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

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

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

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

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

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( )

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

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 http://cern.ch/DIANE Developed by J. Moscicki, CERN

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