Hi Ralf,Hello Umut,

some guesses (not checked with your code!!)

There are two values for the number of nonzeros in ublas

m.nnz() and m.nnz_capacity().

1. m.nnz_capacity() gives you the size of the array m.value_data().

2. m.nnz() gives you the size of the actually used number of nonzeros.

Thanks for the reply, indeed the nnz_capacity returns 8 for the nnz count. Explains why I get 8 values in the vectors instead...

But I still did not understand the reasoning in the codes of ublas where (it seems) there is not a check for the completion of the fill of the elements of a matrix...

The problem is that I have an assembled stiffness matrix in a FE application and I wrote a matrix market interface to export matrices to MATLAB however I iterate over the nonzeros now, which is pretty fast, however I guess If I understand you right now, I can allocate the arrays in my code with number of nnz and then assign to them somehow, not tested though, but many thanks for the explanation. I guess the best bet is to continue in this direction...

Best ,

Umut