[vtkusers] create a parallel, distributed dataset from scratch

[Berk Geveci]

What do you mean by "connectivity information"? There is fairly limited
support for inter-process connectivity information in VTK other than ghost
cells. For generating ghost cells, see this:

http://www.vtk.org/doc/nightly/html/classvtkPUnstructuredGridGhostCellsGenerator.html

Best,
-berk

On Fri, Jun 10, 2016 at 5:41 AM, Sven Kramer <svenkramer40 at gmail.com> wrote:

> Hello,
> Vtk comes with a few parallel data sources and readers that distribute the
> memory usage (and thus later cpu usage of algorithms) between a number of
> MPI processes. I am wondering, how I can create such parallel datasets
> "from scratch".
>
> The starting point, from which I'd like to build a parallel Vtk dataset,
> is the equivalent of a vtkUnstructuredGrid (namely points and their
> connectivity, making cells), which is already decomposed so that each MPI
> process carries only a fraction of all available points and cells. Of
> cause, I could simply create one vtkUnstructuredGrid per process from the
> points an cells local to that process. However, these grids wouldn't have
> any information about which points and cell surfaces they share with
> neighbouring pieces. But such connectivity information is essential, if
> some algorithm has to add additional layers of ghost cells.
>
> What I have:
>
> MPI rank #0
> points p00..p0{n0}
> cells c00..c0{m0}
> connectivity information between boundary cells and pieces on other ranks
>
> MPI rank #1
> points p1{n0+1}..p1{n1}
> cells c1{n0+1}..c1{m1}
> connectivity information between boundary cells and pieces on other ranks
>
> ...
>
> MPI rank #R
> points pR{n{R-1}+1}..pR{nR}
> cells cR{n{R-1}+1}..cR{mR}
> connectivity information between boundary cells and pieces on other ranks
>
> What I need:
> a parallel vtkUnstructuredGrid, decomposed into the same pieces as the
> input data, including ghost cells and connectivity information between the
> pieces.
>
> Is the construction of such a parallel dataset described in some tutorial
> or blog?
>
> Regards,
> Sven
>
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