[petsc-users] snes options for rough solution

[Matthew Knepley]

On Mon, Dec 12, 2016 at 1:04 AM, Matthew Knepley <knepley at gmail.com> wrote:

> On Mon, Dec 12, 2016 at 12:56 AM, Praveen C <cpraveen at gmail.com> wrote:
>
>> Increasing number of snes iterations, I get convergence.
>>
>> So it is a problem of initial guess being too far from the solution of
>> the nonlinear equation.
>>
>> Solution can be seen here
>>
>> https://github.com/cpraveen/fenics/blob/master/1d/cosmic_ray
>> /cosmic_ray.ipynb
>>
>
Also, how is this a parabolic equation? It looks like u/|u'| to me, which
does not look parabolic at all.

  Matt


> Green curve is solution after two time steps.
>>
>> It took about 100 snes iterations in first time step and about 50 in
>> second time step.
>>
>> I use exact Jacobian and direct LU solve.
>>
>
> I do not believe its the correct Jacobian. Did you test it as I asked?
> Also run with
>
>   -snes_monitor -ksp_monitor_true_residual -snes_view
> -snes_converged_reason
>
> and then
>
>   -snes_fd
>
> and send all the output
>
>    Matt
>
>
>> Thanks
>> praveen
>>
>
>
>
> --
> 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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