Dear Wolfgang, I wrote the sequential code first and It converged to the exact solution using SolverCG and SSOR preconditioner. However, the parallel code diverges at the first call to SolverCG but using GMRES or Bicgstab it works though up to 150000 DoFs not more.
First and the most important question to me is what parallelization does to my system_matrix that it is not solved by SolverCG anymore. I guess the source of the problem is there. Second, why it is solved by GMRES and Bicgstab for few DoFs (up to 150000) and not more( for example, 1 million). It seems that my system_matrix is not s.p.d any more although in sequential code it was. Thanks for your time, Hamed On Wednesday, November 2, 2016 at 8:00:23 AM UTC-5, Wolfgang Bangerth wrote: > > On 11/01/2016 10:31 AM, Hamed Babaei wrote: > > > > I mean non of the standard preconditioners helped to make it converged. > > Like Bruno mentioned, if the standard preconditioners don't work, then you > will need to think about more complicated ones. Take a look at my video > lectures on preconditioners, for example. > > There is of course also the possibility that your matrix is not correct > and > indeed singular. In that case, you *have* to expect problems. Have you > verified that your numerical solutions converge to the exact ones for > small > problems? > > Best > W. > > -- > ------------------------------------------------------------------------ > Wolfgang Bangerth email: bang...@colostate.edu > <javascript:> > 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. For more options, visit https://groups.google.com/d/optout.
