<chapter name="ProMC files"> 
 
<h2>ProMC Files</h2> 
 
<a href="http://atlaswww.hep.anl.gov/asc/promc/">ProMC</a> 
<ref>Che14</ref> is a library 
for the storage of Monte Carlo event records, or other data, in a very 
compact binary form. It provides routines for fast input to and output 
from these compact data files. It uses "varints" as a way to store and 
compress an integer using a variable number of bytes, based on Google's 
platform- and language-neutral Protocol Buffers. Real numbers are converted 
to integers, e.g. by specifying a smallest unit of energy, momentum and 
length. Thereby a low-energy particle can be represented by a smaller 
number of bytes. 
 
<p/> 
The current PYTHIA linking and interface is based on ProMC version 1.5; 
earlier version will not do. Once you have to installed the ProMC library, 
you should configure PYTHIA with 
<pre> 
  ./configure --with-promc=/path/to/ProMC 
</pre> 
and recompile the PYTHIA library. As usual more fine-grained options 
are available to set paths to binaries, libraries and headers separately, 
if need be. 
 
<p/> 
The <code>examples/main46.cc</code> sample program illustrates how to 
write PYTHIA events onto a ProMC file. 
 
</chapter> 
 
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