Hi Emmanuel, On 8/1/07, Emmanuel Viaud wrote:

Hello.

Using Boost 1.34.1 (with g++-3.4.2) and more specifically the Boost Graph library, I stumbled on a small problem with the transitive_closure algorithm.

I saw in the documentation that I can get a map containing the mapping between the vertices of the original graph and the ones in the transitive closure graph (the orig_to_copy parameter). But every time I call the method, I get an empty map as a result. To sum up my code, I use the following data structures for the graph:

typedef boost::adjacency_list < boost::vecS, boost::vecS, boost::directedS > graph_t; typedef boost::graph_traits < graph_t >::vertex_descriptor vertex_t;

and the following one for the expected map:

typedef std::map < vertex_t, vertex_t > ioMap_t;

The graphs and map are declared the following way:

graph_t myGraph; graph_t myTCGraph;

ioMap_t ioMap;

I used both versions of the algorithm: 1) using named parameters, I call: transitive_closure(myGraph, myTCGraph, orig_to_copy(ioMap));

2) using "standard" parameters, I call: transitive_closure(myGraph, myTCGraph, ioMap, get(vertex_index, myGraph));

So, the main question is easy: Where did I write something wrong ? :-)

You did not pass transitive_closure a property map. Instead you give the algorithm a std::map. typedef std::map < vertex_t, vertex_t > ioMap_t; ioMap_t vertex_vertex_map; boost::associative_property_map< std::map > ioMap(vertex_vertex_map); Should work. To speed things up, you could also use a std::vector and let the specialization of property maps for pointers kick in. Create the container: std::vector ioMap(num_vertices(myGraph)); and use it: transitive_closure(myGraph, myTCGraph, &ioMap[0], get(vertex_index, myGraph)); An additional function_requires < Mutable_LvaluePropertyMapConcept < G_to_TC_VertexMap, vertex > >(); in transitive_closure would have spotted that problem. HTH, Stephan