I’ve tested applying the material averaging to the viscosity used in the reaction rates as well (dashed pink line), and that leads to stable velocities and stresses, much more similar to the Newton/AMG cases.
Great news, fingers crossed that change helps improve convergence behavior across a range of models.
@tjhei, not having to material average could be useful when trying to match benchmark results or in simulations with limited resolution, where you don’t want to lose the in-element variation. However, I think we should first look into those cases that people in John’s and my group have come across where GMG doesn’t converge, but could provide large speed up, like in 3D setups. What do you think @jbnaliboff ?
I agree. Having a ‘no material averaging’ for GMG may certainly be useful in some cases, but I think sorting out why the GMG performance breaks for some complicated models would be beneficial to a wider class of simulations.
Please do let me know if there’s anything I can help with regarding further testing or analysis. I’m happy to assist in any way I can.
Thanks for the offer @tiannh7. If you don’t mind sharing, posting the results of your testing/benchmarking to the forum (or via github issues) is certainly helpful. Longer term, contributing any new benchmarks or cookbooks repository would likewise be very helpful.
Please let us know how further testing goes (I would use AMG in the interim), and we can update here as well once further testing is done on our side with the changes Anne implemented.
Cheers,
John