[firedrake] Error - NonlinearVariationalSolver

[Lawrence Mitchell]

Failed with sending to the list, so copying below.

Lawrence
On 10 Nov 2014, at 19:02, Lawrence Mitchell <lawrence.mitchell at imperial.ac.uk> wrote:

> On 10 Nov 2014, at 18:48, Anna Kalogirou <a.kalogirou at leeds.ac.uk> wrote:
> 
>> Dear Lawrence,
>> 
>> Thank you very much for the reply. Very useful. It now gives the error:
>> 
>> ======================
>> Traceback (most recent call last):
>> File "nonlinear_swe.py", line 73, in <module>
>>   phi_solver.solve()
>> File "<string>", line 2, in solve
>> File "/opt/firedrake/2.0/lib/python2.7/site-packages/PyOP2-0.11.0_117_gcfe592d-py2.7-linux-x86_64.egg/pyop2/profiling.py", line 197, in wrapper
>>   return f(*args, **kwargs)
>> File "/opt/firedrake/2.0/lib/python2.7/site-packages/firedrake/solving.py", line 336, in solve
>>   %s""" % (self.snes.getIterationNumber(), msg))
>> RuntimeError: Nonlinear solve failed to converge after 0 nonlinear iterations.
>> Reason:
>>  DIVERGED_LINE_SEARCH
>> ======================
>> 
>> Do you have any idea what that might be? Do I need do give any arguments in the phi_solver.solve()?
>> 
> 
> So this tells me that the nonlinear solver (line search newton) failed because the line search failed.  You can try running with
> 
> solver_parameters={'snes_monitor': True, 'ksp_monitor': True, 'snes_linesearch_monitor': True}
> 
> (add this as an argument to the construction of the nonlinearvariationalsolver)
> 
> to see what's going on.
> 
> If I make what I /think/ are the correct changes to your initial script, I see that the phi solver has the same diverged line search.  This looks to be because at the second time step, the residual is already 1e-14 before we start.  But I don't know if that's expected, or if I changed bits correctly.
> 
> Lawrence

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