Transcript Seminario Geant4 INFN

Overview of the
Geant4 OO Simulation Toolkit
Maria Grazia Pia
INFN Genova, Italy and CERN/IT
[email protected]
S. Agostinelli, S. Chauvie, F. Foppiano, P. Nieminen, S. Garelli, V. Rolando
32nd Meeting of the Proton Therapy Cooperative Group
Uppsala, 16 April 2000
http://www.ge.infn.it/geant4/talks/Uppsala/index.html
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Outline
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What is Geant?
Status of Geant3 and motivations for Geant4
The Geant4 R&D phase: RD44
The role of software engineering and OO technology
Main features of the Geant4 toolkit
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the kernel
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physics
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other tools
Performance
The Geant4 Collaboration
A selection of Geant4 applications
Conclusions
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The role of Geant
 Geant is a simulation tool, that provides a general infrastructure for
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the description of geometry and materials
particle transport and interaction with matter
the description of detector response
visualisation of geometries, tracks and hits
 The user develops the specific code for
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the primary event generator
the geometrical description of the set-up
the digitisation of the detector response
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The past: Geant3
 Geant 3
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has been used by most major HEP experiments
Frozen since March 1994 (Geant3.21)
~200K lines of code
equivalent of ~50 man-years, along 15 years
used also in nuclear physics experiments, medical physics, radiation background
studies, space applications etc.
 The result is a complex system
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because its problem domain is complex
because it requires flexibility for a variety of applications
because its management and maintenance are complex
 It is not self-sufficient
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hadronic physics is not native, it is handled through the interface to external packages
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New simulation requirements
 Very high statistics to be simulated
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robustness and reliability for large scale production
 Exchange of CAD detector descriptions
 Transparent physics for validation of physics results
 Physics extensions to high energies
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LHC, cosmic ray experiments...
 Physics extensions to low energies
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space applications, medical physics, X-ray analysis, astrophysics, nuclear and atomic physics...
 Reliable hadronic physics
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not only for calorimetry, but also for PID applications (CP violation experiments)
 ...etc.
 User requirements formally collected and coded according to PSS05 standard
Geant4 User Requirements Document
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What is Geant4?
OO toolkit for the simulation of next generation HEP detectors
...of the current generation too
...not only of HEP detectors
 already used also in nuclear physics, medical physics, space applications, radiation
background studies etc.
 It is also an experiment of distributed software production and management,
as a large international collaboration with the participation of various experiments,
labs and institutes
 It is also an experiment of application of rigorous software engineering and
Object Oriented technologies to the HEP environment
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A bit of history...
 Approved as R&D end 1994 (RD44)
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>100 physicits and software engineers
~40 institutes, international
collaboration
responded to DRCC/LCB
 Milestones: end 1995
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OO methodology, problem domain
analysis, full OOAD
tracking prototype, performance
evaluation
 Milestones: spring 1997
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-release with the same functionality
as Geant 3.21
persistency (hits), ODBMS
transparency of physics models
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 Milestone: July 1998
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public -release
 Milestone: end 1998
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production release: Geant4.0, end of the
R&D phase
 All milestones have been met by RD44
 Reconfiguration at the end of the R&D
phase
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International Geant4 Collaboration sincel
1/1/1999
Management of the production phase
Continuing R&D also in the production
phase
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Software Engineering
Software Engineering plays a fundamental role in Geant4
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Software process
User requirements
OOAD
Quality Assurance
 User Requirements
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Collected initially and
systematically updated
Coded according to
ESA PSS-05 standard
 Software process
 based on Booch methodology
 spiral type, with cycles of
design-implementation
iterations
 OO Analysis
 OO Design
 Evolution
 Maintenance
in a worldwide collaboration!
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OO technologies
OO design fundamental for distributed parallel approach
every part can be developed, refined, maintained independently
 Problem domain decomposition and OOAD result into a unidirectional dependency of
class categories
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 Transparency
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decoupling from implementation
 Open to evolution
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 Flexibility
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alternative models and implementations
 Interface to external software, without
dependencies
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extensibility, implementation of new
models and algorithms without
interfering with existing software
the user can extend the toolkit with
his/her model and data
databases for persistency
visualisation libraries
tools for UI
etc.
