Dear Bruno and Wolfgang, thank you very much for your comments and help, it is very helpful. Actually, I think that is what I am experiencing. When running with my actual direct solver a system with 15 elements per direction (4th polynomial order with 0.5million dof), the solver takes 50 seconds. However, increasing to 30 elements per direction (3.5 million dof) the solver takes 1.5 hours. I think this shows how it does not scale well in terms of time as you mentioned. I will definitely try with the iterative solver.
Thannk you again Regards, H. El jueves, 10 de marzo de 2022 a las 17:17:47 UTC+1, Wolfgang Bangerth escribió: > On 3/10/22 07:00, Hermes Sampedro wrote: > > I am experiencing long computational times with the solver function. I > am > > trying to use DoFRenumbering::Cuthill_McKee(dof_handler), > > DoFRenumbering::boost::Cuthill_McKee(dof_handler,false,false) > > but I get even higher computational times. Am I doing something wrong? > > Renumbering makes an enormous difference for sparse direct solvers, and as > a > consequence all such solvers I know of do it internally (though they use > variations of the "minimum degree" renumbering, rather than > Cuthill-McKee). As > a consequence, renumbering yourself likely makes no difference. > > But, as you discover and as Bruno already pointed out, even with optimal > ordering, direct solvers do not scale well both in terms of overall time > and > in parallelism. You may want to take a look at the several video lectures > on > solvers and preconditioners to see what you can do about your case. > > Best > W. > > -- > ------------------------------------------------------------------------ > Wolfgang Bangerth email: [email protected] > 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 [email protected]. To view this discussion on the web visit https://groups.google.com/d/msgid/dealii/c13e9b57-12cd-48fc-ba62-f48d3da3b6b2n%40googlegroups.com.
