Software engineering, programming methodology, languages, verification, general technology, publication culture, and more
A group of us is preparing a survey on systems that have been both formally verified and deployed for actual use. To make sure we do not forget any important development, we have devised a questionnaire. If you have experience with such a system, please help by filling the questionnaire. It only includes a few questions and takes a few minutes to fill. You can find it here.
Please also bring it to the attention of others who might have relevant information.
Thanks in advance!
I have started a new series of video lectures, which I call “Meyer’s Object-Oriented Classes” (MOOC). The goal is to share insights I have gained over the years on various aspects of programming and software engineering. Many presentations are focused on one area, such as coding, design, analysis, theoretical computer science (even there you find a division between “Theory A”, i.e. complexity, Turing machines and the like, and “Theory B”, i.e. semantics, type theory etc.), software project management, concurrency… I have an interest in all and try to explain connections.
The first lecture describes the edit distance (Levenshtein) algorithm, explains its correctness by introducing the loop invariant, expands on that notion, then shows a recursive version, explores the connection with the original version (it’s the invariant), and probes further into another view of recursive computations, leading to the concept of dynamic programming.
The videos are on YouTube and can be accessed from bertrandmeyer.com/levenshtein. (The general page for all lectures is at bertrandmeyer.com/mooc.)
The lecture is recorded in four segments of about 15 minutes each. In the future I will limit myself to 8-10 minutes. In fact I may record this lecture again; for example it would be better if I had a live audience rather than talking to my screen, and in general the recording is somewhat low-tech, but circumstances command. Also, I will correct a few hiccups (at some point in the recording I notice a typo on a slide and fix it on the fly), but the content will remain the same.
Feedback is of course welcome. I hope to record about a lecture a week from now on.
Received this today from a heretofore unknown correspondent (I don’t often check Facebook Messenger but just happened to). Name removed (I am not sure he would want me to identify him), text translated from another language into English.
Hello, thanks for your book “Object-Oriented Software Construction” [read in a translation]. I read it after a horrible failure of a project on which I was a consultant. Another consultant was my technical leader. He was truly insufferable but I appreciated him for one reason: his code! I had never seen such “beautiful” program code; he was using principles of genericity, dynamic binding and others, which were totally unknown to me after the lousy programming education I had received. He had insulted me, telling me that I was no developer at all; I was deeply offended since I could feel that he was right. In spite of his unbearable personality I wanted to learn at his side, but he was far too selfish, seeing me just as a competitor, even if a pathetic one. He had a book on the side of his desk… and it’s that book that enabled me to understand where he had learned all those OO design methods. That book, obviously, was yours, and I acquired a copy for myself. I sincerely think that it should be used as textbook in educational institutions. And I really wanted to thank you for writing it. I hope to become a real developer thanks to you. So, thank you.
Note 1: Thanks to you.
Note 2: There is also the intro programming text, Touch of Class (Amazon page).
Note 3 (to my fan club): You are welcome to take advantage of the ideas and there is actually no compelling requirement to be, in addition, “insufferable”.
A 1949 book I just bought* has the following printer’s label, hand-glued on the title page:
Because of a change in pagination, you will need to add the digit 9 [actually, the number, not the digit] to references to page numbers between 1 and 114, and the digit 8 to those between 116 and the end of the volume.
Examples: The reference that says “see page 92” should be read as “see page 101”
The reference that says “ see page 150” should be read as “see page 158”
*Précis d’histoire de la langue et du vocabulaire français (handbook of the history of French language and vocabulary) by Albert Dauzat, Larousse, Paris, 1949.
Vous souvenez-vous de ce discours ?
Françaises, Français, mes chers compatriotes,
Je voulais vous parler hier mais on m’a dit que l’expression “appel du 18 juin” était déjà prise et j’ai décidé d’attendre jusqu’aujourd’hui, 19 juin 2020. Un jour ne devrait pas faire une grande différence.
Mon message à toutes et à tous est simple :
Ne partez pas en vacances cette année.
