RIVET usage
 
 
RIVET is a toolkit for 
the validation of Monte Carlo event generators [Buc10]. It 
contains the results of many experimental analyses, so that generator 
output can easily be compared to data, as well as providing a framework to 
implement your own analyses.  Although using PYTHIA with RIVET is not 
officially supported, some helpful hints are given below. The full RIVET 
manual is available online. 
 
 
 
Using PYTHIA with RIVET
 
The following assumes that you already have RIVET installed. Instructions 
for this may be found 
 
here. 
 
 
Events are passed from PYTHIA to RIVET using the HepMC format. PYTHIA must 
be compiled with HepMC support, using the same version of HepMC used when 
compiling RIVET. This is setup through the PYTHIA configure 
script e.g. 
 
  ./configure --with-hepmc=/path/to/HepMC 
 
 
The PYTHIA library itself does not need to be recompiled. 
 
 
The examples/main132.cc sample program can then be used to 
generate events in HepMC format (which examples/main133.cc 
extends by allowing subruns). When in the examples directory, 
the main program can be built and used as follows 
 
  make main132 
  ./main132 main132.cmnd main132.hepmc 
 
 
The first argument is the input file which provides the options for event 
generation, while the second is the output file where the HepMC events 
should be written. 
 
 
This HepMC file may now be read and processed by RIVET 
 
  rivet --analysis=ANALYSIS_NAME main132.hepmc 
 
 
where ANALYSIS_NAME is a 
built-in RIVET 
analysis, or one you have created yourself. The output of RIVET is in 
the form of .aida files, containing the histograms for the 
analysis, which can be processed further with RIVET (see the 
 
RIVET documentation for more details). 
 
 
The above examples requires that (potentially large) HepMC events are stored 
to disk before being read by RIVET. It is possible, instead, to pass the 
events directly to RIVET as they are produced by using a FIFO 
pipe. This is done with the mkfifo command 
 
  mkfifo my_fifo 
  ./main132.exe main132.cmnd my_fifo & 
  rivet --analysis=ANALYSIS_NAME my_fifo 
 
 
Note that main132 is run in the background. 
 
 
Compiling PYTHIA with RIVET 
 
 
It is also possible to compile a PYTHIA main program together with the RIVET 
library. To facilitate this, there is a header file called 
Pythia8Plugins/Pythia8Rivet.h defining a helper class called 
Pythia8::Pythia8Rivet. To use this class, a main program needs to 
be modified as follows: 
 
 
  #include "Pythia8/Pythia.h" 
 
  // Include the Pythia8Rivet header file. 
  #include "Pythia8Plugins/Pythia8Rivet.h" 
 
  int main() { 
 
    Pythia pythia; 
 
    // Setup the run by reading strings or a command file. 
 
    pythia.init(); 
 
    // Create a Pythia8Rivet object and add (one or several) analyses. 
 
    Pythia8Rivet rivet(pythia, "outputfile.yoda"); 
    rivet.addAnalysis("AnalysisName"); 
    rivet.addAnalysis("AnotherAnalysisName"); 
 
    for (int iEvent = 0; iEvent < 100; ++iEvent) { 
      if (!pythia.next()) continue; 
 
      // Push event to Rivet. 
      rivet(); 
 
      // Maybe do other non-Rivet analysis. 
    } 
 
    // Tell Rivet to finalise the run. 
    rivet.done(); 
 
  } 
 
 
To compile the program, information about where Rivet and its 
dependencies are installed is needed. This information is available 
via the rivet-config script via the following. 
 
  rivet-config --includedir --libdir --cppflags --libs 
 
 
 
 
The example program main421.cc includes optional analysis with 
Pythia8::Pythia8Rivet. To use it configure Pythia with 
the option --with-rivet. This will automatically use the 
rivet-config script to determine all the necessary 
paths. If one wishes to pass a specific config script, use the option 
--with-rivet-config=CONFIG where CONFIG is 
the Rivet configuration script. Note, a RIVET configuration script 
must be available to compile the Rivet examples. 
 
 
The most common user case (run PYTHIA with a run card, using one or 
several RIVET analyses) is implemented in the example main144. 
The sample command file main144.cmnd provides a good starting 
point. The lines: 
 
    Main:runRivet = on 
    Main:analyses = ATLAS_2010_S8817804,ALICE_2010_S8625980,CMS_2011_S8957746 
    Main:writeHepMC = on 
 
 
provides the switch to run RIVET, and gives the user the possibility 
to add any number of (installed) RIVET analyses to the run, as a comma 
separated list. The last line is the switch needed to write a HepMC 
file.  The example is run with: 
 
  ./main144 -c main144.cmnd 
 
 
and a .yoda file (the RIVET output) is then written. 
 
There are several other useful command line options to main144. 
They are all displayed by running ./main144 -h.