Applications

Standalone simulation app (celer-sim)

The celer-sim application is the primary means of running EM test problems for independent validation and performance analysis. See Celeritas for standalone profiling for an example.

Usage:

usage: celer-sim {input}.json
       celer-sim [--help|-h]
       celer-sim --version
       celer-sim --config
       celer-sim --device
       celer-sim --dump-default

• input.json is the path to the input file, or - to read the JSON from stdin.

• The --config option prints the contents of the ["system"]["build"] diagnostic output. It includes configuration options and the version number.

• The --device option prints diagnostic output for the default GPU, similar to the output from the deviceQuery CUDA example.

• The --dump-default option prints the default options for the execution. Not all variables will be shown, because some are conditional on others.

Input

In addition to these input parameters, Environment variables can be specified to change the program behavior.

Output

The primary output from celer-sim is a JSON object that includes several levels of diagnostic and result data (see I/O). The JSON output should be the only data sent to stdout, so it should be suitable for piping directly into other executables such as Python or jq.

Additional user-oriented output is sent to stderr via the Logger facility (see Logging).

Integrated Geant4 application (celer-g4)

The celer-g4 app is a Geant4 application that offloads EM tracks to Celeritas. It takes as input a GDML file with the detector description and sensitive detectors marked via an auxiliary annotation. The input particles must be specified with a HepMC3-compatible file or with a JSON-specified “particle gun.” See Celeritas+Geant4 for verification for an example.

Usage:

celer-g4 {input}.json
         {commands}.mac
         --interactive
         --dump-default

Input

Physics is set up using the top-level physics_option key in the JSON input, corresponding to Geant4 physics options. The magnetic field is specified with a combination of the field_type, field, and field_file keys, and detailed field driver configuration options are set with field_options corresponding to the FieldOptions class in Field data input and options.

Deprecated since version v0.5: The macro file usage is in the process of being replaced by JSON input for improved automation. The input parameters will be documented for version 1. Until then, refer to the source code at app/celer-g4/RunInput.hh .

The input is a Geant4 macro file for executing the program. Celeritas defines several macros in the /celer and (if CUDA is available) /celer/cuda/ directories: see High-level interface for a listing.

The celer-g4 app defines several additional configuration commands under /celerg4:

Geant4 UI commands defined by celer-g4.

Command	Description
geometryFile	Filename of the GDML detector geometry
eventFile	Filename of the event input read by HepMC3
rootBufferSize	Buffer size of output root file [bytes]
writeSDHits	Write a ROOT output file with hits from the SDs
stepDiagnostic	Collect the distribution of steps per Geant4 track
stepDiagnosticBins	Number of bins for the Geant4 step diagnostic
fieldType	Select the field type [rzmap|uniform]
fieldFile	Filename of the rz-map loaded by RZMapFieldInput
magFieldZ	Set Z-axis magnetic field strength (T)

In addition to these input parameters, Environment variables can be specified to change the program behavior.

Output

The ROOT “MC truth” output file, if enabled with the command above, contains hits from all the sensitive detectors.