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<div>vtk-experts: I am looking for guidance and suggestions on handling the following problem.</div>
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<div>Question Set-up:</div>
<div>I have a very large multiprocessor simulation where we output to .pvd, .pvtu, .vtu files for each time step. There are thousands of time steps and <font face="Monospace" size="2"><span style="font-size:10pt;">t</span></font><font face="Monospace" size="2"><span style="font-size:10pt;">he
jobs are run on hundreds and even thousands of processors</span></font><font face="Monospace" size="2"><span style="font-size:10pt;">. T</span></font><font face="Monospace" size="2"><span style="font-size:10pt;">he</span></font><font face="Monospace" size="2"><span style="font-size:10pt;">
number of files </span></font><font face="Monospace" size="2"><span style="font-size:10pt;">created is in the thousands and post-processing of computed results quickly bec</span></font><font face="Monospace" size="2"><span style="font-size:10pt;">omes unmanageable.</span></font><font face="Monospace" size="2"><span style="font-size:10pt;">
</span></font> Calculations and data is associated with points and we create a vtkUnstructuredGrid and use <font face="Monospace" size="2"><span style="font-size:10pt;">vtkXMLPUnstructuredGridWriter</span></font><font face="Monospace" size="2"><span style="font-size:10pt;">
to write </span></font><font face="Monospace" size="2"><span style="font-size:10pt;">mesh points</span></font><font face="Monospace" size="2"><span style="font-size:10pt;"> and results </span></font><font face="Monospace" size="2"><span style="font-size:10pt;">for
each time step. </span></font><font face="Monospace" size="2"><span style="font-size:10pt;">We write both </span></font><font face="Monospace" size="2"><span style="font-size:10pt;">cells (</span></font><font face="Monospace" size="2"><span style="font-size:10pt;">‘</span></font><font face="Monospace" size="2"><span style="font-size:10pt;">type=VTK_VERTEX</span></font><font face="Monospace" size="2"><span style="font-size:10pt;">’</span></font><font face="Monospace" size="2"><span style="font-size:10pt;">)</span></font><font face="Monospace" size="2"><span style="font-size:10pt;">
and </span></font><font face="Monospace" size="2"><span style="font-size:10pt;">points</span></font><font face="Monospace" size="2"><span style="font-size:10pt;"> but hang field da</span></font><font face="Monospace" size="2"><span style="font-size:10pt;">ta
off of the points.</span></font><font face="Monospace" size="2"><span style="font-size:10pt;"> </span></font><font face="Monospace" size="2"><span style="font-size:10pt;">The challenge is post-processing computed results.</span></font><font face="Monospace" size="2"><span style="font-size:10pt;">
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<div><font face="Monospace" size="2"><span style="font-size:10pt;">Perhaps one way to handle post-processing is to filter the data down to a very small region of interest during the simulation. I was thinking of using ‘vtkClipVolume’ to obtain a set of points
within a cubic-like region. Then I would write this relatively small number of points (and other data) out to ‘1’ vtk file for each time step – ie just one file for each time step. I want to eliminate the parallel decomposition of the output data at this
stage. This means that I will need to communicate points found within the clipping volume to one processor (say proc=0) , create a vtkUnstructuredGrid, and then write this grid and data to a file for the time step. After the simulation is done I would have
‘one’ .vtu file for each time step that contains a relatively few number of points. I can post-process these files in a straight forward manner.</span></font></div>
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<div><font face="Monospace" size="2"><span style="font-size:10pt;">Question (s):</span></font></div>
<div><font face="Monospace" size="2"><span style="font-size:10pt;">Does this process make sense?</span></font></div>
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<div><font face="Monospace" size="2"><span style="font-size:10pt;">Is there any existing functionality that can perform this algorithm now?</span></font></div>
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<div><font face="Monospace" size="2"><span style="font-size:10pt;">Will ‘vtkClipVolume’ keep the data associated with points it finds?</span></font></div>
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<div><font face="Monospace" size="2"><span style="font-size:10pt;">How do I configure ’vtkClipVolume’ for positioning a Cartesian like cube (say dx, dy, dz) where dx, dy, and dz are the length of each edge? </span></font></div>
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<div><font face="Monospace" size="2"><span style="font-size:10pt;">Does anyone have any suggestions or specifics on how to handle this case – which vtk filters, how to handle the communications?</span></font></div>
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<div><font face="Monospace" size="2"><span style="font-size:10pt;">Any suggestions/comments are requested. Thank you.</span></font></div>
<div><font face="Monospace" size="2"><span style="font-size:10pt;">John Mitchell</span></font></div>
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