Thanks for the many answers! Still, according to the PETSc manual "matrix-free methods cannot be used if a direct solver is to be employed", I think this means I cannot use -snes_mf_operator and "-ksp_type preonly -pc_type lu -pc_factor_nonzeros_along_diagonal" at the same time. Do I need some other kind of preconditioning in case I want to use the direct LU linear solver and get convergence?
Thanks! Lorenzo On Mar 7, 2013, at 6:55 PM, Derek Gaston wrote: > A couple of things: > > 1. -pre is just an option for that particular example. It was an attempt to > provide a solver agnostic way of turning on preconditioning. If you don't > specify -pre or a petsc option to turn on preconditioning then you are doing > zero preconditioning... which is bound to fail. > > 2. To specify to petsc that you want to turn on preconditioned jacobian free > newton krylov (P-JFNK) use -snes_mf_operator on the command-line (this is > what -pre does in that example). Use this in conjunction with your LU > options and you will have better luck ;-) > > Derek > > > On Thu, Mar 7, 2013 at 10:33 AM, John Peterson <jwpeter...@gmail.com> wrote: > > > > On Thu, Mar 7, 2013 at 9:31 AM, Subramanya Gautam Sadasiva > <ssada...@purdue.edu> wrote: > Yes, that is right... my bad.. > > > Nevertheless, I think you are correct that there is *something* wrong with > his Jacobian. Maybe it's "good enough" to work with non-direct solvers but > fails on LU? > > -- > John > ------------------------------------------------------------------------------ Symantec Endpoint Protection 12 positioned as A LEADER in The Forrester Wave(TM): Endpoint Security, Q1 2013 and "remains a good choice" in the endpoint security space. For insight on selecting the right partner to tackle endpoint security challenges, access the full report. http://p.sf.net/sfu/symantec-dev2dev _______________________________________________ Libmesh-users mailing list Libmesh-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/libmesh-users
