[jgrapht-users] ChromaticNumber always 1

[Nick E. <nic...@gm...>]

Dear all,

I have just started using JGraphT and have got it to produce a graph from
my data. I can get the edgeSet().size() and vertexSet().size fine, but if I
try to calculate the Chromatic number I get 1 no matter what the number of
edges and vertices!

The code I am using is bellow: (where create.getCluster(x) returns a graph
generated from some data).

UndirectedGraph<StringCount, DefaultEdge> graph = create.getCluster(x);
      int colour=ChromaticNumber.findGreedyChromaticNumber(graph);
      System.out.println("Cluster with "+graph.edgeSet().size()+" edges and
"+graph.vertexSet().size()+" verticies "+" colours:"+colour);


which gives the output bellow:

Cluster with 8 edges and 5 vertices  colours:1
Cluster with 47 edges and 14 vertices  colours:1
Cluster with 4 edges and 4 vertices  colours:1
Cluster with 478 edges and 90 vertices  colours:1
Cluster with 34 edges and 14 vertices  colours:1
Cluster with 13 edges and 24 vertices  colours:1

It seems a bit unusual that .findGreedyChromaticNumber always returns 1!

My Vertex class is a Pair of a String and an int which delegates the
hashCode() and equals() methods to the string it contains.

Any help would be appreciated!

Thanks

Nick England