Je sais, c’est dur. Pour les Français, les vacances sont sacrées depuis 1936. Toute l’année vous parlez essentiellement des dernières et des prochaines vacances. Mais cette fois-ci ce n’est vraiment pas le moment. Même si vous ne partez pas à l’étranger, avec la meilleure volonté du monde vous allez quand même vous entasser sur les plages et dans les hôtels. Vous essayerez le masque mais il suffit de se promener dans la rue pour voir combien sont au-dessous du nez ou au-dessus de la bouche ou les deux, ne servant strictement à rien.
Si nous partons comme tous les ans, imaginez la situation qui s’ensuivra inéluctablement. Projetez-vous quelques mois en avant ; le 28 octobre, pour choisir une date au hasard. Êtes-vous prêts pour 35 000 cas et 240 décès par jour, en croissance sans fin prévisible ? Pour un retour de l’engorgement des hôpitaux ? Pour — j’hésite à prononcer le mot honni ! — un nouveau reconfinement, celui que nous avions promis d’éviter mais qui serait devenu inévitable ? Et tout ce qui en découle — faillites, licenciements, séparations ? Sans même mentionner des fêtes de fin d’année sinistres sans la moindre lumière au bout du tunnel.
Non, j’en suis sûr, tout cela est impensable et n’est pas ce que vous voulez.
Alors, sacrifiez vos vacances cette année pour ne pas avoir à sacrifier bien plus les mois et les années qui suivront. Restez chez vous. Économisez votre argent, ne serait-ce que pour vous offrir d’excellentes vacances l’année prochaine. Lisez des livres, regardez des films, faites votre gymnastique, mais évitez déplacements et rencontres. Arrêtons-nous pour mieux rebondir ensuite. Si vous travaillez dans le tourisme, la passe sera difficile, et l’État vous aidera, mais céder à la facilité ne ferait que rendre vos perspectives pires encore.
En ces derniers jours de printemps, où tout semble vous sourire, vous n’en avez peut-être pas entièrement conscience encore, mais bientôt la bise sera venue : ne risquez pas, pour le bref plaisir d’un bel été, un automne et un hiver pires que ce que notre époque a jamais connu.
Pas de départ en vacances à l’été 2020.
Pour ma part, je ne m’en souviens pas.
D’autant plus qu’il n’a jamais été prononcé.
What can you do to or with an algorithm? In other words, what is a good verb to substitute for the hyphen in “— the algorithm”?
You can learn an algorithm. Discovering classical algorithms is a large part of the Bildungsroman of a computer scientist. Sorting algorithms, graph algorithms, parsing algorithms, numerical algorithms, matrix algorithms, graphical algorithms…
You can teach an algorithm. Whether a professor or just a team leader, you explain to others why the obvious solution is not always the right one. As when I saw that someone had implemented the traversal part of a garbage collection scheme (the “mark” of mark-and-sweep) using a recursive algorithm. Recursion is a great tool, but not here: it needs a stack of unpredictable size, and garbage collection, which you trigger when you run out of space, is not precisely the moment to start wildly allocating memory. In comes the Deutsch-Schorr-Waite algorithm, which improbably (as if tightrope-walking) subverts the structure itself to find its way forth and back.
To teach it, you can dance an algorithm. Sounds strange, but Informatics Europe gave its 2013 education award to the “AlgoRhythmics” group from at Sapientia University in Romania, which demonstrates algorithms using central-European dances; see their rendering of Merge Sort:
(Their page has more examples. I see that recently they expanded to other kinds of dance and will let you discover binary search as flamenco and backtracking as classical ballet.) More generally you can simulate or animate an algorithm.
You can admire an algorithm. Many indeed are a source of wonder. The inner beauty of topological sort, Levenshtein or AVL can leave no one indifferent.
You can improve an algorithm. At least you can try.
You can invent an algorithm. Small or large, ambitious or mundane, but not imagined yet by anyone. Devising a new algorithm is a sort of rite of passage in our profession. If it does prove elegant, useful and elegant, you’ll get a real kick (trust me). Then you can publish the algorithm.
