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Burning the midnight oil with Abou

By 6 July 2022February 10th, 2024Stories, team and partners

« Ami du soir, bonsoir »

It’s around midnight, everything is calm and we start to light up. An email comes in… « Ami du soir, bonsoir ». This is our glorious friend Abou. Saab Abou-Jaoude, to be precise. He has been a teacher for over 40 years at one of the most top-notch school in France, Lycée Sainte-Geneviève, and has sent hundreds of students to Ecole Polytechnique and ENS Ulm. He’s a mix of a mathematical genius, a modern knight, a generous benefactor, a social case, a millionaire and a tramp. If you have enough guts to engage with this character, you will successfully experience pure delight, awe at stunning intellectual prowess, spectacle, outrageous bluff, tenderness, smile, rage, conflict, disgust, pain in the ass, and a real true friendship. 

Burning the midnight oil with Abou

It’s late at a night. 2013. Everybody’s asleep, that’s when we start to feel good. Our minds start to wander freely about new ideas, projects, code, early computer history, poetry, puns, and mathematical conversations. It is, as he likes to say by quoting Victor Hugo, « l’heure tranquille où les lions vont boire » (the quiet hour when lions go to drink). We were working on the first version of the GRACE Plotter. He was working on mathematical conjectures about Farey integers. We were working on the decomposition of musical signals into images (Fourier series and Gnuplot). He was working on the reedition of his 1971 book on topology, the first item in a series of three: Topology, Functions and Riemann Integrals. But we also had a common burning topic of collaboration: how to cleverly invert normal matrices of gravity field. How could we design an alternative to the Cholesky inversion in order to get rid of the noise and deliver the most possible signal out of the matrices. We just started a study with CNES on the topic (you can read about it here). This challenging topic was a gift for a maths lover. We were working on it every night. On top of this, he would write in Alexandrines. 

How did we get there?

MP*2 in Sainte-Geneviève, 2001-2002, that’s how. The mathematics classes with Abou were epic. Let’s give you a picture. The man would bump into the class, dressed in his old tired beige jacket. This is probably the same single jacket he ever wore since the start of time. The one jacket that hundreds of students will remember, even though they entered the class with a 20-year delay. He would throw his briefcase over the table and would start writing on the board while roaring in a loud resonant voice the content of the theorem. Like an ogre. Topology, arithmetics, algebra, matrices, series, functions, differential analysis, whatever was on the menu of the week. He would throw you in the fire right away, smile at his trick, and then let you stomach the spectacle. He did all his classes without a single written note. This was not easy content, the stakes were high, and the audience was a highly clever one. You could not fool them with an imprecise statement, it would backfire on you immediately with a question or a remark. In this type of environment, there was always one or two crazy supernatural students every year who were much smarter than all the professors combined. The only advantage of the professor was that he had seen the question several times before, and the student only once. Abou gladly admitted a mistake when he made one, but he worked so hard on himself that it would almost never happen. And if a student said something brilliant, his bulging eyes would light up, a teasing smile would appear on his face, and he would nod and approve in contentment. He was the only teacher who would correct the 40 copies of the 4-hour math exam over the course of the week-end. The exam was always on Saturday afternoon, and by Monday morning at 8 o’clock we had the grades and the copies. Another specific trait was his very pleasant handwriting, which is a precious quality, when students have to bear it 20 hours per week. It had harmonious and dynamic curves, both relaxed and optimist. The man had a rough exterior, but there were unmistakable signs that he was very refined in his thoughts, his emotions, and his judgements.

The celebration in Versailles and the Japanese restaurant

Fast forward 10 years later in September 2011, there was a celebration for his retirement. We jumped on the opportunity to meet our old teacher again. We were one day early and the man was available, so we took a walk together inside Versailles, to exchange news and remember our old moments. Since the discussion was pleasant and not ending anytime soon, we continued to a Japanese restaurant. We had had an argument during the class. At the time, no one would back down from his position. Believe it or not, 10 years later, no one had forgotten. It resurfaced sharply as if it was yesterday. He still had a grudge, we still had a grudge, and we started to fight again. Haha. How funny. This time, we settled the matter once and for all, in all humor and friendliness.

Fortran 4, Bezier, Renault, Air France and Matra

He started to talk about all his exploits besides being a mathematics teacher. He had been a pioneer in the era of early computers. He would program in assembler language, Fortran 4, Basic and other prehistoric languages none of you have ever heard about. He also designed hardware, such as one specific motherboard which he sold thousands of copies of. Those printed circuit boards were a piece of history now, but at the retirement celebration, he threw them away like candies as gifts to the public. He did consulting work for Matra, Aérospatiale, Air France, and Renault. His glorious era extended from the late seventies to the early nineties. In Renault, he worked together with Pierre Bézier on automated machines to design and cut automobile parts. Yes, this is the same Bézier that is in « Bézier curves », the one who is in all your drawing softwares, including Photoshop. He told stories of how he liked to make pranks and tricks, as a seed for a new venture, and watch how they would unfold over time. He told his stories about entrepreneurship and his consulting exploits in a very inspiring manner. He said: « You must give them the Moon plus ten percent ». Meaning extraordinary results, plus a bonus. It was uplifting and exciting. He was also among the very few people we met in France who had a healthy approach about money. Do exceptional work, be generous with it, please and stun your clients, and get rich. That too was refreshing. That meeting planted a seed in our mind, which later grew into Stellar Space Studies. 

