Dear Bruno, These are the basic steps that you need to take:
1. Create and initialise a PreconditionAMG::AdditionalData object (“additional_data”) as per usual. Here you set up the constant modes as is needed using DoFTools::extract_constant_modes(). 2. Create a Teuchos::ParameterList (“parameter_ml”) and std::unique_ptr< Epetra_MultiVector > (“distributed_constant_modes”). Neither of these need be initialised with any data. 3. Now call additional_data.set_parameters(parameter_ml, distributed_constant_modes, matrix); . This initialises “ parameter_ml” and “”distributed_constant_modes” for you, and transcribes the settings stored in “additional_data” into the equivalent “parameters_ml”. The “distributed_constant_modes” is internally referenced by “ parameters_ml”, so thats why you need that vector lying around. 4. Lastly, you initialise the preconditioner using ” parameter_ml” for the “matrix” that you sent into “ additional_data.set_parameters()”, i.e. something like this: const PreconditionAMG prec (matrix, parameter_ml); . As for the second point, you should be able to find a link to the ML documentation in the description to this function: https://dealii.org/developer/doxygen/deal.II/classTrilinosWrappers_1_1PreconditionAMG.html#a9703cc100be147a47358cf99fc53beb0 <https://dealii.org/developer/doxygen/deal.II/classTrilinosWrappers_1_1PreconditionAMG.html#a9703cc100be147a47358cf99fc53beb0> You can also search for this technical report which should outline most if not all of the possible settings: TechReport (Gee2006a) <> Gee, M. W.; Siefert, C. M.; Hu, J. J.; Tuminaro, R. S. & Sala, M. G. ML 5.0 Smoothed Aggregation User's Guide Sandia National Laboratories, Sandia National Laboratories, 2006 Best, Jean-Paul > On 01 Apr 2019, at 17:53, Bruno Blais <blais.br...@gmail.com> wrote: > > Dear Jean-Paul, > I've compiled the new DEALII version with your changes, but I am unsure of > how to use the changes correctly. > If I understand correctly, you can now set Teuchos parameters after you have > initialized the TrilinosWrappers::PreconditionAMG. > This is achieved by creating a Teuchos::ParameterList object and using it in > the set_parameters public function of the > Preconditioner::AdditionalParameters. > So for instance in my case it would be something like: > > > // Still need to figure out the syntax for the additional_parameters > Teuchos::ParameterList additional_parameter("smoother: params"); > > > And then I would set the parameters in the preconditioner additional > parameters > > I have two things i am unsure: > 1) For the set the additional parameters I need a > std::unique_ptr<Epetra_MultiVector> &distributed_constant_modes . I presume > this vector is created in the initialization from the std::vector of constant > boolean modes? Is there a way to grab it again and reuse it? I do not > understand why I need to specify the constant modes for every change of > parameters. > 2) Is there any documentation on the various parameter list. What I would > like to change is the atol of the ILU smoother and ILU preconditions. I think > this will be in the smoother: params, but I am unsure how to proceed from > there. I have found the MULUE documentation, but it seems to be more tailored > around their XML interface? > > > Thank you so much, > Bruno > > > > On Tuesday, 12 March 2019 05:06:03 UTC-4, Jean-Paul Pelteret wrote: > Dear Bruno, > > I believe that my proposed changes are working now, so you could always pull > that branch from my repository and use it immediately. That might be the most > convenient way for you to move forward. > > Thanks for being willing to share your findings wrt. AMG parameters. I think > that would be really useful. I also think that encapsulating a parameter > study for NS + AMG/GMG within a tutorial could be interesting and valuable. > Maybe you could open up an issue on the GitHub repository and we could all > discuss the specifics there. > > Best, > Jean-Paul > >> On 11 Mar 2019, at 14:25, Bruno Blais <blais...@gmail.com <javascript:>> >> wrote: >> >> Dear Jean-Paul and Wolfgang, >> Is it better if I try to go with the Teuchos way or should I wait until >> Jean-Paul finishes the merge on his branch ? I think the latter might be a >> good option. >> In all cases, I would be more than glad to share my experience in parameters >> tuning for the AMG solver with ILU type of smoother and coarse solve. >> >> On a slightly related note. Hopefully I will have finished the basis of my >> GLS stabilized navier-stokes solver by June or so. It already works pretty >> well in parallel with GMRES + ILU, but I want to test more what can be done >> in terms of multigrid and AMG. >> In a way, it is very reminescent of a similar work done in MOOSE, but using >> Trilinos, P4est and deal.II. The MOOSE paper is here: >> https://www.sciencedirect.com/science/article/pii/S0965997817310591 >> <https://www.sciencedirect.com/science/article/pii/S0965997817310591> >> >> I am more than willing to share everything about the solver. Do you believe >> this could be something that could make an interesting Tutorial? I could >> wrap-it around the study of the flow around a cylinder or a backward facing >> step to have some validation. Verification would be done using MMS. >> Best >> Bruno >> >> -- >> The deal.II project is located at http://www.dealii.org/ >> <http://www.dealii.org/> >> For mailing list/forum options, see >> https://groups.google.com/d/forum/dealii?hl=en >> <https://groups.google.com/d/forum/dealii?hl=en> >> --- >> You received this message because you are subscribed to the Google Groups >> "deal.II User Group" group. >> To unsubscribe from this group and stop receiving emails from it, send an >> email to dea...@googlegroups.com <javascript:>. >> For more options, visit https://groups.google.com/d/optout >> <https://groups.google.com/d/optout>. > > > -- > The deal.II project is located at http://www.dealii.org/ > <http://www.dealii.org/> > For mailing list/forum options, see > https://groups.google.com/d/forum/dealii?hl=en > <https://groups.google.com/d/forum/dealii?hl=en> > --- > You received this message because you are subscribed to the Google Groups > "deal.II User Group" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to dealii+unsubscr...@googlegroups.com > <mailto:dealii+unsubscr...@googlegroups.com>. > For more options, visit https://groups.google.com/d/optout > <https://groups.google.com/d/optout>. -- The deal.II project is located at http://www.dealii.org/ For mailing list/forum options, see https://groups.google.com/d/forum/dealii?hl=en --- You received this message because you are subscribed to the Google Groups "deal.II User Group" group. 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