EEE4120F High Performance Embedded Systems Lecture 24

EEE4120F High Performance Embedded Systems Lecture 24 [Software] Quality Assurance Lecturer: Simon Winberg Attribution-ShareAlike 4.0 International (CC BY-SA 4.0) ct e p As al n e tion Z i Ka ts op par ソフトウェア

Lecture Overview What is quality? Software quality Software quality assurance (SQA) Software quality systems Consequences of bad SQA Evolutionary model of SQA in orgs Kaizen of software Formal Specifications

What is Quality? General definition of quality: It is a products ‘fitness of purpose’ A product is good quality if it does exactly what the users wants it to do! ‘Fitness of purpose’ The system satisfies the requirements as specified in requirements document (agreed contract) requirements

Consider this A computer system (e.g. accounting program) that - is functionally correct (e.g. accurately records debits/credits) - meets all the requirements as laid out in the contract ck y u l r You !! day but one that - is sometimes incredibly slow (takes 5 minutes or more to complete a transaction) - the user interface is very difficult to use takes days for a new user to learn how to use it - occasionally hangs for no reason (but doesn’t loose/corrupt data) Is that Software Quality? ! O N Gi me v e br a ea k!

Brief Brainstorm Software and product quality is not just about satisfying requirements, it is also about Work with a buddy and decide at least 5 things besides satisfying requirements that a quality system – or your YODA project – should provide.

reflections on your Brief Brainstorm The answer to this question may also depend on who you ask Software and product quality is not just about satisfying product requirements and clients. Asked: Not all the roles may have the same sense of what the top priorities are but generally, regards a good product, there may be many dimensions to that. Software and product quality is not just about satisfying requirements, it is also about Work with a buddy and decide at least 5 things besides satisfying requirements that a quality system – or your YODA project – should provide.

Software (and generally product) Quality Software quality is not just about satisfying requirements, it is also about: Correctness 1. 2. 3. 4. 5. 6. 7. 7 desirable ‘ilities” : Usability Maintainability (incl. documentation) Scalability / Extensibility Reliability Reusability Securability (more formally ‘security’) Portability You should know what these 7 ilities are, read up if you don’t T I “The and L I I E S

Software Quality Assurance (SQA) Software quality assurance is the: Guidance/process for recognizing, defining, analysing, and improving the software production process. It is achieved through a software quality system

Software Quality System (SQS) Organizational responsibility Managerial structures Individual SQA Responsibilities

Software Quality System Activities Auditing software projects Establishing: Standards Procedures Guidelines, etc. Often quite specific to a particular organization but often based around published recommended practices Producing reports for high-level management Continuously review & refining the organization’s quality system

Software Quality System Activities Effective quality system are well documented Without a properly documented quality system, application of quality procedures become ad-hoc, results in large variations in the quality of the products delivered*. * Sadly this is commonly what happens to most hons and postgrad projects. because there tends not to be enough time to learn or apply quality practices; imagine how impressive out projects could become if there was sufficient time for this!!

Bad/Inconsistent SQA Bad Attitudes and Behaviour An undocumented/poor quality system: Sends clear messages to the staff about the organization’s attitude of quality assurance. Can contribute towards project failure/delays Rubbish, no My code was Can make maintenance one confirms perfect, you your story! broke it! impossible/expensive Can leads to disagreements between staff

Evolution of Quality Assurance The SQA of a particular organization can usually be placed into the following continuum of Software Quality Systems evolved 4. Total Quality Management (TQM) 3. Quality Assurance (QA) 2. Quality Control (QC) 1. Inspection unevolved It’s up to you to decide where programmers are the happiest!

The Levels Inspection Check Quality for defects and eliminate them Control Not just detect & eliminate defects Also determine causes behind defects Quality Above Assurance this basic premise: If quality processes are good, and followed rigorously, the products are bound to be good! Includes guidance for recognizing, defining, analysing, and improving the production process

The Levels Total Quality Management (TQM) Continuous improvements to the quality process through measurement and refinement. “Continuous Process Improvement” There is a Japanize term for this and people who strive toward this ideal in their work are considered something like Samurai Warriors (or like an ‘Iron Chef’) the work is

Kaizen OP re TIO ad N ing AL ; a su us pp ef lem ul co ent nc ary ep t Kaizen : The method of continuous incremental improvements is an originally Japanese management concept for incremental (gradual, continuous) change towards improvement. Kaizen is actually a way of life philosophy, assuming that every aspect of our life deserves to be constantly improved. Samurai warriors strove towards the kaizen of the warrior, that is to say they aimed to become perfection in all areas of combat, from the appearance of their armour, the way they moved, to the mental preparation, and physical preparation for strategy, defensive tactics, striking skill, etc. Toyota the huge automotive giant proudly strives towards the kaizen of automobile manufacture What would it take to strive towards the kaizen of HPEC system development?. Like a samurai, it takes much time & practice!

sup OP ple TIO me N nta AL ry rea din g Formal Specification Towards precision of implementation meeting the requirements

Formal Specification In sup OP ple TIO me N nta AL ry rea din g computer science Formal Specifications (FS) Mathematically based techniques the purpose of which is to help the implementation of a systems and its software meet its requirements. Formal specifications are used to Describe a system Analyse its behaviour Aid the design by verifying key properties of interest through rigorous and effective reasoning tools. These specifications are formal in that they have a syntax and semantics that can be used to infer useful information and formulate proofs.

