[Paraview] Programmable filter in parallel

[Tim Gallagher]

Hi,

I know many of the built-in readers/filters already work in parallel, but how does one write a parallel programmable filter?

Our data files are XDMF and split into blocks of data. We have a single XDMF file that we can read that reads all the blocks and generates a vtkMultiBlockDataset (this works with the built in XDMF reader). 

However, each block has some ghost cells around it that are needed to do the CellDataToPointData interpolation. For large numbers of blocks, this creates far too many grid points for our machines to load. So, I've written a programmable filter that does:

start with empty vtkMultiBlockDataset
for each block in restart file
   read block file with XDMFReader
   CellDataToPointData
   strip off the extra layers of cells
   append to output vtkMultiBlockDataset

If I run this in parallel, what exactly is parallel? Is the reading and CD2PD done in parallel on each block? Is none of it parallel? Ideally, I would have the loop over blocks done in parallel, but I don't know how to indicate that in the programmable filter (if it's possible).

Any advice would be great,

Tim