boost graph that doesn't allow circular references - c++

Question

I'm new to boost graphs and are researching the graph that best fits my need. I need to create a dependency graph and given a vertex, I need access to in and out edges. An adjacency_list with Directed=bidirectionalS is what I'm thinking.
But I need to make sure when I call add_edge and that causes a circular reference then it has to error out. I can't seem to find how to do this.

Answer 1

In general, there's only one way to discover whether a graph is a-cyclic: traverse all nodes.
So you'd just need to check whether the graph is still a-cyclic after adding each edge.
However, depending on how you are adding the nodes, you can optimize. If, e.g. you add edges by traversing nodes from a source in DFS order, you can just keep track of nodes "seen" in the current path and refuse to add an out edge to those.
Simplistic example based on topological_sort Live On Coliru:
#include <iostream> // for std::cout
#include <boost/graph/adjacency_list.hpp>
#include <boost/graph/graphviz.hpp>
#include <boost/graph/topological_sort.hpp>
#include <boost/function_output_iterator.hpp>
using namespace boost;
int main()
{
srand(time(0));
typedef adjacency_list<vecS, vecS, bidirectionalS> Graph;
const int num_vertices = 10;
Graph g(num_vertices);
// add random edges to the graph object
for (size_t i = 0; i < 10; ++i)
{
auto f = rand()%num_vertices,
s = rand()%num_vertices;
add_edge(f, s, g);
try {
topological_sort(g, boost::make_function_output_iterator([](int){}));
} catch(not_a_dag const& e)
{
remove_edge(f, s, g);
std::cerr << "dropped edge: " << e.what() << "\n";
}
}
write_graphviz(std::cout, g);
}
Creates random DAGs like

Answer 2

In boost graph BidirectinalS indicates that the edge will be having soruce and target vertices both.
Here is the example for it:
#include <QtCore/QCoreApplication>
#include <boost/graph/adjacency_list.hpp>
#include <boost/graph/subgraph.hpp>
int main(int argc, char *argv[])
{
QCoreApplication a(argc, argv);
using namespace std;
using namespace boost;
typedef boost::subgraph<boost::adjacency_list< boost::listS,
boost::vecS,
boost::bidirectionalS,
boost::property<boost::vertex_index_t, int , property<boost::vertex_color_t, boost::default_color_type > > ,
boost::property<boost::edge_index_t,int, property<boost::edge_color_t , default_color_type> > > >
Graph;
const int num_vertices = 5;
Graph g(num_vertices);
add_edge(0, 1, g);
add_edge(1, 2, g);
add_edge(1, 3, g);
add_edge(2, 4, g);
add_edge(3, 4, g);
boost::graph_traits<Graph>::vertex_iterator VertexItr, VertexItr_end;
boost::graph_traits<Graph>::in_edge_iterator in, in_end;
boost::graph_traits<Graph>::out_edge_iterator out,out_end;
typedef boost::graph_traits < Graph >::adjacency_iterator adjacency_iterator;
// This loop is for getting in edges at vertex
cout<<"In Edge :- "<<endl;
for(boost::tie(VertexItr,VertexItr_end) = vertices(g); VertexItr != VertexItr_end; ++VertexItr) {
cout << *VertexItr << " <-- ";
for (boost::tie(in,in_end) = in_edges(*VertexItr, g); in != in_end; ++in)
cout << source(*in, g) << " ";
cout << endl;
}
// This loop is for getting out edges from vertex
cout<<endl<<"Out Edge :- "<<endl;
for(boost::tie(VertexItr,VertexItr_end) = vertices(g); VertexItr != VertexItr_end; ++VertexItr) {
cout<<*VertexItr<<"--->";
for (boost::tie(out,out_end) = out_edges(*VertexItr, g); out != out_end; ++out)
cout << target(*out, g) << " ";
cout << endl;
}
// This loop is for getting the neighbour vertices of vertex
typedef boost::property_map<Graph, boost::vertex_index_t>::type IndexMap;
IndexMap index = get(boost::vertex_index, g);
cout<<"Adjacent vertices"<<endl;
for(boost::tie(VertexItr,VertexItr_end) = vertices(g); VertexItr != VertexItr_end; ++VertexItr) {
cout<<*VertexItr<<"--->";
std::pair<adjacency_iterator, adjacency_iterator> neighbors =
boost::adjacent_vertices(vertex(*VertexItr,g), g);
for(; neighbors.first != neighbors.second; ++neighbors.first)
{
std::cout << index[*neighbors.first] << " ";
}
cout<<endl;
}
return a.exec();
}

Answer 3

I found this section on the boost documentation discussing how to detect dependencies:
http://www.boost.org/doc/libs/1_55_0/libs/graph/doc/file_dependency_example.html#sec:cycles
But for the adjacency_list the VertexList and EdgeList have to be of type vecS. There's discussion about this here:
How to print a boost graph in graphviz with one of the properties displayed?