Archive for Alps

off to SimStat2019, Salzburg

Posted in Mountains, Running, Statistics, University life with tags , , , , , , , , , , , , , on September 2, 2019 by xi'an

Today, I am off to Salzburg for the SimStat 2019 workshop, or more formally the 10th International Workshop on Simulation and Statistics, where I give a talk on ABC. The program of the workshop is quite diverse and rich and so I do not think I will have time to take advantage of the Hohe Tauern or the Berchtesgaden Alps to go climbing. Especially since I am also discussing papers in an ABC session.

trailers versus mountaineers?

Posted in Kids, Mountains, Running, Travel with tags , , , , , , , , , , , on August 31, 2019 by xi'an

A slight altercation in a swimming corridor during lunch put me back into this Le Monde paper I read yesterday about (real?!) mountaineers being annoyed at trailers, especially those currently running the Ultra-Trail du Mont Blanc (UTMB). A lady stopped me from going further for not crawling as this was a “crawl only” lane and started a lengthy tirade that I cut short by moving to another lane. I find such debates pretty absurd and rather hypocritical. When the fundamental goal is mostly to reduce the number of people on the trails, in the mountains, or in the pool by creating categories with those in and those out. This seems an unavoidable human trend that happened several times in mountaineering, from the early days when going above a certain limited was prohibited to those when climbing solo, rope-free, mixed style, without a registered guide or certificate, &tc. base-jumping, was or became taboo. It is annoying to see crowds in the mountains, whether on the Everest final sketch or on the UTMB track, for sure, but by nature these are singular events and the next peak is almost surely free. It is also annoying to find other climbers on one’s chosen route as they will certainly cause delays, but this is the nature of the game and the next route may well be free. I thus find pretty annoying that some claim their rights to enjoy mountains are higher or purer than others, whom they accuse of elitism and ill-placed competition, when themselves are far from free of the same defect.


another Nice shot [jatp]

Posted in Statistics with tags , , , , , , , on May 22, 2019 by xi'an

Les Grandes Jorasses, from 342 to 2 hours

Posted in Mountains with tags , , , , , , , , , , on September 7, 2018 by xi'an

Last month Dani Arnold, a Swiss climber, climbed the classic Cassin route of Les Grandes Jorasses [in my dreams!] in two hours (and obviously completely free-solo, with no protection whatsoever). This route was opened by Cassin, Esposito and Tizzoni, 1938, is part of the three great north walls of the Alps, with Eiger and Matterhorn, and is graded TD+/ED1, IV, 5c/6a, A1, for a vertical climb of 1200m. It is an extremely challenging and engaged climb, with almost no possibility to escape once started, and climbing parties often take more than a day to complete the climb. On his way up, Arnold passed nine groups of climbers. Here is another video of his in Scotland, when repeating for the first time Anubis, a mixed climbing route on Ben Nevis. (The title of the post is relating to Desmaison’s 342 heures dans les Grandes Jorasses.)

Chamonix snapshot #3 [jatp]

Posted in Kids, Mountains, pictures, Running, Travel with tags , , , , , , , , , , , on March 10, 2018 by xi'an

Astrostatistics school

Posted in Mountains, pictures, R, Statistics, Travel, University life with tags , , , , , , , , , , , , , , , , , , , , , on October 17, 2017 by xi'an

What a wonderful week at the Astrostat [Indian] summer school in Autrans! The setting was superb, on the high Vercors plateau overlooking both Grenoble [north] and Valence [west], with the colours of the Fall at their brightest on the foliage of the forests rising on both sides of the valley and a perfect green on the fields at the centre, with sun all along, sharp mornings and warm afternoons worthy of a late Indian summer, too many running trails [turning into X country ski trails in the Winter] to contemplate for a single week [even with three hours of running over two days], many climbing sites on the numerous chalk cliffs all around [but a single afternoon for that, more later in another post!]. And of course a group of participants eager to learn about Bayesian methodology and computational algorithms, from diverse [astronomy, cosmology and more] backgrounds, trainings and countries. I was surprised at the dedication of the participants travelling all the way from Chile, Péru, and Hong Kong for the sole purpose of attending the school. David van Dyk gave the first part of the school on Bayesian concepts and MCMC methods, Roberto Trotta the second part on Bayesian model choice and hierarchical models, and myself a third part on, surprise, surprise!, approximate Bayesian computation. Plus practicals on R.

As it happens Roberto had to cancel his participation and I turned for a session into Christian Roberto, presenting his slides in the most objective possible fashion!, as a significant part covered nested sampling and Savage-Dickey ratios, not exactly my favourites for estimating constants. David joked that he was considering postponing his flight to see me talk about these, but I hope I refrained from engaging into controversy and criticisms… If anything because this was not of interest for the participants. Indeed when I started presenting ABC through what I thought was a pedestrian example, namely Rasmus Baath’s socks, I found that the main concern was not running an MCMC sampler or a substitute ABC algorithm but rather an healthy questioning of the construction of the informative prior in that artificial setting, which made me quite glad I had planned to cover this example rather than an advanced model [as, e.g., one of those covered in the packages abc, abctools, or abcrf]. Because it generated those questions about the prior [why a Negative Binomial? why these hyperparameters? &tc.] and showed how programming ABC turned into a difficult exercise even in this toy setting. And while I wanted to give my usual warning about ABC model choice and argue for random forests as a summary selection tool, I feel I should have focussed instead on another example, as this exercise brings out so clearly the conceptual difficulties with what is taught. Making me quite sorry I had to leave one day earlier. [As did missing an extra run!] Coming back by train through the sunny and grape-covered slopes of Burgundy hills was an extra reward [and no one in the train commented about the local cheese travelling in my bag!]


Autrans, Vercors [jatp]

Posted in Mountains, pictures, Running, Travel with tags , , , , , , , on October 16, 2017 by xi'an