Breaking the curse of retirement, and the birth of Stellar

The purpose of the celebration was his retirement. A concept he, as a hyperactive workaholic fellow, hated. Furthermore, it was forced retirement. On our side, the meeting in Versailles had been so interesting that we couldn’t stop thinking of how to find a pretext to do something together. The opportunity to embark on such an adventure came from CNES. Exactly at the right timing. We were still employees working as subcontractors for the space geodesy team. That CNES team had been working on techniques to improve the inversion of normal matrices for gravity field. They were not happy with traditional filtering and were exploring the SVD method. They had started a cooperation with CERFACS on the topic, but after three years, nothing tangible had come out of it. That was our chance. We had a special wild card in our sleeve. A former genius maths teacher just thrown into retirement, with an adventurous mind and a history of successful consulting work for the industry. He should come and help us. Let’s do it! So we enthusiastically presented the idea to CNES. And we enthusiastically presented the idea to Abou. Let’s apply the lessons from the master: start a prank and see how it unfolds. The people in charge in CNES were very open-minded and willing to risk a try. They had a small budget for missions and guest experts, so they could make it possible. Abou was reluctant at first. He was frustrated from his retirement episode and he felt he had unjustly been thrown to the dust because of his age. He didn’t want to be confronted to that again. But we just couldn’t take no for an answer. We insisted, and insisted, and envisioned how great it would be to work on gravity field together. Finally, we convinced everyone to make it happen. That move ended up being a fantastic success for all parties involved. Abou digested the pain of retirement and opened a new page with meaning and purpose. CNES started to devise its SVD method that would make them famous across the world of space geodesy. Stellar Space Studies (Géode & Cie at the time) came to life, and with the help of both the GRACE Plotter and our relentless late-night work on SVD with Abou, the young company had some serious tangible value to offer. What a great story!

Work on cognitive sciences

Let’s also mention Abou’s work on brain and cognitive sciences, with another of his former alumni. Abou had hundreds of them, many of whom had become very successful. Stellar was indeed not the only one to be blessed with Abou’s participation. On this topic, he asked us to provide absurd short sentences with no meaning, without disclosing the end purpose (except sharing them with his former student). There is a quote by a certain Dr. Seuss, which says: « I like nonsense, it wakes up the brain cells ». We took pleasure in the challenge, and here are a few excerpts from the Stellar contribution. We hope you appreciate our fertile imagination and our profusion in absurd literature. This is in French and really can’t be translated.

Le grand huit est la septième merveille du monde.
Le zéro est la roue des mathématiques.
Buffalo Grill est le dernier des bisons.
La soupe aux joules produit la plaque à induction.
Le mille-feuilles est en vente sur l’A4.
Fizeau tailla son museau en biseau avec des ciseaux.
Napoléon était l’empereur des Francs.
Les moutons australiens donnent la laine d’eucalyptus.
L’amour a des oreilles, les murs rendent aveugle.
Cendrillon s’est transformée en quenouille.
Les flèches du clavier indiquent les points cardinaux.
Le grève des martins-pêcheurs a provoqué la fermeture des huîtres.
Stabilo est le boss.
Gutenberg a imprimé l’inventerie.
Tout chronomètre possède un point de non rebours.
Il faut tourner la manivelle pour soulever Al Capone.
La potion atmosphérique est un principe de mécanique des druides.
Le gnou a la pampa, le bambou le panda.
Les athlètes augmentent le prix à la pompe.
Le verlan est un langage dissymétrique.

Stellar’s sentences for Abou’s project.

Abou also wrote and performed a theater show « Je parle à mon cerveau » (« I speak to my brain »). From mathematics to consulting to geodesy to cognitive sciences to theater, he definitely has an eclectic profile.

Three quotes from Abou

To finish off the article, let’s give you three quotes from Abou. This is part of the wisdom we soaked up from him, from the privilege of sharing work and friendship with him for over ten years.

  • This first quote reflects a feeling he had inevitably experienced, as a man trying to foster progress around him with smart but unconventional ideas. He has always faced a lot of backslash and hate for his suggestions, mostly from people who were primarily looking to maintain their own power and who did everything to stop anything from going anywhere. Disappointed that he made such efforts for nothing, and despaired at all the waste and the damage, he often said: « Il ne faut pas donner de la confiture aux cochons » (« Don’t feed marmelade to pigs »). He said it often, but he actually never applied it.
  • The second quote is a sentence he said when things started to get complex and sensitive, when a situation could potentially slide into serious consequences, needed adroit handling, or when panic started to set in on a given topic. When reason commanded to stop and think, he would say this: « Il est urgent de ne rien faire ». That means: « It is urgent to do nothing ».
  • The third and last quote is an illustration of his sense of provocation, of his humility about the relative importance of things in life, of his full awareness of what he was doing, and of his sense of humor.  He would say this with a smile: « Il faut savoir jusqu’où aller trop loin » (« You must know until where to go too far »).


How to summarize Abou? A master teacher, a brilliant mathematician, a generous man, with a true sense of friendship, a playful character, outwardly rough but inwardly refined, always on the brink of conflict and provocation, profoundly altruistic, visionary and brilliant. He is a major figure in the history of Stellar and he deserves a dignified place in this website. To give you an image, here is a picture from the 2011 Versailles retirement celebration (with his iconic tired old beige jacket).

He who laughs last, laughs best