[aspect-devel] convergence failure

[Mohamed Gouiza]

Hi All,

I am trying to run a modified version of the Morency & Doin example.
The major modification I made is to the materiel model which now consists of a crust (30km thick) and a mantle lithosphere with variable thickness (170km thick for 0<x<1000km; 90km thick for 1000<x<2000km). I also modified the temperature model accordingly (the temperature increase linearly until the base of the lithosphere which is at 1330C; temperature in the sublisthospheric mantle is constant at 1330C; temperature increase linearly in the lower mantle)
The model doesn't converge on timestep 0 (t=0 years).

I increased the Max nonlinear iterations to 100,000, it didn't work.
I changed the solver scheme from iterated IMPES to iterated Stokes, it didn't work.

Am I doing something wrong?

I've attached the parameter file as well (m-cvx-003.prm).

Thank you for your help.



## Hosts assigned to job 404757.1:
##
## h3s3b12.arc2.leeds.ac.uk 16 slots
## h3s3b14.arc2.leeds.ac.uk 16 slots
## h3s3b15.arc2.leeds.ac.uk 16 slots
## h6s2b4.arc2.leeds.ac.uk 16 slots
##
## Resources granted:
##
## h_vmem = 2G (per slot)
## h_rt   = 48:00:00

## nodes/ppn parallel request:
##
## nodes = 4     np  = 64
## ppn   = 16    tpp = 1

-----------------------------------------------------------------------------
-- This is ASPECT, the Advanced Solver for Problems in Earth's ConvecTion.
--     . version 1.4.0-pre
--     . running in DEBUG mode
--     . running with 64 MPI processes
--     . using Trilinos
-----------------------------------------------------------------------------


-----------------------------------------------------------------------------
The output directory <output/> provided in the input file appears not to exist.
ASPECT will create it for you.
-----------------------------------------------------------------------------


Number of active cells: 4,096 (on 6 levels)
Number of degrees of freedom: 87,782 (33,410+4,257+16,705+16,705+16,705)

*** Timestep 0:  t=0 years
   Solving temperature system... 0 iterations.
   Solving crust system ... 0 iterations.
   Solving lithosphere system ... 0 iterations.
   Rebuilding Stokes preconditioner...
   Solving Stokes system... 0+82 iterations.
   Residual after nonlinear iteration 1: 1

   Rebuilding Stokes preconditioner...
   Solving Stokes system...


----------------------------------------------------
Exception on processing:

--------------------------------------------------------
An error occurred in line <760> of file </home/ufaserv1_k/earmgo/safe/aspect/source/simulator/solver.cc> in function
    double aspect::Simulator<dim>::solve_stokes() [with int dim = 2]
The violated condition was:
    false
The name and call sequence of the exception was:
    ExcMessage (std::string("The iterative Stokes solver " "did not converge. It reported the following error:\n\n") + exc.what() + "\n See " + parameters.output_directory+"solver_history.txt" + " for convergence history.")
Additional Information:
The iterative Stokes solver did not converge. It reported the following error:


--------------------------------------------------------
An error occurred in line <1216> of file </home/ufaserv1_k/earmgo/safe/dealii/include/deal.II/lac/solver_gmres.h> in function
    void dealii::SolverFGMRES<VectorType>::solve(const MatrixType&, VectorType&, const VectorType&, const PreconditionerType&) [with MatrixType = aspect::internal::StokesBlock; PreconditionerType = aspect::internal::BlockSchurPreconditioner<dealii::TrilinosWrappers::PreconditionAMG, dealii::TrilinosWrappers::PreconditionILU>; VectorType = dealii::TrilinosWrappers::MPI::BlockVector]
The violated condition was:
    false
The name and call sequence of the exception was:
    SolverControl::NoConvergence (accumulated_iterations, res)
Additional Information:
Iterative method reported convergence failure in step 37667. The residual in the last step was 1.50021e+12.

This error message can indicate that you have simply not allowed a sufficiently large number of iterations for your iterative solver to converge. 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 residual in the last iteration is likely going to be large.
--------------------------------------------------------

See output/solver_history.txt for convergence history.
--------------------------------------------------------

Aborting!
----------------------------------------------------
--------------------------------------------------------------------------
mpirun noticed that the job aborted, but has no info as to the process
that caused that situation.
--------------------------------------------------------------------------


-------------------------------------------------
Mohamed Gouiza, Research Fellow
Basin Structure Group, Institute of Applied Geosciences
University of Leeds, School of Earth and Environment
Leeds,  LS2 9JT, UK
M.Gouiza at leeds.ac.uk<mailto:M.Gouiza at leeds.ac.uk>
+44 7985 782073
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