Hi, I would like to know how are sparse matrices stored in Eigen when I assemble them using triplets? Are they stored in the compressed column storage or compressed row storage or some other format?

Thanks

In whatever ordering (row/col) your matrix was defined, and into a uncompressed format. See the sparse module documentation and set_from_triplets() in /src/SparseCore/SparseMatrix.h as reference.

All the details are there: http://eigen.tuxfamily.org/dox-devel/gr ... tml#title0