[CIG-SHORT] ***UNCHECKED*** Re: Applying Gravitational Forces with Pylith

[Niloufar Abolfathian]

Hi,

I followed the 2D gravity example and I could run my models with gravity
and add initial stresses. But in models including finite strain, the
nonlinear solver could not converge. I have tried running the model with
gravitation on and off, applying depth dependent initial stress and no
initial stress, applying multigrid preconditioner and also not applying the
preconditioner and also modifying the linear and nonlinear tolerances, but
could not converge the model. I have attached the setting when setting when
I am using the gravity on, applying initial stress and using
preconditioning, I am wondering why it is always giving the error after
6000 years. I really appreciate all your help solving these issues.

Thanks,
Niloufar



On Thu, Aug 2, 2018 at 8:43 AM, Brad Aagaard <baagaard at usgs.gov> wrote:

> Is this the gravity only problem to compute the initial stresses? If so,
> then you should remove the fault.
>
> On 08/01/2018 08:59 PM, Niloufar Abolfathian wrote:
>
>> Thanks, Charles.
>>
>> My error is due to the convergence of the nonlinear solver. I have made
>> some modifications but not sure if it is a good idea to decrease my
>> residual norms.
>>
>> Best,
>> Niloufar
>>
>>
>> This is the setting I am using:
>>
>>
>> [pylithapp.timedependent]
>> formulation =pylith.problems.ImplicitLgDeform
>>
>>
>> [pylithapp.timedependent.formulation]
>> output =[domain,subdomain]
>> output.subdomain =pylith.meshio.OutputSolnSubset
>> solver =pylith.problems.SolverNonlinear
>>
>> [pylithapp.timedependent.formulation.time_step]
>> total_time =50000.0*year
>> dt =2.0*year
>>
>> [pylithapp.timedependent.interfaces]
>> fault =pylith.faults.FaultCohesiveDyn
>>
>> [pylithapp.timedependent.interfaces.fault]
>> label =fault
>> edge =fault_edge
>> zero_tolerance =1.0e-11
>>
>> # Use the slip-weakening friction model.
>> friction.db_properties =spatialdata.spatialdb.UniformDB
>> friction.db_properties.label =Slip weakening
>> friction.db_properties.values =[static-coefficient,dynamic-c
>> oefficient,slip-weakening-parameter,cohesion]
>>
>> friction.db_properties.data =[0.6,0.4,0.2*m,0.0*Pa]
>>
>> # ----------------------------------------------------------------------
>> # PETSc settings
>> # ----------------------------------------------------------------------
>> [pylithapp.petsc]
>> malloc_dump =
>>
>> # Preconditioner settings.
>> pc_type =asm
>> sub_pc_factor_shift_type =nonzero
>>
>
> When you encounter convergence errors, a good strategy is to revert to the
> direct solver. Note that this only works when you don't have a fault.
>
> pc_type = lu
>
>
> For most real applications (after you have debugged the setup)l, we
> recommend using the multigrid preconditioner. See
> solver_algebraicmultigrid.cfg (no fault) and solver_fieldsplit.cfg )with
> fault) in examples/3d/subduction.
>
>
>> # Friction sensitivity solve used to compute the increment in slip
>> # associated with changes in the Lagrange multiplier imposed by the
>> # fault constitutive model.
>> friction_pc_type =asm
>> friction_sub_pc_factor_shift_type =nonzero
>> friction_ksp_max_it =50
>> friction_ksp_gmres_restart =30
>>
>> # Uncomment to view details of friction sensitivity solve.
>> #friction_ksp_monitor = true
>> #friction_ksp_view = true
>> friction_ksp_converged_reason =true
>>
>> # Reduce convergence tolerances.
>> ksp_rtol =1.0e-16
>> ksp_atol =1.0e-12
>> ksp_max_it =4000
>> ksp_gmres_restart =100
>>
>> snes_rtol =1.0e-9
>> snes_atol =1.0e-8
>> snes_max_it =4000
>>
>>
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