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<LinearSolverTraits<GridGeometry>>; 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<LinearSolverTraits<GridGeometry>, LinearAlgebraTraitsFromAssembler<Assembler>>; 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 1.0000e+00->2.0094e-02@lambda=1.0000 Newton iteration 2 done, maximum relative shift = 1.6123e-02, residual = 2.5193e-01, residual reduction 2.0094e-02->3.8426e-04@lambda=1.0000 Newton iteration 3 done, maximum relative shift = 3.1727e-04, residual = 4.9623e-03, residual reduction 3.8426e-04->7.5690e-06@lambda=1.0000 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 1.0000e+00->2.1931e-01@lambda=1.0000 Newton iteration 2 done, maximum relative shift = 1.6123e-02, residual = 3.6247e+01, residual reduction 2.1931e-01->5.5287e-02@lambda=1.0000 Newton iteration 3 done, maximum relative shift = 3.1751e-04, residual = 9.2089e+00, residual reduction 5.5287e-02->1.4046e-02@lambda=1.0000 Newton iteration 4 done, maximum relative shift = 2.0686e-05, residual = 2.2909e+00, residual reduction 1.4046e-02->3.4943e-03@lambda=1.0000 Newton iteration 5 done, maximum relative shift = 8.9205e-06, residual = 5.6879e-01, residual reduction 3.4943e-03->8.6757e-04@lambda=1.0000 Newton iteration 6 done, maximum relative shift = 3.6801e-06, residual = 1.3881e-01, residual reduction 8.6757e-04->2.1172e-04@lambda=1.0000 Newton iteration 7 done, maximum relative shift = 1.7669e-06, residual = 3.1597e-02, residual reduction 2.1172e-04->4.8194e-05@lambda=1.0000 Assemble/solve/update time: 0.15(76.02%)/0.029(14.98%)/0.017(9.01%) While the relative shift remains nearly the same during the first three Newton steps, the residual has increased. I guess that we have just missed to change some further parameters/options to ensure that the residual is computed correctly. Are there any hints and tips? Best regards, Leo
Im Auftrag Dr.-Ing. Leopold Stadler -- Referat Numerische Verfahren im Wasserbau Abteilung Wasserbau im Binnenbereich Bundesanstalt für Wasserbau Federal Waterways Engineering and Research Institute Kußmaulstraße 17 | 76187 Karlsruhe
_______________________________________________ DuMux mailing list [email protected] https://listserv.uni-stuttgart.de/mailman/listinfo/dumux
