[Paraview-developers] Guide to using ghost levels (old style)

[Schlottke-Lakemper, Michael]

Hi Dan,

Thanks a lot for this clarification - this should be enough information for us to get started.

Indeed, our reader plugin is designed to be used in a parallel fashion. Due to the size of the grid/data files, we typically use O(10)-O(1000) MPI ranks for pvserver. Currently we use the D3 filter if we need smooth gradients/statistics across domain boundaries, but the D3 filter does not scale well beyond a hundred or so cores.

Michael

On 06 Jul 2015, at 18:16 , Dan Lipsa <dan.lipsa at kitware.com<mailto:dan.lipsa at kitware.com>> wrote:

Hi Michael,
Yes, indeed this is how you would do it. I believe the array has to be unsigned char array though. On the first layer of ghost cells you store a 1, on the second layer you store a 2 and so on.
(we just set a bit for the new version, so we don't store information about how many layers we have)

Also note that ghost cells are only useful if your reader reads different parts of the dataset on different mpi processors. If you split your dataset on different mpi nodes latter on, this is when you need to add ghost cells (because this is when you know how your data is split). If you run on a single processor ghosts cells are not used.

Dan


On Mon, Jul 6, 2015 at 11:43 AM Schlottke-Lakemper, Michael <m.schlottke-lakemper at aia.rwth-aachen.de<mailto:m.schlottke-lakemper at aia.rwth-aachen.de>> wrote:
Hi Dan,

Thank you for your answer. From a first impression, it seems like the only really open question right now is how to generate the “vtkGhostLevels” array if I am working with an vtkUnstructuredGrid in my custom reader plugin? “GenerateGhostLevelArray” in vtkDataSet seems to be only relevant for structured grids. Maybe I just need to create a vtkIntArray myself, add it as a cell array, and name it “vtkGhostLevels”?

Regards,

Michael


On 06 Jul 2015, at 17:10 , Dan Lipsa <dan.lipsa at kitware.com<mailto:dan.lipsa at kitware.com>> wrote:

Hi Michael,
I am not aware of a guide to the old way of storing/accessing ghost cells but I'll be happy to try to answer any specific questions you may have.
I can also add a link in the blog to the document if someone points it out.

Dan


On Sun, Jul 5, 2015 at 4:47 AM Schlottke-Lakemper, Michael <m.schlottke-lakemper at aia.rwth-aachen.de<mailto:m.schlottke-lakemper at aia.rwth-aachen.de>> wrote:
Dear all,

this (http://www.kitware.com/blog/home/post/856) excellent blog post details how to use the vtkGhostLevels with the next ParaView release. However, it focuses on the changes in comparison to the previous way of doing things. Thus I am wondering if there is a comprehensive guide online that describes in a little more depth how to properly use ghost levels in the “old” (or current as of PV 4.3.1) way?

Thanks a lot in advance

Michael


--
Michael Schlottke-Lakemper

SimLab Highly Scalable Fluids & Solids Engineering
Jülich Aachen Research Alliance (JARA-HPC)
RWTH Aachen University
Wüllnerstraße 5a
52062 Aachen
Germany

Phone: +49 (241) 80 95188
Fax: +49 (241) 80 92257
Mail: m.schlottke-lakemper at aia.rwth-aachen.de<mailto:m.schlottke-lakemper at aia.rwth-aachen.de>
Web: http://www.jara.org/jara-hpc

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