Enable generation of self_loops in condensation_graph()

src/graph/community/graph_community.cc

@@ -101,7 +101,7 @@ extern void community_network(GraphInterface& gi, GraphInterface& cgi,
                               boost::any condensed_community_property,
                               boost::any vertex_count,
                               boost::any edge_count, boost::any vweight,
-                              boost::any eweight);
+                              boost::any eweight, bool self_loops);
 
 BOOST_PYTHON_MODULE(libgraph_tool_community)
 {

src/graph/community/graph_community_network.cc

@@ -43,6 +43,9 @@ typedef DynamicPropertyMapWrap<python::object,GraphInterface::edge_t> eoweight_m
 
 struct get_community_network_dispatch
 {
+    get_community_network_dispatch(bool self_loops): _self_loops(self_loops) {}
+    bool _self_loops;
+
     template <class Graph, class CommunityGraph, class CommunityMap,
               class VertexWeightMap, class EdgeWeightMap, class EdgeIndex,
               class VertexIndex>
@@ -66,7 +69,7 @@ struct get_community_network_dispatch
 
         get_community_network()(g, cg, cvertex_index, cedge_index, s_map,
                                 cs_map, vweight, eweight, vertex_count,
-                                edge_count);
+                                edge_count, _self_loops);
     }
 
     struct get_checked_t
@@ -104,7 +107,7 @@ void community_network(GraphInterface& gi, GraphInterface& cgi,
                        boost::any condensed_community_property,
                        boost::any vertex_count,
                        boost::any edge_count, boost::any vweight,
-                       boost::any eweight)
+                       boost::any eweight, bool self_loops)
 {
     typedef typename mpl::vector<vweight_map_t, voweight_map_t, no_vweight_map_t>::type
         vweight_properties;
@@ -149,8 +152,8 @@ void community_network(GraphInterface& gi, GraphInterface& cgi,
         }
     }
 
-     run_action<>()(gi, bind<void>(get_community_network_dispatch(), _1,
-                                   ref(cgi.GetGraph()), cgi.GetVertexIndex(),
+     run_action<>()(gi, bind<void>(get_community_network_dispatch(self_loops),
+                                   _1, ref(cgi.GetGraph()), cgi.GetVertexIndex(),
                                    cgi.GetEdgeIndex(), _2,
                                    condensed_community_property,
                                    _3, _4, make_pair(vertex_count, edge_count)),

src/graph/community/graph_community_network.hh

@@ -44,7 +44,8 @@ struct get_community_network
                     VertexIndex cvertex_index, EdgeIndex cedge_index,
                     CommunityMap s_map, CCommunityMap cs_map,
                     VertexWeightMap vweight, EdgeWeightMap eweight,
-                    VertexProperty vertex_count, EdgeProperty edge_count) const
+                    VertexProperty vertex_count, EdgeProperty edge_count,
+                    bool self_loops) const
     {
         typedef typename graph_traits<Graph>::vertex_descriptor vertex_t;
         typedef typename graph_traits<Graph>::edge_descriptor edge_t;
@@ -98,7 +99,7 @@ struct get_community_network
                 {
                     vertex_t t = target(*e, g);
                     cvertex_t ct = comm_vertices[get(s_map, t)];
-                    if (ct == cs) // self-loops are pointless
+                    if (ct == cs && !self_loops)
                         continue;
                     cedge_t ce;
                     if (comm_edges.find(make_pair(cs, ct)) != comm_edges.end())

src/graph_tool/community/__init__.py

@@ -278,7 +278,7 @@ def modularity(g, prop, weight=None):
     return m
 
 
-def condensation_graph(g, prop, vweight=None, eweight=None):
+def condensation_graph(g, prop, vweight=None, eweight=None, self_loops=False):
     r"""
     Obtain the condensation graph, where each vertex with the same 'prop' value
     is condensed in one vertex.
@@ -293,6 +293,9 @@ def condensation_graph(g, prop, vweight=None, eweight=None):
         Vertex property map with the optional vertex weights.
     eweight : :class:`~graph_tool.PropertyMap` (optional, default: None)
         Edge property map with the optional edge weights.
+    self_loops : ``bool`` (optional, default: ``False``)
+        If ``True``, self-loops due to intra-block edges are also included in
+        the condensation graph.
 
     Returns
     -------
@@ -355,5 +358,6 @@ def condensation_graph(g, prop, vweight=None, eweight=None):
                                               _prop("v", gp, vcount),
                                               _prop("e", gp, ecount),
                                               _prop("v", g, vweight),
-                                              _prop("e", g, eweight))
+                                              _prop("e", g, eweight),
+                                              self_loops)
     return gp, cprop, vcount, ecount