Dear Guyer,
Thank you for your wonderful example. I tried it in my own problem, and
I found much better convergence that simply sweeping the solution as
suggested in FiPy documentation.
I also tried to figure how to extend your example to a "second order"
Newton iteration, but could not get anything useful (apart from the fact
that we would probably get a second order differential equation for
\delta c). Do you think is that feasible?
Marcel
El 13/05/16 a les 20:12, Guyer, Jonathan E. Dr. (Fed) ha escrit:
I have posted an implementation at
https://gist.github.com/guyer/f29c759fd7f0f01363b8483c7bc644cb
I'm not sure the way that I determine the Jacobian expression is completely
legitimate, but it seems to work. Please don't hesitate to ask any questions
(or offer corrections!).
On May 11, 2016, at 4:57 PM, Guyer, Jonathan E. Dr. (Fed)
<[email protected]> wrote:
I'm not sure I have anything posted publicly. I will put together a minimal
example.
On May 11, 2016, at 12:42 PM, Daniel Wheeler <[email protected]> wrote:
Hi Kris,
FiPy doesn't have an automated way to do Newton iterations. You can
always construct your own Newton iteration scheme using the terms and
equations as you would ordinarily, but then you have to do the
variational derivatives and the coupling by hand. This also assumes
that you are familiar with the Newton method. You can query an
equation for its residual which then needs to be added to the Newton
version of the equation. I think that means that each equation
requires two implementations, the regular and the Newton.
Regarding examples of using FiPy with Newton iterations, I don't
believe that we have any examples in the source code although I do
know that some people have used it in this way including Jon Guyer. He
may have examples in Github somewhere that would help you get started,
but I'll let him point you to them.
Cheers,
Daniel
On Tue, May 10, 2016 at 9:31 AM, Kris Kuhlman
<[email protected]> wrote:
I am interested in trying to use newton iterations, rather than simply
fixed-point iterations, to speed up the convergence of the non-linear
iterations in my fipy problem.
I have found this mention of a term useful for newton iterations,
http://www.ctcms.nist.gov/fipy/fipy/generated/fipy.terms.html#module-fipy.terms.residualTerm
and I see this mention of an example using newton iterations
https://github.com/usnistgov/fipy/wiki/ScharfetterGummel
but I don't see the actual code it is talking about. Is there an example
available somewhere?
Kris
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Daniel Wheeler
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Dr. Marcel Aguilella-Arzo
Professor Titular d'Universitat, Física Aplicada
Coordinador de la Subcomissió d'Especialitat de Ciències Experimentals i
Tecnologia
del Màster Universitari en Professor d'Educació Secundària Obligatòria i
Batxillerat,
Formació Professional i Ensenyament d'Idiomes
Departament de Física
Escola Superior de Tecnologia i Ciències Experimentals
Universitat Jaume I
Av. Sos Baynat, s/n
12071 Castelló de la Plana (Spain)
+34 964 728 046
[email protected]
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