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DatABriCxx Examples

Random MCA Events Calibration with ROOT I/O

This is a typical particle/nuclear physics example. It simulates random events from a multi-channel analyser (MCA) for a bogus spectrum (landau background plus a Gaussian peak), and writes them to a ROOT TTree in a TFile out-mc.root, also including the MCA spectrum as a TH1D. It then reads the tree, calibrates the events using the custom linear calibration bric LinCalibBric and writes the calibrated values and the calibrated spectrum to a new file out-ana.root.

The examples consists of the DatABriCxx configuration file mca-calib.json, and the ROOT script LinCalibBric.C (containing the implementation of the custom class LinCalibBric).

Run the example like this:

# dbrx run mca-calib.json

To run the example with debugging output and with the HTTP server (on port 8080) enabled, and to keep the program running (so you can browse to http://localhost:8080/), run

# dbrx run -l debug -k -w -p 8080 mca-calib.json

Note that you can also run the example from within a different directory:

# dbrx run doc/examples/mca-calib.json

as mca-calib.json uses

"requires": [ "$_/LinCalibBric.C" ]

to refer to LinCalibBric.C. The special variable $_ is automatically substituted with the path to the configuration file, allowing to specify file names relative it's location.

The example also include an additional configuration file mca-calib-vars.json, that overrides the fixed calibration values in mca-calib.json with variables. Run

# offset=-19.157 dbrx run -Vslope=0.10403 mca-calib.json mca-calib-vars.json

to see the effect of cascading multiple configuration files and variable substitution. Note that you can supply variable values both as environment variables (used above to set offset) or via the dbrx -V option (used above to set slope).

You can also print the effective configuration after cascading and with variable substitution using

# offset=-19.157 dbrx get-config -Vslope=0.10403 mca-calib.json mca-calib-vars.json

and also without variable substitution using

# dbrx get-config -s mca-calib.json mca-calib-vars.json

Parameter Groups

This example shows how to nest parameters in groups using the class ParameterGroup. It also show how to write parameter values to JSON files and how read them again. The example consists of the ROOT script param_group_example.C.

Run the example like this:

# root param_groups.C