[petsc-dev] DMSetUseNatural() and DMPlexConstructGhostCells()

Adrian Croucher a.croucher at auckland.ac.nz
Mon Jul 20 17:24:34 CDT 2015

On 20/07/15 22:51, Matthew Knepley wrote:
> Thats a bug. CreateGhostCells() makes an entirely new DM, and the 
> SetNatural is a piece of state which did not get carried over. I will
> fix it.

OK, that's what I suspected. Thanks.
> I have a question about this strategy. The design philosophy for the 
> PETSc discretization stuff is to make as much
> mesh-independent as possible. I usually think of boundary and initial 
> conditions as analytic functions that are
> applied to a given geometric region on the mesh, and then projected 
> into a function space once I choose my
> discretization. Why doesn't that work in this case?

Yeah, I noticed that's the way all the example problems work, and I'd do 
it that way too if I could.

However my initial conditions aren't defined by analytic functions. 
Often they are taken from the end result of a previous model run, so 
they're defined as values on particular cells. In most such cases I 
should be able to load them in from HDF5 files, but even then I gather 
I'll still need this natural ordering stuff to make them end up on the 
right cells in the mesh, especially as the number of processors won't 
necessarily be the same between runs.

- Adrian

Dr Adrian Croucher
Senior Research Fellow
Department of Engineering Science
University of Auckland, New Zealand
email: a.croucher at auckland.ac.nz
tel: +64 (0)9 923 84611

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