DG and Newtons method linearization

Dear All,

First of all, congratulations to the developers of Netgen. I think it is a very good solver and what is more, the documentation is also properly developed which is not that usual.

I'm working on a solver for a system of 3 nonlinear equations. Following the tutorials and documentation, I wrote a Newton solver that solves the problem using a 1D mesh. As some of the parameters in my equations are discontinuous I got into troubles and wanted to implement a DG method to include the discontinuity of the parameters. I followed the DDG tutorial and added the jumps on the boundaries of the elements. In my case that would be points as I am working with 1D mesh.

Unfortunately, during the linearization of the form, I got an error

a.AssembleLinearization(u.vec)
RuntimeError: CalcLinearization for element-wise skeleton-VOL not implementedin AssembleLinearization


Is there anything I can do to overcome this problem or is it just something that is not implemented and won't change?

Hi,

could you please attach your python file.
Sounds like you used a combination of arguments in the SymbolicBFI which is not implemented.

Best regards
Christoph

Hi,

Here is the interesting part of the code. I cut it out of a bigger code to show where the problem is.

Best wishes,
B

Hi B,

thank you for the flowers ...

it is as the error tells us, linearization for DG is not implemented:
RuntimeError: CalcLinearization for element-wise skeleton-VOL not implementedin AssembleLinearization

you can replace your DG formulation by an hybrid-DG (HDG), then it shall work.

It is not a principal problem with non-linear DG, but we mainly use HDG (rather than DG), and so nobody found time to implement that.

Best, Joachim

Hi Joachim,

Thanks for the answer.
I will implement it and see how it works.
Thanks,
Bart

Hi Joachim,

I was trying the HDG as you suggested but it looks like im still doing something very wrong. Now it crashes when I try to define the Facet space. Might it be a problem of 1D mesh?

The message I obtain when I try to create the Facet space is

setting all_dofs_together 0
Segmentation fault: 11
My space definition looks like
Y = H1(mesh, order=ord, dirichlet=[1,2])
F = FacetFESpace(mesh, order=ord)
and the second line is where the code collapses. Do you have an idea what might be the reason?

Best wishes and thanks again,
Bart