[CIG-SHORT] Parallel computing problem

[Brad Aagaard]

Romain,

I found a parallel bug in FaultCohesiveDyn that could cause problems 
when running faults with friction in parallel. I pushed the fix to our 
PyLith version 1.7 code. We hope to release Fri June 1.

Your problem runs for me but the nonlinear solve runs out of iterations 
before it converges. It looks like the problem is related to the absence 
of realistic fault normal tractions. You impose Dirichlet BC, which will 
create very small (in some cases negligible) fault normal compressive 
tractions. I recommend imposing initial fault tractions (compressive 
normal tractions and, optionally, shear tractions) or gravitational body 
forces consistent with the overburden. This will yield more realistic 
conditions and facilitate convergence.

I used the following solver settings for your 2-D problem in addition to 
the ones you used in your pylithapp.cfg file. This accelerates the rate 
of convergence in the linear solve. These are more appropriate for your 
problem than the ones that Charles provided (which were for a 3-D 
problem and didn't use the custom constraint preconditioner).

Sorry for the delayed reply. I was out of the office all last week.

[pylithapp.timedependent.formulation]
split_fields = True
matrix_type = aij
use_custom_constraint_pc = True

[pylithapp.petsc]
ksp_gmres_restart = 100
fs_pc_type = fieldsplit
fs_pc_fieldsplit_real_diagonal = True
fs_pc_fieldsplit_type = multiplicative
fs_fieldsplit_0_pc_type = ml
fs_fieldsplit_1_pc_type = ml
fs_fieldsplit_2_pc_type = jacobi
fs_fieldsplit_0_ksp_type = preonly
fs_fieldsplit_1_ksp_type = preonly
fs_fieldsplit_2_ksp_type = preonly

Regards,
Brad


On 05/22/2012 06:36 PM, Romain Jolivet wrote:
> Hi,
>
> I have a problem running pylith on multiple nodes.
>
> My model is based on an elastic medium with a fault in it. When I use the FaultCohesiveKin property and impose the displacement, everything is fine.
> However, when I use the FaultCohesiveDyn property, with StaticFriction, it starts getting messy. My files are attached.
> I run:
> pylith step01.cfg
> and the run is fine
> If I run
> pylith --nodes=10 step01.cfg
> it crashes at the first time step. I tried with nodes=2 to nodes=12 (the number of cores on my machine) and I had the same result. The error message comes from petsc.
>
> I went into the pylith examples to find a similar, but simpler, problem. In example/3d/hex8/, I tried to run step10.cfg:
> with one node, it is fine:
> pyltih step10.cfg
> However, when you ask for several nodes (more than 2), it crashes:
> pylith --nodes=3 step10.cfg
> with 2 nodes, it seems to be fine, but you have a petsc error message at the end.
>
> I someone has an idea on this....
> Thank you
> Romain
>
>
>
>
>
>
>
>
> Romain Jolivet
> Postdoctoral Scholar
> Geological and Planetary Sciences
> California Institute of Technology, Pasadena, CA
> rjolivet at caltech.edu
> +1 (626) 560 6356
>
>
>
>
> _______________________________________________
> CIG-SHORT mailing list
> CIG-SHORT at geodynamics.org
> http://geodynamics.org/cgi-bin/mailman/listinfo/cig-short