Maria Grazia Pia

1
Advanced software engineering in simulation
development and applications

• Maria Grazia Pia
• INFN Genova, Italy
• Maria.Grazia.Pia_at_cern.ch

2
The lesson learned...
Courtesy of NASA/CXC/SAO
3
Why software engineering in experimental physics?

• Software engineering is somewhat new to the
  HEP/astroparticle environment
• other engineering branches more consolidated in
  this environment (mechanics, electronics,
  accelerators etc.)
• Benefits derive from a rigorous approach to
  software
• the lesson can be learned from the world of
  software professionals!
• even the most talented professionals need an
  organized environment to do cooperative work
• advanced technology cannot be fully effective
  without an organizational framework

Software Engineering plays a fundamental role in
Geant4
Software process SPI
User requirements OOAD Quality Assurance
4
25 years
5
Evolution of software

• 10 years mean in every domain (HW,SW,OS)
• 12 market cycles
• 1 revolution
• and the trend towards a greater variability
• together with the evolution of requirements!
• Consequences
• Todays software will not be the final one
• We should foresee change

6
Object Oriented technology

• OO technology is built upon a sound engineering
  foundation, whose elements are called the object
  model
• The object model encompasses the principles of
• abstraction
• encapsulation
• modularity
• hierarchy
• typing
• concurrency
• persistence
• brought together in a synergistic way
• Geant4 is based on Object Oriented technology

7
The dream of any software

• The Open Closed Principle
• Open for extension, Closed for modification
• A software module that is designed to be
  reusable, maintainable and robust must be
  extensible without requiring modification
• new features are added by adding new code, rather
  than by changing old, already working, code
• The primary mechanisms behind are abstraction and
  polymorphism

8
ADT (Interface)

• Abstract Data Type it is a class that defines
  only methods, that must be implemented by derived
  classes
• No implementation constraint
• Depending on the implementation language, it can
  be
• C pure virtual function
• Java Interfaces
• High flexibility
• Many different implementations derived from, and
  interchangeable with, the ADT
• Minimize the coupling between components
• Each component can evolve independently
• Reduce the chain of dependencies

9
Large scale software

• Large scale software systems
• Well defined and homogeneous structure
  (architecture)
• Partition into manageable units (components)
• Communication between components defined in a
  unique way (interfaces)

10
The Toolkit approach

• A toolkit is a set of compatible components
• each component is specialised for a specific
  functionality
• each component can be refined independently to a
  great detail
• components can be integrated at any degree of
  complexity
• components can work together to handle
  inter-connected domains
• it is easy to provide (and use) alternative
  components
• the simulation application can be customised by
  the user according to his/her needs
• maintenance and evolution - both of the
  components and of the user application - is
  greatly facilitated
• ...but what is the price to pay?
• the user is invested of a greater responsibility
• he/she must critically evaluate and decide what
  he/she needs and wants to use

11
OO technology in Geant4

• 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

Transparency decoupling from implementation Flexib
ility alternative models and implementations Inter
face to external software, without
dependencies databases for persistency visualisati
on libraries tools for UI etc.

• Open to evolution
• extensibility, implementation of new models and
  algorithms without interfering with existing
  software
• the user can extend the toolkit with his/her
  model and data

12
The benefits of software engineering
The goal producing better software at lower
cost, within predictable resource allocations and
time estimates, and happier users of the software

• the people involved
• the organization of the development process
• the technology used

Three key components

• The way to progress is to study and improve the
  way software is produced
• better technology only helps once the
  organizational framework is set
• there is evidence that going for new technology
  instead of improving the process can make things
  worst
• The practices of SPI are well established, and
  have been applied in a large number of
  organizations for several years
• the results prove that the economical benefits
  are largely worth the investment
• early defect detection, time to market, and
  quality also improve, to the point that the
  return on investment for SPI is about 500

13
Software life-cycle

• Various phases
• User Requirements definition
• Software Requirements definition
• Architectural Design
• Detailed Design and construction
• Delivery to the user
• Operations
• Frequently the tasks of different life cycle
  phases are performed somewhat in parallel
• to consider them disjoint in time is a
  simplification
• It is however important
• to distinguish them logically
• to identify documents that are the outcome of the
  various phases

