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Message ID: 833     Entry time: 05 Sep 2012
Author: Stefan Ritt 
Topic: Info 
Subject: New pipe compression implemented in mlogger 
A new pipe compression has been implemented in mlogger thanks to Fedor Ignatov from BINP 
Novosibirsk. The way it works that the logger write into a pipe instead directly into a file. The pipe can 
then be connected to any compression program without the need to copile against any additional C 

To use is, enter as the filename for example

|bzip2>run%05d.mid     (note the pipe '|' in front of the bzip2)

This way the data stream is run through the bzip2 program, which is known to have better compression 
ratio than gzip. Furthermore, the parallel version of bzip2 can be used, which spreads over all available 
CPU cures and speeds up compression almost linearly with the number of cores. This parallel version 
called pbzip2 can be found here:

It can be easily compiled and installed. Using this method in the MEG experiment at PSI, we can compress 
our waveform data to 37% or it's original size (49% with gzip), and on 8 cores we get a compression rate 
of about 40 MBytes/sec (23 MBytes with gzip on a single core).

The disadvantage of that method is that one cannot see the compression ratio online, but this is not a big 
deal I guess. The new version has been committed as rev. 5324. 

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