Hi Bernd,
Thank you fro your advice. My code does not compile with the old interface
OldIstlSolverFactoryBackend.
However, I've tested the Issue with the roughchannel test case of DuMux. There
are no differences for the AMGBackend between DuMux 3.7 and DuMux 3.5. When
switching from the AMGBackend to the ISTLSolverFactory there were also no
differences. I will have to check this twice to ensure that I didn't made some
mistake. The last big difference between our application and the DuMux test
case is the mesh. We use a triangular mesh with ALUGrid, the test case uses a
simple quad mesh.
I will write back when I've a reproducible test case for a standard DuMux
example.
Best regards,
Leo
> Flemisch, Bernd hat am 23.06.2023 11:29
> CEST geschrieben:
>
>
>
>
>
> Hi Leo,
>
>
>
> Thank you for bringing this up. Indeed, the norm calculation changed from
> "manual" in the assembler to being handed to the parallel scalarproduct. This
> should rather fix things by avoiding multiple contributions from elements
> present on more than one process. And therefore decreasing the norm rather
> than increasing it.
>
>
>
> I can't draw the connection to the source term at the moment.
>
>
>
> Can you check that you get the 3.6 numbers with 3.7 using the
> OldIstlSolverFactoryBackend with the old interface?
>
>
>
> Kind regards
>
> Bernd
>
>
>
>
>
> --
> _
>
> Bernd Flemisch
> IWS, Universität Stuttgart phone: +49 711 685 69162
> Pfaffenwaldring 61 email: be...@iws.uni-stuttgart.de
> D-70569 Stuttgart url: www.iws.uni-stuttgart.de/en/lh2/
> http://www.iws.uni-stuttgart.de/en/lh2/
> _
>
> -
> Von: DuMux im Auftrag von
> leopold.stad...@baw.de
> Gesendet: Freitag, 23. Juni 2023 11:24:53
> An: DuMux User Mailing List
> Betreff: Re: [DuMux] Problem with linear solver residual computation
>
> Dear DuMux community,
>
> Martin and I did some further testeing and it looks like the source term
> (friciton source) causes the differences in the residual computation. When we
> turn of the friction source, the residual becomes equal between DuMux 3.7 and
> DuMux 3.6.
>
> So the question is how the source term can be correctly included into the
> residual computation?
>
> Best regards,
>
> Leo
>
>
> > leopold.stad...@baw.de hat am 23.06.2023 09:55 CEST geschrieben:
> >
> >
> > Dear DuMux community,
> >
> > in DuMux 3.7 there are some changes in the parallel linear solver. In DuMux
> > 3.6 we used the following code for the linear solver
> >
> > using LinearSolver =
> > IstlSolverFactoryBackend>;
> >
> > for a parallel (MPI) shallow water equations model. In the new version
> > DuMux 3.7, the code/interface has changed and a second argument is needed
> >
> > using LinearSolver =
> > IstlSolverFactoryBackend,
> > LinearAlgebraTraitsFromAssembler>;
> >
> > We added the second argument and the code compiles and runs. However, the
> > model runs much slower. It looks like the computation of the residual has
> > changed. With DuMux 3.6 the output of the Newton solver was:
> >
> > Newton iteration 1 done, maximum relative shift = 6.9188e-02, residual =
> > 1.3174e+01, residual reduction 1.e+00->2.0094e-02@lambda=1.
> > Newton iteration 2 done, maximum relative shift = 1.6123e-02, residual =
> > 2.5193e-01, residual reduction 2.0094e-02->3.8426e-04@lambda=1.
> > Newton iteration 3 done, maximum relative shift = 3.1727e-04, residual =
> > 4.9623e-03, residual reduction 3.8426e-04->7.5690e-06@lambda=1.
> > Assemble/solve/update time: 0.044(24.32%)/0.13(71.15%)/0.0082(4.53%)
> >
> > With DuMux 3.7 the output has changed to
> >
> > Newton iteration 1 done, maximum relative shift = 6.9188e-02, residual =
> > 1.4379e+02, residual reduction 1.e+00->2.1931e-01@lambda=1.
> > Newton iteration 2 done, maximum relative shift = 1.6123e-02, residual =
> > 3.6247e+01, residual reduction 2.1931e-01->5.5287e-02@lambda=1.
> > Newton iteration 3 done, maximum relative shift = 3.1751e-04, residual =
> > 9.2089e+00, residual reduction 5.5287e-02->1.4046e-02@lambda=1.
> > Newton iteration 4 done, maximum relative shift = 2.0686e-05, residual =
> > 2.2909e+00, residual reduction 1.4046e-02->3.4943e-03@lambda=1.
> > Newton iteration 5 done, maximum relative shift = 8.9205e-06, residual =
> > 5.6879e-01, residual reduction 3.4943e-03->8.6757e-04@lambda=1.
> > Newton iteration 6 done, maximum relative shift = 3.6801e-06, residual =
> > 1.3881e-01, residual reduction 8.6757e-04->2.1172e-04@lambda=1.
> > Newton iteration 7 done, maximum relative shift = 1.7669e-06, residual =
> > 3.1597e-02, residual reduction 2.1172e-04->4.8194e-05@lambda=1.
> > Assemble/solve/update time:
