Archive for Vancouver

Thin Air [book review]

Posted in Books with tags , , , , , , , , , , , , , , on April 3, 2020 by xi'an

When visiting Vancouver last December [at a time when traveling was still possible], I had the opportunity to revisit White Dwarf Books [thirty years after my first visit] and among other books bought a Richard Morgan‘s novel, Thin Air, that I did not know existed and which was recommended by the [friendly] book seller. As superior to Morgan’s foray into dark fantasy (that I did not dislike so much). As I had really enjoyed the Altered Carbon series, I jumped on this new novel, which is a form of sequel to Th1rt3en, and very very similar in its futuristic pastiche of tough detectives à la Marlowe, dry humour included. A form of space noir, as The Guardian puts it. I sort of got quickly lost in the plot and (unusually) could not keep track of some characters, which made reading the book a chore towards the end. Thanks to the COVID-19 quarantine, I still managed to finish it, while home cycling!, the very end being more exciting than the beginning drudgery and the predictable sex scenes bound to occur in every of his novels. The Martian world in the novel is only alluded to, which makes it more appealing, despite the invasive jargon, however it sounds too much like a copy of our 20th century with car chase and gun/knife fights. Enhanced by an embedded AI when one can afford it. Certainly not the best read in the series but enough to tempt me into looking at the first episodes of Altered Carbon on Netflix. [Note: the book is not to be confused with the bestselling Krakauer’s Into Thin Air, which relates the 1996 Everest disaster, soon turned into a rather poor movie. I had not realised till today that the same Krakauer wrote Into the Wild…!]

Nature tidbits [the Bayesian brain]

Posted in Statistics with tags , , , , , , , , , , , , , , on March 8, 2020 by xi'an

In the latest Nature issue, a long cover of Asimov’s contributions to science and rationality. And a five page article on the dopamine reward in the brain seen as a probability distribution, seen as distributional reinforcement learning by researchers from DeepMind, UCL, and Harvard. Going as far as “testing” for this theory with a p-value of 0.008..! Which could be as well a signal of variability between neurons to dopamine rewards (with a p-value of 10⁻¹⁴, whatever that means). Another article about deep learning about protein (3D) structure prediction. And another one about learning neural networks via specially designed devices called memristors. And yet another one on West Africa population genetics based on four individuals from the Stone to Metal age (8000 and 3000 years ago), SNPs, PCA, and admixtures. With no ABC mentioned (I no longer have access to the journal, having missed renewal time for my subscription!). And the literal plague of a locust invasion in Eastern Africa. Making me wonder anew as to why proteins could not be recovered from the swarms of locust to partly compensate for the damages. (Locusts eat their bodyweight in food every day.) And the latest news from NeurIPS about diversity and inclusion. And ethics, as in checking for responsibility and societal consequences of research papers. Reviewing the maths of a submitted paper or the reproducibility of an experiment is already challenging at times, but evaluating the biases in massive proprietary datasets or the long-term societal impact of a classification algorithm may prove beyond the realistic.

Metropolis in 95 characters

Posted in pictures, R, Statistics, Travel with tags , , , , , , , , on January 2, 2020 by xi'an

Here is an R function that produces a Metropolis-Hastings sample for the univariate log-target f when the later is defined outside as another function. And when using a Gaussian random walk with scale one as proposal. (Inspired from a X validated question.)

m<-function(T,y=rnorm(1))ifelse(rep(T>1,T),
  c(y*{f({z<-m(T-1)}[1])-f(y+z[1])<rexp(1)}+z[1],z),y)

The function is definitely not optimal, crashes for values of T larger than 580 (unless one modifies the stack size), and operates the most basic version of a Metropolis-Hastings algorithm. But as a codegolf challenge (on a late plane ride), this was a fun exercise.

local mayhem, again and again and again…

Posted in Kids, pictures, Travel, University life with tags , , , , , , , , , , , , , , , , , , on December 27, 2019 by xi'an

The public transports in France and in particular in Paris have now been on strike for three weeks. In connection with a planned reform of the retirement conditions of workers with special status, like those in the train and metro companies, who can retire earlier than the legal age (62). As usual with social unrest in France, other categories joined the strike and the protest, including teachers and health service public workers, as well as police officers, fire-fighters and opera dancers, and even some students. Below are some figures from the OECD about average retirement conditions in nearby EU countries that show that these conditions are apparently better in France. (With the usual provision that these figures have been correctly reported.) In particular, the life expectancy at the start of retirement is the highest for both men and women. Coincidence (or not), my UCU affiliated colleagues in Warwick were also on strike a few weeks ago about their pensions…

Travelling through and around Paris by bike, I have not been directly affected by the strikes (as heavy traffic makes biking easier!), except for the morning of last week when I was teaching at ENSAE, when I blew up a tyre midway there and had to hop to the nearest train station to board the last train of the morning, arriving (only) 10mn late. Going back home was only feasible by taxi, which happened to be large enough to take my bicycle as well… Travelling to and from the airport for Vancouver and Birmingham was equally impossible by public transportation, meaning spending fair amounts of time in and money on taxis! And listening to taxi-drivers’ opinions or musical tastes. Nothing to moan about when considering the five to six hours spent by some friends of mine to get to work and back.

tea tasting at Van Cha

Posted in Kids, pictures, Travel with tags , , , , , , , , , , , , , on December 26, 2019 by xi'an

This recent trip to Vancouver gave me the opportunity of enjoying a Chinese tea tasting experience. On my last visit to the city, I had noticed a small tea shop very near the convention centre but could not find the time to stop there. This round I took advantage of the AABI lunch break to get back to the shop, which was open (on a Sunday), and sat for a ripe Pu-Ehr tasting. A fatal if minor mistake in ordering, namely that this was Pu-Ehr withing a dried yuzu shell, which gave the tea a mixed taste of fruit and tea, as least for the first brews. And remaining very far from the very earthy tastes I was expecting. (But it reminded me of a tangerine based Pu-Ehr Yulia gave me last time we went to Banff. And I missed an ice climbing opportunity!)
This was nonetheless a very pleasant tasting experience, with the tea hostess brewing one tiny tea pot after another, including a first one to wet and clean the tea, with very short infusion times, and tea rounds keeping their strong flavour even after several passes. In a very quiet atmosphere altogether, with a well-used piece of wood (as shown on top) in lieu of a sink to get rid of the water used to warm and clean pots and mugs (and a clay frog which role remained mysterious throughout!).
At some point in the degustation, another customer came in, obviously from a quite different league as he was carrying his own tea pancake, from which the hostess extracted a few grams and processed most carefully. This must have been an exceptional tea as she was rewarded by a small cup of the first brew, which she seemed to appreciate a lot (albeit in Chinese so I could not say).
As I was about to leave, having spent more time than expected and drank five brews of my tea, plus extra cups of a delicate Oolong, hence missing a talk by Matt Hoffman to which I was looking forward!, I discussed for a little while with this connoisseur, who told me of the importance of using porous clay pots and not mix them for different teas. Incidentally he was also quite dismissive of Japanese teas, (iron) teapots, and tea ceremony, which I found in petto a rather amusing attitude (if expected from some aficionados).