Geoff Hilton wrote:

Geoff Hilton wrote:

...

Quick question, was the fact that there is no bellman_ford_shortest_paths overload in the BGL that allows for the specification of the root vertex intentional? I'm using MSVC9 and tried using the named parameters overload but it won't compile. Ditto for dijkstra_shortest_paths and dag_shortest_paths actually.

Here's what I have that won't compile with (twice) the error message: error C2248: 'Weight<long long>::Weight': cannot access private member declared in class 'Weight<long long>' c:\program files\boost\boost_1_37_0\boost\graph\bellman_ford_shortest_paths.hpp 155

class ShortestPathBellmanFordForward: public ShortestPathFunction { public: virtual ~ShortestPathBellmanFordForward(){} virtual AlgoResult operator()( const vertex_descriptor startingVertex, const WeightComparer<long long>& comparer, Graph& graph) const { const size_t numVertices = boost::num_vertices(graph); AlgoResult retval; retval.first = PredecessorMap(numVertices); retval.second = DistanceMap(numVertices); vertex_index_prop_t vindex = get(boost::vertex_index, graph); boost::bellman_ford_shortest_paths(graph, numVertices, weight_map(boost::get(&EdgeProp::weights, graph)). predecessor_map(boost::make_iterator_property_map( retval.first.begin(), vindex)). distance_map(boost::make_iterator_property_map( retval.second.begin(), vindex)). root_vertex(startingVertex). distance_combine(WeightCombiner<long long>()). distance_compare(comparer)); return retval; } };

Thanks, Geoff

Hmm, so I realized that the above error was because my Weight datatype happens to have a private constructor which takes a template-type-specified value in the constructor for default initialization (it's really only used (in my code) by my named constructors CreateInfinity() and CreateZero() though). When I comment out the word "private:" which hides the constructor in question, everything compiles fine, but when I comment out the constructor entirely (and adjust the named constructors accordingly) the compiler goes nuts with 30 errors (all of which are attributed by the compiler to bellman_ford_shortest_paths.hpp), the first of which is:

error C2440: '<function-style-cast>': cannot convert from 'int' to 'weight_type' c:\program files\boost\boost_1_37_0\boost\graph\bellman_ford_shortest_paths.hpp 155

"cannot convert from 'int' to 'weight_type'"... well duh. But notice line 155 as mentioned above... is this really desirable? That line does indeed force the requirement that the weight type have a constructor which takes a POD as a parameter.

I'd like to propose replacing the above mentioned behaviour with that which is similar to dijkstra or dag; namely that a weight of value infinity and zero be supplied to the algorithm by named/unnamed parameter.

Thanks, Geoff

Oh, although the above means that I don't need to worry about the unnamed function variant for now, I'd just like to reiterate that I think it would be a good idea that root_vertex be added as a (default-able) parameter. Thanks, Geoff