Optimize process lookup using Geant4 model catalog

[atolosadelgado]

Dear developers,

Please consider using the Geant4 model catalog [1] to identify the process responsible for creating the particle from the G4Track object [2].

This approach is expected to improve simulation performance, as comparing an integer identifier from G4Track is more efficient than comparing the process name [3] or performing multiple levels of indirection [4].

Best,
Alvaro

[1] https://github.com/Geant4/geant4/blob/a499fb82e9d3310f83c34f52806127561bdaab40/source/global/management/src/G4PhysicsModelCatalog.cc
[2] https://github.com/Geant4/geant4/blob/a499fb82e9d3310f83c34f52806127561bdaab40/source/track/include/G4Track.hh#L224
[3]

k4geo/plugins/SCEPCal_MainSDAction.cpp

Line 65 in f19536d

auto procName = track->GetCreatorProcess()->GetProcessName();

[4]

k4geo/plugins/DRCaloFastSimModel.h

Line 273 in f19536d

G4ProcessManager* pm = track->GetDefinition()->GetProcessManager();