[eigen] Sparse Matrix with block sparsity pattern

[Justin Carpentier <jcarpent@xxxxxxx>]

Hi Eigen's users,

I'm currently looking for a C++ implementation of Sparse Matrices with a 
generic Block Sparse pattern, compatible or inspired from the Eigen library.
What I mean by Block Sparse pattern is that each non-zero element 
belongs to a non-zero block of a given dimension. In other words, the 
sparsity is not element-wise but much more block-wise.

Is someone has any idea of such existing implementation?

Best,

Justin