[petsc-users] flux vector

[Adrian Croucher]

hi

I have a DMPlex in a finite volume simulation and I want to create a Vec 
containing flux data only on the mesh faces where fluxes are computed 
(e.g. not on closed boundaries). Basically these are all the faces with 
support size 2 (aside from some complications related to boundary 
conditions).

To do this I clone the DM using DMClone() and create a section on it 
with DMPlexCreateSection(), passing in a label which has value 1 on all 
the required faces. The problem then consists of labelling the 
appropriate faces.

The tricky part is that when a face exists on more than one process, you 
have to make sure it has the same label value on all processes, 
otherwise an error results when you try and create a global vector on 
the DM. Because I distribute the DMPlex with overlap = 1, a face can 
have different support sizes on different processes.

So on each process, I need to label a face if it has support size 2 on 
*any* process.

Would it be possible to use PetscSFBcast and the point SF from 
DMGetPointSF() to somehow broadcast the support sizes? Or is there a 
simpler way?

- 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 4611