I'm working on a similar pure Neumann problem with a rank-1 deficiency
(pressure known only up to a constant). I've implemented the subspace
projection method Konrad mentioned, with good results. However, I'm
interested in comparing it to the single DoF constraint method, as well as
an alternat
Corbin,
- Using ARPACK might indeed be an option. Do you really need to know the
whole spectrum, though?
- Yes, you would just call AffineConstraints::add_line() to add constrain a
given DoF to zero. Note that it's a no-op if the DoF is already
constrained. This doesn't change the size of the line