Formal Specification Why sup OP ple TIO me N nta AL ry rea din g FS Computer systems have become increasingly more powerful and integrated into society over the years, have impacted society and the environment to an ever greater extent – people have become more dependent on their computer systems Due to their increasing complexity and ubiquity, they have also become more difficult to analyse, both their workings and their impact on other systems. For these reasons methods are needed to more decisively, if not undisputedly, reason and know that these systems will do what they are supposed to do. Formal specifications are one such way to achieve this in software engineering, particularly for applications where reliability and predictability is paramount, and regimes of testing may not be adequate – such as in medical systems and rocket control modules where you want an unequivocal proof that the system satisfy its requirements.

Formal Specifications To sup OP ple TIO me N nta AL ry rea din g do FS properly, we would probably need a whole course on it. So in this course the concept is just introduced so that you know about it, as FS is indeed highly relevant to HPEC where these types of systems are often used in safety-critical applications. One thing I do want to delve into is the concepts of pre- and postconditions

sup OP ple TIO me N nta AL ry rea din g Preconditions and Postconditions Often a programmer must needs to describe exactly what a function needs to accomplish, without any indication of how the function does its work. i.e. you need to describe what the result of the function will be, and conditions in which it is expected to work, without explaining in details (of a particular programming language) what it does.

sup OP ple TIO me N nta AL ry rea din g Preconditions and Postconditions One method to explain the operation of a function without explaining its implementation is using Preconditions A statement indicates what must be true before the function is called. Programmer needs to ensure the precondition is valid when function is called Postconditions A statement indicates what will be true when the function finishes its work.

OPTIONAL supplementary reading Preconditions and Postconditions Example Consider this disp sqrt function. void disp sqrt ( float x ) { // calculate the square root and print the result to the stdout }

OPTIONAL supplementary reading Preconditions and Postconditions Example Consider the sqrt function. void disp sqrt ( float x ) { // calculate the square root r and print this result to the stdout } We know that for negative x it should give imaginary numbers, but assume that use of imaginary numbers are not possible by the specification. So in that case, we can specify the post condition for the function: that it will only work for non-zero numbers

OPTIONAL supplementary reading Preconditions and Postconditions Example Consider the sqrt function. We could add void disp sqrt ( float x ) { // PRECONDITION: (x 0) // calculate the square root r and print this result to the stdout } We know that for negative x it should give imaginary numbers, but assume that use of imaginary numbers are not possible by the specification. So in that case, we can specify the post condition for the function: that it will only work for non-zero numbers

OPTIONAL supplementary reading Preconditions and Postconditions Example Consider the sqrt function. void disp sqrt ( float x ) { // PRECONDITION: (x 0) // calculate the square root r and print this result to the stdout } What should happen after the function? It should come out with a result r such that r*r x, and print this result to the screen

OPTIONAL supplementary reading Preconditions and Postconditions Example Consider the sqrt function. void disp sqrt ( float x ) { // PRECONDITION: (x 0) // calculate the square root r and print this result to the stdout // POSTCONDITION: (r * r x) & has send data to stdout } What should happen after the function? It should come out with a result r such that r*r x, and print this result to the screen

sup OP ple TIO me N nta AL ry rea din g Pre- and post-conditions in C The assert function can be used to test conditions in a simple way void disp sqrt ( float x ) { assert(x 0); // check precondition // calculate the square root r and print this result to the stdout assert(r*r x); // check postcondition } How assert(val) works: if val is true, does nothing, if val is false then prints an error that indicates the module file name, the line number and what val is. e.g. Assertion violation: file mysqrt.c, line 12: x 0

Any Questions? End of Slideshow

Disclaimers and copyright/licensing details I have tried to follow the correct practices concerning copyright and licensing of material, particularly image sources that have been used in this presentation. I have put much effort into trying to make this material open access so that it can be of benefit to others in their teaching and learning practice. Any mistakes or omissions with regards to these issues I will correct when notified. To the best of my understanding the material in these slides can be shared according to the Creative Commons “Attribution-ShareAlike 4.0 International (CC BY-SA 4.0)” license, and that is why I selected that license to apply to this presentation (it’s not because I particulate want my slides referenced but more to acknowledge the sources and generosity of others who have provided free material such as the images I have used). Image sources: – Wikipedia open commons Businessman juggling - Pixabay Samurai, Kaizen Japanese lettering – sources include flickr and openclipart.org