Robin boundary conditions

[kalosu]

Hi there findiff community,

I am wondering if it is possible to set Robin boundary conditions either directly on the finite difference matrix or via a BoundaryConditions object.

I have a finite differences implementation of a Laplacian equation with Robin boundary conditions.

In my implementation, for the boundary points I have used the ghost point based approach, meaning that I duplicate the weight of the only neighbor point for a boundary point.

In this form, I am able to directly impose the Robin boundary conditions by modifying the entries of my finite difference matrix.

I wanted to do the same with a FinDiff operator but I realized that for all boundary points, 4 points are used instead of just 2 (from the ghost-point based approach)

Any idea about how could I modify the entries of the sparse matrix obtained from the FinDiff operator in order to account for my Robin BC?

Or if possible, could I impose the Robin BC via the BoundaryConditions class so that the modifications are done without me explicitly needing to modify the entries?

Any comment will be highly appreciated!