[petsc-dev] Algebraic Multigrid

[Mark Adams]

So remove one of the -mg_levels_pc_type jacobi and add -mg_coarse_ksp_type
preonly, then verify that this works on one proc and then try two procs.

On Tue, Jul 26, 2016 at 6:56 PM, Mark Adams <mfadams at lbl.gov> wrote:

> Oh, actually this worked.  You have this ...pc_type jacobi in there twice,
> so one of them was "unused".
>
> Try this with 2 processors now.
>
> On Tue, Jul 26, 2016 at 6:42 PM, Mark Adams <mfadams at lbl.gov> wrote:
>
>>
>>
>> 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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