Archive for Hyperion
corrida de Noël, Issy-les-Moulineaux [10K, 41’00, 701/3335, 1/38 M6M, 4´06/km]
Posted in pictures, Running, Travel with tags 10k, Brooks, corrida, Hyperion, Issy-les-Moulineaux, Paris suburbs, PariSanté campus, PHOTO running, road race, starting gate, Xmas on December 16, 2025 by xi'an
flow contrastive estimation
Posted in Books, Statistics with tags Bayesian inference, flight, GAN, generative adversarial networks, Hyperion, noise-contrastive estimation, normalising constant, normalising flow, Université de Montpellier on March 15, 2021 by xi'anOn the flight back from Montpellier, last week, I read a 2019 paper by Gao et al. revisiting the MLE estimation of a parametric family parameter when the normalising constant Z=Z(θ) is unknown. Via noise-contrastive estimation à la Guttman & Hyvärinnen (or à la Charlie Geyer). Treating the normalising constant Z as an extra parameter (as in Kong et al.) and the classification probability as an objective function and calling it a likelihood, which it is not in my opinion as (i) the allocation to the groups is not random and (ii) the original density of the actual observations does not appear in the so-called likelihood.
“When q appears on the right of KL-divergence [against p], it is forced to cover most of the modes of p, When q appears on the left of KL-divergence, it tends to chase the major modes of p while ignoring the minor modes.”
The flow in the title indicates that the contrastive distribution q is estimated by a flow-based estimator, namely the transform of a basic noise distribution via easily invertible and differentiable transforms, for instance with lower triangular Jacobians. This flow is also estimated directly from the data but the authors complain this estimation is not good enough for noise contrastive estimation and suggest instead resorting to a GAN version where the classification log-probability is maximised in the model parameters and minimsed in the flow parameters. Except that I feel it misses the true likelihood part. In other words, why on Hyperion would estimating all θ, Z=Z(θ), and α at once improve the estimation of Z?
The other aspect that puzzles me is that (12) uses integrated classification probabilities (with the unknown Z as extra parameter), rather than conditioning on the data, Bayes-like. (The difference between (12) and GAN is that here the discriminator function is constrained.) Esp. when the first expectation is replaced with its empirical version.
the 101 favourite novels of Le Monde readers
Posted in Books, Kids, pictures with tags Albert Camus, Alexandre Dumas, André Malraux, Barbey d'Aurevilly, book reviews, Céline, Charlotte Bronte, Cormac McCarthy, Don Quixote, Emile Zola, Faulkner, Fiodor Dostoïevski, Foundation, Gabriel Garcia Márquez, George Pérec, Graham Greene, Harry Potter, Haruki Murakami, Honoré de Balzac, Hyperion, Iain Pears, Jane Austen, Jean-Paul Sartre, John Steinbeck, Jules Verne, Kafka on the shore, Le Monde, Leo Tolstoy, Marcel Proust, Marguerite Yourcenar, Maupassant, Memoirs of Hadrian, Nobel Prize, Spanish Civil War, Stendhal, Stephen Zweig, The Lord of the Rings, The Road, Umberto Eco, Victor Hugo on January 1, 2020 by xi'an
Le Monde called its readers to vote for their five favourite novels, with no major surprise in the results, except maybe Harry Potter coming up top. Before Voyage au bout de la nuit and (the predictable) A la recherche du temps perdu. And a complete unknown, Damasio’s La Horde du Contrevent, as 12th and first science fiction book. Above both the Foundation novels (16th). And Dune (32nd). And Hyperion Cantos (52). But no Jules Verne! In a sense, it reflects upon the French high school curriculum on literature that almost uniquely focus on French 19th and 20th books. (Missing also Abe, Conrad, Chandler, Dickens, Ishiguro, Joyce, Kawabata, Madame de Lafayette, Levi, Morante, Naipaul, Rabelais, Rushdie, Singer, and so many others…) Interestingly (or not), Sartre did not make it to the list, despite his literature 1953 Nobel Prize, maybe because so few read the (appalling) books of his chemins de la liberté trilogy.
I did send my vote in due time but cannot remember for certain all the five titles I chose except for Céline’s Voyage au bout de la nuit (2nd), Cormac McCarthy’s The Road (74th) and maybe Fedor Dostoievski’s Brothers Karamazov (24th). Maybe not as I may have included Barbey d’Aurevilly’s L’ensorcelée, Iain Pears’ An instance at the fingerpost, and Graham Greene’s The End of the affair, neither of which made it in the list. Here are some books from the list that would have made it to my own 101 list, although not necessarily as my first choice of titles for authors like Hugo (1793!) or Malraux (l’Espoir). (Warning: Amazon Associate links).
