Re: [Boost-users] BGL python: dijkstra_shortest_paths

27 Apr 2007

      ping - is absolutely no one interested in this problem?

John.

John Reid wrote:
...
ping
This looks like a bug in the BGL python bindings.
John.
John Reid wrote:
...
Hi,
I can't seem to use dijkstra_shortest_paths as I think I should via the 
python bindings. It works fine when I pass a weight_map and 
predecessor_map. What I want to do is to pass a predecessor_map and a 
distance_map. Unfortunately boost.python can't convert the arguments.
I'm using a bgl that says bgl.__version__ = '1.0' although I haven't 
updated it from SVN recently.
This works:
import boost.graph as bgl
graph = bgl.Graph()
a = graph.add_vertex()
b = graph.add_vertex()
e = graph.add_edge(a, b)
weights = graph.add_edge_property('integer')
weights[e] = 5
predecessors = graph.add_vertex_property('vertex')
bgl.dijkstra_shortest_paths(
        graph,
        a,
        predecessor_map = predecessors,
        weight_map = weights
)
This doesn't work:
import boost.graph as bgl
graph = bgl.Graph()
a = graph.add_vertex()
b = graph.add_vertex()
e = graph.add_edge(a, b)
distances = graph.add_edge_property('float')
predecessors = graph.add_vertex_property('vertex')
bgl.dijkstra_shortest_paths(
        graph,
        a,
        predecessor_map = predecessors,
        distance_map = distances
)
...
...
* pr
edecessor_map=None, class boost::vector_property_map
...
{lvalu
e} weight_map, class boost::python::api::object visitor=None, class 
boost::vecto
r_property_map
This is the error I get:
: Python argument types in
    boost.graph._graph.dijkstra_shortest_paths(Graph, Vertex)
did not match C++ signature:
    dijkstra_shortest_paths(class 
boost::graph::python::basic_graph<struct boost
::bidirectionalS> graph, struct 
boost::graph::python::basic_descriptor root_vertex, class 
boost::vector_property_map,str
uct boost::graph::python::basic_index_map,struct 
boost::adj_list_vertex_prope
rty_map,struct boost::property,struct 
boost::no_property,struct boos
t::listS>,unsigned int,unsigned int const &,enum boost::vertex_index_t> 
python::basic_index_map,struct 
boost::adj_list_vertex_property_map,struct boost::property,struct boost::no_property,struct 
boost::listS>,unsigned
 int,unsigned int const &,enum boost::vertex_index_t> > > * 
distance_map=None, c
lass boost::vector_property_map,struct 
boost::bidirectionalS>,struc
t boost::adj_list_edge_property_map const ,enum boost::edge_index_t> > 
directionalS>,struct boost::adj_list_vertex_property_map,struct boost::property,struct boost::no_property,struct boost::listS>,unsigned 
int,unsigned
 int const &,enum boost::vertex_index_t> > > * color_map=None)
    dijkstra_shortest_paths(class 
boost::graph::python::basic_graph<struct boost
::undirectedS> graph, struct boost::graph::python::basic_descriptor root_vertex, class 
boost::vector_property_map,struct boost
::graph::python::basic_index_map,struct 
boost::adj_list_vertex_property_map,struct boost::property,struct boost::no_property,struct 
boost::listS>,unsig
ned int,unsigned int const &,enum boost::vertex_index_t> > > * 
predecessor_map=N
one, class boost::vector_property_map,struct boost::adj_list_vertex_property_map,stru
ct boost::property,struct boost::no_property,struct boost::listS>,unsigned int,unsigned 
int con
st &,enum boost::vertex_index_t> > > * distance_map=None, class 
boost::vector_pr
operty_map,struct boost::undirectedS>,struct 
boost::adj_list_edge_prop
erty_map const ,enum boost::edge_index_t> > > {lvalue} weight_map, class 
boost::py
thon::api::object visitor=None, class boost::vector_property_map,struct 
boost::adj_l
ist_vertex_property_map,struct 
boost::property,struct 
boost::no_propert
y,struct boost::listS>,unsigned int,unsigned int const &,enum 
boost::vertex_inde
x_t> > > * color_map=None)
For reference here is the docstring bgl gives me:
Type:           function
Base Class:     
String Form:    
Namespace:      Interactive
Docstring:
    dijkstra_shortest_paths(graph, root_vertex, predecessor_map = None,
                        distance_map = None, weight_map = None,
                        visitor = None)
Computes the shortest paths from the root vertex to every other vertex
in a graph.
Parameters:
  graph            the graph on which to compute shortest paths will
                   run. It may be either a directed or undirected graph.
root_vertex      the starting vertex for the shortest-path search.
predecessor_map  a vertex -> vertex map that stores the predecessor of
                   each vertex in the shortest paths tree. From a given
                   vertex, one can follow the predecessor_map back to
                   the root_vertex to reconstruct the shortest path.
distance_map     a vertex -> float map that stores the distance from
                   the root_vertex to each vertex in the tree. A
                   distance of infinity in this property map indicates
                   that the vertex is unreachable from the root_vertex.
weight_map       an edge -> float map that stores the weight of each
                   edge in the graph. Negative edge weights are not
                   permitted. If no weight map is provided, each edge
                   will be assumed to have a weight of 1.0.
visitor          a visitor that will receive events as the
                   shortest-paths computation progresses. Typically this
                   visitor should be derived from
                   boost.graph.dijkstra_visitor.
See also:
  bellman_ford_shortest_paths
  dag_shortest_paths
  dijkstra_visitor
Complete C++ documentation is available at:
  http://www.boost.org/libs/graph/doc/dijkstra_shortest_paths.html
Any help appreciated,
John.