[Trilinos-Users] ilut setting

Hoang Giang Bui hgbk2008 at gmail.com
Tue Sep 17 16:28:26 MDT 2013


Hi Erik

I tried to increase "fact: ilut level-of-fill" to 50.0 and it still doesn't
converge. In fact, with this value the preconditioner take very long to
compute. Is there other option we can set for Ifpack ILUT?

Giang Bui


On Tue, Sep 17, 2013 at 8:01 PM, Erik Boman <egboman at sandia.gov> wrote:

> Giang Bui,
>
> You will not get exactly the same answer because the ILUT implementations
> are different in AztecOO and Ifpack. Also, the meaning of "fill" may be
> slightly different. Try increase the value of  "fact: ilut level-of-fill"
> in the Ifpack parameter to see if you can make it converge.
>
> Erik
>
> Hoang Giang Bui wrote:
>
>> Dear Trilinos developers,
>>
>> Is there difference between 2 settings:
>>
>> solver_parameters.set("AZ_**solver", "AZ_bicgstab")
>> solver_parameters.set("AZ_**kspace", 1000)
>> solver_parameters.set("AZ_**output", 100)
>> solver_parameters.set("AZ_**precond", "AZ_dom_decomp")
>> solver_parameters.set("AZ_**subdomain_solve", "AZ_ilut")
>> solver_parameters.set("AZ_**drop", 0.0)
>> solver_parameters.set("AZ_**ilut_fill", 10.0)
>> aztec_solver.SetParameters(**solver_parameter, true);
>>
>> And:
>> solver_parameters.set("AZ_**solver", "AZ_bicgstab")
>> solver_parameters.set("AZ_**kspace", 1000)
>> solver_parameters.set("AZ_**output", 100)
>> solver_parameters.set("AZ_**precond", "AZ_none")
>> aztec_solver.SetParameters(**solver_parameter, true);
>> IFPreconditionerType = "ILUT"
>> preconditioner_parameters.set(**"fact: ilut level-of-fill", 10.0);
>> preconditioner_parameters.set(**"fact: drop tolerance", 0.0);
>> overlap_level = 1
>> mPrec = Teuchos::rcp(Factory.Create(**IFPreconditionerType, &rA,
>> overlap_level));
>> mPrec->SetParameters(**preconditioner_parameters);
>> aztec_solver.SetPrecOperator(&***(mpPrec->GetOperator()))
>>
>> I thought it all resulted in Additive-Schwartz preconditioner with ILUT
>> as local subdomain preconditioner. But it gives different performance. The
>> first setting works well but the second failed to converge.
>>
>> Best regards
>> Giang Bui
>>
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>>
>>
>
>


-- 
With Best Regards !
Giang Bui
To learn and to excel
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