[petsc-users] Creating a 3D dmplex mesh with cell list and distributing it

[Matthew Knepley]

DMView() the mesh before and after distribution, so we can see what we have.

  Thanks,

     Matt

On Wed, Aug 14, 2019 at 5:30 PM Swarnava Ghosh via petsc-users <
petsc-users at mcs.anl.gov> wrote:

> Hi PETSc team and users,
>
> I am trying to create a 3D dmplex mesh using DMPlexCreateFromCellList,
> then distribute it, and find out the coordinates of the vertices owned by
> each process.
> My cell list is as follows:
> numCells: 6
> numVertices: 7
> numCorners: 4
> cells:
> 0
> 3
> 2
> 1
> 4
> 0
> 2
> 1
> 6
> 4
> 2
> 1
> 3
> 6
> 2
> 1
> 5
> 4
> 6
> 1
> 3
> 5
> 6
> 1
> vertexCoords:
> -6.043000
> -5.233392
> -4.924000
> -3.021500
> 0.000000
> -4.924000
> -3.021500
> -3.488928
> 0.000000
> -6.043000
> 1.744464
> 0.000000
> 0.000000
> -5.233392
> -4.924000
> 3.021500
> 0.000000
> -4.924000
> 3.021500
> -3.488928
> 0.000000
>
> After reading this information, I do
>  ierr=
> DMPlexCreateFromCellList(PETSC_COMM_WORLD,3,pCgdft->numCellsESP,pCgdft->NESP,pCgdft->numCornersESP,interpolate,pCgdft->cellsESP,3,pCgdft->vertexCoordsESP,&pCgdft->dmplex);
>
> ierr = DMPlexDistribute(pCgdft->dmplex,0,&pCgdft->dmplexSF,
> &distributedMesh);CHKERRQ(ierr);
>
>    if (distributedMesh) {
>      printf("mesh is distributed \n");
>    ierr = DMDestroy(&pCgdft->dmplex);CHKERRQ(ierr);
>      pCgdft->dmplex  = distributedMesh;
>   }
>
>  DMGetCoordinates(pCgdft->dmplex,&VC);
>  VecView(VC,PETSC_VIEWER_STDOUT_WORLD);
>
> On running this with 3 mpi processes, From VecView, I see that all the
> processes own all the vertices.  Why is the dmplex not being distributed?
>
> The VecView is :
> Process [0]
> -6.043
> -5.23339
> -4.924
> -3.0215
> 0.
> -4.924
> -3.0215
> -3.48893
> 0.
> -6.043
> 1.74446
> 0.
> 0.
> -5.23339
> -4.924
> 3.0215
> 0.
> -4.924
> 3.0215
> -3.48893
> 0.
> Process [1]
> -6.043
> -5.23339
> -4.924
> -3.0215
> 0.
> -4.924
> -3.0215
> -3.48893
> 0.
> -6.043
> 1.74446
> 0.
> 0.
> -5.23339
> -4.924
> 3.0215
> 0.
> -4.924
> 3.0215
> -3.48893
> 0.
> Process [2]
> -6.043
> -5.23339
> -4.924
> -3.0215
> 0.
> -4.924
> -3.0215
> -3.48893
> 0.
> -6.043
> 1.74446
> 0.
> 0.
> -5.23339
> -4.924
> 3.0215
> 0.
> -4.924
> 3.0215
> -3.48893
> 0.
>
> Thanks,
> SG
>
>

-- 
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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