CODEWITHSUNDEEP
c++visual-studiovisual-c++igraph
Miguel
Miguel

Reputation: 787

Igraph eigenvector centrality Run-Time error c++

I'm writing program on c++ that needs to generate graphs and calculate some measures.I'm working with Visual Studio 2013 and Igraph C library. At this point I can create graphs from custom info and calculate some metrics like betweennes and closeness centrality, but when i try to calculate eigenvector centrality, the program crash and show me this message:

"Run-Time Check Failure #3 - The variable 'tgetv0' is being used without being initialized."

The tgetv0 variable is used inside of dgetv.c from Igraph source. Here is my code:

void GraphObject::calcEigen()
{
igraph_arpack_options_t options;
igraph_real_t value;
igraph_vector_t weights;
igraph_vector_init(&weights, igraph_ecount(&cGraph));  //cGraph is already created.
igraph_vector_init(&eigenRes, igraph_vcount(&cGraph));  //All ..Res igraph_vector_t are declarated in header
igraph_vector_init(&betweennesRes, 0);
igraph_vector_init(&closenessRes, 0);
igraph_arpack_options_init(&options);

igraph_betweenness(&cGraph, &betweennesRes, igraph_vss_all(), 0, 0, 1);
igraph_closeness(&cGraph, &closenessRes, igraph_vss_all(), IGRAPH_ALL, 0, 1);
igraph_eigenvector_centrality(&cGraph, &eigenRes, &value, 0, 1, &weights, &options);
}

The closeness and betwenness are correctly calculated an "couted" but crash on eigenvector function.

After lot of research on documentation, internet and the debugger i cant't figure which is the problem, especially when I tryed the example code in the documentation http://igraph.org/c/doc/igraph-Structural.html#igraph_eigenvector_centrality (copy/paste) and makes the same. Is this a library or example issue, I a'm missing something?

When I init the weights vector and then I call igraph_null(&weights), it works but the result of all eigenvalues is 1, and this is incorrect result. What I'm doing wrong?

Upvotes: 2

Views: 357

Answers (1)

Tamás
Tamás

Reputation: 48051

Let us assume that Visual Studio is right and we indeed have a variable named tgetv0 that is being used uninitialized. I scanned igraph's source code and it looks like there are two places where it could indeed be the case. One of them is in src/lapack/dnaupd.c, the other one is in src/lapack/dsaupd.c. Both of these files were converted from Fortran using f2c so it is hard to tell whether the issue was present in the original Fortran code or whether this was introduced during the conversion. Either way, you can probably fix this easily by looking up the lines where tgetv0 is declared in src/lapack/dnaupd.c and src/lapack/dsaupd.c and initializing it to a value of 0. In my version, the lines to change are line 486 in src/lapack/dnaupd.c and line 482 in src/lapack/dsaupd.c.

Please add a comment to confirm whether the solution works for you or not - if it works, I'll commit a patch to the igraph source tree.

Upvotes: 0

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