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Quality Assurance
 Extensive use of Quality
Assurance systems
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fundamental for a toolkit of wide
public use
 Commercial tools
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 Testing
 Unit testing
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Integration testing
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Insure++, Logiscope etc.
scripts to verify their applications
automatically
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within working groups and across
groups
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exercising all Geant4
functionalities in realistic set-ups
Physics testing
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eg.: test-suite of 375 tests for
hadronic physics parameterised
models
System testing
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 Code inspections
sets of logically connected classes
Test-bench for each category
 C++ coding guidelines
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in most cases down to class level
granularity
comparisons with experimental
data
Performance Benchmarks
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Standards
Based on standards, ISO e de facto
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STEP
engineering and CAD systems
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ODMG
RD45
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OpenGL e VRML for graphics
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CVS for code management
C++ as programming
language
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Units
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Geant4 is independent from the system of units
all numerical quantities expressed with their units explicitly
user not constrained to use any specific system of units
have you heard of the “accident” with NASA’s Mars Climate Orbiter ($125 million)?
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What is needed to run Geant4
 Platforms
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AIX, HP, DEC, Sun, (SGI):
native compilers, , g++
Linux: g++
Windows-NT: Visual C++
 Commercial software
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CVS
gmake, g++
CLHEP
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OpenGL, X11, OpenInventor,
DAWN, VRML...
OPACS, GAG, MOMO...
 Persistence
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ObjectStore STL (optional)
 Free software
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 Graphics
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it is possible to run in transient
mode
in persistent mode use a HepDB
interface, ODMG standard
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The Geant4 kit
 Code
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~1M lines of code, ~2000 classes
(continuously growing)
publicly available from the web
 Documentation
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6 manuals
publicly available from the web
 Examples
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distributed with the code
navigation between documentation and examples code
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The kernel
 Run and event
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the Run Manager can handle multiple events
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multiple runs in the same job
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possibility to handle the pile-up
with different geometries, materials etc.
powerful stacking mechanism
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three levels by default: handle trigger studies, loopers etc.
 Tracking
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decoupled from physics: all processes handled through the same abstract interface
tracking is independent from particle type
it is possible to add new physics processes without affecting the tracking
 Geant4 has only production thresholds , no tracking cuts
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all particles are tracked down to zero range
energy, TOF ... cuts can be defined by the user
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Geometry
 Role: detailed detector description and efficient navigation
 CAD exchange
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interface through ISO STEP (Standard for the Exchange of Product Model Data)
 Multiple representations
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CGS (Constructed Solid Geometries)
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STEP extensions
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simple solids
polyhedra,, spheres, cylinders, cones, toroids, etc.
BREPS (Boundary REPresented Solids)
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volumes defined by boundary surfaces
include solids defined by NURBS (Non-Uniform Rational B-Splines)
 External tool for g3tog4 geometry conversion
 Fields
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of variable non-uniformity and differentiability
use of various integrators, beyond Runge-Kutta
time of flight correction along particle transport
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Processes
Processes describe how particles interact with material or with a volume itself
 Three basic types
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At rest process
(e.g. decay at rest)
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Continuous process
(e.g. ionization)
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Discrete process
(e.g. decay in flight)
 Transportation is a process
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interacting with volume boundary
 A process which requires the shortest interaction length limits the step
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Physics
From the Minutes of LCB (LHCC Computing Board) meeting on 21 October, 1997:
“It was noted that experiments have requirements for
independent, alternative physics models. In Geant4 these
models, differently from the concept of packages, allow the
user to understand how the results are produced, and hence
improve the physics validation. Geant4 is developed with a
modular architecture and is the ideal framework where
existing components are integrated and new models
continue to be developed.”
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The approach to physics
Ample variety of independent, alternative physics
models available in Geant4
No more black boxes of packages
The users are directly exposed to the physics they use
in their simulation
This approach is fundamental for the validation of the
experiments’ physics results
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Transparency of Geant4 physics
 No “hard coded” numbers
 Explicit use of units throughout the code
 Separation between the calculation of cross sections and the generation of the
final state
 Calculation of cross-sections independent from the way they are accessed
(data files, analytical formulae etc.)
 Distinction between processes and models
 Cuts in range (rather than in energy, as usual)
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consistent treatment of interactions near boundaries between materials
 Modular design, at a fine granularity, to expose the physics
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physics independent from tracking
 Public distribution of the code, from one reference repository worldwide
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Physics: general features
 Abstract interface to physics processes
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tracking independent from processes
 Distinction between processes and models
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often multiple models for the same process
 Data encapsulation and polymorfism
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Transparent access to cross sections, from files, interpolation from tables, analytical
formulae etc.
Distinction between the calculation of cross sections and their use
Calculation of the final state independent from tracking
 Uniform treatment of electromagnetic and hadronic physics
 Open system
Users can easily create and use their own models
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Data libraries
 Systematic collection and evaluation of experimental data from
many sources worldwide
 Databases
 ENDF/B, JENDL, FENDL, CENDL, ENSDF,JEF, BROND, EFF,
MENDL, IRDF, SAID, EPDL, EEDL, EADL, SANDIA, ICRU etc.
