[dune-pdelab] some problems in dune

[Rebecca de Cuveland]

Hey Robert,
perhaps you can show us your program and output? (verbosity 3 or 4 for AMG and 1 for linear solver)
AMG is quite sensible for the used options. I only use Q1, but as far as I know Q2 should also work...
Bye,
Rebecca

-- 
Rebecca de Cuveland
Universität Heidelberg
Interdisziplinäres Zentrum für Wissenschaftliches Rechnen
Im Neuenheimer Feld 368, 69120 Heidelberg
Tel: 06221/548890   Fax: 06221/548884
e-mail: <rebecca.cuveland at iwr.uni-heidelberg.de>

> On 23.10.2014 10:16, Robert Jendrny wrote:
> Moin moin,
> 
> thank you for these options ....
> 
> I have one last question:
> If I calculate Poisson with Q1-elements, I get mesh-independent convergence with AMG, i.e. I needed the same iterations for meshsize h, 1/2*h, 1/4*h,....
> But I have problems with Q2-elements: The iteration number "explodes"
> 
> How can I fix it? Is it a consequence from mesh-transfer?
> 
> It would be nice if you can help me,
> 
> Robert
> 
> 
>> On 10/15/2014 09:22 PM, Rebecca de Cuveland wrote:
>> Hey Robert,
>> there should be another possibility, Markus implemented this some time ago.
>> You can use the parameters class to change the variable, I used it in my code like this:
>> 
>>    typedef Dune::PDELab::ISTLBackend_BCGS_AMG_ILU0<IGO> LS;
>>    LS ls(tpgfs,250,1);
>>    Dune::Amg::Parameters params;
>>    params.setAccumulate(Dune::Amg::noAccu);
>>    ls.setparams(params);
>> 
>> Bye,
>> Rebecca