[petsc-dev] higher-order coordiate fields in DMPlex

Matthew Knepley knepley at gmail.com
Fri Jun 2 17:36:04 CDT 2017

On Fri, Jun 2, 2017 at 5:04 PM, Alberto Paganini <
Alberto.Paganini at maths.ox.ac.uk> wrote:

> Dear PETSc developers,
> I'm Alberto and I'm a user of the finite element library Firedrake,
> which relies on DMPlex to import meshes.


> In order to use higher-order FEs, it is desirable to import higher-order
> meshes.

I really do not like that term. Let me try and convince you that it is
wrong. The topology of the
mesh is unchanged. You are only talking about the order of the
representation of the geometry
field. Thus, it is not the mesh that is "higher order", but the geometry.

> I've been told that DMPlex does not offer this future (at present).

Toby just merged this to master, so I think we can say that we have alpha
support for this. How
does it work? We already have a coordinateDM and coordinates Vec, so you
just choose a
higher order discretization for the DS inside the coordinateDM. Does that
make sense?

> I would be happy to contribute and add higher-order coordinate fields.
> Would someone be interested in giving me some support?
> I'm not the greatest programmer and I have (a limited) experience in C(++),

Gentlemen do not write C++.

> but I'm motivated and I have a certain knowledge of FEs (which might be
> relevant).

The most valuable thing for us is writing a good test. Preferably one in
which an exact
solution can only be obtained if the high order geometry is being used
correctly. If you
write that, we can make it work. Again, preferably in the style of existing
PETSc tests.



> Best
> Alberto

What most experimenters take for granted before they begin their
experiments is infinitely more interesting than any results to which their
experiments lead.
-- Norbert Wiener

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