dear me! [on strike]

air static

[On an Air France flight for Birmingham, two young French students apparently studying in Warwick kept blathering the entire time, with an utter lack of concern for their surroundings. Note: Les Marseillais is a particularly idiotic reality show on French TV.]

•  …j’ai arrêté de regarder les Marseillais, c’est même pas conscient, tu vois…
• …grave, c’est sûr, moi aussi j’ai arrêté, j’avais trop d’épisodes à rattraper…

The Terminal [#2]

For the third time within a year, I have been stuck in an airport hotel by missing a connection! This time on my way to Calgary, thanks to fog over Paris and Amsterdam. And to Air France refusing to switch me to an earlier flight from Paris. Not as strictly stuck as in Delhi, as I could get outside in a sort of no man’s land between runways and expressways, or even reach downtown Amsterdam by public transportation, but with 24 hours to wait for the next flight. The most frustrating part is missing the ice-climbing day I had organised in Banff…

travel madness

Certainly the 43 hours trip to San Francisco on Friday and Saturday was one of the worst travels I ever experienced as we were delayed, disembarked and left waiting in queues for most of two days. The August vacation peak weekend “coincided” with an Air France strike action by flight attendants and a correlated lack of ground personal in the airport. Rather than cancelling flights, Air France chose to downsize the number of passengers on board depending on the available flight attendants on that flight, which is presumably less expensive for the company. And so nice for the disembarked passengers, frequent fliers included. This was the Friday morning flight. We got rebooked to the Friday afternoon flight. Meaning six hours in the Air France lounge. After one hour delay, the afternoon flight rode for about 100 meters when leaking fuel was detected, apparently due to overfull tanks. Getting this sorted took around three hours, after which the captain told us that labour regulations prevented him and the crew to fly to San Francisco as it would be too long a working day. The whole plane was disembarked, which took another hour, to a transit area with hundred of people and no airline representative. Eventually someone from Air France appeared and started talking to people around rather than making a global announcement. Herding us back outside the restricted area with vague indications to get to another part of the terminal for rerouting. After more delays and chaos we ended up in another queue for hotel vouchers as the only choice was to wait for a specially chartered plane at noon the next day, our baggage being sealed and inaccessible. It took hours to get those vouchers and reach the airport hotel by midnight, before rushing back the next morn to another vaguely specified rendez-vous. This worked out more smoothly, except for another three hours delay waiting for enough flight attendants to show up.  This ruined our chances to get there in time to recover material for the race. Fortunately, our son managed to board an earlier plane [if last on board!] and grab it for us.

The worst thing about this [first world problem!] trip was not the strike or the cancellations, but the complete disorganisation of the management of the issues, with the passengers being herded from one place to another with contradictory items of information by clueless airline representatives. I figure this may be a consequence of the strike as well, the airport desks being poorly staffed for a major vacation weekend.  [Again, first world problem, no one was hurt and we just lost one vacation day. Plus the opportunity to write half a dozen posts.]

off to Northern California

Before attending MCqMC in Stanford in two weeks, I will take some vacations in Northern California [really North!] with my family. Starting with the San Francisco ½ marathon tomorrow. So expect delays [as we already got stuck six twenty-seven thirty hours in De Gaulle airport thanks to a strike!] and mostly non-statistical entries on the ‘Og. And pictures.

ISBA 2016 [#6]

Fifth and final day of ISBA 2016, which was as full and intense as the previous ones. (Or even more if taking into account the late evening social activities pursued by most participants.) First thing in the morning, I managed to get very close to a hill top, thanks to the hints provided by Jeff Miller!, and with no further scratches from the nasty local thorn bushes. And I was back with plenty of time for a Bayesian robustness session with great talks. (Session organised by Judith Rousseau whom I crossed while running, rushing to the airport thanks to an Air France last-minute cancellation.) First talk by James Watson (on his paper with Chris Holmes on Kullback neighbourhoods on priors that Judith and I discussed recently in Statistical Science). Then as a contrapunto Peter Grünwald gave a neat geometric motivation for possible misbehaviour of Bayesian inference in non-convex misspecified environments and discussed his SafeBayes resolution that weights down the likelihood. In a sort of PAC-Bayesian way. And Erlis Ruli presented the ABC-R approach he developed with Laura Ventura and Nicola Sartori based on M-estimators and score functions. Making wonder [idly, as usual] whether cumulating different M-estimators would make a difference in the performances of the ABC algorithm.

David Dunson delivered one of the plenary lectures on high-dimensional discrete parameter estimation, including for instance categorical data. This wide-range talk covered many aspects and papers of David’s work, including a use of tensors I had neither seen nor heard of before before. With sparse modelling to resist the combinatoric explosion of contingency tables. However, and you may blame my Gallic pessimistic daemon for this remark, I have trouble to picture the meaning and relevance of a joint distribution on a space of hundreds and hundreds of dimension and similarly the ability to check the adequacy of any modelling in terms of goodness of fit. For instance, to borrow a non-military example from David’s talk, handling genetic data on ACGT sequences to infer its distribution sounds unreasonable unless most of the bases are mono-allelic. And the only way I see to test the realism of a model in this framework would be to engineer realisations of this distribution to observe the outcome, a test that seems neither feasible not desirable. Prediction based on such models may obviously operate satisfactorily without such realism requirements.

My first afternoon session (after the ISBA assembly that announced the location of ISBA 2020 in Yunnan, China!, home of Pu’ Ehr tea) was about accelerated MCMC schemes with talks by Sanvesh Srivastava on divide-and-conquer MCMC using Wasserstein barycentres, already discussed here, Minsuk Shin on a faster stochastic search variable selection which I could not understand, and Alex Beskos on the extension of Giles’ multilevel Monte Carlo to MCMC settings, which sounded worth investigating further even though I did not follow the notion all the way through. After listening to Luke Bornn explaining how to recalibrate grid data for climate science by accounting for correlation (with the fun title of `lost moments’), I rushed to my rental to [help] cook dinner for friends and… the ISBA 2016 conference was over!

snapshot from Amiens [#1]