14
The software process
It is the set of actions, tasks and procedures
involved in producing a software system, through
its life-cycle

• Complex domain, evolving, with many types of
  models available some examples of software
  process models are, for instance
• The Waterfall model
• analysis ? design ? coding
• each phase starts following the completion of the
  previous one
• The Iterative Incremental Development model
• cycles of analysis ? design ? coding, with
  incremental refinement

15
Software process standards

• Development or Engineering processes system and
  software requirements analysis, software design,
  software construction, software integration and
  unit testing, software maintenance
• Documentation
• Configuration and Change Management
• Problem Resolution
• Quality Assurance and Measurement
• System Testing, Acceptance and Releasing
• Verification and Validation
• Reviews, Audits and Joint Reviews
• Project tasks Management
• Improvement Process
• Process Establishment
• Human resource Management
• Infrastructure
• User Support, Distribution

• Capability Maturity Model
• Software Engineering Institute
• SPICE, ISO 15504
• the path to an international standard
• PSS-05, ECSS
• ESA

Process categories
Primary life-cycle of software development Support
ing life-cycle Management process Organizational
life-cycle User-supplier processes
etc.
16
The software process in Geant4

• a large international collaboration
• complex software
• mature categories in production and maintenance
  mode as well as categories in full development
• sensitive and mission-critical user applications
• product with a long life-time

A challenge

• Spiral-type life-cycle model adopted in most
  domains
• both iterative and incremental

• Software Process Improvement
• understand, determine and propose procedures to
  software development and maintenance
• gradual process, life-cycle driven
• regular assessment, according to the ISO 15504
  model

17
Requirements

• Requirements are the quantifiable and verifiable
• behaviours that a system must possess
• constraints that a system must work within
• User requirements
• this phase defines the scope of the system
• Software requirements
• this is the analysis phase of a software project
• builds a model describing what the software has
  to do (not how to do it)
• Requirements are subject to evolution in the
  lifetime of a software project!
• ability to cope with the evolution of the
  requirements

18
UR capture
Various methodologies adopted

• Elicitation through interviews and surveys
• Useful to ensure that UR are complete and there
  is wide agreement
• Joint workshops with user groups
• Direct requests from users to WG coordinators or
  members
• Use cases

• Analysis of existing Monte Carlo codes
• Study of past and current experiments
• Prototyping
• Useful especially if requirements are unclear or
  incomplete
• Prototype based on tentative requirements, then
  explore what is really wanted

• The requirements derive from many sources, in
  diverse domains
• HEP, astrophysics, space, medical etc.

User requirements evolve and we should be able
to cope with their evolution!
19
OOAD
Spiral approach
The life-cycle model adopted for most domains in
Geant4 is both iterative and incremental ?
especially relevant in the physics domain!
Booch methodology for OOAD

• has been chosen as the common language for
  documentation of designs and internal design
  reviews
• old documents in Booch notation are being
  progressively updated and converted to UML

UML notation

• extensively used for the initial generation of
  design documents
• where required, also for reverse engineering
• (Hadronic Physics, Standard EM, LowE EM initially)

Rational Rose CASE tool
20
Quality Assurance
Extensive use of QA systems in Geant4
fundamental for a toolkit of wide public use

• Testing
• Unit testing
• in most cases down to class level granularity
• Integration testing
• sets of logically connected classes
• Test-bench for each category
• eg. test-suite of 375 tests for hadronic physics
  parameterised models
• System testing
• exercising all Geant4 functionalities in
  realistic set-ups
• Physics testing
• comparisons with experimental data

• Commercial tools
• Insure, CodeWizard, Workshop etc.
• C coding guidelines
• scripts to verify their applications
  automatically
• Code inspections
• within working groups and across groups
• Walk-throughs with specialized tools for
  monitoring against violations of coding rules
• Checks on run-time memory management
• Checks for violations of the dependency structure
  of categories
• Performance benchmarks and monitoring

21
Risk factors

• Maturity of the experimental community?
• to appreciate the need of a new software
  environment
• to work in a simulation environment based on
  advanced software engineering
• to invest in learning new technologies