[Paraview] Writing Binary files

[SamuelKey]

Noel Harrison,

If you can write XML appended-binary files
from Fortran90/95, there are modest pros
and cons in comparison to EnSight c-binary
files. (I cannot write XML appended-binary
from Fortran, so for me, EnSight c-binary is
my current preference.)

If you are generating a transient response
(a solution that varies in time in ways significant
to understanding the simulation), then one can
make the following observations:

1) VTK XML appended-binary
  Puts all of the node and cell results for each
  simulation time in a single file. Thus, 100 time
  steps => 100 files.

2) EnSight c-binary
  Puts all time steps for each point/cell result in
  single file. Thus, 15 point/cell results => 15
  files. Has provisions for files-sets if results produce
  files reaching some file-size limit, frequently 2GBytes.

I prefer to break my models into component parts
and write a displayable data set for each part.
I then have ParaView  read them as a "parallel
data set." PV VTK XML reader is quite happy to
do this. I use a *.pvd file to Collect them together.
This works quite nicely even though the simulation
was conducted on a single processor. But file count
= n-parts * m-timesteps

The EnSight file format has provisions for "parts;"
it just complicates the writer a little bit and adds no
more files.

My current largest model is 840K 4-node tetrahedrons
with 37 different material parts. The Ensight c-binary
handles this just fine as does PV. (Sun dual Opteron
4GB RAM workstation with an Nvidia F4000 Graphics
card.) I would not dream of using VTK XML ASCII-formatted
results files for this simulation.

There is a third very credible option for creating data files
for PV, namely an ExodusII binary format. The ExodusII file
format  handles big data and parallel file-sets easily. The
I/O library is OpenSource. It is very well tested and compiles
on practically every hardware-O/S platform going back
10+ years (actually more). see http://sourceforge.net/index.php
search for "exodusii"  It uses netCDF which has a huge benefit,
namely, the binary data is platform independent. Run the
simulation on a Cray T3D, move the results to a Wintel box,
look at the results with PV. The ExodusII reader in PV is quite
advanced and very actively maintained by Sandia National
Laboratories in the US. All but the Fortran binding is delivered
pre-compiled with PV.
*\ParaView\ParaView 2.4\bin\vtkexoIIc.dll
*\ParaView\ParaView 2.4\bin\vtkNetCDF.dll

Hope this helps.

Sam Key



----- Original Message ----- 
From: "N Harrison" <noel.harrison at nuigalway.ie>
To: <paraview at paraview.org>
Sent: Monday, February 20, 2006 4:44 AM
Subject: [Paraview] Writing Binary files


Sam,Stephane,Renato
Thanks very much for your information to date. Seeing as you have tried
using VTK-XML and Ensight file format, which type would you recommend using
for large models? I am generating large models at the moment using FORTRAN
90 to create legacy ASCII VTK files and they are getting quite large. I have
started to write them in a binary format  because of their small file size.
I don't have any experience yet of XML or Ensight, what are their main
advantages/disadvantages in your opinion for displaying large models? Quite
a lot of information has been posted lately on this mailing service about
creating Ensight files, including your own responses (very helpful), so I
just wanted to see if this format was recommended over binary XML files.

Kind regards,
Noel


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