Plan for face-centered fields

[Yurlungur]

From Hackathon:

• Cell vars generalized to become differently shaped fields
• Generalize "WithFluxes" to be more verbose about what kind of fluxes
• "EMF correction" implemented as "line integral correction"
• Keep in mind concern about order of operations

TODOS:

• Flux correction in one (Luke)
• Remove all the old face-centered stuff leftover from athena++ (Forrest) Remove old face-centered stuff #738
• Rename CC and Cell to Var (Josh) Rename CellVariable to Variable, etc. #867
• Implement newly shaped vars. (Josh) Add local face fields #868
• Add metadata. (Josh) Add local face fields #868
• Pull newly shaped vars through packs. Remove GetDim from packs (Luke, Deferred to pack discussion) Add local face fields #868
• Update/Fix single-level comms and fluxes (Philipp) Boundary communication for non-cell centered fields #872
• Physical boundary conditions -> MeshData so prolongation/restriction can be done in-one
• Pull Prolongation/Restriction hooks to userspace (Jonah) userspace prolongation #769
• Pull prolongation/restriction through new vars (Pull from AthenaK) Boundary communication for non-cell centered fields #872
• Include face-centered fields, etc. in output
• Post-implementation cleanup
• Documentation

[Yurlungur]

Additional note: AMR load balance is missing some logic for tensor-valued quantities to communicate tensor values accross mesh boundaries. We need to repeat what @brryan did for buffer packing.

[lroberts36]

One of the TODOs is to "Add metadata", does anyone know what this refers to? It looks like metadata already exists for faces, edges, and nodes. Is is just referring to update metadata to change the shapes of variables based on their topological type?

[pgrete]

Good question. Your first guess would have also been mine.

[Yurlungur]

I'm not sure either. Let's just check it off lol.