- Harry Potter
- Voyage au bout de la nuit
- One hundred years of solitude
- The Lord of the rings
- L’étranger
- Belle du seigneur
- Les misérables
- Mémoires d’Hadrien
- Pride and prejudices
- The unbearable lightness of being
- Foundation
- Crime and punishment
- Madame Bovary
- Le rouge et le noir
- The Brothers Karamazov
- La peste
- War and peace
- The grapes of wrath
- Les liaisons dangereuses
- Bel-Ami
- Anna Karenina
- The name of the rose
- Germinal
- To kill a mocking bird
- The three musketeers
- Kafka on the shore
- La vie mode d’emploi
- Lolita
- Wuthering heights
- Mort à crédit
- The picture of Dorian Gray
- Life and fate
- Chess story
- La chartreuse de Parme
- L’œuvre au noir
- The idiot
- L’assommoir
- The road
- Le père Goriot
- The trial
- Don Quixote
- Notre-Dame de Paris
- Illusions perdues
- The sound and the fury
- La condition humaine
space opera by John Scalzi [book review]
Posted in Books, pictures, Travel with tags AI, Anathem, ancillary justice, Auvergne, Cryptonomicon, Hyperion, John Scalzi, Locus Award, Normandy, Picardy, redshirts, religion, science fiction, space opera, The Baroque Cycle, The Collapsing Empire, The Consuming Fire, The Three Body Problem on June 15, 2019 by xi'an
John Scalzi, author of the memorable Old Man’s War, has started a trilogy of which I only became aware recently (or more precisely became re-aware!), which has the perk of making two of the three books already published and hence available without a one or two year break. And having the book win the 2018 Locus Award in the meanwhile. This new series is yet again a space opera with space travel made possible by a fairly unclear Flow that even the mathematicians in the story have trouble understanding. And The Flow is used by guilds to carry goods and people to planets that are too hostile an environment for the “local” inhabitants to survive on their own. The whole setup is both homely and old-fashioned: the different guilds are associated with families, despite being centuries old, and the empire of 48 planets is still governed by the same dominant family, who also controls a fairly bland religion. Although the later managed to become the de facto religion.
“I’m a Flow physicist. It’s high-order math. You don’t have to go out into the field for that.”
This does not sound much exciting, even for space operas, but things are starting to deteriorate when the novels start. Or more exactly, as hinted by the title, the Empire is about to collapse! (No spoiler, since this is the title!!!) However, the story-telling gets a wee bit lazy from that (early) point. In that it fixates on a very few characters [among millions of billions of inhabitants of this universe] who set the cogs spinning one way then the other then the earlier way… Dialogues are witty and often funny, those few characters are mostly well-drawn, albeit too one-dimensional, and cataclysmic events seem to be held at bay by the cleverness of one single person, double-crossing the bad guys. Mostly. While the second volume (unusually) sounds better and sees more action, more surprises, and an improvement in the plot itself, and while this makes for a pleasant travel read (I forgot The Collapsing Empire in a plane from B’ham!), I am surprised at the book winning the 2018 Locus Award indeed. It definitely lacks the scope and ambiguity of the two Ancillary novels. The convoluted philosophical construct and math background of Anathem. The historical background of Cryptonomicon and of the Baroque Cycle. Or the singularity of the Hyperion universe. (But I was also unimpressed by the Three-Body Problem! And by Scalzi’s Hugo Award Redshirts!) The third volume is not yet out.
As a French aside, a former king turned AI is called Tomas Chenevert, on a space-ship called Auvergne, with an attempt at coming from a French speaking planet, Ponthieu, except that is should have been spelled Thomas Chênevert (green oak!). Incidentally, Ponthieu is a county in the Norman marches, north of Rouen, that is now part of Picardy, although I do not think this has anything to do with the current novel!
Great North Road [book review]
Posted in Books, Running, Travel with tags Alien, Avatar, book review, book reviews, brands, Brexit, England, Great North Road, Hyoer, Hyperion, India, Newcastle-upon-Tyne, science fiction, space opera, Speaker for the Dead, Travel on January 6, 2017 by xi'an
As I was unsure of the Internet connections and of the more than likely delays I would face during my trip to India, I went fishing for a massive novel on Amazon and eventually ordered Peter Hamilton’s Great North Road, a 1088 pages behemoth! I fear the book qualifies as space opera, with the conventional load of planet invasions, incomprehensible and infinitely wise aliens, gateways for instantaneous space travels, and sentient biospheres. But the core of the story is very, very, Earth-bound, with a detective story taking place in a future Newcastle that is not so distant from now in many ways. (Or even from the past as the 2012 book did not forecast Brexit…) With an occurrence of the town moor where I went running a few years ago.
The book is mostly well-designed, with a plot gripping enough to keep me hooked for Indian evenings in Kolkata and most of the flight back. I actually finished it just before landing in Paris. There is no true depth in the story, though, and the science fiction part is rather lame: a very long part of the detective plot is spent on the hunt for a taxi by an army of detectives, a task one would think should be delegated to a machine-learning algorithm and solved in a nano-second or so. The themes heavily borrow from those of classics like Avatar, Speaker for the Dead, Hyperion [very much Hyperion!], Alien… And from The Girl with the Dragon Tattoo for an hardcore heroin who is perfect at anything she undertakes. Furthermore, the Earth at the centre of this extended universe is very close to its present version, with English style taxis, pub culture, and a geopolitic structure of the World pretty much unchanged. Plus main brands identical to currents ones (Apple, BMW, &tc), to the point it sounds like sponsored links! And no clue of a major climate change despite the continued use of fuel engines. Nonetheless, an easy read when stuck in an airport or a plane seat for several hours.