You can prove an algorithm, that is to say, mathematically establish its correctness. It is indeed increasingly unreasonable to publish an algorithm without correctness arguments. Maybe I have an excuse here to advertize for an an article that examines important algorithms across a wide variety of fields and showcases their main claim to correctness: their loop invariants.
You can implement an algorithm. That is much of what we do in software engineering, even if as an OO guy I would immediately add “as part of the associated data structure”.
Of late, algorithms have come to be associated with yet another verb; one that I would definitely not have envisioned when first learning about algorithms in Knuth (the book) and from Knuth (the man — who most certainly does not use foul language).
You can fuck an algorithm.
Thousands of British students marched recently to that slogan:
chants of “fuck the algorithm” as a speaker talks of losing her place at medical school because she was downgraded. pic.twitter.com/P15jpuBscB
— huck (@HUCKmagazine) August 16, 2020
They were demonstrating against a formula (the Guardian gives the details) that decided on university admissions. The starting point for these events was a ministerial decision to select students not from their grades at exams (“A-level”), which could not take place because of Covid, but instead from their assessed performance in their schools. So far so good but the authorities decided to calibrate these results with parameters deduced from each school’s past performance. Your grade is no longer your grade: if Jill and Joan both got a B, but Jill’s school has been better at getting students into (say) Oxford in the past, then Jill’s B is worth more than Joan’s B.
The outcry was easy to predict, or should have been for a more savvy government. Students want to be judged by their own performance, not by the results of some other students they do not even know. Arguments that the sole concern was a legimitate one (an effort to compensate for possible grade inflation in some schools) ceased to be credible when it came out that on average the algorithm boosted grades from private schools by 4.7. No theoretical justification was going to be of much comfort anyway to the many students who had been admitted to the universities of their dreams on the basis of their raw grades, and after the adjustment found themselves rejected.
In the end, “Fuck the Algorithm!” worked. The government withdrew the whole scheme; it tried to lay the blame for the fiasco on the regulatory authority (Ofqual), fooling no one.
These U.K. events of August 2020 will mark a turning point in the relationship between computer science and society. Not for the revelation that our technical choices have human consequences; that is old news, even if we often pretend to ignore it. Not for the use of Information Technology as an excuse; it is as old (“Sorry, the computer does not allow that!”) as IT itself. What “Fuck the Algorithm!” highlights is the massive danger of the current rush to apply machine learning to everything.
As long as we are talking marketing campaigns (“customers who bought the product you just ordered also bought …”) or image recognition, the admiring mood remains appropriate. But now, ever more often, machine learning (usually presented as “Artificial Intelligence” to sound more impressive) gets applied to decisions affecting human lives. In the US, for example, machine-learning algorithms increasingly help judges make decisions, or make the decisions themselves. Following this slippery path is crazy and unethical. It is also dangerous, as the U.K. students’ reaction indicates.
Machine learning does what the name indicates: it reproduces and generalizes the dominant behaviors of the past. The algorithms have no notion of right and wrong; they just learn. When they affect societal issues, the potential for societal disaster is everywhere.
Amid all the enthusiasm generated by the elegant techniques invented by machine-learning pioneers over the last two decades, one barely encounters any serious reservation. Codes of ethics (from ACM and others) have little to contribute.
We should be careful, though. Either we get our act together and define exacting controls on the use of machine learning for matters affecting people’s fates, or we will see a massive rejection of algorithmic technology, the right parts along with the wrong ones.
The British students of the year 2020’s weird summer will not be the last ones to tell us to fuck the algorithm.
This article was first published in the Communications of the ACM blog.
No one seems until now [1] to have identified a key element of any scientific article being submitted or revised for publication. It is guaranteed to increase, if not the quality of your articles, at least their chances of publication, which after all is what counts.
