[Lemon-user] Run algorithm on SubDigraph but use (original) Digraph maps

[David Franz Koza]

Dear all,

I'm trying to get a better understanding of lemon graph adaptors in combination with algorithms (function vs class interface). I have a Digraph and a corresponding SubDigraph. I would like to run an algorithm (e.g. Dijkstra) on the SubDigraph, but use the original Digraph maps as input. This is what I tried:

using namespace lemon;
typedef SmartDigraph Digraph;
typedef lemon::SubDigraph<Digraph, Digraph::NodeMap<bool>, Digraph::ArcMap<bool>> SubDigraph;

Digraph g;
Digraph::Node s = g.addNode();
// add further nodes here...
Digraph::NodeMap<bool> node_filter(g);
Digraph::ArcMap<bool> arc_filter(g);
Digraph::ArcMap<int> length(g);
// fill above maps with values...
Digraph::NodeMap<int> dist(g);

// this works:
Dijkstra<Digraph> dijkstra_alg(g, length);

// create a SubDigraph of g based on node_filter and arc_filter maps:
SubDigraph sub_dg(g, node_filter, arc_filter);

// this would work, but requires a new map defined over the SubDigraph:
SubDigraph::ArcMap<int> length_sub(sub_dg);
Dijkstra<SubDigraph> dijkstra_alg2(sub_dg, length_sub);

// this gives an error:
Dijkstra<SubDigraph> dijkstra_alg3(sub_dg, length);
// when using the function interface, this works:
dijkstra(subDigraph(g, node_filter, arc_filter), length).distMap(dist).run(s);

Why can I use subDigraph() (which returns a SubDigraph adaptor) in the dijkstra function interface together with maps of the original graph, and why does the line above using the class interface not work? Am I not using the class interface correctly or, in other words, how can I use the Dijkstra class interface for a SubDigraph while using the original Digraph maps?

Thanks,
David
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