[Trilinos-Users] AztecOO convergence using Sundance

Kevin Long kevin.long at ttu.edu
Mon Mar 12 21:09:50 MDT 2012


Andrea,

You'll have trouble solving the linear subproblem with ILU 
preconditioning. You might talk to Vicki Howle, who has implemented 
physics-based preconditioners for NS equations using Sundance.

Kevin


On 03/12/2012 08:31 PM, Andrea Penza wrote:
> Dear experts,
>
> I'm trying since days to achieve convergence solving Navier-Stokes 
> equations using Aztec solver. Particularly I'm intended to use a GMRES 
> method and ILU preconditioner (I think this should be suit right to my 
> problem), and the current solver parameters are the following:
>
> <ParameterList>
> <ParameterList name="NOX Solver">
> <Parameter name="Nonlinear Solver"type="string"value="Line Search Based"/>
> <ParameterList name="Line Search">
> <Parameter name="Method" type="string" value="More'-Thuente"/>
> </ParameterList>
> <ParameterList name="Status Test">
> <Parameter name="Max Iterations" type="int" value="20"/>
> <Parameter name="Tolerance" type="double" value="1e-8"/>
> </ParameterList>
> <ParameterList name="Printing">
> <ParameterList name="Output Information">
> <Parameter name="Error" type="bool" value="true"/>
> <Parameter name="Warning" type="bool" value="true"/>
> <Parameter name="Outer Iteration" type="bool" value="true"/>
> <Parameter name="Inner Iteration" type="bool" value="true"/>
> <Parameter name="Parameters" type="bool" value="false"/>
> <Parameter name="Details" type="bool" value="false"/>
> <Parameter name="Linear Solver Details" type="bool" value="true"/>
> <Parameter name="Outer Iteration StatusTest"type="bool"value="true"/>
> <Parameter name="Test Details" type="bool" value="false"/>
> <Parameter name="Stepper Iteration" type="bool" value="false"/>
> <Parameter name="Stepper Details" type="bool" value="false"/>
> <Parameter name="Stepper Parameters" type="bool" value="false"/>
> <Parameter name="Debug" type="bool" value="false"/>
> </ParameterList>
> </ParameterList>
> <ParameterList name="Linear Solver">
> <Parameter name="Max Iterations" type="int" value="1000"/>
> <Parameter name="Method" type="string" value="GMRES"/>
> <ParameterList name="Preconditioner">
> <Parameter name="Type" type="string" value="Ifpack"/>
> <Parameter name="Prec Type" type="string" value="ILU"/>
> <Parameter name="Overlap" type="int" value="1"/>
> <ParameterList name="Ifpack Settings">
> <Parameter name="fact: level-of-fill" type="int" value="2"/>
> </ParameterList>
> </ParameterList>
> <Parameter name="Tolerance" type="double" value="1e-10"/>
> <Parameter name="Type" type="string" value="Aztec"/>
> <Parameter name="Verbosity" type="int" value="0"/>
> </ParameterList>
> </ParameterList>
> </ParameterList>
>
>
>
> This brings to message like:
>
> WARNING: NOX::Direction::Newton::compute() - Linear solve failed to 
> achieve convergence - using the step anyway since "Rescue Bad Newton 
> Solve" is true
>
> Notice that the same problem was solved without problems using 
> NOX-AMESOS solver, but this did not suit fine to run in parallel as I 
> need.
> So now I'm investigating iterative methods in order to run parallel 
> jobs. Maybe I'm using some parameter in a wrong way, has anyone idea 
> about something could improve this issue?
> Thanks in advance for your support.
> Kind regards,
>
> Andrea
>
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-- 
Kevin Long
Associate Professor
Department of Mathematics and Statistics
Texas Tech University

"The end of fear is the beginning of wisdom"
- Bertrand Russell

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