[petsc-users] PETSC FVM view gradient

[Thibault Bridel-Bertomeu]

Thank you Matthew for your answer.

I cannot provide an exact listing of the error as the computation is ran on
a closed network but in substance it goes like this :

Argument out of range
Field number 0 must be in [0, 0)
.
.
.
#1 DMGetField() line 4657 in dm.c
#2 DMPlexVTKWriteAll_VTU() line 273 in plexvtu.c
#3 DMPlexVTKWriteAll() . . .
.
.
.

The HEAD of my repo is at commit # g2115eb0.
I checked the sources in PETSc and the case where a DM has no field seems
to be handled so I do not understand here what it does not like ..?

Thanks !!!

Thibault


Le mar. 21 juil. 2020 à 12:53, Matthew Knepley <knepley at gmail.com> a écrit :

> On Tue, Jul 21, 2020 at 6:12 AM Thibault Bridel-Bertomeu <
> thibault.bridelbertomeu at gmail.com> wrote:
>
>> Dear all,
>>
>> This request stems from the "How to add a source term for PETSCFV ?"
>> thread.
>> Basically, I would like to output in a VTK file all the components of the
>> gradient computed using the following piece of code (given sol is a global
>> representation of the solution over the whole mesh described by the manager
>> dm with a unique field fvm).
>>
>>   ierr = PetscFVSetComputeGradients(fvm,PETSC_TRUE);CHKERRQ(ierr);  ierr = DMConvert(dm, DMPLEX, &plex);CHKERRQ(ierr);  ierr = DMPlexGetDataFVM(plex, fvm, &cellGeom, &faceGeom, &gradDM);CHKERRQ(ierr);  ierr = DMCreateLocalVector(plex,&locX);CHKERRQ(ierr);  ierr = DMPlexInsertBoundaryValues(plex, PETSC_TRUE, locX, 0.0, faceGeom, cellGeom, NULL);CHKERRQ(ierr);  ierr = DMGlobalToLocalBegin(plex, sol, INSERT_VALUES, locX);CHKERRQ(ierr);  ierr = DMGlobalToLocalEnd  (plex, sol, INSERT_VALUES, locX);CHKERRQ(ierr);  ierr = DMCreateGlobalVector(gradDM, &grad);CHKERRQ(ierr);  ierr = DMPlexReconstructGradientsFVM(plex, locX, grad);CHKERRQ(ierr);  ierr = DMCreateLocalVector(gradDM, &locGrad);CHKERRQ(ierr);  ierr = DMGlobalToLocalBegin(gradDM, grad, INSERT_VALUES, locGrad);CHKERRQ(ierr);  ierr = DMGlobalToLocalEnd(gradDM, grad, INSERT_VALUES, locGrad);CHKERRQ(ierr);  ierr = VecDestroy(&grad);CHKERRQ(ierr);
>>
>>   ierr = PetscViewerCreate(PetscObjectComm((PetscObject)gradDM), &viewer);CHKERRQ(ierr);
>>
>>   ierr = PetscSNPrintf(filename,sizeof filename,"%s-%03D-gradient.vtu",user->outputBasename,stepnum);CHKERRQ(ierr);
>>
>>   ierr = PetscViewerSetType(viewer, PETSCVIEWERVTK);CHKERRQ(ierr);  ierr = PetscViewerFileSetName(viewer, filename);CHKERRQ(ierr);
>>
>>   ierr = VecView(locGrad,viewer);CHKERRQ(ierr);
>>
>>
>> I am having troubles with a few things I think but I cannot figure out
>> how to put it together in the right order ...
>> (i) I am not sure whether VecView should be called with a local or a
>> global vector
>>
>
> Does not matter, so you can just use the global vector.
>
>
>> (ii) I can see from the error log that gradDM does not have fields and
>> thus when it goes through dmplexvtu.c it crashes and cannot write the file.
>> I tried to add the fvm as a field, but it does not work either, it crashes
>> on a memory corruption.
>>
>
> Can you show the error? The above looks correct to me.
>
>   Thanks,
>
>     Matt
>
>
>> Could somebody please advise ?
>>
>> Thank you very much in advance,
>>
>> Thibault Bridel-Bertomeu
>> —
>> Eng, MSc, PhD
>> Research Engineer
>> CEA/CESTA
>> 33114 LE BARP
>> Tel.: (+33)557046924
>> Mob.: (+33)611025322
>> Mail: thibault.bridelbertomeu at gmail.com
>>
>>
>>>>
>>>>
>
> --
> 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
>
> https://www.cse.buffalo.edu/~knepley/
> <http://www.cse.buffalo.edu/~knepley/>
>
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