Timo Heister

Alright, then let us know when we should take a look.

Elodie, try reading the error messages. The first one says paraphrased "You are trying to add a double and a Tensor. I don't know know how to do that." That...

> Would it be difficult to extend the GMG to work for periodic boundary conditions? I would be interested in using it for a 3D cartesian model with periodic x-...

> Thoughts? Interestingly, DGQ1 gives slightly better errors and same rates compared to DGQ2 and the reference. I thought there are cases where this is not the case and DGQ1...

#4251 extends supported boundary conditions. #4217 implements Newton derivatives (first Part)

I know things are not ideal for free slip and things work for 0 velocity. I have not tested with other prescribed velocities. Do you have an easy test prm...

Makes sense to me.

We can basically just change the default of https://github.com/geodynamics/aspect/blob/edad8df4dacd0d43afbd8d57e0914d683630cea4/source/simulator/parameters.cc#L170-L179

The resulting iteration numbers do not differ by much (+/- a few iterations). Did you test this on a more difficult problem that requires more iterations?

And it makes sense to do that separately for free surface and newton terms. It might be that only one of them is correct to use on the levels.