On 01/31/2014 12:36 PM, John Peterson wrote: >> Hello, >> >> I'm trying to solve a linear elasticity problem based on a tetraheadral >> mesh with over a million degrees of freedom. >> >> I've been using the LU solver in MUMPS but I'm now forced to switch to an >> iterative solver because of the memory requirements of that solver. >> >> CG and BoomerAMG in hypre seem to be a good combination, but I've not been >> able to achieve convergence. The residual never goes below 1 even after >> several thousand iterations and shows high oscillations. >> >> The parameters I'm using are >> -ksp_type cg >> -ksp_monitor >> -ksp_converged_reason >> -pc_type hypre >> -pc_hypre_type boomeramg >> -pc_hypre_boomeramg_strong_threshold 0.7 >> -log_summary >> > First thing I would think of is that the problem isn't actually symmetric > even though logically it should be? > > Does it work any better with -ksp_type bcgs? > > > >> -eps_monitor >> -st_type sinvert >> > Is this an eigenvalue problem too?
Dana is working with me on this. It's not an eigenproblem, so "-eps_monitor -st_type sinvert" isn't meant to be there (but it those options would've just been ignored I believe). Regarding symmetry: That's a good thought. The PDE is linear elasticity, hence it's symmetric. But we enforce boundary conditions using DirchletBoundary, so that'll ruin symmetry on the Dirichlet rows/cols. Not sure if that's the problem here or not, but Dana will try "-ksp_type bcgs" to see if that helps convergence. Thanks, David ------------------------------------------------------------------------------ WatchGuard Dimension instantly turns raw network data into actionable security intelligence. It gives you real-time visual feedback on key security issues and trends. Skip the complicated setup - simply import a virtual appliance and go from zero to informed in seconds. http://pubads.g.doubleclick.net/gampad/clk?id=123612991&iu=/4140/ostg.clktrk _______________________________________________ Libmesh-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/libmesh-users
