[petsc-users] Configure nested PCFIELDSPLIT with general index sets

[Natacha BEREUX]

Thanks for your explanation. It is much clearer now.
I have just submitted an issue on the bugtracker (for
DMShellSetCreateFieldDecomposition Fortran interface)
I am going to work on your other proposals (using PetscObjectCompose or
wrap my decomposition).
I'll let you know what it gives !
Thanks a lot
Natacha

On Thu, May 4, 2017 at 5:07 PM, Matthew Knepley <knepley at gmail.com> wrote:

> On Thu, May 4, 2017 at 9:17 AM, Natacha BEREUX <natacha.bereux at gmail.com>
> wrote:
>
>> Dear Matt,
>> I re-checked the master branch. To be precise, I downloaded the nightly
>> tarball this morning (from http://ftp.mcs.anl.gov/pub/pet
>> sc/petsc-master.tar.gz)
>> I am sure that the Fortran interface of DMSellSetCreateFieldDecomposition
>> is missing.
>> And it is quite tricky to add it. I have tried to write something in
>> src/dm/impls/shell/ftn-custom/zdmshellf.c but I am not familiar with
>> callbacks.
>> Any help would be greatly appreciated!
>>
>
> I added PetscObjectCompose() to Fortran, so you could compose IS objects
> when needed. Setting function pointers from Fortran is indeed
> complicated and I do not yet know how to do it. Could you submit and Issue
> (https://bitbucket.org/petsc/petsc/issues?status=new&status=open)
> and someone will add this as soon as we have time?
>
> In the meantime, it would not be hard to create the DMShell in C and have
> a small C wrapper for your Fortran function to create the decomposition.
>
>   Thanks,
>
>     Matt
>
>
>> Best regards
>> Natacha
>>
>> On Fri, Apr 28, 2017 at 8:11 PM, Matthew Knepley <knepley at gmail.com>
>> wrote:
>>
>>> On Fri, Apr 28, 2017 at 1:09 PM, Matthew Knepley <knepley at gmail.com>
>>> wrote:
>>>
>>>> On Fri, Apr 28, 2017 at 11:48 AM, Natacha BEREUX <
>>>> natacha.bereux at gmail.com> wrote:
>>>>
>>>>> Dear Matt,
>>>>> Sorry for my (very) late reply.
>>>>> I was not able to find the Fortran interface of
>>>>> DMSellSetCreateFieldDecomposition in the late petsc-3.7.6 fortran
>>>>> (and my code still fails to link).
>>>>> I have the feeling that it is missing in the master branch.
>>>>> And I was not able to get it on bitbucket either.
>>>>> Is there a branch from which I can pull your commit  ?
>>>>>
>>>>
>>>> I would either:
>>>>
>>>>   a) Use the 'next' branch
>>>>
>>>> or
>>>>
>>>>   b) wait until Monday for me to merge to 'master'
>>>>
>>>> This merge has been held up, but can now go forward.
>>>>
>>>
>>> I just checked master. It was already merged. Please recheck your master.
>>>
>>>   Thanks,
>>>
>>>      Matt
>>>
>>>
>>>>   Thanks,
>>>>
>>>>      Matt
>>>>
>>>>
>>>>> Thans a lot for your help,
>>>>> Natacha
>>>>>
>>>>> On Thu, Mar 30, 2017 at 9:25 PM, Matthew Knepley <knepley at gmail.com>
>>>>> wrote:
>>>>>
>>>>>> On Wed, Mar 22, 2017 at 1:45 PM, Natacha BEREUX <
>>>>>> natacha.bereux at gmail.com> wrote:
>>>>>>
>>>>>>> Hello Matt,
>>>>>>> Thanks a lot for your answers.
>>>>>>> Since I am working on a large FEM Fortran code, I have to stick to
>>>>>>> Fortran.
>>>>>>> Do you know if  someone plans to add this Fortran interface? Or may
>>>>>>> be I could do it myself ? Is this particular interface very hard to add ?
>>>>>>> Perhaps could  I mimic some other interface ?
>>>>>>> What would you advise ?
>>>>>>>
>>>>>>
>>>>>> I have added the interface in branch knepley/feature-fortran-compose.
>>>>>> I also put this in the 'next' branch. It
>>>>>> should make it to master soon. There is a test in
>>>>>> sys/examples/tests/ex13f
>>>>>>
>>>>>>   Thanks,
>>>>>>
>>>>>>     Matt
>>>>>>
>>>>>>
>>>>>>> Best regards,
>>>>>>> Natacha
>>>>>>>
>>>>>>> On Wed, Mar 22, 2017 at 12:33 PM, Matthew Knepley <knepley at gmail.com
