On Thu, Sep 13, 2012 at 4:16 PM, David Knezevic <[email protected]>wrote:
> > Calling > > ./systems_of_equations_ex6-opt -ksp_type cg > > runs fast, but gives the wrong answer > > > > > > That's alarming... > > > > Is ICC the default preconditioner with CG? If not, give that a try > > (maybe with -pc_factor_levels 4 or something) > > > ahh, "-pc_type icc" did the trick, thanks! I'll add that to the Makefile. Use -ksp_monitor_true_residual. If ILU does something meaningfully different from ICC, the system is almost certainly nonsymmetric. Check boundary conditions. But for elasticity, it's well worth getting algebraic multigrid working. Hypre does classical AMG which isn't much good for systems. Use petsc-3.3 or later and call MatSetNearNullSpace() to provide the rigid body modes, then use either -pc_type gamg or -pc_type ml. Either should do fine (and can usually be tuned to do about the same algorithm, but have different defaults). If you use a nodal basis, you can stuff the nodal coordinates in a vector with suitable block size and call MatNullSpaceCreateRigidBody(). ------------------------------------------------------------------------------ Everyone hates slow websites. So do we. Make your web apps faster with AppDynamics Download AppDynamics Lite for free today: http://ad.doubleclick.net/clk;258768047;13503038;j? http://info.appdynamics.com/FreeJavaPerformanceDownload.html _______________________________________________ Libmesh-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/libmesh-users
