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

Thu Jul 9 10:06:17 EDT 2015

Hi Michael,

If you already have the information handy, simply creating the
vtkGhostLevels array as Dan described is the way to go. We have plans on
writing a filter that generates ghost levels without redistributing the
entire dataset, which will hopefully scale better. Having said that if the
simulation has ghost levels, simply writing them out and marking them as
such will always scale better.

Best,
-berk

On Mon, Jul 6, 2015 at 2:36 PM, Schlottke-Lakemper, Michael <
m.schlottke-lakemper at aia.rwth-aachen.de> wrote:

>  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> 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> 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> 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> 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
>>> Web: http://www.jara.org/jara-hpc
>>>
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>>
>
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