Configure And Run CP Algorithm Sequence

The basic sequence

There is a file in your MyAnalysis/python directory called MyAnalysisAlgorithms.py. This creates and returns an algorithm sequence:

def makeSequence (dataType) :

    algSeq = AlgSequence()

    ...

    return algSeq

It additionally loads a SystematicsSvc algorithm at the beginning of the sequence to load/handle systematics:

    # Set up the systematics loader/handler service:
    sysService = createService( 'CP::SystematicsSvc', 'SystematicsSvc', sequence = algSeq )
    sysService.sigmaRecommended = 1

This takes care of registering all the systematics to run on, so that subsequent algorithms can just pick it up (and don’t have to be configured for it one-by-one). Note that even if you have a large number of algorithms for various object types with a lot of different systematics, you will only ever need/have a single SystematicsSvc. The individual algorithms are smart enough that they will only run for systematics that actually affect them.

We won’t worry about using systematic uncertainties for now and will use them later in the tutorial.

The following line in MyAnalysis/CMakeLists.txt enables the use of the sequence:

atlas_install_python_modules( python/*.py )

Adding the sequence to your job (EventLoop)

To run the CP algorithm sequence, it needs to be added to your steering macro MyAnalysis/share/ATestRun_eljob.py. To do this, add the following lines after the job is created and before your analysis algorithm is created:

from MyAnalysis.MyAnalysisAlgorithms import makeSequence
algSeq = makeSequence (dataType)
print(algSeq) # For debugging
for alg in algSeq:
    job.algsAdd( alg )
    pass

The makeSequence method takes an argument indicating whether a data or MC sample is used as input. This is defined in the steering macro:

# Set data type to MC
dataType = "mc"

Adding the sequence to your job (Athena)

Adding the sequence to your job in Athena is very similar to doing so in EventLoop. Add the following code to ATestRun_jobOptions.py before your algorithm is added to the main sequence:

# Set data type
dataType = "mc" # "mc" or "data"

from MyAnalysis.MyAnalysisAlgorithms import makeSequence
algSeq = makeSequence (dataType)

print(algSeq) # For debugging

# Add all algorithms from the sequence to the job.
athAlgSeq += algSeq

Test and commit your changes

Recompile and rerun your code to see what changes in the output messages. When you are happy that it is running correctly, commit and push your changes.