DG Euler eqautions (step-33 and step-67)

[giuseppe orlando]

Dear Deal.II community,

I'm currently working on DG formulation for Euler equations with implicit time-stepping, trying to combine in some sense the two approaches of ste-33 and step-67. I'm wondering if there is a way to employ automatic differentiation in the matrix-free approach; I think that the point is building a MatrixFree object with typename Number = Sacado::Fad::DFad<double>, but then I don't see how to use the diff function to flag the independent degrees of freedom using a FEEvaluation (or a FEFaceEvaluation) instance.

Thanks in advance.

Best regards,

Giuseppe