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OpenFoam logfile compression tip

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Old   April 23, 2009, 02:37
Default OpenFoam logfile compression tip
  #1
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Dr. Alexander Vakhrushev
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Hi all!

Making simulations in OpenFoam sometimes I get really huge log files. In some cases it can result in hard drive freespace running out! But all information can be useful afterwards and I cannot just redirect output to /dev/null.
So it is necessary to compress output on the fly. One solution in Linux OS is piping it to gzip/bzip2:
openfoamSolver 2>&1 | gzip > log.gz
But worst thing is that gzip blocks log.gz pipe for reading during simulation and one cannot get access to log data until task is finished! The solution is to use "compress" package. To obtain it in Ubuntu use
sudo apt-get install ncompress
Then it is possible
openfoamSolver 2>&1 | compress > log.Z
or make run script, containing
Code:
#!/bin/sh

checkMesh

if [ $? -eq 0 ]; then
    nohup openfoamSolver 2>&1 | compress > logfileName.Z &    
else
    exit -1
fi
Then you have a simulation running at background. Have a coffee break before coming back and analysing results!
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Dr. Alexander VAKHRUSHEV

Christian Doppler Laboratory for "Advanced Process Simulation of
Solidification and Melting"

Simulation and Modelling of Metallurgical Processes
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Old   January 18, 2011, 05:53
Default Continue with logfile
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José Rodrigues
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Hi! great post tip, btw..

My problem is a bit different though: I would like to know how it is possible to continue a logfile of a simulation that was interrupted and I wish to resume with the same logfile, without erasing the previous timesteps.

Thx

Jose
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Old   January 18, 2011, 06:35
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Roman Thiele
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Quote:
Originally Posted by jose_rodrig View Post
My problem is a bit different though: I would like to know how it is possible to continue a logfile of a simulation that was interrupted and I wish to resume with the same logfile, without erasing the previous timesteps.
This can be done with
Code:
foamProgram >> logFile
the double error uses an already existing file. since the simulation will start from the last saved folder, you should delete everything that is written in the logfile after the folder save point.
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Old   January 18, 2011, 06:39
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José Rodrigues
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Great! many Thx

Regards
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Old   January 18, 2011, 10:15
Default Compress VTK files
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Eelco van Vliet
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Thanks for the compress tip!

In line with compression of data files, another question.
I commonly create output sample planes using the function object libfieldFunctionObjects.so. The problems is that the planes are only written in uncompressed ascii, so a lot of data is generated (especially for isocontour).
An example

Code:
PlanesVTK
{functions
(

      enabled   true;
      type surfaces;
      setFormat raw;
      surfaceFormat vtk;
      writeFormat binary;
      timePrecision 0;
      interpolationScheme cellPointFace;
      writeCompression compressed;
      functionObjectLibs ("libsampling.so");
      outputControl   timeStep;
      outputInterval  1;
      fields
      (
         magVorticity
      );
      surfaces
      (
         iso_magU0p5
          {
            type        isoSurfaceCell;
            isoField    magU;
            isoValue    0.8;
            interpolate true;
            regularise  false;
          }
      );
   } // END PlanesVTK is
);
creates asci data files of more then 40 MB, whereas I can compress it for almost 80%. The compression write option does not seem to work. Does somebody has an idea how to compress these kind of data output files during the run ?.
Thanks!

Regards,

Eelc
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