On a related issue, I wanted to mention 3D linear elasticity example that I added: systems_of_equations_ex6. It seems very slow with the default iterative solver in PETSc (ILU + GMRES, right?). The example takes 26 seconds on my laptop.
But this is a symmetric problem, so you'd expect CG to be good. Calling ./systems_of_equations_ex6-opt -ksp_type cg runs fast, but gives the wrong answer (I should add some code to check the final residual...) The best thing for me is just a direct solver: ./systems_of_equations_ex6-opt -ksp_type preonly -pc_type lu -pc_factor_mat_solver_package umfpack But I guess there must be a good KSP/PC combo for this simple problem, any recommendations? Best, David On 09/13/2012 04:56 PM, John Peterson wrote: > On Thu, Sep 13, 2012 at 2:49 PM, Paul T. Bauman <[email protected]> wrote: >> This is what I do usually, but with the external packages. The internal >> PETSc lu doesn't handle pivoting. > > http://www.mcs.anl.gov/petsc/petsc-current/docs/manualpages/PC/PCLU.html > > -pc_factor_nonzeros_along_diagonal - permutes the rows and columns > to > try to put nonzero value along the diagonal. > > That's pivoting, right? > ------------------------------------------------------------------------------ Live Security Virtual Conference Exclusive live event will cover all the ways today's security and threat landscape has changed and how IT managers can respond. Discussions will include endpoint security, mobile security and the latest in malware threats. http://www.accelacomm.com/jaw/sfrnl04242012/114/50122263/ _______________________________________________ Libmesh-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/libmesh-users
