> > Everything is fine with GAMG I think, please find the (trimmed) -eps_view > attached. >
This looks fine. The eigen estimates are pretty low, but I don't know what they really are. > The problem is that, correct me if I’m wrong, there is no easy way to > redistribute data efficiently from within PETSc when using fieldsplit with > unbalanced number of unknowns per field. > Note, as you scale up the coarse grids become more important re complexity. So the process reduction and potential repartitioning will become more noticable. At extreme scale you can spend a majority of the time in the coarse grids. > For the other three fields, the solvers are still behaving somehow > properly. Now if I’d like to optimize this some more, I’d probably need to > switch from a fieldsplit to a MatNest, with submatrices from different > communicators, so that I don’t have all processes handling the pressure > space. But this is apparently not allowed. > > Thanks, > Pierre > > > > >> >> 2) have the sub_0_ and the sub_1_ work on two different nonoverlapping >>> communicators of size PETSC_COMM_WORLD/2, do the solve concurrently, and >>> then sum the solutions (only worth doing because of -pc_composite_type >>> additive). I have no idea if this easily doable with PETSc command line >>> arguments >>> > >>> > 1) is the more flexible approach, as you have better control over the >>> system sizes after 'telescoping’. >>> >>> Right, but the advantage of 2) is that I wouldn't have one half or more >>> of processes idling and I could overlap the solves of both subpc in the >>> PCCOMPOSITE. >>> >>> I’m attaching the -log_view for both runs (I trimmed some options). >>> >>> Thanks for your help, >>> Pierre >>> >>> >>> > Best regards, >>> > Karli >> >> >> >
