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# Getting started

BoGEMMS-HPC uses a configuration file to set-up the physics, geometry and the I/O interface, while the input can be set with the Geant4 GPS macro file, or from a list of particles in ASCII, FITS, or ROOT format.

#### Volume ID configuration

The XYZ data model writes both the currect volume ID and its mother. The user can select one of the following configurations to also get the volume ID from previous layers (e.g. the grandmother). The following configurations are currently active in BoGEMMS-HPC:

- `GEOM.VOLID.TYPE = 0`: the IDs are the baseline IDs provided by Geant4

- `GEOM.VOLID.TYPE = 0`: the IDs are the baseline IDs provided by Geant4 (default = 0)

- `GEOM.VOLID.TYPE = 1`: the mother and grandmother IDs are summed, used in case of replicas 

- `GEOM.VOLID.TYPE = 2`: the current volume ID is the mother ID and the mother ID is the grandmother ID

- `GEOM.VOLID.TYPE = 3`: the current volume ID is the mother ID is the grandmother + grandgrandgrandmother ID (use case: XMM/MOS)

- `EVENT.PRIMARY.FORMAT` = 0 (ASCII), 1 (ROOT), 2 (FITS) (default = 0)

- `EVENT.PRIMARY.LIST.FILENAME` = path to the file

### Multithreading

Multithreading is activated by default, but the user can select how many threads to use in the simulation:

- `MT.NUM.THREADS = 1 (default = 1)`

## Physics

### Setting the physics

The `PHYS.VERSION` flag sets the name of the physics class to use in the application:

`PHYS.VERSION = <class_name>` [example: OPTPhys]