 Collaborating distribution centres
 NEA, LLNL, BNL, KEK, IAEA, IHEP, TRIUMF, FNAL, Helsinki,
Durham, Japan etc.
 The use of evaluated data is important for the validation of physics results of
the experiments
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Electromagnetic physics
 Comparable to Geant3 and EGS already in the -release
 Substantial further extensions
 Multiple alternatives for various processes
 High energy extensions
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models for  up to PeV
fundamental for LHC experiments, cosmic ray experiments etc.
 Low energy extensions
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e, down to 250 eV
(EGS, ITS etc. to 1 keV, Geant3 to 10 keV))
low energy hadrons and ions models based on Ziegler and ICRU data and parametrisations
models for antiprotons
fundamental for space and medical applications, neutrino experiments, antimatter
spectroscopy etc.
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E.M. processes in Geant4
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multiple scattering
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transition radiation
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energy loss
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Cherenkov
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Bremsstrahlung
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Rayleigh effect
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ionisation
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rifraction
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annihilation
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reflection
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photoelectric effect
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absorption
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Compton scattering
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scintillation
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pair production
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fluorescence
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synchrotron radiation
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Auger (in progress)
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Hadronic physics
 Completely different approach w.r.t. the past
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transparent
native
no longer interface to external packages
clear separation between data and their use in algorithms
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 Cross section data sets
 transparent and interchangeable
 Final state calculation
 models by particle, energy, material
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Completeness
of Geant4 hadronic physics
Ample variety of models
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the most complete hadronic simulation kit on the market
alternative and complementary models
it is possible to mix-and-match, with fine granularity
data-driven, parameterised and theoretical models
Consequences for the users
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no more confined to the black box of one package
the user has control on the physics used in the simulation,
which contributes to the validation of physics results
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Hadronic physics
Parameterised and data-driven models
 Based on experimental data
 Some models originally from
GHEISHA
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completely reengineered into OO
design
refined physics parameterisations
 New parameterisations
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pp, elastic differential cross section
nN, total cross section
pN, total cross section
np, elastic differential cross section
N, total cross section
N, coherent elastic scattering
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 Other models are completely new,
such as
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stopping particles (- , K- )
neutron transport
isotope production
 All databases existing worldwide used
in neutron transport
Brond, CENDL, EFF, ENDFB, JEF,
JENDL, MENDL etc.
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Hadronic physics
Theoretical models
 They fall into different parts
 the evaporation phase
 the low energy range, pre-equilibrium, O(100 MeV),
 the intermediate energy range, O(100 MeV) to O(5 GeV), intra-nuclear
transport
 the high energy range, hadronic generator régime
 Geant4 provides complementary theoretical models to cover all the various parts
 Geant4 provides alternative models within the same part
 All this is made possible by the powerful Object Oriented design of Geant4
hadronic physics
 Easy evolution: new models can be easily added, existing models can be extended
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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
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Other components
 Materials
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elements, isotopes, compounds, chemical
formulae
 Visualisation
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 Particles
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all PDG data
and more, for specific Geant4 use, like ions
 User Interfaces
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 Hits & Digi
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to describe detector response
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 Persistency
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possibility to run in transient or persistent
mode
no dependence on any specific persistency
model
persistency handled through abstract
interfaces to ODBMS
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Various drivers
OpenGL, OpenInventor, X11,
Postscript, DAWN, OPACS, VRML
Command-line, Tcl/Tk, Tcl/Java,
batch+macros, OPACS, GAG, MOMO
automatic code generation for
geometry and materials
 Interface to Event Generators
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through ASCII file for generators
supporting /HEPEVT/
abstract interface to Lund++
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ESA projects in Geant4
 Low energy extensions of
electromagnetic physics
 Source Particle Module
 Radioactivity Decay
Module
 Sector Shielding Analysis
Tool
 CAD Tool Front-End
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Fast simulation
 Geant4 allows to perform full simulation and fast simulation in the same environment
 Geant4 parameterisation produces a direct detector response, from the knowledge of
particle and volume properties
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hits, digis, reconstructed-like objects (tracks, clusters etc.)
 Great flexibility
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activate fast /full simulation by detector
example: full simulation for inner detectors, fast simulation per 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/ parameterisation and 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
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Performance
 Various Geant4 - Geant3.21 comparisons
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realistic detector configurations
results and plots in
Geant4 Web Gallery (from Geant4 homepage)
RD44 Status Report, 1995
 Benchmark in liquid Argon/Pb calorimeter
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at comparable physics performance Geant4 is faster than (fully optimised) Geant3.21 by
 a factor >3 using exactly the same cuts
 a factor >10 optimising Geant4 cuts, while keeping the same physics performance
at comparable speed Geant4 physics performance is greatly superior to Geant3.21
 Benchmark in thin silicon layer
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at comparable physics performance Geant4 is 25% faster than Geant3.21 (single volume,
single material)
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Geant4 Collaboration
 New organization for the production
phase, MoU based
 Geant4 distribution, development and
User Support
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Atlas, BaBar, CMS, LHCB
CERN, KEK, SLAC, TRIUMF, JNL
ESA, Frankfurt Univ, INFN, IN2P3,
Karolinska Inst., Lebedev, TERA
COMMON (Serpukov, Novosibirsk,
Pittsburg etc.)
