[petsc-dev] Algebraic Multigrid

[Mark Adams]

On Tue, Jul 26, 2016 at 6:24 PM, Ari Rappaport <arir at vosssci.com> wrote:

> So I commented out the line PCSetType(pc, PCGAMG). The line
> KSPSetFromOptions(ksp) was already in the code at the end of our
> initialization routine. I also added .petscrc to the working dir. Here is
> the current output. It seems as if Option left: name:-mg_levels_pc_type
> jacobi (no value) is still present in the output..I dunno.
>

Yea, I dunno either.  If you use -help you will get printout of the
available options.  If you do this you will see stuff like -mg_levels_1_
... you can also see this in the ksp_view.  There is a shortcut that lets
you _not_ put "_1" in.  Try putting this in for each level like so:

-mg_levels_1_pc_type jacobi
-mg_levels_2_pc_type jacobi
-mg_levels_3_pc_type jacobi

I also notice that the coarse grid ksp is GMRES.  This is our fault.  It
should be preonly. Add:

-mg_coarse_ksp_type preonly








>
> -Ari
>
> ----- Original Message -----
> From: "Mark Adams" <mfadams at lbl.gov>
> To: "Ari Rappaport" <arir at vosssci.com>, "For users of the development
> version of PETSc" <petsc-dev at mcs.anl.gov>
> Sent: Tuesday, July 26, 2016 4:03:03 PM
> Subject: Re: [petsc-dev] Algebraic Multigrid
>
>
> At the end of this you have:
>
>
>
> #PETSc Option Table entries:
> -ksp_view
> -mg_levels_pc_type jacobi
> -options_left
> #End of PETSc Option Table entries
> There is one unused database option. It is:
> Option left: name:-mg_levels_pc_type jacobi (no value)
>
>
> So this jacobi parameter is not being used.
>
>
> Do you call KPSSetFromOptions? Do you set solver parameters in the code?
> Like PCGAMG?
>
>
> You should not set anything in the code, it just confuses things at this
> point. Use KSPSetFromOptions(). You can hardwire stuff before this call,
> this just lets you set the defaults, but you should always call this last
> to let command line parameters override the defaults.
>
>
> You can put this in a .petscrc file in the working directory and try again.
>
>
>
> -ksp_type cg
> -ksp_max_it 50
>
> -ksp_rtol 1.e-6
> -ksp_converged_reason
> -pc_type gamg
> -pc_gamg_type agg
> -pc_gamg_agg_nsmooths 1
> -pc_gamg_coarse_eq_limit 10
> -pc_gamg_reuse_interpolation true
> -pc_gamg_square_graph 1
> -pc_gamg_threshold -0.05
> -mg_levels_ksp_max_it 2
> -mg_levels_ksp_type chebyshev
> -mg_levels_esteig_ksp_type cg
> -mg_levels_esteig_ksp_max_it 10
> -mg_levels_ksp_chebyshev_esteig 0,.05,0,1.05
> -mg_levels_pc_type jacobi
> -pc_hypre_type boomeramg
> -pc_hypre_boomeramg_no_CF
> -pc_hypre_boomeramg_agg_nl 1
> -pc_hypre_boomeramg_coarsen_type HMIS
> -pc_hypre_boomeramg_interp_type ext+i
>
>
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