[aspect-devel] convergence failure

Tue Mar 15 16:14:25 PDT 2016

Hi Juliane,

Thank for the reply.

The large viscosity contrasts is in the initial model from the cookbook, which converges just fine.
So I guess that adding the complexity of the compositional fields is what prevent it from converging.
I will try to reduce the viscosity contrast to see if that helps.

I thought that the Drucker Prager model (which I am also using but for a different setup) is a linear materiel model. It is mentioned in the manual that it does not take into account any dependencies of material properties on compositional fields.

I am also thinking that the diffusion dislocation model could be the best alternative, but I am a bit struggling to fully understand all its parameters.

Thanks again for your help

Regards
Mohamed

On Mar 15, 2016, at 8:42 PM, Juliane Dannberg <dannberg at gfz-potsdam.de<mailto:dannberg at gfz-potsdam.de>> wrote:

Hi Mohamed,

At the moment, the other non-linear material models we have are drucker prager and diffusion dislocation; and which model is best for you depends on what you want to do.
The drucker prager model implements plasticity (and there is the cookbook "Crustal deformation" in the manual where it is described in more detail), while the diffusion dislocation model implements a combination of diffusion and dislocation creep.

For the model setup you posted, I can imagine that one point that causes problems are the large viscosity contrasts. If you set the solver scheme to "IMPES" and the "Initial adaptive refinement" to zero, the Stokes solver will converge for this very first iteration, and you can see in the output that you have a viscosity contrast of ~13 orders of magnitude in the uppermost layer of your model (~10 cells). Such a strong viscosity contrast makes it difficult for the Stokes solver to converge. I never used the Morency & Doin material model, so I do not know which parameters lead to such a strong viscosity contrast, but no matter which model you use as a starting point, it will probably help you to find problems in your model if you start from a simpler setup with lower viscosity contrasts and weaker non-linearity and then increase the complexity of your model step by step.

Best,
Juliane

On 03/13/2016 11:31 PM, Jonathan Perry-Houts wrote:

I haven't worked with nonlinear models much, so I can't recommend a good
one. I wrote that plugin to reproduce their 2004 paper results, but
never used it outside of that context. I'm sure someone else on this
mailing list can be more helpful!

Cheers,
Jonathan

On 03/12/2016 04:38 PM, Mohamed Gouiza wrote:

Hi Jonathan,

Thank you for the recommandation.
I will try another material model. Do you have any advice on which one
to use instead of the Morency and Doin?

Regards,
Mohamed

On Mar 11, 2016, at 7:03 PM, Jonathan Perry-Houts
<jperryh2 at uoregon.edu<mailto:jperryh2 at uoregon.edu> <mailto:jperryh2 at uoregon.edu><mailto:jperryh2 at uoregon.edu>> wrote:

Hi Mohamed,

The Morency Doin material model has always been problematic. (I can
verify that your model also fails to converge on my computer, for what
it's worth.)

I'll look into it more later, but to be honest my recommendation is to
avoid using that material model. It's a good starting point for building
your own nonlinear material model, but for some reason it's always been
trouble in practice.

Sorry to not be more help. Maybe after looking more closely at your
model I'll have more suggestions, but at first glance it doesn't look
like you've changed anything too significant from the cookbook.

-Jonathan

On 03/11/2016 12:34 AM, Mohamed Gouiza wrote:

*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<http://h3s3b12.arc2.leeds.ac.uk> <http://h3s3b12.arc2.leeds.ac.uk><http://h3s3b12.arc2.leeds.ac.uk/> 16 slots

## h3s3b14.arc2.leeds.ac.uk<http://h3s3b14.arc2.leeds.ac.uk> <http://h3s3b14.arc2.leeds.ac.uk><http://h3s3b14.arc2.leeds.ac.uk/> 16 slots

## h3s3b15.arc2.leeds.ac.uk<http://h3s3b15.arc2.leeds.ac.uk> <http://h3s3b15.arc2.leeds.ac.uk><http://h3s3b15.arc2.leeds.ac.uk/> 16 slots

## h6s2b4.arc2.leeds.ac.uk<http://h6s2b4.arc2.leeds.ac.uk> <http://h6s2b4.arc2.leeds.ac.uk><http://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<http://solver.cc>
<http://solver.cc><http://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> <mailto:M.Gouiza at leeds.ac.uk><mailto:M.Gouiza at leeds.ac.uk>
<mailto:M.Gouiza at leeds.ac.uk><mailto:M.Gouiza at leeds.ac.uk>
+44 7985 782073
-------------------------------------------------

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