[aspect-devel] Problem: Iterative advection solver does not converge

[John Naliboff]

Hi Felipe,

Ouch -  The residual in the last step was 1.99733e+21.  Something is definitely amiss ;)

Can you describe briefly how you built the model?  Is it based off the ‘3d convection’ cookbook model?  If so, what parameters did you change?  

What does the flow field look like in the first 10 steps that do converge?  Does something look off?

Incrementally varying parameters as you build up a model is a very helpful way to pinpoint the source of errors … let’s backtrack through the setup and see what is afoot.

Cheers,
John

*************************************************
Assistant Project Scientist, CIG
Earth & Planetary Sciences Dept., UC Davis





> On Jun 6, 2016, at 12:47 AM, FELIPE ORELLANA ROVIROSA <f_orellana at berkeley.edu> wrote:
> 
> 
>  Hi,
> 
>        I am in trouble trying to solve convection in a rectangular box. The setting consists of 'real' dimensions. The Rayleigh number is like ~3 x 10^5.
> 
>        Before crash, the timestep is slightly less than 1000 years.
> 
>        The error message is related to the advection Solver. On this, I have tried many many cases: I have set up different values for Linear solver tolerance, and different values for Max nonlinear iterations, but my program keeps crashing after some time..
> 
>        I am attaching the parameter file.
> 
>        Maybe I am taking 'bad parameter combinations'..  Hope you guys have some clue on what parameter I should alter.
> 
> cheers,
> 
> Felipe
> ps: The error message I get is this:
> 
>    *** Timestep 11:  t=626743 years
>    Solving temperature system... 
> 
> ----------------------------------------------------
> Exception on processing: 
> 
> --------------------------------------------------------
> An error occurred in line <434> of file </root/SEISMO/usr-local-src/aspect/aspect-1.3/source/simulator/solver.cc
> > in function
>     double aspect::Simulator<dim>::solve_advection(const aspect::Simulator<dim>::AdvectionField&) [with int dim 
> = 3]
> The violated condition was: 
>     false
> The name and call sequence of the exception was:
>     ExcMessage (std::string("The iterative advection solver " "did not converge. It reported the following error
> :\n\n") + exc.what())
> Additional Information: 
> The iterative advection solver did not converge. It reported the following error:
> 
> 
> --------------------------------------------------------
> An error occurred in line <1042> of file </share/apps/deal.II/include/deal.II/lac/solver_gmres.h> in function
>     void dealii::SolverGMRES<VectorType>::solve(const MatrixType&, VectorType&, const VectorType&, const PreconditionerType&) [with MatrixT
> ype = dealii::TrilinosWrappers::SparseMatrix, PreconditionerType = dealii::TrilinosWrappers::PreconditionILU, VectorType = dealii::Trilinos
> Wrappers::MPI::Vector]
> The violated condition was: 
>     iteration_state == SolverControl::success
> The name and call sequence of the exception was:
>     SolverControl::NoConvergence (accumulated_iterations, last_res)
> Additional Information: 
> Iterative method reported convergence failure in step 1000. The residual in the last step was 1.99733e+21.
> 
> This error message can indicate that you have simply not allowed a sufficiently large number of iterations for your iterative solver to con
> verge. This often happens when you increase the size of your problem. In such cases, the last residual will likely still be very small, and
>  you can make the error go away by increasing the allowed number of iterations when setting up the SolverControl object that determines the
>  maximal number of iterations you allow.
> 
> The other situation where this error may occur is when your matrix is not invertible (e.g., your matrix has a null-space), or if you try to
>  apply the wrong solver to a matrix (e.g., using CG for a matrix that is not symmetric or not positive definite). In these cases, the resid
> ual in the last iteration is likely going to be large.
> --------------------------------------------------------
> 
> --------------------------------------------------------
> 
> Aborting!
> ----------------------------------------------------
> --------------------------------------------------------------------------
> mpiexec noticed that the job aborted, but has no info as to the process
> that caused that situation.
> 
> 
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