 Collaboration Board
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manages resources and responsibilities
 Technical Steering Board
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manages scientific and technical
matters
manages the Production Service and
User Support
 Working Groups
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do maintenance, development, QA,
user support etc.
other memberships currently being discussed
Members of National Institutes, laboratories and experiments participating in Geant4
Collaboration acquire the right to the Production Service and User Support
For others: free code and user support on best effort basis
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Bragg peak, Magic cube data and Geant4
Experimental data: Bragg
peak of a 270 MeV/u carbon
ion beam
Geant4 and experimental data,
PSI test with proton beam
distance(cm)
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Brachyterapy at Nat. Inst. Cancer Research, Genova
S. Agostinelli, R. Corvo, F. Foppiano, S. Garelli, G. Sanguineti
 The source holder is a standard
endobronchial treatment catheter,
the chamber is a 0.6 cc Capintec
chamber connected to a Capintec
192 electrometer
 The IST group follows the
direction of Basic Dosimetry on
Radiotherapy with Brachytherapy
Source of the Italian Association
of Biomedical Physics (AIFB)
The custom calibration plexiglas jig,
used for in air measurements.
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CT interface and treatment planning
Two possible approaches:
 CT interface + Geant4 “full simulation”
 CT interface + Geant4 “fast simulation”
(physics processes parameterised through an analytical treatment)
 Geant-based tools for
 inverse planning
 technique of active dose delivery
 Software interface for Geant4 that reads input data in DICOM3
format developed at Medical Dept., University of Piemonte
Orientale and INFN Torino
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Geant4 for scatter compensation in Megavoltage
3D CT
 Use GEANT4 to obtain
digitally reconstructed
radiographs (DRRs),
including full scatter
simulation
This represents a great
improvement over
approaches based on raycasting
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In vivo dosimetry for mammography
 TLD characterization for mammography screening
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simulation of dose deposition and glow curve
 Mammography simulation
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Goal: minimize dose on patient
Comparison between experimental data TLD in vivo dosimetry and
Geant4 simulation
 Activity at Medical Physics Dept., Umberto I Hospital of Ordine
Mauriziano, Torino
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in progress
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An ambitious project
What if the geometry to describe with Geant4 were DNA and the
process were mutagenesis?
 Study of radiation damage at the cellular
and DNA level in the space radiation
environment
ESA-sponsored project,
in collaboration with INFN
 INFN (Genova, Torino, Cosenza)
 Istituto Nazionale per la Ricerca sul
Cancro
 Università del Piemonte Orientale
 ESA
 CERN
 Karolinska Institute
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 Multi-disciplinary Collaboration of
 astrophysicists and space
scientists
 particle physicists
 medical physicists
 biologists
 physicians
 First phase of the project:
User Requirements
 Other applications (not only in space
programmes)
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Geant4 features relevant for medical applications
 The transparency of physics
 Advanced functionalities in every domain: geometry, physics, visualisation etc.
 Extensibility in any domain to satisfy new user requirements
 thanks to OO technology
 open design: new physics, new features can be easily added, without any
perturbation to the existing code
 Adopts standards wherever available (de jure or de facto)
 Use of evaluated data libraries
 Quality Assurance based on sound software engineering
 Subject to independent validation by a large user community worldwide
 User support organization by a large international Collaboration of experts
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Documentation
http://wwwinfo.cern.ch/asd/geant4/geant4.html
 User Documentation
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Introduction to Geant4
Installation Guide
Geant4 User’s Guide - For Application
Developers
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Geant4 User’s Guide - For Toolkit
Developers
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for those wishing to extend Geant4
functionality
Software Reference Manual
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for those wishing to use Geant4
 Examples
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a set of Novice, Extended and Advanced
examples illustrating the main functionalities of
Geant4 in realistic set-ups
 The Gallery
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a web collection of performance and physics
evaluations
http://wwwinfo.cern.ch/asd/geant4/reports/gallery/
 Publication and Results web page
http://wwwinfo.cern.ch/asd/geant4/reports/reports.html
documentation of the public interface of all
Geant4 classes
Physics Reference Manual
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extended documentation on Geant4 physics
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