Archive for the Mountains Category

coupling for the Gibbs sampler

Posted in Books, Mountains, pictures, Running, Statistics, Travel, University life with tags , , , , , , , , , , on November 27, 2022 by xi'an

At BNP13, Brian Trippe presented the AISTAT 2022 paper he recently wrote with Tin D. Nguyen and Tamara Broderick. Which made me read their 2021 paper on the topic. There, they note that coupling may prove challenging, which they blame on label switching. Considering a naïve Gibbs sampler on the space of partitions, meaning allocating each data-point to one of the existing partitions or to a singleton, they construct an optimal transport coupling under Hamming distance. Which appears to be achievable in O(NK³log{K}), if K is the maximal number of partitions among both chains. The paper does not goes deeply into the implementation, which involves [to quote] (a) computing the distances between each pair of partitions in the Cartesian product of supports of the Gibbs conditionals and (b) solving the optimal transport problem. Except in the appendix where the book-keeping necessary to achieve O(K²) for pairwise distances and the remaining complexity follows from the standard Orlin’s algorithm. What remains unclear from the paper is that, while the chains couple faster (fastest?), the resulting estimators do not necessarily improve upon budget-equivalent alternatives. (The reason for the failure of the single chain in Figure 2 is hard to fathom.)

call for posters at BayesComp²³ satellite [AG:DC]

Posted in Mountains, pictures, Statistics, Travel, University life with tags , , , , , , , , , on November 22, 2022 by xi'an

An urgent reminder that the early bird deadline for BayesComp²³ and the different satellites is 30 November (with a difference of $50) and also a call for poster presentations at our AG:DC (aka, Bayesian computing without exact likelihood) satellite workshop. Poster spots will be attributed to presenters on a first come – first served basis, so do not delay in sending me an abstract at my gmail account bayesianstatistics

optimal leap year

Posted in Books, Kids, Mountains, pictures, R with tags , , , , , , , on November 19, 2022 by xi'an

A riddle about leap years: a solar year consists of approximately 365.24217 mean solar days, which is why there is a leap year approximately every four years. Approximately because the Gregorian calendar plans 97 and not 100 leap years over 400 years. Is this the optimal solution? No, since the Gregorian difference is 3.3 10⁻⁴ day per year, or 0.132 day per 400 years, while using 85 leap years over every 351 years leads to a difference of 4.76 10⁻⁶ day per year, or 0.002 day per 400 years… (With a further gain by a factor 4 with 116 leap years every 479 years.) This can be found by a basic R code

for(N in 10:1000)
for(L in 1:N){
  p=abs(L/N-.24217)
  if(p<T){T=p;lo=L;no=N}}

a journal of the [downplayed] plague and [endless] pestilence year

Posted in Books, Kids, Mountains, pictures, Running, Travel, University life with tags , , , , , , , , , , , , , , , , , , , , on November 13, 2022 by xi'an

Read another novel by Fred Vargas, the early This Night’s Foul Work which carries the usual Vargas’ themes more focussed on the psychology of the characters than on the police work, with no pretense at realism (from police work, to ignored regulations and procedures, to superhuman abilities of the improbable villein), and a rather simplistic (and surprising for a CNRS researcher) vision of regional idiosyncrasies. Again. (Maybe I am being thin-skinned because Normans are the targets this time.) Adamsberg, the main detective gets positively (or rather negatively) sleazy when spying on a romantic rival.

Read [in planes] The Traitor God sounded like an interesting plot when I picked it: a rogue mage, having left its order and city ten years ago, and coming to the rescue of old friends in trouble. However, the blob-like evil behind said trouble got particularly grotesque and absurd, till a ridiculous finale that was only the premise to a second volume. While sounding similar in concept, Paladin’s Grace proved much more enjoyable [in the same planes], if pure mindcandy (and hence hardly at level with a Hugo or Nebula Award). More a form of fantasy sleuthing than anything of a cosmologic scale (and no explanation as to why the god died), with a perfume-maker as the scientific police equivalent!  (But this is definitely not Süskind’s Parfum.) A bit heavy-handed on the romance part, though, with endless internal debates of both central characters. And also read The Maleficent Sevens, whose most redeeming quality is its title, as otherwise, I found little to enjoy there: the characters are not compelling, even in their maleficiency (facade grim only if this qualifies as grimdark fantasy), their motivation for (re)banding together is unconvincing, the magical abilities and actions hold no coherence, usual plot u-turns aplenty (like walking dead, krakens, subterranean demons), the naval battle is beyond stretching belief, contrary to the other (anti)heroes, the orcs are discriminated against in being the only ones to miss salvation in the final chapter, the dialogues are far from witty (far far away from Terry Pratchett if this qualifies as comic fantasy).

In contrast with my earlier light encounter with COVID, I attended a COVID funeral in Normandy a few weeks ago, which, besides the deep sadness of seeing a relative depart, made me question the general laisser-faire attitude about COVID, despite the dozens of thousands of daily cases (in France) and more than an hundred death. With hardly anyone wearing a mask in public transportation for instance. (In a cruel if not unexpected irony, some people attending the funeral later tested positive.)

Watched Hokusai in the plane to Santiago, and back, which I found a little bit stiff in its historical reconstruction and somewhat missing in getting the uniqueness and genius of Hkusai’s paintings. But interestingly bringing to light that paintings and sketches became somehow prohibited unless restricted to actors and courtesans, after the demise of the Tokugawa shogunate, during the Meiji Restoration. And un-enthusiastically completed the House of the Dragon, still lacking in scope. And in dragons.

a journal of the [experienced] plague and pestilence year

Posted in Books, Kids, Mountains, pictures, Running, Travel, University life with tags , , , , , , , , , , , , , , , , , on November 4, 2022 by xi'an

Read The Cybernetic Tea Shop, by Meredith Katz, which is a short and rather clever (if YA) novel about the hazy boundary between humans and humanoids. Plus involving tea addicts! (Which is presumably why Amazon suggested it to me following my reading A Psalm for the Wide Built). And further read over a few sleepless nights the terrible Isandor series starting with City of Strife, by Claudie Arseneault, which had an interesting built of characters and fantasy universe, only to collapse into the usual cracks of super-evil villeins, a massive imbalance of power and a focus on the mundane (like foods and romantic attractions) when their society is under attack. The writing style is also heavily handed, to the point that I found myself skipping more and more paragraphs as the story unfolded. And will definitely not consider the incoming volume.

Went smoothly through my first (?) COVID positivity, which only caused a mild fever over one single day, amidst common cold symptom. Luckily did not pass it to anyone in my immediate vicinity, and resumed running if not swimming almost immediately (if not hard enough to train for the Argentan 1/2 marathon!). But sadly missed the 800th anniversary conference in Padova, as I was still testing positive the day before. I may have gotten infected in Britain or Belgium, despite my constant use of a mask (except in restaurants!).

Watched three more episodes of House of the Dragon, with great characters but a definitive lack of scope (when compared with Game of Thrones). The story remains at a highly local level of power fights and bickering, with existential threats inexistent. Still relatively enjoyable.

%d bloggers like this: