Geant4 Software Process 3rd LCB Computing Workshop, Marseilles 29 September, 1999 John Apostolakis...

Geant4

Software Process 3rd LCB Computing Workshop, Marseilles

29 September, 1999

John Apostolakis (CERN) for Geant4

with thanks for material and suggestions to Katsuya Amako,

Simone Giani

23rd LHC Workshop, Marseilles J.Apostolakis29th September 1999

Overview of the talk

Aspects of Geant4 software process

Context: Worldwide Collaboration

Software Methodology Macro and Micro Processes

OOA&D

Testing, Quality Assurance

Software Tools


Geant4 Overview What is Geant4?

Toolkit to simulate the passage of particles through the matter.

It’s for Monte Carlo simulations of detectors in high energy physics.

But also for space and cosmic rays applications, nuclear and radiation computations, heavy ions and medical applications.

How has it been developed?Development based totally on the object-oriented

software technology.Benefit from experience and the algorithmic

techniques accumulated in GEANT.Worldwide collaboration of ~100 physicists,

engineers, computer scientists from 15 countries.


Software Methodology Why software methodology?

For development of a complex software like Geant4, introduction of an engineering discipline is essential

OO methodology à la Booch employed because itprovides a very pragmatic approachhas easy-to-understand models with rich notations. provides a way to design a system into independent su

bsystem allows efficient work sharing in design and implementation sta

ges.


OO Methodology a la Booch: Benefits

Common-sense approach:Common-sense approach:with an incremental and iterative process

Clear models with rich notations fill the gap between desiClear models with rich notations fill the gap between design and implementation.gn and implementation. these models/notations help to exchange idea of desi

gn between people dispersed over the world

Seperation into independent subsystemsSeperation into independent subsystemsallows efficient job sharing scheme can be defined bot

h in design and implementation stages.


Software development in Booch method

Structure of the software process:

Macro process This provides the framework for a global software

process. Borrowing from the waterfall and spiral

model

Micro process This provides the framework for a fine structure of the

software process, which consist of an iterative and incremental approach.

Similar to spiral model


The Macro Development Process

OO Analysis

Requirement

Maintenance

OO Design

Evolution

Establish core requirement

Develop a model of the system’s desired behavior

Create an architecture for the implementation

Manage post-deliveryevolution

Evolve the implementationthrough successive refinement


Application of Booch method to Geant4

Basic principle Don’t blindly follow the method.

There is no “silver bullet” in constructing a complex software system.

Judge ourselves which elements of the method are important and applicable to our project.Adapt not adopt

Booch method is flexible enough to allow this.


Macro Process: OO Analysis Goal:

To identify all major objects/classes in the problem domain.

To produce a central model (class diagram) using objects/classes already found.

To identify clusters of classes that are themselves cohesive, but are loosely coupled relative to other clusters.

Major Products:Requirements document (ESA PSS-05: URD v.06)

Class diagram - analysis phase Scenario (Object/Interaction) diagram - analysis phase

Class category diagram (preliminary)


Macro Process: OO Analysis - continued

OO analysis and the worldwide collaboration: Close collaboration of people dispersed worldwide f

rom the beginning stage of OOA.The fundamental design of Geant4 was totally defin

ed in this phase. In Geant4 a core team was 6 / 7 people played an

essential role. As the number was small, the core people could work ver

y closely together even from various countries.

Yet the number was large enough to bring together different expertise (and was 1/3 of Geant in 1994)

no clear rule of thumb


Macro Process: OO Design

Goal:To refine the diagrams produced in the OOA phase

using the computing domain classes and objects (for example, manager objects, interface objects, etc) so that objects and classes can be coded and executed.

[Note] OOA and OOD progressed concurrently in most category

developments. The 2/3 of the first year was spent for OOA and OOD.

Major Products: Object diagram - design phaseScenario (Object/Interaction) diagram - design phase


Macro Process: OO Design - continued Set of classes that are closely coupled make a Class Category.

Class categories are cohesive and have looser couplings with each other.

We used class category as a unit to share tasks in OOD (and also in the implementation phase) .

Loose couplings enabled each category to work relatively independent.

Essential for worldwide collaboration

Class Category Diagram had a fundamental importance in the worldwide collaboration.

Much larger number of people could work together under each category.

[Note] Class category is NOT a functional separation of the software

system - well defined interface to other category. Class category is not a class wrapping “FORTRAN”.


Class Category Diagram

RunRun Geant4Geant4ReadoutReadout

EventEvent Event Gen.Event Gen.DigiDigi

HitHit MagneticFields

MagneticFields

TrackingTrackingDetectorDetector

PhysicsPhysics

TrackTrack

MaterialMaterial

ParticleDefinitionParticle

Definition

VisualizationVisualization

ODBMSODBMS

UtilitiesUtilities

GeometryGeometry CADInterface

CADInterface


The Micro Development Process

Identify classesand objects

Specify class and object interface and

implementation

Identify class and object relationships

Identify class and object semantics


The Micro Development Process It deals with the OO analysis & design at the small,

detailed level

In contrast with large scale macro development process

Great similarities in its process with macro process

analysis and design

detailed class diagrams

Tools (micro & macro) CASE Rose/C++

extensive use for OOA/OOD stage


Macro Process: Evolution

Goal: Construct the production version via incremental u

nofficial and official releases.Provide usage examples and user’s documents.

Major Products: Refined OOA/OOD via prototype coding. Regular incremental releases of the product. Official release of the product/examples/docume

nts.[Note] Micro process played a major role in this phase.

Regular incremental releases of the prototype provided a clean milestone in the project.


Testing Procedures

Different levels of testing:

unit testing of classes by developers required for each class - exercising it thoroughly

testing single physics model against data

system integration testing tests developed together by developers & test team

continuously refined as components are added

run regularly (see following slide)

system testing continuous comparisons of “full setups” with selected

data

under discussion


Testing procedures - continued

Category coordinators create tags submit them to system testing team

Testing teamdoes incremental testing, category by category

following dependency order of class-category diagram

accepts or rejects tags if they succeed or fail to pass (global) system tests

So we avoid “big bang” integration of parts by regular incremental releases.

Loosely couplings of class categories prevent wide-spread influence caused of a design change in a class.


Macro Process: Maintenance

Goal: No final goal in maintenance!

Major Products: Major upgrade releaseMinor bug fixed release

Improved examples and documents

[Note] The maintenance phase is the new big

challenge that Geant4 has faced this year.


Code Management

Current status of Geant4 codes Over a thousand classes, plus associated data.

Code management and class category Class category is a unit of a code management and code

release.Careful design to avoid circular dependencies is crucial. The dependency structure sets the release order.The release order dictates the working group schedule.

One coordinator per class category. A coordinator has a total responsibility to manage codes.

Coding rule Few coding rules -- global guide lines

Tools: CVS, remote CVS


Quality assurance

Software reliability and metrics: Insure++ and Logiscope

Coding guidelines automatic checking by scripts

Code inspection within class categories

Code and design inspection for categories interfaces

Test to ensure that categories respect dependencies on other categories - using our own tool


Collaboration management

Distributed managementCode release coordinator - SLACExample w.g. coordinator - HiroshimaDocument coordinator - KEK

Progress review and planning General workshops: KEK/CERN 95, TRIUMF 96, SLAC 97,

Niigata-JP 98 Specific local workshops: per sub-domain or group

Formal reports & milestonesCERN/DRDC 94, CERN/LCRB 95, CERN/LCB 97 & 98Geant4 collaboration milestones (1999)


GEANT4: Conclusions Worldwide software development allows us to exploit the

expertise of world authorities on physics (& more) distributed resources (people) and results in a greatly improved product (“quantum-leap”)

To successfully manage worldwide software development, the engineering discipline of a rigorous software process is an absolute necessity.

Key parts user requirements OO Analysis and design according to recognised method a detail design before coding is vital

OO design had fundamental importance in the Geant4 construction, offering clear tools e.g.

The concept of class category provided a excellent scheme of sharing the code development.

THE END


Atlas Geometry - 1


Atlas Geometry - 2


Hadronic Interaction: G3 vs. G4

Preliminary results reported in CERN/LCB report ‘97

CERN/LHCC/97-40, 10 June 1997

Distributions obtained by G3 and G4 are overlaid.

Can’t distinguish

Neutron Capture

Coherent elastic scattering

Neutron induced fission


VRML: Walk Through Atlas Detector


DAVID: Detector Overlap Viewer

Example:

Overlap of a box and

parameterized volumes.


Geant4 Collaboration Map

Member countryMember institute


The Macro Development Process

OO Analysis

Requirement

Maintenance

OO Design

Evolution

Establish core requirement

Develop a model of the system’s desired behavior

Create an architecture for the implementation

Manage post-deliveryevolution

Evolve the implementationthrough successive refinement


The Micro Development Process

Identify classesand objects

Specify class and object interface and

implementation

Identify class and object relationships

Identify class and object semantics


Collaboration management Management

Technical Steering Board (TSB)Collaboration Board

Working groupsResponsible for design and implementation work in specific

class categories:Event/Digi/Hits - CERN, Hiroshima Geometry - CERNTracks+Tracking - KEK, Kyoto Persistency - SLAC, KEKHadronics - TRIUMF, Aachen E.Mag. - TRIUMF, LAPP FastMC - PNHE, SLACGUI/Visualisation - Naruto, ManchesterQA/Tools - CERN, KEK, SLAC, TRIUMF


Collaboration management - continued

Other distributed managementCode release coordinator - SLACSystem Testing Team coordinator - ManchesterExample codes working group coordinator - HiroshimaDocument coordinator - KEK

Progress review and planningGeneral workshops: KEK/CERN 95, TRIUMF 96,

SLAC 97, Niigata-JP 98Specific local workshops: per sub-domain or group

Formal reportsCERN/DRDC 94, CERN/LCRB 95, CERN/LCB 97


Software tools

Basic principleNo special tools for the distributed development.

Employ commonly available ones.

List of tools RationalRose/C++ , C++/g++ RW-Tools.h++ , STL, LHC++OODBMS (CERN/ RD45) CVS , GNUmake gdb, prof, gprof Fukui Graphic System, OpenGL/OpenInventor,OX,

VRML Purify, Logiscope


Object Diagram - Tracking


Scenario Diagram - Tracking


Class Category Diagram

RunRun Geant4Geant4ReadoutReadout

EventEvent Event Gen.Event Gen.DigiDigi

HitHit MagneticFields

MagneticFields

TrackingTrackingDetectorDetector

PhysicsPhysics

TrackTrack

MaterialMaterial

ParticleDefinitionParticle

Definition

VisualizationVisualization

ODBMSODBMS

UtilitiesUtilities

GeometryGeometry CADInterface

CADInterface


Infrastructure

NetworkWithout INTERNET, we couldn’t make it - it’s obvious!Bandwidth has been improved much better since we

started the project - though we need more.

Tools for everyday life telnet, ftp, WWW, e-mail Video conference

CODEC for most cases

Telephone and teleconference

Face-to-face Meeting Still most efficient and critical for concentrated works

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