Julian Andrej

I like the entity approach (obviously). The function names don't make sense though. `ChildrenInEntity`, there is no children in an entity. There can be children of an entity. `ParentsTouchedByEntities` looks...

I'd vote for plural only. Also, `MeshEntityIDs` should really be a namespace object s.t. `Mesh::EntityID` is valid. I'm not convinced on the need of `EntityIDs`. `std::vector` (or `mfem::Array` if it...

The PR is not huge so I'd opt for adding the methods for LinearForm here as well.

I'm working on the transfer between multi-level submesh objects on this branch. Before reviewing, be aware that I'll be adding some functionality.

The PR is now in a good state to review it.

> Hi @jandrej ， just ask a related usage question. If I can get a SubMesh or ParSubMesh, how can I add a bounding box outside the SubMesh and then...

That is not supported. In order to keep track of the mappings, a `SubMesh` always has to be an existing subset of the parent. If you add one element to...

> Yes!

If Hooke works with NCMesh this is a happy accident. I never ran non-conforming meshes during development.

The only code I can share is a similar MFE https://fwd.gymni.ch/2szOgk @samuelpmishLLNL