We are told to include a “related work” section, but just as important is the unrelated work section. For example:
Unrelated work
The following publications have no attested relevance to the topic of this paper but, as pointed out by an anonymous reviewer [2], they are breathtakingly brilliant: [Meyer 1997], [Meyer 2005], [Meyer et al. 2009], [Al et Meyer 2011]. In addition, having taken a look at the composition of the Editorial Board, we would like to point out the pioneering results introduced by [Meyer 2017] and [Meyer 2019].
This insight is shared with the sole selfless purpose of helping the community, particularly young and aspiring researchers.
[1] I did find a 2018 Twitter thread started by Arvind Narayanan, with the insightful (if dejected) observation that “`related work’ sections exclusively cite unrelated work”.
[2] Example only, for the sake of an example, since for my part I actually refuse to be an anonymous reviewer; I always sign my reviews, so if I want to tell the authors “I think you should cite my such-and-such paper here” I can do so without any qualms.
The Schaffhausen Institute of Technology (SIT) is holding a Webinar tomorrow with a set of three talks by: Serguei Beloussov, founder of Acronis and president of SIT; Michael Widenius, CTO of MariaDB and creator of MySQL Server; and Mauro Pezzè, my colleague at SIT, who will present the new master program that we have just announced, combining CS/SE topics with management and marketing courses to train future technology leaders.
The talks are in the form of a Webinar, starting at 9 AM this Tuesday (9 June). You can find all the details on the corresponding SIT page at here.
My group, the Chair of Software Engineering, at the newly created Schaffhausen Institute of Technology has open positions for both PhD students and postdocs. We are looking for candidates with a passion for reliable software and a mix of theoretical knowledge and practical experience in software engineering. Candidates should have degrees in computer science or related fields: a doctorate for postdoc positions, a master’s degree for PhD positions. Postdoc candidates should have a substantial publication record. Experience in one or more of the following fields is a plus:
Compensation at both levels is attractive. The PhD program is conducted in cooperation with partner universities.
Interested candidates should send a CV and relevant documents or links to bm@sit.org. They are also welcome to contact me for details.
I recently read the autobiography [1] of the great mathematician André Weil and came across the following comment (slightly abridged):
Any mathematician worthy of the name has known such states of lucid exaltation, when ideas magically fall into place. Poincaré, in a famous passage, described how he experienced such a moment when he discovered fuchsian functions. Of these states, Gauss reportedly said procreare jucundum (to procreate is a pleasure), while adding: sed parturire molestum (but giving birth is a pain). Unlike sexual pleasure, this one can last hours or even days. Whoever has experienced it wants to renew it, but is impotent to provoke it, except at best through obstinate work, of which it then appears as the reward.
This penetrating observation (if I may use the expression) brings a new perspective to the 18th-century French song famously revived by Joan Baez:
“The joy of love lasts but an instant”, it says, “the pain of love lasts a lifetime” (plaisir d’amour ne dure qu’un moment, chagrin d’amour dure toute la vie). Clearly, the second part of the verse contains an error: “chagrin d’amour” (the pain of love) must have been a transcription mistake for “comprendre la démonstration par Paul Cohen de l’indépendance de l’hypothèse du continu” (understanding Paul Cohen’s proof of the independence of the continuum hypothesis, which unlike most pains of love does take a lifetime, or two). It is not hard how the confusion could have arisen, as both sound French.
Still, Weil’s observation, if true, is worrying. As everyone can witness almost daily, mathematical ability in humankind is progressing by leaps and bounds. Does this trend portend bad news (echoes of Tolstoi’s Kreutzer Sonata) for our collective reproductive future?
A grave question indeed. To help address it, I have started a scientific poll, which you will find here. The question it asks is of the utmost importance: do you prefer sex or math? To preserve the integrity of the study, please note that by answering the poll you are declaring that you have engaged in both sex and math, although not necessarily at the same time.
As soon as I get the research grant for which I have applied, I will submit the results to the Proceedings of the National Academy of Sciences.
[1] André Weil, Souvenirs d’Apprentissage, Birkhäuser, Boston, 1991. English translation: The Apprenticeship of a Mathematician, Springer, 1992.