neighbors_in = boost::in_edges(boost::vertex(4, graph), graph); for(; neighbors_in.first != neighbors_in.second; ++neighbors_in.first) { std::cout << neighbors_in.first->idx << std::endl; } == OUTPUT == Outward adjacents 5 6 Inward adjacents 2 3 4