Thanks Jens, we'll try this next week.
On 02/01/2014 04:06 AM, Jens Lohne Eftang wrote: > 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 ------------------------------------------------------------------------------ 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
