Re: [jgrapht-users] Node degree in the case of a looping edge

[John V. S. <js...@gm...>]

Thanks; this is definitely a bug (the test should be using equals 
instead of == in all cases).  I've checked in the fix and unit test in 
Subversion.

JVS

Michaël Michaud wrote:
> Hi,
> 
> Maybe somebody can tell me if this behaviour is normal or if it's a bug.
> I want to build a graph with a unique cycle (one edge, one vertex)
> I use two classes MyVertex and MyEdge, a WeightedPseudograph (version 
> 0.7.3 of jGraphT), and here is my test case :
> 
> v1 = new MyVertex();
> graph.addVertex(v1);
> graph.addEdge(v1,v1,new MyEdge());
> ==> build a graph with 1 vertex and 1 edge, vertex has degree 2 (that is 
> OK!)
> 
> v1 = new MyVertex();
> v2 = new MyVertex(); // where n2.equals(n1)
> graph.addVertex(v1);
> graph.addVertex(v2);
> graph.addEdge(v1,v2,new MyEdge());
> ==> build a graph with 1 vertex and 1 edge, vertex has degree 4 !
> 
> Seems like addVertex  uses equals to compare vertices and add only one 
> vertex if v1!=v2 but v1.equals(v2)
> That's fine for me
> There is still 1 vertex after addEdge, but that time, the degreeOf 
> method returns 4 instead of 2
> 
> I find this code in AbstractBaseGraph (line 1109) :
> if (source != target) {getEdgeContainer(target).addEdge(e);}
> //here == is used, not equals
> and also this (line 1125) :
> if (getEdgeSource(e).equals(getEdgeTarget(e))) { degree += 2;}
> 
> Any help is welcome
> 
> Michaël
> 
> 
> 
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