Thanks for your suggestion, Dr. Bangerth. After some tests, I realized that sparse direct solver mumps is the best choice for my application. Therefore, there is no need for me to find a way to set up the preconditioner. But I will try it next time.
Best regards, Yiliang Wang On Wed, Dec 17, 2025 at 10:54 PM 'Wolfgang Bangerth' via deal.II User Group <[email protected]> wrote: > On 12/17/25 18:55, Yiliang Wang wrote: > > > > I think I have found the solution. I use add -ksp_norm_type > unpreconditioned > > flag when run the simulation. > > My suggestion is that it will be better if this flag is automatically > turned > > on when using petsc CG. Otherwise, the convergence test is not > consistent > > between the built-in CG and petsc CG. > > Ah, that's an interesting observation -- nice job figuring this out! I'm > not > sure any of us ever realized that. Is there a way to set this flag in the > program, rather than on the command line? Would you like to see if you > could > write a patch that does that? Presumably, one would make this modification > here: > > https://github.com/dealii/dealii/blob/master/source/lac/petsc_solver.cc#L327-L335 > I don't know what we should do about the other PETSc solvers. Presumably, > we > would want to make these similar to the deal.II solvers as well, but I'd > be > happy to fix one of them at a time. > > Best > W. > > -- > The deal.II project is located at http://www.dealii.org/ > For mailing list/forum options, see > https://groups.google.com/d/forum/dealii?hl=en > --- > You received this message because you are subscribed to the Google Groups > "deal.II User Group" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to [email protected]. > To view this discussion visit > https://groups.google.com/d/msgid/dealii/d77817e1-0109-4219-a88d-da39a87e0dc1%40colostate.edu > . > -- The deal.II project is located at http://www.dealii.org/ For mailing list/forum options, see https://groups.google.com/d/forum/dealii?hl=en --- You received this message because you are subscribed to the Google Groups "deal.II User Group" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To view this discussion visit https://groups.google.com/d/msgid/dealii/CAMSe0ng5HDBGEF3qK%2BgUrCWhDo-oY2T6XFPKanzviX-6QQGiCQ%40mail.gmail.com.
