Local operators allocate std::vectors

OK, this is tricky. The finite element interface from dune-localfunctions expects a std::vector to fill. This is hardcoded.

So, I can get rid of extra allocations by using some kind of cache structure, but still that will be uses of std::vector on the device later.

I suppose in the long run we'll have to reimplement the Q1/P1 basis such that it accepts std::arrays, and exports the number of basis functions in a constexpr way.

An alternative would be to use ReservedVector, but that still needs an upper bound on the number of entries.

mentioned in merge request !18 (merged)

mentioned in commit 57a75aae

closed via merge request !18 (merged)