[yt-dev] vertex-centered data

[Jonah Miller]

Hi yt-dev,

Nathan Goldbaum and I were discussing the possibility of handling 
vertex-centered data natively in yt. We think that roughly this is quite 
do-able and that most of the pieces are already in place. Nathan 
suggested I summarize our discussion and email it to all of you to ask 
for your opinions.

Internally, all that's required is using the generated ghost cells to 
convert between cell- and vertex-centered data. (For non-periodic 
boundaries, linear extrapolation, which would need to be implemented, 
should be good enough.)

In the userspace side, we need a concept for this type of data so that 
it can be extracted and manipulated. One option would be to make 
centering an attribute for datasets. It could be immutable or mutable, 
depending on design choices. In both cases, we would create a method to 
go between centerings:
ds.to_centering(centering_type)

in the former case, this method would return a new dataset. In the 
latter case, it would reset the dataset.

In principle, centering is a metadata property. The input data can be 
interpolated when it's explored and not before. So for this reason, it 
makes some sense to leave the centering as a dataset property rather 
than as, say, a field property.

I think that's about it. Nathan can correct me if I forgot something.

Thanks!

Best,
Jonah Miller