[Paraview] Parallel running slower than serial case

[Moreland, Kenneth]

The parallel rendering in ParaView was designed to run on clusters that have multiple GPUs (or CPUs simulating GPUs).  All of the artifacts that you see are because each process in the server is assuming it has independent hardware.  Both processes are opening a rendering window to grab a rendering context on the local graphics hardware.  That's why you see the two extra windows.

Your dual processor machine probably only has one GPU.  You cannot expect faster rendering performance by running in parallel because they are both trying to render to the same GPU.  Any parallel rendering system is guaranteed to be slower because the graphics hardware now has the added overhead of flipping between rendering contexts of the two processes (something they generally are not designed to do extremely well).  There is also the added overhead of the image compositing required for the parallel rendering and the image transfer for client server.

In short, in your case you will maximize your rendering performance by running in serial mode.  1 GPU, 1 process.

-Ken

> -----Original Message-----
> From: paraview-bounces+kmorel=sandia.gov at paraview.org [mailto:paraview-
> bounces+kmorel=sandia.gov at paraview.org] On Behalf Of Luis Martins
> Sent: Wednesday, October 03, 2007 8:26 AM
> To: paraview at paraview.org
> Subject: [Paraview] Parallel running slower than serial case
> 
> Hi,
> 
> I'm running Paraview 3.1.0 on a Intel Centrino Duo with Ubuntu 7.04 and
> trying to visualize some CFD data on Ensigth Gold files(velocity on a
> 256x256x128 mesh) and when I run it in parallel the results arrive slower
> than on serial. Another weird thing (maybe a symptom) happens when
> I connect to the pvserverlaunched before: paraview opens 2 extra windows
> titled "Visualization Toolkit - OpenGL", one of witch reproduces the image
>  in the main Paraview window.
> 
> This is how I'm running the program:
> server: mpirun -np 2 ./pvserver
> program: ./paraview
> 
> The following options we're activating according to the info available at
> the wiki faq page and on the mailing list:
> In Edit/Settings/Active View Properties/Server
> Remote Render Threshold -> 0 MBytes
> Disable Ordered Compositing -> Unchecked
> Subsample Rate -> 4 Pixels
> Squirt Compression -> 19 Bits
> 
> I see the pixelization when I rotate the picture, everything happens as
> it's
> described to suppose to happen, except for the two windows and, the real
> question here, the speed difference: slower in parallel mode.
> 
> Can anyone help?
> 
> Thanks
> Luís Martins
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