[Trilinos-Users] ilut setting

Erik Boman egboman at sandia.gov
Tue Sep 17 12:01:11 MDT 2013


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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>   



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