I am adaptively refining the grid. --
From: John Peterson <jwpeter...@gmail.com> Date: Wednesday, May 31, 2017 at 10:14 AM To: "Salazar De Troya, Miguel" <salazardet...@llnl.gov> Cc: "libmesh-users@lists.sourceforge.net" <libmesh-users@lists.sourceforge.net> Subject: Re: [Libmesh-users] Adaptive mesh refinement and preconditions On Wed, May 31, 2017 at 10:18 AM, Salazar De Troya, Miguel <salazardet...@llnl.gov<mailto:salazardet...@llnl.gov>> wrote: Hi I am solving an elasticity problem with the following iterative solver options: -ksp_monitor_true_residual -ksp_converged_reason -ksp_type cg -log_view -mg_levels_esteig_ksp_type cg -mg_levels_ksp_chebyshev_esteig_steps 50 -mg_levels_ksp_type chebyshev -mg_levels_pc_type jacobi -pc_type gamg -snes_linesearch_type basic -snes_atol 1e-6 -ksp_atol 1e-7 -ksp_rtol 1e-9 -ksp_norm_type unpreconditioned I am passing the rigid body bodes to the KSP solver. There is a noticeable increase in the number of iterations when the size ratio between biggest and smallest element increases. This problem is also solving for two materials with a high contrast in their properties, so this could have an effect, but the iterations don’t increase as much when the mesh is uniform. I wonder if there is some information about the mesh that could be passed to the preconditioner to improve its performance. I'm not sure exactly what type of multigrid preconditioner your mg_ options are setting up, but you might also want to try/compare your results with the options "-pc_type hypre -pc_hypre_type boomeramg" as well. Since you mention a ratio between biggest and smallest elements, are you referring to an adaptively refined grid, or just a continuously graded mesh? I don't know too much about MG, but there may be some special approach needed for meshes with a large hmax/hmin ratio. -- John ------------------------------------------------------------------------------ Check out the vibrant tech community on one of the world's most engaging tech sites, Slashdot.org! http://sdm.link/slashdot _______________________________________________ Libmesh-users mailing list Libmesh-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/libmesh-users
