This tutorial uses ATLAS connect. All lessons discussed in ASC/ANL tutorial were adopted by Ilija Vukotic for the use with ATLAS connect.

Please also look at the CERN tutorial SoftwareTutorialxAODAnalysisInROOT wiki.

First, we will setup ATLAS release.

1) Setup kinit as: kinit [email protected] where username is your user name at CERN.

2) Create a bash script to setup ATLAS software:

setup.sh

#!/bin/bash
export ATLAS_LOCAL_ROOT_BASE=/cvmfs/atlas.cern.ch/repo/ATLASLocalRootBase
source ${ATLAS_LOCAL_ROOT_BASE}/user/atlasLocalSetup.sh
setupATLAS

and then do “source setup.sh”. Setup FAX and ROOT so we can access data remotely:

localSetupFAX --rootVersion=current-SL6

Create the usual grid proxy. You will be prompted to enter your password.

voms-proxy-init -voms atlas

Let's us take a look at a typical xAOD file. You can open it with ROOT TBrowser as:

For ANL:

mkdir lesson_1; cd ./lesson_1
xrdcp $STORAGEPREFIX/atlas/rucio/valid2:AOD.01482225._000140.pool.root.1 AOD.01482225._000140.pool.root.1
root -l AOD.01482225._000140.pool.root.1
TBrowser a

Then click on the branch with the extension “Aux” (for example, “AntiKt4TruthJetsAux”) and then plot “AntiKt4TruthJetsAux.pt”

See other detail in CERN tutorial

Now we will read the above line in Python and print some values for electron (eta and phi)

First, we setup our environment in the directory “lesson_1” that has the xAOD file:

source setup.sh
rcSetup -u; rcSetup Base,2.1.12

Now you can check what versions of packages are linked:

rc version

that shows a long version of packe versions.

The let's create a new directory and put this file:

"xAODPythonMacro.py

#!/usr/bin/env python
 
# Set up ROOT and RootCore:
import ROOT
ROOT.gROOT.Macro( '$ROOTCOREDIR/scripts/load_packages.C' )
 
ROOT.xAOD.Init() # Initialize the xAOD infrastructure
 
fileName="AOD.01482225._000140.pool.root" # Set up the input files
treeName = "CollectionTree" # default when making transient tree anyway
 
f = ROOT.TFile.Open(fileName)
t = ROOT.xAOD.MakeTransientTree( f, treeName) # Make the "transient tree"
 
# Print some information:
print( "Number of input events: %s" % t.GetEntries() )
for entry in xrange( t.GetEntries() ):
   t.GetEntry( entry )
   print( "Processing run #%i, event #%i" % ( t.EventInfo.runNumber(), t.EventInfo.eventNumber() ) )
   print( "Number of electrons: %i" % len( t.ElectronCollection ) )
   for el in t.ElectronCollection:  # loop over electron collection
      print( "  Electron trackParticle eta = %g, phi = %g" %  ( el.trackParticle().eta(), el.trackParticle().phi() ) )
      pass # end for loop over electron collection
   pass # end loop over entries
f.Close()   

If you copy this script, correct indentation (the lines should start from the column position 0). This is a good for your to learn this code! Then run it as:

chmod +x xAODPythonMacro.py
./xAODPythonMacro.py

Using this code, one can fill histograms. But the code runs slow. Below we will show how to use C++/ROOT compiled code to run over this file.

How will you find xAOD variables without using ROOT TBrowser? Try this code:

asetup 19.1.1.1,slc6,gcc47,64,here
checkSG.py AOD.01482225._000140.pool.root

You will see a table with the names of the variables.

