[CIG-SHORT] small-scale crack opening convergence problem

[Matthew Knepley]

On Tue, Oct 30, 2012 at 11:15 AM, Scott Henderson <sth54 at cornell.edu> wrote:

> Here is an output log with all the flags on. I'm thinking maybe the
> problem is not sufficiently constrained by the boundary conditions I've
> applied here...
>

There are all sorts of improvements that can be made to this solver, but
lets defer that until
the modeling is cleared up. Since this problem is so small, just crank up
the linear solver to
get exact results:

  --petsc.ksp_rtol=1.0e-10

However, it appears to be making no progress at all after the Newton solve,
so as you say, its
likely to be something with the problem setup. Brad is the best at
diagnosing friction problems.

   Matt


> On Oct 30, 2012, at 11:03 AM, Matthew Knepley <knepley at mcs.anl.gov> wrote:
>
> On Mon, Oct 29, 2012 at 11:25 AM, Scott Henderson <scottyhq at gmail.com>wrote:
>
>> Hello CIG-users,
>>
>> I've been trying to use Pylith for a "single edge notch in tension
>> (SENT)" fracture mechanics simulation. In order to do this I've modified
>> step20.cfg to be a 2D plane-stress problem. I've also followed what I could
>> from this mailing-list post (
>> http://www.geodynamics.org/pipermail/cig-short/2012-September/001120.html).
>> I'm still not able to get expected results, which makes me think I' doing
>> something incorrectly with the pylith settings (PETSC in particular). I'm
>> pretty new to the software, so any tips on the cubit mesh or pylith cfg
>> files would be appreciated (zipped folder attached).
>>
>> Essentially, I'm not getting the expected u2 displacements from this
>> analysis (but they are not unreasonable), and the following SNES output
>> makes me concerned:
>>
>> 500 SNES Function norm 2.483466683115e-06
>> Nonlinear solve did not converge due to DIVERGED_MAX_IT iterations 500
>>
>> Increasing snes_max_it doesn't seem to lead to convergence.
>>
>
> Always send all output. The nonlinear solver is not converging, but the
> first thing to check is
> how the linear solver is doing inside. Also, I want to see exactly what
> solver setup you have.
>
>     Matt
>
>
>> Any suggestions appreciated,
>> Scott
>>
>>
>>
>>
>> _______________________________________________
>> CIG-SHORT mailing list
>> CIG-SHORT at geodynamics.org
>> http://geodynamics.org/cgi-bin/mailman/listinfo/cig-short
>>
>>
>
>
> --
> 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
> _______________________________________________
> CIG-SHORT mailing list
> CIG-SHORT at geodynamics.org
> http://geodynamics.org/cgi-bin/mailman/listinfo/cig-short
>
>
>
>


-- 
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
-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://geodynamics.org/pipermail/cig-short/attachments/20121030/69bc4b9d/attachment.htm