Archive for Sweden

postdocs positions in Uppsala in computational stats for machine learning

Posted in Kids, pictures, Statistics, Travel, University life with tags , , , , , , , , , , , on October 22, 2017 by xi'an

Lawrence Murray sent me a call for two postdoc positions in computational statistics and machine learning. In Uppsala, Sweden. With deadline November 17. Definitely attractive for a fresh PhD! Here are some of the contemplated themes:

(1) Developing efficient Bayesian inference algorithms for large-scale latent variable models in data rich scenarios.

(2) Finding ways of systematically combining different inference techniques, such as variational inference, sequential Monte Carlo, and deep inference networks, resulting in new methodology that can reap the benefits of these different approaches.

(3) Developing efficient black-box inference algorithms specifically targeted at inference in probabilistic programs. This line of research may include implementation of the new methods in the probabilistic programming language Birch, currently under development at the department.

the nihilist girl [book review]

Posted in Books, Kids with tags , , , , , , , , , , , , on October 7, 2017 by xi'an

When stopping by an enticing bookstore on Rue Saint-Jacques, in front of La Sorbonne, last July, I came across a book by the mathematician Sofia Kovaleskaya called the nihilist girl. Having never heard of non-mathematical books written by this Russian mathematician whose poster stood in my high school classroom, I bought it (along with other summer reads). And then discovered that besides being a woman of many “firsts”, from getting a PhD at Heidelberg (under Weirstraß) to getting a professor position in Stockholm, to being nominated to a Chair in the Russian Academy of Sciences, she also took an active part in the Commune de Paris, along with many emigrated Russian revolutionaries (or nihilists). Which explains for this book about a nihilist girl leaving everything to follow a revolutionary deported to Siberia. While not autobiographical (Sweden is not Siberia!), the novel contains many aspects inspired from the (amazing if desperately short) life of Sofia Kovaleskaya herself. A most interesting coincidence is that Sofia’s sister, Anna, was engaged for a while to Fyodor Dostoyevsky, whose novel The Demons takes the opposite view on nihilists. (As a feminist and anarchist, Anna took a significant part in the Commune de Paris, to the point of having to flee to Switzerland to escape deportation to New Caledonia, while her husband was sentenced to death.) The book itself is not particularly enjoyable, as being quite naïve in its plot and construction. It is nonetheless a great testimony of the situation of Russia in the 19th Century and of the move of the upper-class liberals towards revolutionary ideals, while the exploited peasant class they wanted to free showed no inclination to join them. I think Dostoyevsky expresses much more clearly this most ambiguous posturing of the cultivated classes at the time, yearning for more freedom and fairness for all, but fearing the Tsarist police, unable to connect with the peasantry, and above all getting a living from revenues produced by their farmlands.

wet summer reads [book reviews]

Posted in Books, Kids, Mountains, pictures, Travel with tags , , , , , , , , , , , , , , , , , , , , on September 24, 2017 by xi'an

“‘Oh ye of little faith.’ Rebus picked up his lamb chop and bit into it.” Ian Rankin, Rather be the Devil

Rebus’ latest case, a stray cat, a tree that should not be there, psychological worries in Uppsala, maths formulas, these are the themes of some of my vacation books. I read more than usual because of the heavy rains we faced in Northern Italy (rather than Scotland!). Ian Rankin’s latest novel Rather be the Devil reunites most of the characters of past novels, from John Rebus to Siobhan Clarke, Malcolm Fox, Big Ger’ Cafferty, and others. The book is just as fun to read as the previous ones (but only if one has read those I presume!), not particularly innovative in its plot, which recalls some earlier ones, and a wee bit disappointing in the way Big Ger’ seems to get the upper hand against Rebus and the (actual) police. Nonetheless pleasant for the characters themselves, including the City of Edinburgh itself!, and the dialogues. Rebus is not dead yet (spoiler?!) so there should be more volumes to come as Rankin does not seem to manage without his trademark detective. (And the above quote comes in connection with the muttonesque puzzle I mention in my post about Skye.)

The second book is a short story by Takashi Hiraide called The Guest Cat (in French, The cat who came from Heaven, both differing from the Japanese Neko ko kyaku) and which reads more like a prose poem than like a novel. It is about a (Japanese) middle-aged childless couple living in a small rented house that is next to a beautiful and decaying Japanese garden. And starting a relation with the neighbours’ beautiful and mysterious cat. Until the cat dies, somewhat inexplicably, and the couple has to go over its sorrow, compounded by the need to leave the special place where they live. This does not sound much of a story but I appreciated the beautiful way it is written (and translated), as well as related to it because of the stray cat that also visits us on a regular basis! (I do not know how well the book has been translated from Japanese into English.)

The third book is called Debout les Morts (translated as The Three Evangelists) and is one of the first detective stories of Fred Vargas, written in 1995. It is funny with well-conceived characters (although they sometimes verge so much on the caricature as to make the novel neo-picaresque) and a fairly original scenario that has a Russian doll or onion structure, involving many (many) layers. I was definitely expecting anything but the shocking ending! The three main characters (hence the English translation title) in the novel are 35-ish jobless historians whose interests range from hunter-gatherers [shouldn’t then he be a pre-historian?!] to the Great [WWI] War, with a medieval expert in the middle. (The author herself is a medieval historian.) As written above, it is excessive in everything, from the characters to the plot, to the number of murders, but or maybe hence it is quite fun to read.

