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 >')
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_graphboost::bidirectionalS
boost_graph;
typedef boost::graph_traits::vertex_iterator vertex_iterator;
typedef boost::graph_traits::adjacency_iterator
adjacency_iterator;
typedef boost::graph_traits::out_edge_iterator
outward_iterator;
typedef boost::graph_traits::in_edge_iterator
inward_iterator;
// ...
std::vector> 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 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 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
