I can not use taucs & cholmod backend as they cause compile error (SuperLU backend works well). So I consider using raw taucs functions.

In Ax=b, my A is rectangle and I use AT*A to make it symmetric and positive definition. However, taucs need only triangular sparse matrix to make llt factor. How could I get a triangular sparse matrix via AT*A using a simple Eigen function?

BTW, if I use coeffRef(i, j) = 0 to insert an element to dynamicSparseMatrix and convert it to SparseMatrix, Eigen regards this "0" as an element.

Thank you.