EDAnalyzers

Overview

Teaching: 7 min
Exercises: 1 min

Questions

• What is an EDAnalyzer and what does it contain?

• What files are relevant in an EDAnalyzer?

Objectives

• Learn what an EDAnalyzer is and how it is structured

• Learn what c++, python and xml files are relevant.

Structure

First, make sure you start up your container as discussed in the previous episode.

EDAnalyzers are modules that allow read-only access to the Event. They are useful to produce histograms, reports, statistics, etc. Take a look at the DemoAnalyzer package that we created while validating our CMSSW working environment; it is an example of an EDAnalyzer.

Go to your CMSSW_7_6_7/src area, for example:

cd /code/CMSSW_7_6_7/src

Let’s explore the DemoAnalyzer package:

ls Demo/DemoAnalyzer/

doc  plugins  python  test

ls Demo/DemoAnalyzer/plugins/

BuildFile.xml  DemoAnalyzer.cc

ls Demo/DemoAnalyzer/python/

CfiFile_cfi.py  CfiFile_cfi.pyc  ConfFile_cfg.py  ConfFile_cfg.pyc  __init__.py  __init__.pyc

Note that it has a similar structure as any of the CMSSW packages we mentioned before. In this sense, our DemoAnalyzer is just one more CMSSW package that we created privately. However, the headers and implementation of our simple DemoAnalyzer are coded in one single file under the plugins directory. The file was automatically named DemoAnalyzer.cc when we created the package.

CMSSW could be very picky about the structure of its packages. Most of the time, scripts or other tools expect to have a Package/Sub-Package structure, just like our Demo/DemoAnalyzer example.

We also notice we have a python configuration file called ConfFile_cfg inside the python directory. This is the default configurator for the DemoAnalyzer.cc code.

Finally, there is a BuildFile.xml, inside the plugins directory, where we can include any dependencies if needed so our code can compile without problems.

All EDAnalyzers are created equal; of course, if made with the same mkedanlzr, they will look identical. The DemoAnalyzer.cc is a skeleton, written in C++, that contains all the basic ingredients to use CMSSW libraries. So, in order to perform a physics analysis, and extract information from our CMS open data, we just need to understand what to add to this code and how to configure it. This is, one way or another, the first and unskippable step when using CMS open data.

Key Points

• An EDAnalyzer is a an edm class that generates a template for any analysis code using CMSSW.

• There are essentially three important files in an EDAnalyzer package, the source code in c++, the python config file and a Buildfile for tracking dependencies.