Hi Nick,
Could it be possible that the same iterator is being used for multiple
traversals. It maintains state internally so if it were say reused for a
second call it would not return any graph objects since they have already
been marked as "seen".
Other then that the only thing I can think of is the graph itself... is it
directed?
If all else fails and you can write a test case that reproduces the problem
we can look at it.
-Justin
On Thu, Aug 11, 2011 at 5:34 AM, Nick Malleson <[email protected]>wrote:
> Hi,
>
> I'm having a problem with a graph traversal and I was wondering if anyone
> has some suggestions.
>
> What I want to do is quite simple: given an origin edge in a graph, I want
> to create a sub-graph around the origin containing N edges. To do this I
> have created a visitor (called SubGraphVisitor) which counts and records
> the
> number of graph components it has visitted. It termines once it has
> visitted
> N componets and can be used to create a subgraph from the components it has
> seen.
>
> The problem is that sometimes it doesn't work, the 'visit' method of my
> SubGraphVisitor isn't called and so no sub-graph is created. I have checked
> that paths can be created from the edge so I think the graph is correct. I
> have also checked that the graph is complete.
>
> Here is the code that does the walking:
>
> SubGraphVisitor graphVisitor = new SubGraphVisitor(); // This is my visitor
> BreadthFirstIterator iterator = new BreadthFirstIterator();
> BasicGraphTraversal bgt = new BasicGraphTraversal(
> this.graph,
> new SimpleGraphWalker(graphVisitor),
> iterator);
> iterator.setSource(edge1);
> bgt.traverse();
> Graph subGraph = graphVisitor.getSubGraph(); // Sometimes the graph is
> empty
>
> Can anyone sugggest why the call to traverse() doesn't lead to my visitor's
> visit() method being called? I've had a look through the source code for
> BasicGraphTraversal it looks as if the iterator isn't returning a
> component,
> but I'm not sure why this might be.
>
> Thanks for your help,
> Nick
>
> P.S.
> Thanks for all the work that has gone into gt-graph and geotools in
> general,
> it's invaluable for my work.
>
> --
> View this message in context:
> http://osgeo-org.1803224.n2.nabble.com/Problem-iterating-over-a-graph-tp6676019p6676019.html
> Sent from the geotools-gt2-users mailing list archive at Nabble.com.
>
>
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--
Justin Deoliveira
OpenGeo - http://opengeo.org
Enterprise support for open source geospatial.
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