Dear members,
using the graph concepts for a case where I frequently add or remove
edges I came across an inconsistency:
removing an edge may invalidate the edge counter because it does not
check whether the edge existed or not. This is the code from the header
file boost/graph/adjacency_matrix.hpp:
template
void
remove_edge(typename adjacency_matrix::vertex_descriptor
u,
typename adjacency_matrix::vertex_descriptor
v,
adjacency_matrix& g)
{
--(g.m_num_edges);
detail::set_edge_exists(g.get_edge(u,v), false, 0);
}
Whereas in the case of adding an edge the check is done:
template
std::pair::edge_descriptor,
bool>
add_edge(typename adjacency_matrix::vertex_descriptor u,
typename adjacency_matrix::vertex_descriptor v,
const EP& ep,
adjacency_matrix& g)
{
typedef typename adjacency_matrix::edge_descriptor
edge_descriptor;
if (detail::get_edge_exists(g.get_edge(u,v), 0) == false) {
++(g.m_num_edges);
detail::set_property(g.get_edge(u,v), ep, 0);
detail::set_edge_exists(g.get_edge(u,v), true, 0);
return std::make_pair
(edge_descriptor(true, u, v,
&detail::get_property(g.get_edge(u,v))),
true);
} else
return std::make_pair
(edge_descriptor(true, u, v,
&detail::get_property(g.get_edge(u,v))),
false);
}
I would suggest a similar check for "remove_edge" instead of blindly
counting down.
Regards,
Moritz