>>>>>>> > wrote:
>>>>>>>
>>>>>>>> On Wed, Mar 22, 2017 at 10:03 AM, Natacha BEREUX <
>>>>>>>> natacha.bereux at gmail.com> wrote:
>>>>>>>>
>>>>>>>>> Hello,
>>>>>>>>> if my understanding is correct, the approach proposed by Matt and
>>>>>>>>> Lawrence is the following :
>>>>>>>>> - create a DMShell (DMShellCreate)
>>>>>>>>> - define my own CreateFieldDecomposition to return the index sets
>>>>>>>>> I need (for displacement, pressure and temperature degrees of freedom) :
>>>>>>>>> myCreateFieldDecomposition(... )
>>>>>>>>> - set it in the DMShell ( DMShellSetCreateFieldDecomposition)
>>>>>>>>> - then sets  the DM in KSP context  (KSPSetDM)
>>>>>>>>>
>>>>>>>>> I  have some more questions
>>>>>>>>> - I did not succeed in setting my own CreateFieldDecomposition in
>>>>>>>>> the DMShell : link  fails with " unknown reference to «
>>>>>>>>> dmshellsetcreatefielddecomposition_ ». Could it be a Fortran
>>>>>>>>> problem (I am using Fortran)?  Is this routine available in PETSc  Fortran
>>>>>>>>> interface ? \
>>>>>>>>>
>>>>>>>>
>>>>>>>> Yes, exactly. The Fortran interface for passing function pointers
>>>>>>>> is complex, and no one has added this function yet.
>>>>>>>>
>>>>>>>>
>>>>>>>>> - CreateFieldDecomposition is supposed to return an array of dms
>>>>>>>>> (to define the fields). I am not able to return such datas.  Do I return a
>>>>>>>>> PETSC_NULL_OBJECT instead ?
>>>>>>>>>
>>>>>>>>
>>>>>>>> Yes.
>>>>>>>>
>>>>>>>>
>>>>>>>>> - do I have to provide something else to define the DMShell ?
>>>>>>>>>
>>>>>>>>
>>>>>>>> I think you will have to return local and global vectors, but this
>>>>>>>> just means creating a vector of the correct size and distribution.
>>>>>>>>
>>>>>>>>   Thanks,
>>>>>>>>
>>>>>>>>      Matt
>>>>>>>>
>>>>>>>>
>>>>>>>>> Thanks a lot for your help
>>>>>>>>> Natacha
>>>>>>>>>
>>>>>>>>> On Tue, Mar 21, 2017 at 2:44 PM, Natacha BEREUX <
>>>>>>>>> natacha.bereux at gmail.com> wrote:
>>>>>>>>>
>>>>>>>>>> Thanks for your quick answers. To be honest, I am not familiar at
>>>>>>>>>> all with DMShells and DMPlexes. But since it is what I need, I am going to
>>>>>>>>>> try it.
>>>>>>>>>> Thanks again  for your advices,
>>>>>>>>>> Natacha
>>>>>>>>>>
>>>>>>>>>> On Tue, Mar 21, 2017 at 2:27 PM, Lawrence Mitchell <
>>>>>>>>>> lawrence.mitchell at imperial.ac.uk> wrote:
>>>>>>>>>>
>>>>>>>>>>>
>>>>>>>>>>> > On 21 Mar 2017, at 13:24, Matthew Knepley <knepley at gmail.com>
>>>>>>>>>>> wrote:
>>>>>>>>>>> >
>>>>>>>>>>> > I think the remedy is as easy as specifying a DMShell that has
>>>>>>>>>>> a PetscSection (DMSetDefaultSection) with your ordering, and
>>>>>>>>>>> > I think this is how Firedrake (http://www.firedrakeproject.o
>>>>>>>>>>> rg/) does it.
>>>>>>>>>>>
>>>>>>>>>>> We actually don't use a section, but we do provide
>>>>>>>>>>> DMCreateFieldDecomposition_Shell.
>>>>>>>>>>>
>>>>>>>>>>> If you have a section that describes all the fields, then I
>>>>>>>>>>> think if the DMShell knows about it, you effectively get the same behaviour
>>>>>>>>>>> as DMPlex (which does the decomposition in the same manner?).
>>>>>>>>>>>
>>>>>>>>>>> > However, I usually use a DMPlex which knows about my
>>>>>>>>>>> > mesh, so I am not sure if this strategy has any holes.
>>>>>>>>>>>
>>>>>>>>>>> I haven't noticed anything yet.
>>>>>>>>>>>
>>>>>>>>>>> Lawrence
>>>>>>>>>>
>>>>>>>>>>
>>>>>>>>>>
>>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>>> --
>>>>>>>> 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
>>>>>>
>>>>>
>>>>>
>>>>
>>>>
>>>> --
>>>> 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
>>>
>>
>>
>
>
> --
> 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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