[vtkusers] PStructuredGrid questions and ghostlevels

[George Zagaris]

Hi Jeremy,

To the best of my knowledge, partition interfaces in VTK need to abut.

Although I do understand the reasoning of what you are trying to achieve,
from a finite difference code perspective, leaving a gap is problematic b/c
it creates an implicit cell that could span two or more partitions/zones.
For most post-processing/visualization operations, the algorithms need to
loop over cells, e.g., consider contouring or interpolating the data over a
line. Not having an explicit definition of all the cells in a partition
makes this more complicated -- it would require building that information
when reading in the partitioned grid, e.g., by growing the grid to the
right and communicating the data (assuming we run in parallel).

More importantly, VTK structured grids can also store values at
cell-centers. The output scheme that you describe would only work for
node-centered data.

So, to best support node-centered and cell-centered data, partition
interfaces need to abut.

Hope this helps.

Best,
George



On Thu, Jun 27, 2013 at 4:04 PM, Kozdon, Jeremy (CIV) <jekozdon at nps.edu>wrote:

> Hello,
>
> I am trying to get vtk to properly work with a parallel finite difference
> code. What I would like to do is have each processor write the data they
> "own" to a separate file. For instance
>    processor 0 would write local extends "0 9 0 10 0 0" to file file0.vts
>    processor 1 would write local extends "10 19 0 10 0 0" to file file1.vts
>    processor 2 would write local extends "20 29 0 10 0 0" to file file2.vts
>    ...
> I thought that when I wrote the pvts file to combine the data this would
> be ghostlevel="0" since there is no overlap of the data, but I get errors
> on a lack of extents. For instance in the above it would be for lack of
> extents "9 10 0 10 0 0" and "19 20 0 10 0 0", i.e., where the parallel
> boundary occurs.
>
> I am wondering if there is a better way to do what I am trying to
> accomplish / whether it is possible to do such formatting with vtk. I would
> prefer not having processors write duplicated data if possible.
>
> Thanks!
> Jeremy
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