Now we will create a C++/ROOT analysis program and run over this input xAOD file. Do not forget to run “kinit [email protected]”. Use the same setup file as above.

mkdir lesson3
cd lesson3
rcSetup -u; rcSetup Base,2.0.12
rc find_packages  # find needed packages
rc compile        # compiles them

This takes some time to compile. Next we will us a simple example code that runs over multiple files located in some directory

wget https://ci-connect.atlassian.net/wiki/download/attachments/10780723/MyAnalysis3.zip
unzip MyAnalysis3.zip
rc find_packages    # find this package
rc compile          # compiles it

go to the program starting directory and recreate an input files list (Since this dataset is rather large we suggest to remove all but a few files from the inputdata.txt.):

cd MyAnalysis/util  # go to the analysis code
fax-get-gLFNs valid2.117050.PowhegPythia_P2011C_ttbar.digit.AOD.e2657_s1933_s1964_r5534_tid01482225_00 > inputdata.txt

Your analysis is started using testRun.cxx. We pass “submitDir” which will be the output directory with ROOT file. You must delete it every time you run the code (or use different output). The code runs over a list of files inputdata.txt. The actual analysis should be put to “Root/MyxAODAnalysis.cxx” (called from testRun.cxx).

testRun submitDir   # runs over all files inside inputdata.txt

The actual analysis should be put in “Root/MyxAODAnalysis.cxx”.

Now we will make a number of changes to the above program. We will fill histograms with pT of jets and muons. To do this, added the following changes: We have added:

 PACKAGE_DEP = EventLoop xAODRootAccess xAODEventInfo GoodRunsLists xAODJet xAODTrigger xAODEgamma JetSelectorTools JetResolution xAODMuon

in “cmt/Makefile.RootCore”. Then we have modified:

MyAnalysis/MyxAODAnalysis.h # added new pointers to histograms
Root/MyxAODAnalysis.cxx     # initialized histograms and put loops over jets and muons

Now we will create a C++/ROOT analysis program and run over this input xAOD file.

mkdir lesson_4; cd lesson_4
rcSetup -u; rcSetup Base,2.0.12
rc find_packages 
rc compile

wget https://ci-connect.atlassian.net/wiki/download/attachments/10780723/MyAnalysis4.zip
unzip MyAnalysis4.zip
rc find_packages    # find this package
rc compile          # compiles it

The actual analysis should is in “Root/MyxAODAnalysis.cxx”.

Run it as:

cd MyAnalysis/util  # go to the analysis code
fax-get-gLFNs valid2.117050.PowhegPythia_P2011C_ttbar.digit.AOD.e2657_s1933_s1964_r5534_tid01482225_00 > inputdata.txt
testRun submitDir   # runs over all files inside inputdata.txt

This example is ANL-specific. If you ran analysis code for RUN I, you should be a familiar with it. We used Condor/Arcod system to submit jobs to the farm. Data are distributed on the farm nodes to avoid IO bottleneck.

First, create a directory for this example:

Prepare a fresh directory:

mkdir lesson_6

Copy the needed directories with RootCore example:

cp -r /users/chakanau/public/2014_tutorial_october_anl/lesson_6/*  lesson_6/

Then check that you can compile the analysis example using RootCore:

cd lesson_6/
source setup.sh

As usual, our analysis is in “MyAnalysis/util/testRun.cxx”

Now we want to submit jobs to the data distributed on several computers of the farm. Go to the upper directory and setup the farm:

cd ../; source s_asc;

We will send jobs using the directory “submit”. Go to this directory and check the data:

cd submit
arc_ls -s /data2/valid2/117050/PowhegPythia_P2011C_ttbar.digit.AOD.e2657_s1933_s1964_r5534/
arc_ls    /data2/valid2/117050/PowhegPythia_P2011C_ttbar.digit.AOD.e2657_s1933_s1964_r5534/  

The first command shows the summary of distributed data (12 files per server), while the second lists all available data on each node. Now we will send the job to the farm. Change the line:

package_dir=/users/chakanau/public/2014_tutorial_october_anl/lesson_6/ANLanalysis

inside “arcond.conf” to reflect the correct path to your program. Then run “arcond” and say “y” to all questions. This sends jobs to the farm (2 jobs per server). Check the status as:

condor_q

When the jobs are done, the output files will be inside “Jobs” directory. Merge the ROOT outputs into one file as:

arc_add

This will create the final output file “Analysis_all.root”