Automatic Differentiation (AD)
What does this feature / why does DuMux need it:
Often used in other software packages, should be more accurate than numerical differentiation
Which issue does this feature fix (if any)
Removes numerical differentiation imprecision, more similar to a hand built jacobian.
Anything else we need to know?:
OPM has implemented this already, and their method seems compatible with Dumux. Dumux AD could likely be copied from OPM for the most part. OPM does Forward AD, set up with operator overloading. See MR (...)