1. Other GEANT4 capabilities
Event biasing
Parameterisation (fast simulation)
Persistency
Parallelisation and integration in a distributed computing environment

2. Fast simulation
Geant4 allows to perform full and fast simulation in the same environment
The parameterisation process produces a direct detector response, from the knowledge of particle and volume properties
hits, digis, reconstructed-like objects (tracks, clusters etc.)
Great flexibility
activate fast /full simulation by detector
example: full simulation for inner detectors, fast simulation for calorimeters
activate fast /full simulation by geometry region
example: fast simulation in central areas and full simulation near cracks
activate fast /full simulation by particle type
example: in e.m. calorimeter, e/g parameterisation + full simulation of hadrons
parallel geometries in fast/full simulation
example: inner and outer tracking detectors distinct in full simulation, but handled together in fast simulation

3. Event biasing Geant4 provides facilities for event biasing
The effect consists in producing a small number of secondaries, which are artificially recognized as a huge number of particles by their statistical weights
Event biasing can be used, for instance, for the transportation of slow neutrons or in the radioactive decay simulation
Various variance reduction techniques available

4. Leading particle biasing
Simulating a full shower is an expensive calculation
Instead of generating a full shower, trace only the most energetic secondary
Other secondary particles are immediately killed before being stacked
Convenient way to roughly estimate, e.g. the thickness of a shield
Physical quantities such as energy are not conserved for each event

5. Geometrical importance biasing
W=0.5
W=1.0
P = 0.5
Define importance for each geometrical region
Duplicate a track with half (or relative) weight if it goes toward more important region
Russian-roulette in another direction
Scoring particle flux with weights
at the surface of volumes

6. Persistency
Geant4 Persistency makes run, event, hits, digits and geometry information be persistent, to be read back later by user programs
no dependence on any specific persistency model
use industrial standard ODMG C++ binding and HepODBMS as persistency interface
Possibility to run in transient or persistent mode
G4 kernel objects have corresponding “P” objects in G4Persistency
G4Run  G4PRun
G4Event  G4PEvent
G4Hit  G4PHit
: :
Store( )
Retrieve( )
Inherits from HepPersObj
in HepODBMS
“Parallel World” approach
Data members of transient and persistent objects are copied by Store( ) and Retrieve( )

7. Access to distributed computing
By design, Geant4 can be executed in more than one process/machine in parallel
Geant4 itself does not provide any mechanism of parallelisation
use external utilities
IMRT
An example of parallelisation of a Geant4 based medical application
IRCC LAN SW I T C H
Node01
Node02
Node03
Node04
Geant4 Simulation and Anaphe Analysis on a dedicated Beowulf Cluster
S. Chauvie et al., IRCC Torino, Siena 2002

8. DIANE DIstributed ANalysis Environment
Parallelisation
Access to the GRID
Transparent access
to a distributed computing environment
Hide complex details of underlying technology
prototype for an intermediate layer between applications and the GRID
R&D in progress for
Large Scale
Master-Worker Computing
Developed by
J. Moscicki, CERN

9. Parallel mode: local cluster
Parallel mode: distributed resources
DIANE framework and generic GRID middleware
Current #Grid setup (computing elements):
5000 events, 2 workers, 10 tasks (500 events each)
- aocegrid.uab.es:2119/jobmanager-pbs-workq
- bee001.ific.uv.es:2119/jobmanager-pbs-qgrid
- cgnode00.di.uoa.gr:2119/jobmanager-pbs-workq
- cms.fuw.edu.pl:2119/jobmanager-pbs-workq
- grid01.physics.auth.gr:2119/jobmanager-pbs-workq
- xg001.inp.demokritos.gr:2119/jobmanager-pbs-workq
- xgrid.icm.edu.pl:2119/jobmanager-pbs-workq
- zeus24.cyf-kr.edu.pl:2119/jobmanager-pbs-infinite
- zeus24.cyf-kr.edu.pl:2119/jobmanager-pbs-long
- zeus24.cyf-kr.edu.pl:2119/jobmanager-pbs-medium
- zeus24.cyf-kr.edu.pl:2119/jobmanager-pbs-short
- ce01.lip.pt:2119/jobmanager-pbs-qgrid
Spain
Poland
Greece
Portugal
Traceback from a run of the Geant4 brachytherapy advanced example on CrossGrid testbed