[petsc-users] DMPlex Interpolation

[Lawrence Mitchell]

>
> I am not sure Injection is going to "do the right thing" when you move between spaces. At least my memory of the implementation
> was that it just did local interpolation, which is not right when injecting P0 into P1.

Ah, that could be the case. For discontinuous things I think what you
want is the L2 projection of the fine function into the coarse space
(which on nested meshes you can compute locally), this is what I
implemented in Firedrake IIRC.

I agree that point interpolating won't work, and I guess in that case
some kind of scaling of a dual thing is approximating the L2
projection.

Lawrence