Python Orchestration

G4E provides Python orchestration library ‘g4epy’ which is a thin wrapper around g4e executable.

g4epy allows to configure G4E run in python. When run() method is executed, the appropriate Geant4 macro file is created and g4e executable is run with the right flags.

Example configuration

from g4epy import Geant4Eic

g4e = Geant4Eic(beamline='ip6')

# Set output file names. Extension is omitted here as g4e creates
# several files with this name and different extensions
g4e.output('work/g4e_emcal')

# (!) g4e.py will automatically identify the file format
g4e.source('work/beagle.txt') \

g4e.beam_on(1000)   # Process 1000 events
g4e.run()           # Runs G4E with the above configuration

Functions can be stacked. The same configuration can be written as:

from g4epy import Geant4Eic

g4e = Geant4Eic(beamline='ip6')

g4e.source('work/beagle.txt') \
   .output('work/g4e_emcal') \
   .beam_on(1000) \
   .run()

vis() function can be added to run the same configuration with Geant4 GUI event/geometry viewer

from g4epy import Geant4Eic

g4e = Geant4Eic(beamline='ip6')

# For bare geometry display we don't need source and output
g4e.beam_on(0)
g4e.vis()        # <== enable Geant4 GUI
g4e.run()

command() function allows to add any custom Geant4 macro commands. Might be a string or a list

# Set beam energies (use list)
g4e.command(['/eic/refdet/eBeam 5',
             '/eic/refdet/pBeam 50'
             ])

# Single string command
g4e.command('/eic/detector refdet')

Geant4Eic class

Wrapper class responsible for one instance of running G4E

Functions:

• __init__(**kwargs) Parameters:

  • executable : Full path to g4e executable (if not set env variable ‘G4E_HOME’ is used to auto determine g4e path)

  • build_prefix : see ‘Building g4e with python`

  • beamline : Beamline name ip6 or ip8

  • detector : Main detector construction name. Default ‘refdet’

  • is_batch : True - no GUI, False - Geant4 event display

  • thread_count : Number of Threads (parallel workers)

• command(value)->self - executes Geant4 macro command/s

  if value:

  • string - execute string

  • list of strings - execute all strings

  • list of list of strings - each sublist is ” “.join and executed as list of strings

• source(source_file)->self - sets source file names. Might be a list

• vis(run_vis=True)->self - Sets visualization display Geant4 GUI

  All visualization commands should be used after vis() as it does driver activation

  # (!)  no effect, set before vis()
  g4e.command('/vis/geometry/set/visibility World_Logic -1 0')
  
  # Visualization driver is opened here
  g4e.vis()
  
  # Now it will work
  g4e.command('/vis/geometry/set/visibility World_Logic -1 0')
  

• batch(run_batch=True)->self - Sets if Geant runs in batch (no visualization) mode

• threads(thread_count)->self - Sets the number of working threads

• get_run_command()->self - Returns the command that will be used to run g4e

• beam_on(events_number)->self - Sets the number of events to process

• output(base_name)->self - Sets base name of output files (G4E produces a number of files with different extensions)

• run()->retval, start_time, end_time, output_lines - Runs g4e

Geant4EicManager class

G4E might be rebuilt right from the python code. This is sometimes convenient when working with Jupyter notebooks Geant4EicManager allows to do this

from g4epy import Geant4EicManager

manager = Geant4EicManager()
manager.build()

# Most of the time man.build() is the only one needs
# but configure and clean are also available:
#   manager.cmake_configure()
#   manager.clean()