ESTEC 14-Jun-2001 Andreas Pfeiffer, CERN/IT-API, [email protected] Architecture of Collaborating Frameworks Andreas Pfeiffer CERN IT/API [email protected]

ESTEC 14-Jun-2001 Andreas Pfeiffer, CERN/IT-API, [email protected]

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Architecture of Collaborating Frameworks

Andreas PfeifferCERN IT/[email protected]

B.Ferrero Merlino, R.Giannitrapani, F.Longo, R.Nartallo, P.Nieminen, AP, M.G.Pia, G.Santin

Round Table on 21st Century Monte Carlo Methods for Space Applications

June 13-15, ESTEC, Noordwijk NL

ESTEC 14-Jun-2001 Andreas Pfeiffer, CERN/IT-API, [email protected] 2

OutlineOutline

Motivation

Collaborating Frameworks

Geant-4: Simulation, Visualisation, User Interface and Analysis

Summary


Introduction and Motivation

Huge increase in complexity of modern s/wNeeds design on a larger scale

overall system structure: architecture beyond data structures and algorithms

Example: Detector Simulation defining geometry and materials defining physics processes interactive work visualisation data analysis

ESTEC 14-Jun-2001 taken from Bob Jones (ATLAS) 4

Design Levels: an analogy

Architectural design

Mechanistic design

Detailed design

The GreasySpoon

Bill Watterson

Image the project is not to build software but to go on aninter-planetary journey...

decide which planet to fly to

select the flight path

choose where to have lunch


Scale and processes:Building a dog house

• Can be built by one

person

• Minimal modelling

• Simple process

• Simple tools

Rational Software Corporation


Scale and processes:Building a family house

• Built by a team• Modelling

• Simple plans, evolving to blueprints

• Well-defined process• Architect• Planning

permission• Time-tabling and

Scheduling• ...

• Power tools



Scale and processes:Building a skyscraper

• Built by many companies

• Modelling• simple plans,

evolving to blueprints• scale models• engineering plans

• Well-defined process• architectural team• political planning• infrastructure

planning• time-tabling and

scheduling• selling space

• Heavy equipment



Components and Frameworks

Component a correlated group of classes together with their

interactions typically determined during domain composition

of OO analysis phase only very weak dependence on (classes of) other

components through use of Abstract Interfaces

Framework reusable design of (part of) a software system described by sets of abstract classes and the way

instances of these collaborate


Abstract Interfaces

Abstract Interfaces only pure virtual methods, inheritance

only from other A.I. components use other components only

through their A.I. defines a kind of a “protocol” for a component Maximize flexibility and re-use of packages allow each component to develop

independently re-use of existing packages to implement components

reduces start-up time significantly

De-couple implementation of a package from its use


Collaborating Frameworks

Allow re-use (if properly designed) existing libs can be wrapped easily

Maximize flexibility through use of Abstract Interfaces implementation can be changed

Rapid development cycle no need to implement full Interface from beginning

implementation can concentrate on important items

Reduces maintenance overhead implementations evolve independently


Geant-4 Toolkit

Description of detector geometry and material including CAD interface (STEP)

Simulation of physics processes flexible yet accurate simulations needed

User Interface to control flow of execution

Visualisation detector geometry, particle tracks

Analysis histogramming of physics quantities


Geant-4 Simulation (I)

Simulation of physics processes Electromagnetic processes

Standard processes, Low energy extensions, Muon processes, Optical photons

Hadronic processesData driven – neutron transport & isotope productionTheory driven modelling

Transportation in fields Parametrization for fast simulation

User can extend any of the processes through use of abstract interfaces adapt for special needs


Geant-4 Simulation (II)

Control through “steps” through setup Run, Event, Track, Step

Select and apply appropriate physics process at each step

Update list of particles to transport interactions, decays, ...

Possibly interact with user (via call-backs) show selected events (EventDisplay) create/update statistical information

(Histograms, ...) decide to continue/skip/abort event


Geant-4 User Interface

Designed for various categories of users G-4 developer, application developer, end user

Two phases of user user actions setup of simulation control of event generation and processing

User Interface category separated from actual command interpreter (intercoms) using abstract G4UIsession class Several implementations exist

command-line (batch and terminal)GUIs (X11/Motif, Windows, OPACS, Java)


Geant-4 Visualization

Control of several kinds of visualisation Detector geometry particle trajectories hits in the detectors

Using abstract G4VisManager class takes 3-D data from geometry/track/hits passes on to abstract visualization driver

G4VGraphicsSystem (initialization)G4VSceneHandler (processing 3-D data for vis.)G4VViewer (rendering the processed 3-D data)


Geant-4 Analysis

Using abstract G4VAnalysisManager class uses abstract G4VAnalysisSystem class for

initialization but “hides” instance from user using Proxy-pattern

basically forwarding all method calls to analysisSystem

User defined instance of AnalysisManager create histograms (through HistogramFactory) simple plots storing of histograms

More complex analysis (e.g., fit) done in Analysis System started externally


G4Analysis category


GammaRayTelescope

In parallel to event displayOnline histogramming required

fast feedback independent from Analysis Tool


Summary

Abstract Interfaces de-couple components of frameworks

Weakly coupled components and frameworks have large advantages ease of re-use of a component flexibility through independence of

implementation maintainability through independent evolution of

components

Example using Geant-4 and AIDA compliant analysis tools: XRayTelescope

Documents

ESTEC 14-Jun-2001 Andreas Pfeiffer, CERN/IT-API, [email protected] Architecture of Collaborating Frameworks Andreas Pfeiffer CERN IT/API [email protected]