Hi, I used these arguments for 3D elasticity and they seemed to work well also in combination with DirichletBoundary (why does that break symmetry?)
-ksp_type cg -pc_type fieldsplit -pc_fieldsplit_block_size 3 -fieldsplit_pc_type hypre -fieldsplit_pc_hypre_type boomeramg -fieldsplit_pc_hypre_boomeramg_strong_threshold 0.7 -pc_fieldsplit_0 0,1,2 -ksp_atol 1e-11 -ksp_rtol 1e-11 -pc_fieldsplit_type symmetric_multiplicative It is key to use the fieldsplit preconditioner in order to be able to exploit smoothness within each field component. If it's 2D elasticity I believe you'd have to modify to -pc_fieldsplit_block_size 2 and -pc_fieldsplit_0 0,1. I was able to solve a problem with tens of millions dofs in 90 CG iterations using these parameters. Best, Jens On 01/31/2014 11:11 PM, David Knezevic wrote: > 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 ------------------------------------------------------------------------------ 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
