[dune-pdelab] Jacobian_volume vs jacobian_apply_volume

[Amir Peiraviminaei]

Thanks René.
The pdes that I'm working on are highly nonlinear and I'm trying to reduce
the assembly time.
I'm wondering whether it is possible to implement jacobian_volume,i.e.
analytic jacobian and for the skeleton and boundary parts just use the
numerical jacobian(default)?
Best
Amir

On Tue, Jul 7, 2020 at 5:12 PM René Heß <rene.hk-edv at gmx.de> wrote:

> Hi Amir,
>
>
> the jacobian methods will assemble the Jacobian matrix J. This matrix
> will be used by the linear solvers to solve your system.
>
> Some solvers only need J to calculate the application of J to a vector
> x. This means the solvers only needs to be able to compute Jx for a
> given vector x. With the jacobian apply methods it is possible to
> calculate this application of the Jacobian without ever assembling J.
>
> This can be used to implement matrix-free solvers that could be faster
> for certain cases. In your case you can ignore this issue and you won't
> need the jacobian_apply methods (or if the compiler complains you can
> just use the numerical methods, they won't be used anyway).
>
>
> Best regards,
> René
>
>
> Amir Peiraviminaei <apminaei at gmail.com> writes:
>
> > Hi everyone,
> > I'm using pdelab for a FV scheme and tutorial 02 as an example. So far I
> > have used only numerical jacobian, Now I want to implement analytical
> > jacobian myself, my question is
> > 1. What is the difference between jacobian_volume and
> jacobian_apply_volume?
> > (tutorial 02 uses both)
> >
> > Best
> > Amir
> > _______________________________________________
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> > dune-pdelab at lists.dune-project.org
> > https://lists.dune-project.org/mailman/listinfo/dune-pdelab
>
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