David,

Yes, I figured that's what you meant by ghost zones. My point is that you can 
leave these in for the contour operation. Because you have overlapping cells, 
the processors on each side of the boundary will compute the same data at the 
boundary.

The trick is to carry avtGhostZones all the way through the calculations. If 
done correctly, then the surface computed by Contour will have avtGhostZones 
cell data, and you can strip out the ghost zones in the contour. The only 
caveat is to be careful with the Cell Data to Point Data filter because the 
avtGhostZones array will be invalid if converted from cells to points. You can 
tell the Cell Data to Point Data filter to just pass the cell data.

-Ken

From: ParaView 
<[email protected]<mailto:[email protected]>> on behalf 
of David Ortley <[email protected]<mailto:[email protected]>>
Date: Monday, February 8, 2016 at 1:56 PM
Cc: "[email protected]<mailto:[email protected]>" 
<[email protected]<mailto:[email protected]>>
Subject: [EXTERNAL] Re: [Paraview] Parallel unfriendly filters?

Kenneth:

The ghost zones are the contents of the ghost zones stored from the 
calculation. They overlap into the hydro from neighboring processors (the silo 
library stores a block per processor the way we're using it in our code.)  If I 
leave them in there, I get artifacts.  I'm actually thresholding out a variable 
called 'avtGhostZones', which the silo libraries call the stored ghost zone 
values.


Dan:

Cell Data to Point Data is the only way I know of to activate the contour 
filter for silo files.  The results are stored in cell arrays, which apparently 
don't activate the contour filter.  I stumbled upon using Cell Data to Point 
Data by accident, so if there's a better way to do this, I'm open to it.


Thanks.

-David Ortley

On Mon, Feb 8, 2016 at 1:35 PM, Moreland, Kenneth 
<[email protected]<mailto:[email protected]>> wrote:
Have you tried doing the threshold last (after the contour) rather than first? 
Generally, ParaView relies on ghost zones (cells) to avoid artifacts across 
process boundaries.

-Ken


From: ParaView 
<[email protected]<mailto:[email protected]>> on behalf 
of David Ortley <[email protected]<mailto:[email protected]>>
Date: Monday, February 8, 2016 at 1:14 PM
To: "[email protected]<mailto:[email protected]>" 
<[email protected]<mailto:[email protected]>>
Subject: [EXTERNAL] [Paraview] Parallel unfriendly filters?

I'm running Paraview in client/server mode with the server running on an HPC 
platform across multiple nodes.

My input is a multi-block silo file that contains ghost zone information.  The 
way I do a seamless contour when visualizing on my workstation is to do the 
following:

Load the silo file
    -> Threshold out the ghost zones (threshold filter)
        -> Merge the blocks
            -> Cell data to point data
                -> Contour

This works well enough when on a single machine.  But when visualizing 
client/server with the server running across multiple nodes, there appear seams 
on the contours.

Is this an expected behavior given my setup?  Are any of the filters that I 
listed above (Threshold, Merge Blocks, Cell data to point data, and Contour) 
not fully implemented in parallel yet?

nb - I've not spent a lot of time trying to debug the problem, so I don't know 
if the problem exists when a server is running on a single node only.  It looks 
like something that is happening at node boundaries, but I could be wrong and 
it could be a per/processor thing.

Thanks.

-David Ortley

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