[petsc-users] Using -ts_type sundials with -snes-fd

[Peter Brune]

I asked my question because it might be happening automatically.  His
output looked like the equation was solved.  A brief google search on this
makes it look like they do this anyways.  In addition:

http://www.mcs.anl.gov/petsc/petsc-dev/src/ts/impls/implicit/sundials/sundials.c.html#TSView_Sundials

directly refers to "Sundials no. of rhs calls for finite diff.
Jacobian-vector evals."

- Peter

On Thu, Jun 21, 2012 at 9:48 AM, Matthew Knepley <knepley at gmail.com> wrote:

> On Thu, Jun 21, 2012 at 8:45 AM, Peter Brune <prbrune at gmail.com> wrote:
>
>> What do you see when you run with -ts_view?
>>
>> - Peter
>>
>>
>> On Thu, Jun 21, 2012 at 9:40 AM, Geoff Oxberry <goxberry at gmail.com>wrote:
>>
>>> Peter,
>>>
>>> Just wanted to make sure there wasn't some Sundials-specific option for
>>> finite difference Jacobians that I was missing; despite reading the manual,
>>> it's a large package, and it's easy to miss things. If that's the case, I'd
>>> like to make a feature request for such an option.
>>>
>>
> If I understand correctly, you want a MF Jacobian with Sundials. We can't
> do that because Sundials is completely
> closed package, which we cannot pry apart to insert something like this.
> The alternative is to use the stuff solvers
> we currently have in TS. I thought that you had used the Rosenbrock-W
> stuff. Is this sufficient?
>
>   Thanks,
>
>       Matt
>
>
>>  Geoff
>>>
>>> On Jun 21, 2012, at 9:53 AM, Peter Brune wrote:
>>>
>>> Note that in the code in ts/impls/implicit/sundials it says:
>>>
>>> This uses its own nonlinear solver and krylov method so PETSc SNES and
>>> KSP options do not apply...
>>>
>>> - Peter
>>> On Jun 21, 2012 7:59 AM, "Geoff Oxberry" <goxberry at gmail.com> wrote:
>>>
>>>> Running the following example from PETSC 3.3.0-dev (changeset:
>>>> 23631:0e86ac5e4170)
>>>>
>>>> /path/to/petsc-dev/src/ts/examples/tutorials/ex8 -problem_type rober
>>>> -snes_fd -ts_type sundials
>>>>
>>>> gives the following output
>>>>
>>>> steps 1000 (0 rejected, 0 SNES fails), ftime 744.845, nonlinits 3739,
>>>> linits 3739
>>>> WARNING! There are options you set that were not used!
>>>> WARNING! could be spelling mistake, etc!
>>>> Option left: name:-snes_fd no value
>>>>
>>>> Just to confirm, is it currently impossible to use a finite difference
>>>> Jacobian matrix in concert with CVODE? If so, could this feature be
>>>> implemented in a future release? I currently rely on Sundials to integrate
>>>> stiff systems of ODEs, and for my application, it is impractical to derive
>>>> an analytical Jacobian matrix. (It is an issue I've discussed both with Jed
>>>> and Matt on another forum.)
>>>>
>>>> Cheers,
>>>>
>>>> Geoff
>>>
>>>
>>>
>>
>
>
> --
> 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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