Re: [Boost-users] [BGL] johnson_all_pairs_shortest problem compiling

From: Jeremy Siek (jsiek_at_[hidden])
Date: 2004-04-04 13:17:36

Hi Val,

Thanks for your email!

On Apr 4, 2004, at 10:39 AM, Val Samko wrote:
> Hi,
>
> Why doesn't the following code compile (VC++ 7.1, g++ 3.3.3, boost 
> 1.31.0) ?
> ======================================================================
> #include <boost/graph/adjacency_list.hpp>
> #include <boost/graph/johnson_all_pairs_shortest.hpp>
> int main()
> {
>         using namespace boost;
>         typedef adjacency_list<vecS, vecS, bidirectionalS,
>                                                         
> boost::property<boost::vertex_index_t, int,
>                                                         
> boost::property<boost::edge_weight_t, int> >
>> Graph;
>         Graph g;
>         int distance_matrix[100][100];
>         johnson_all_pairs_shortest_paths(g, distance_matrix);
> }
> ======================================================================

You've specified edge_weight_t as a vertex property. Instead you should 
have

adjacency_list<vecS, vecS, bidirectionalS,
                             property<vertex_index_t, int>,
                             property<edge_weight_t, int> >

also, note that since you've got VertexList=vecS, there is a built-in 
vertex index,
so you should instead just have

adjacency_list<vecS, vecS, bidirectionalS,
                             no_property,
                             property<edge_weight_t, int> >

> but it compiles, if we pass the edge weight map (composed from
> std::map<edge_descriptor, int>) as a named parameter to
> johnson_all_pairs_shortest_paths ?
>
> Also, why do
> johnson_all_pairs_shortest_paths(g, distance_matrix);
> and
> johnson_all_pairs_shortest_paths(g, distance_matrix, 
> weight_map(get(vertex_index, g)));
> produce completely different compile time errors?

Because they are different errors.

The second error is that get(vertex_index, g) does not return an edge 
weight map, which
is what weight_map() is expecting.

> Finally, is it possible to use
> johnson_all_pairs_shortest_paths
> with adjacency_list<mapS, mapS, ...> ?
> According to the documentation, this should be possible, but this
> just does not compile.

It is suppose to work...

There were some bugs in johnson's with respect to this. I've checked in 
fixes.

Also, with mapS you will need to specify vertex_index_t as an internal
vertex property map of the adjacency_list.

Cheers,
Jeremy

_______________________________________________
Jeremy Siek <jsiek_at_[hidden]>
http://www.osl.iu.edu/~jsiek
Ph.D. Student, Indiana University Bloomington
Graduating in August 2004 and looking for work
C++ Booster (http://www.boost.org)
_______________________________________________