[CIG-SHORT] Fwd: Rate and State and Initial Traction

[Matthew Knepley]

On Wed, Aug 29, 2012 at 2:36 PM, Brad Aagaard <baagaard at usgs.gov> wrote:

> Romain,
>
> It looks like you are using Schur complement preconditioner settings.
> The jump in the KSP residual at iteration 10 is odd and suggests
> something is not quite right in the linear solve (probably related to
>

Brad is right that the tolerances here will produce some garbage. Going
below
machine epsilon (about 10^-16) means you get randomness and ultimately
underflow which I think you got in a norm calculation since things get
squared.
The solver should have converged on iterate 2, and will with the tolerances
that
Brad suggested.

  Thanks,

     Matt


> the preconditioner). Try using the AMG preconditioner. It may not be
> quite as fast but it is more robust. Matt can probably help you tune the
> Schur complement solver conditions some more if necessary.
>
> Your SNES tolerances are quite large. I suggest using tolerances similar
> to those in examples/3d/hex8/step14.cfg.
>
> SOLVER TOLERANCES
>
> ksp_rtol = 1.0e-16
> ksp_atol = 1.0e-12
>
> snes_rtol = 1.0e-14
> snes_atol = 1.0e-10
>
>
> AMG PRECONDITIONER SETTINGS
>
> [pylithapp.timedependent.formulation]
> split_fields = True
> matrix_type = aij
>
> [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 = jacobi
> fs_fieldsplit_0_ksp_type = preonly
> fs_fieldsplit_1_ksp_type = preonly
>
> Brad
>
>
> On 08/29/2012 11:42 AM, Romain Jolivet wrote:
> > Hello Brad, Matt, Charles and the pylith team,
> >
> > Following your advice from the other day, I am experimenting  how to
> create earthquakes on a frictional interface by applying a traction change
> history. It works fine with the SlipWeakening law in 2D. I'm trying to move
> on to the RateStateAgeing behavior and I have problems applying the initial
> traction conditions:
> >
> > I use a SimpleDB to apply the frictional properties on the fault: one
> domain is rate-strengthening, the other is rate-weakening with a linear
> transition between the two domains. If I do not try to turn on any
> traction_perturbation option, the code runs great, and I have a slow slip
> all the along the fault at any time.
> >
> > As I want the rate-weakening domain to be stuck sometimes, I want to
> turn on traction_perturbation.db_initial. I use a SimpleDB to put a
> negative traction all along the fault, and a shear traction compatible with
> the friction coefficients I impose. However, when I run this, I have the
> following error message from PETSc (I attach the log):
> >
> >   >>
> /Users/jolivetinsar/MYBIN/pylith/pylith-1.7.1-darwin-10.6.8/lib/python2.7/site-packages/pylith/problems/Implicit.py:215:step
> >   -- implicit(info)
> >   -- Solving equations.
> >    0 SNES Function norm 2.679589636063e+01
> >      0 KSP Residual norm 9.637565795900e-01
> >      1 KSP Residual norm 3.564937135471e-08
> >      2 KSP Residual norm 4.313963401911e-16
> >      3 KSP Residual norm 3.050427683646e-16
> >      4 KSP Residual norm 2.490663081181e-16
> >      5 KSP Residual norm 2.156976950523e-16
> >      6 KSP Residual norm 1.929258577738e-16
> >      7 KSP Residual norm 1.761163907914e-16
> >      8 KSP Residual norm 1.630520838230e-16
> >      9 KSP Residual norm 1.525212509706e-16
> >     10 KSP Residual norm 1.833325155789e-11
> >     11 KSP Residual norm 7.039784754868e-23
> >    Linear solve converged due to CONVERGED_ATOL iterations 11
> > [0]PETSC ERROR: --------------------- Error Message
> ------------------------------------
> > [0]PETSC ERROR: Floating point exception!
> > [0]PETSC ERROR: Infinite or not-a-number generated in norm!
> >
> > If anyone has an idea about that error message....
> >
> > I think it has to do with some slip vector. If I set
> friction.min_slip_rate=1e-1, this problem does not happen (the nonlinear
> solver does not converge, but at least, no crash). If I set the normal
> traction to be positive, it does not crash as well (and it does not
> converge as well). I join to this message the cfg file I am using for that
> experiment.
> >
> > 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
> >
>
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-- 
What most experimenters take for granted before they begin their
experiments is infinitely more interesting than any results to which their
experiments lead.
-- Norbert Wiener



-- 
What most experimenters take for granted before they begin their
experiments is infinitely more interesting than any results to which their
experiments lead.
-- Norbert Wiener
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