[aspect-devel] Duplicate Vertices

[Walter Landry]

Wolfgang Bangerth <bangerth at math.tamu.edu> wrote:
>> Although I'm working with HDF5 output, I believe this also applies to
>> the other output formats as well.  Can someone explain why duplicate
>> vertices (and associated values) exist in Aspect?  Is this an
>> artifact of how the mesh is constructed or is there another reason?
>> Can we merge these in the output and/or simulation to improve
>> performance or are they fundamentally required?
> 
> The question is what you intend to do if you have a discontinuous field 
> to visualize. (E.g., when using the conservative pressure element, or if 
> you want to output the error estimator which is a cellwise quantity.) 
> All formats I'm familiar with associate data with vertices but that 
> automatically means that a field can only have a single value at each 
> vertex. For discontinuous fields we need multiple vertices. 
> Unfortunately, you can't choose to have unique vertices for u,p,T and a 
> separate set of duplicated vertices for the error estimator, for example.

For the XDMF format, you can store the values at the integration
points in HDF5 files and then compute the values at vertices.  I did
this for Gale for the pressure.  Doing this kind of computation in the
XDMF format is rather painful, but it is possible.

Cheers,
Walter Landry