CODEWITHSUNDEEP
javaalgorithmjung
Amira
Amira

Reputation: 33

how to test PageRank algorithm for jung?

I'm trying to test Pagerank algorithm for jung but it seems that I have a problem in doing it. I have created a weighted and indirect graph with this portion of code:

private static String getId(int nodeId) 
    {
        return "Node " + nodeId;
    }

    private static String getId(int nodeId, int neighborId) 
    {
        return "Edge " + nodeId + " -> " + neighborId;
    }


public static Graph<String, Integer> createGraphForPageRank(String graphId, double[][] adjacencyMatrix) 
        {
         Graph<String,Integer> g = new UndirectedSparseGraph <String,Integer>();

            for (int nodeId = 0; nodeId < adjacencyMatrix.length; nodeId++)
                g.addVertex(getId(nodeId));



            for (int nodeId = 0; nodeId < adjacencyMatrix.length; nodeId++)
                for (int neighborId = 0; neighborId < adjacencyMatrix[nodeId].length; neighborId++)
                    if (adjacencyMatrix[nodeId][neighborId]>0)

                     g.addEdge(neighborId,getId(nodeId),getId(neighborId));



            return(g);

       }

then, in the main class, I used this code to test pagerank on my graph:

double[][] adjacencyMatrixForPageRank =FileHelper.calculateSimilaritySentences("E:\\my workspace\\TweetsAnalyser2\\outputFiles\\splittedStemmeredFile-1.txt","");
    Graph<String,Integer> g2=FileHelper.createGraphForPageRank("MyGraphForPageRank",adjacencyMatrixForPageRank);
    PageRank<String,Integer> pagerank= new PageRank<String,Integer>(g2,alpha1);
    pagerank.initialize(); 
    pagerank.setTolerance(0.000001);
    pagerank.setMaxIterations(200);
    pagerank.evaluate();

but eclipse generates this error: Exception in thread "main" java.lang.IllegalArgumentException: edge 4 already exists in this graph with endpoints and cannot be added with endpoints at edu.uci.ics.jung.graph.AbstractGraph.getValidatedEndpoints(AbstractGraph.java:93) at edu.uci.ics.jung.graph.UndirectedSparseGraph.addEdge(UndirectedSparseGraph.java:64) at edu.uci.ics.jung.graph.AbstractGraph.addEdge(AbstractGraph.java:60) at edu.uci.ics.jung.graph.AbstractGraph.addEdge(AbstractGraph.java:55) at com.tweets.helpers.FileHelper.createGraphForPageRank(FileHelper.java:1496) at com.tweets.test.Main.main(Main.java:105)

I know that there is a problem with the graph creation, but I don't know how to solve it!!!! Can someone please help me.

Upvotes: 0

Views: 231

Answers (2)

Joshua O&#39;Madadhain
Joshua O&#39;Madadhain

Reputation: 2704

There are a couple of problems that led to your error.

(1) As @amit observed, since your graph is undirected, you don't need to add an edge from x to y and another one from y to x. However, if you have the following code:

g.addEdge(edgeId, x, y);
...
g.addEdge(edgeId, y, x);

The second call to addEdge() will be silently ignored, which is fine.

(2) You can't reuse edge IDs for different sets of incident nodes; that's what that error message is telling you. Edge objects (and node objects) are analogous to map keys: they have to be unique.

Your code suggests that you don't actually care about the edge objects per se, which means that you can just create a Graph<String, Object> and do this when you add an edge:

g.addEdge(new Object(), x, y);

This will get easier in JUNG in its next version, which I hope will be out in a few months. :)

Upvotes: 0

amit
amit

Reputation: 178471

The problem seems to be you defined an undirected graph, and you add the same node twice to it. One in the form of (x,y), and one in the form of (y,x) - for the same values of x and y.

Solve it by iterating in your inner loop only from the nodeID, and not from 0:

for (int nodeId = 0; nodeId < adjacencyMatrix.length; nodeId++)
   for (int neighborId = nodeId; neighborId < adjacencyMatrix[nodeId].length; neighborId++)
                         ^^^

In addition:

g.addEdge(neighborId,getId(nodeId),getId(neighborId));

your edge ID is not unique, which I think it should be, but I am not familiar enough with the API to be sure.

Upvotes: 1

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