Way to speed up a 2x2 block matrix solver?

Hi All,

So I made a package that solves a 2x2 block system, according to:

This assumes that you have some matrix that is predominantly banded.

Using BandedMatrix.jl, I tried to take a crack at optimizing the solver for such a system.

Could you guys take a look at it and point out any obvious efficiency errors?

The main files to look at are:

// the use case is a 2-D finite difference where I put all the boundary points at the end of a matrix

(edit: may also be related to BlockBandedMatrices issue #23)