[Trilinos-Users] AztecOO convergence using Sundance

[Andrea Penza]

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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