The fourth book is Kjell Eriksson‘s Jorden ma rämna that I would translate from the French version as The earth may well split (as it is not translated in English at this stage), the second volume of the Ann Lindell series, which takes place in Uppsala, and in the nearby Swede countryside. I quite enjoyed this book as the detective part was is almost irrelevant. To the point of having the killer known from the start. As in many Scandinavian noir novels, especially Swedish ones, the social and psychological aspects are predominant, from the multiple events leading a drug addict to commit a series of crimes, to the endless introspection of both the main character and her solitude-seeking boyfriend, from the failures of the social services to deal with the addict to a global yearning for the old and vanished countryside community spirit, to the replacement of genuine workers’ Unions by bureaucratic structures. Not the most comforting read for a dark and stormy night, but definitely a good and well-written book.

And the last book is yet again a Japanese novel by Yôko Ogawa, The Housekeeper and The Professor, which title in French is closer to the Japanese title, The professor’s favourite equation (博士の愛した数式), is about a invalid maths professor who has an 80 minutes memory span, following a car accident. His PhD thesis was about the Artin conjecture. And about his carer (rather than housekeeper) who looks after him and manages to communicate despite the 80 mn barrier. And about the carer’s son who is nicknamed Root for having a head like a square root symbol (!). The book is enjoyable enough to read, with a few basic explanations of number theory, but the whole construct is very contrived as why would the professor manage to solve mathematical puzzles and keep some memory of older baseball games despite the 80mn window. (I also found the naivety of the carer as represented throughout the book a wee bit on the heavy side.)

Not a bad summer for books, in the end!!!

Mördar-Anders och hans vänner [book review]

Posted in Books, Travel with tags , , , , , , , , on February 25, 2017 by xi'an

“The medieval city of Visby and its shops were preparing for the approaching Christmas season. Interest rates were down to 0.0, which encouraged people to spend money they did not have so that Christmas sales would break records once again.” (p.332)

Thanks to these forced 24 hours in Schiphol, I bought and read a third book by the Swedish author Jonas Jonasson. Which title is Hitman Anders and the meaning of it all. The themes are almost exactly the same as in the previous novels, namely an improbable bunch of losers, growing like a dustball during the story, being unexpectedly provided (like the hundred-year old man) with a huge sum of money by illegal means and managing to keep it from the reach of the State and of a whole collection of gangsters, with a bit of a road movie outside Stockholm and the same fascination for camper-vans [without an elephant this time] and some mild reflections on the role of religion in Swedish society. Plus the customary appearance of the King and Queen. Not absolutely unpleasant but not superlatively funny and somewhat repetitive. (Like the 20th novel of Paasilinna!)

snapshot from Stockholm

Posted in pictures, Running, Travel with tags , , , , on May 18, 2016 by xi'an

ABC in Stockholm [on-board again]

Posted in Kids, pictures, Statistics, Travel, University life with tags , , , , , , , , , , , , , , , , on May 18, 2016 by xi'an

abcruiseAfter a smooth cruise from Helsinki to Stockholm, a glorious sunrise over the Ålend Islands, and a morning break for getting an hasty view of the city, ABC in Helsinki (a.k.a. ABCruise) resumed while still in Stockholm. The first talk was by Laurent Calvet about dynamic (state-space) models, when the likelihood is not available and replaced with a proximity between the observed and the simulated observables, at each discrete time in the series. The authors are using a proxy predictive for the incoming observable and derive an optimal—in a non-parametric sense—bandwidth based on this proxy. Michael Gutmann then gave a presentation that somewhat connected with his talk at ABC in Roma, and poster at NIPS 2014, about using Bayesian optimisation to reduce the rejections in ABC algorithms. Which means building a model of a discrepancy or distance by Bayesian optimisation. I definitely like this perspective as it reduces the simulation to one of a discrepancy (after a learning step). And does not require a threshold. Aki Vehtari expanded on this idea with a series of illustrations. A difficulty I have with the approach is the construction of the acquisition function… The last session while pretty late was definitely exciting with talks by Richard Wilkinson on surrogate or emulator models, which goes very much in a direction I support, namely that approximate models should be accepted on their own, by Julien Stoehr with clustering and machine learning tools to incorporate more summary statistics, and Tim Meeds who concluded with two (small) talks!, centred on the notion of deterministic algorithms that explicitly incorporate the random generators within the comparison, resulting in post-simulation recentering à la Beaumont et al. (2003), plus new advances with further incorporations of those random generators turned deterministic functions within variational Bayes inference

On Wednesday morning, we will land back in Helsinki and head back to our respective homes, after another exciting ABC in… workshop. I am terribly impressed by the way this workshop at sea operated, providing perfect opportunities for informal interactions and collaborations, without ever getting claustrophobic or dense. Enjoying very long days also helped. While it seems unlikely we can repeat this successful implementation, I hope we can aim at similar formats in the coming occurrences. Kitos paljon to our Finnish hosts!

sunrise on Bothnia

Posted in pictures, Running, Travel with tags , , , , , , , , on May 17, 2016 by xi'an