Re: [Boost-users] [Serialization][BGL] problem serializing an edge

Hi Irek, you did not mention if you tried the operator& instead of operator<<. I could imagine that the fact, that you are using nested properties might impose problems to the operator<<. However, I am not sure if this can be fixed by using operator&, but it could be worth a try. Best, Cedric On Tuesday, 20. July 2010 19:03:23 Ireneusz Szcześniak wrote:

Hi Cedric,

Thanks for your response. My graph in my code is actually a bit more complicated than what I gave in my example. This is what I'm actually using:

typedef adjacency_list > > > >, property > > Graph;

I have many data structures that have edge_descriptors as their fields, and I wouldn't like to refactor them only to make them vertex or edge properties.

I agree that the reason for the compilation error is that the Serialization library doesn't know how to serialize an edge_descriptor. I don't know why the serialization code for the adjacency list doesn't deliver the serialization code for the edge_description. Should I write the serialization code for the edge_descriptor? If so, then how?

I would appreciate it, if someone could fix the initial example, so that it compiles:

#include <iostream> #include #include

using namespace std; using namespace boost;

int main() { typedef adjacency_list Graph; typedef graph_traits<Graph>::edge_descriptor Edge;

Graph g; Edge e;

boost::archive::text_oarchive oa(cout); oa << g; oa << e;

return 0; }

Thanks, Irek

...

Hi Irek,

as far as I can see from the example and the error message, the error seems to be that there is no operator<< implemented for the edge_descriptor. So the serialization does not know how it should save this instance of an edge _descriptor. Same problem as when working with std::cout and custom classes that have no operator<< defined. I remember having encountered issues when first working with boost::serialize and boost graph lib. However, I don't exactly remember what the problems where. In any case, I managed to sucessfully serialize a graph with custom Vertex and Edge-Properties. You're adjacency_list is a rather straight-forward example and thus should work well. At least as long as you don't want to do/store more complex things with your vertices/edges ;) What I used there was the operator& instead of operator<<. So perhaps you might give it a try.

Also you might be interested in the code: #include <iostream> #include <fstream> #include "Graph.hpp" #include "Properties.hpp" #include #include #include

using namespace boost;

int main(int argc, char** argv) {

typedef Graph MyGraph; std::list< std::pair< VertexProperties, VertexProperties> > v_props; v_props.push_back(std::make_pair(VertexProperties("a", "type_of_a"),

VertexProperties("b", "type_of_b")));

MyGraph G(v_props);

//Serialize it! std::ofstream ofs("./serialize_out.dat"); archive::text_oarchive oa(ofs); oa & G;

//DEserialize it!!! std::ifstream ifs("./serialize_in.dat"); archive::text_iarchive ia(ifs); MyGraph g; ia & g; Graph::Vertex v = g.getFirstVertex(); std::cout << ((g.properties(v)).type) << std::endl;

return 0;

}

There's not much of a difference to your example about it, except for the operator& and the custom Graph<>-class. I have not defined the operator& anywhere, so it might very well work for your problem out-of-the-box also. If it doesn't please let the mailinglist, and thus me, know.

Best,

Cedric

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