Thank you Prof. Bangerth, I've considered multigrid preconditioners as the iterations are relatively constant, but isn't it suits diffusion problems more, as mentioned here (A former discussion <https://groups.google.com/g/dealii/c/det9e4HWGrk/m/q0oj-yQlBAAJ#:~:text=-%20lumping%20of%20mass%20matrices%0A-%20AMG/GMG%20for%20laplace-like%20operators%0A-%20ILU/Jacobi%20for%20mass%20matrix-like%20operators%0A-%20spectrally-equivalent%20matrices%20to%20approximate%20Schur%20complements%0A-%20and%20more> )? I assume multigrid works well for M+dt^2K type problem, but it's expensive for such 'easy' problem(when dt is small). The only drawback for jacobi preconditioner is the iteration number scales with problem size ...
在2024年10月4日星期五 UTC+8 22:02:25<Wolfgang Bangerth> 写道： > On 10/4/24 01:38, 'yy.wayne' via deal.II User Group wrote: > > ** > > > > I tried by SSOR gives same behavior as jacobi. > > For mesh with 0, 1, and 2 times of refinement, it needs (jacobi: 20, 31, > 67) > > and (SSOR: 10, 15, 31) iterations. > > Besides, is SSOR not applicable in matrix-free framework? > > Yes, SSOR needs access to matrix elements. If these iteration counts are > too > large for you, then the only alternative you have is to go with > multigrid-type > preconditioners, for which you can use matrix-free methods. > > Best > W. > > -- > ------------------------------------------------------------------------ > Wolfgang Bangerth email: bang...@colostate.edu > www: http://www.math.colostate.edu/~bangerth/ > > > -- 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 dealii+unsubscr...@googlegroups.com. To view this discussion on the web visit https://groups.google.com/d/msgid/dealii/3d360ae7-b0e4-42cf-b708-ba658ea0bcfan%40googlegroups.com.
