java.lang.ArrayIndexOutOfBoundsException when using -q Modularity

[cwtsleiden]

java.lang.ArrayIndexOutOfBoundsException when using -q Modularity

[vtraag]

The problem seems to be caused by the edges with zero weights. For the time being you can circumvent the problem by simply removing those edges. This can be done without any problem since edges with zero weights have no effect anyway.

Nonetheless, this is a bug that should be corrected. We will provide a fix at some later time.

[vtraag]

In particular, the root cause of the problem is that we check whether a neighboring cluster is already added in these conditionals:

networkanalysis/src/main/java/nl/cwts/networkanalysis/LocalMergingAlgorithm.java

Line 188 in a3f342d

if (edgeWeightPerCluster[l] == 0)

networkanalysis/src/main/java/nl/cwts/networkanalysis/FastLocalMovingAlgorithm.java

Line 162 in a3f342d

if (edgeWeightPerCluster[l] == 0)

networkanalysis/src/main/java/nl/cwts/networkanalysis/StandardLocalMovingAlgorithm.java

Line 153 in a3f342d

if (edgeWeightPerCluster[l] == 0)

We should probably use a boolean array isClusterAdded instead of relying on the edge weight. This is the most robust way to address this issue I think. @neesjanvaneck, what do you think?

Ah, I see. Makes perfect sense. I didn't intend to have any edges with zero weight. I'm happy to check for that condition and remove those edges, which are meaningless. Would you like me to close this issue (as far as I'm concerned, it's already resolved)?

[vtraag]

No problem, I imagine that you did not check this condition prior to running the algorithm. No, let's leave the issue open, as the program shouldn't crash on this input.

I suppose a smaller change would simply be to filter out edges with zero weight in the code that reads the edges from the file. This way, you can enforce your own precondition, and leave the downstream code unchanged. The advantage is that it would avoid adding another variable for book-keeping.

[vtraag]

Yes, we would probably do that as well. However, the program still should not crash, even if an edge of zero weight would somehow be included.