[dune-pdelab] Error in PDELab

[Joris Edelmann]

Hi,

I recognized, that in 
dune-pdelab/dune/pdelab/gridfunctionspace/gridfunctionspaceutilities.hh 
is an error:

In the class  VectorDiscreteGridFunctionGradient  and therein in the 
method "evaluate" is a miscalculation. The gradient is transformed via a 
multiplication with

JgeoIT = e.geometry().jacobianInverseTransposed(x);

It should be

JgeoIT = e.geometry().jacobianTransposed(x);

In the latter case, the derivative coincides with the one calculated via 
Paraview. Mathematical argument:

map mu: local to global,

Funktion: local to R^n: f(mu(x))

Gradient: grad(mu)^T grad(f)(mu(x)) (chain rule)


I'm using the dune verion 2.8


Best,

Joris