[Dune-devel] Issues in dune-localfunctions

[Christian Engwer]

Dear all,

I'm currently working on the new functions interface in pdelab and
encountered some issues with dune-localfunctions.

A) what exactly is the definition of the diffOrder in the
   basis-traits?
   Currently it defaults to 0 and most implementaitons will never
   have specified the diffOrder
B) the C1LocalBasisTraits set diffOrder to 1, but we currently have
   no (globally) C1 functions in dune-localfunctions, so what does the
   C0,C1,Ck here refer to?
C) it is a bit surprising (for the user) that in case of diffOrder=1 I
   can use evaluateJacobian(...), but not evaluate(...) with the
   appropriate direction information.
D) diffOrder sounds to me like something mathematically implied and
   locally most local functions are C-infinity. So in these cases the
   appropriate methematical information would be more something like
   differentiable, but non-trivial. On the other hand we usually use
   this entry to tell how man derivatives are _implemented_, but in
   this case the name is imho missleading.

Besides these point there are a few further topics we might want to
discuss seperately.

I hope we can sort out some of these issues.

Ciao
Christian