[petsc-users] DMPlex Interpolation

Mike Michell mi.mike1021 at gmail.com
Mon Aug 29 14:16:34 CDT 2022

@Matt-This is exactly what I wanted to do. Thank you for the help. Mapping
for both directions (Q0->Q1 and Q1->Q0) works well.
@Lawrence-Thank you for the comment. So far, Matt's comment fits my


> >
> > 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
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