Hi Anand,
yes, HDiv is missing. I have two recommendations:
1. If you are in 2D, you can use HCurl instead of HDiv, rotate your field by 90 deg, and replace div by curl. For lowest order HCurl we have the prolongation. This is a pure Python solution.
2. Copy the C++ code from HCurlSpace to HDivFESpace. Also prolongations for lowest order RT tetrahedral elements can be done similarly. Have a look into
ngsolve/multigrid/prolongation.hpp, line 183, class EdgeProlongation
and
comp/hcurlhdivfes.cpp, line 140 for building the edge hierarchy
We only assume from the mesh interface that it provides the hierarchy of vertices and elements, no edges or faces, this is more troublesome for p-version prolongations.
I have heard from people who have added at least second order H1 prolongations.
Joachim
