Archive for Canadian Rockies
And another exciting and animated [last] day of ABC’ory [and practice]! Kyle Cranmer exposed a density ratio density estimation approach I had not seen before [and will comment here soon]. Patrick Muchmore talked about unbiased estimators of Gaussian and non-Gaussian densities in elliptically contoured distributions which allows for running pseudo-MCMC than ABC. This reminded me of using the same tool [for those distributions can be expressed as mixtures of normals] in my PhD thesis, if for completely different purposes. In his talk, including a presentation of an ABC blackbox platform called ELFI, Samuel Kaski did translate statistical inference as inverse reinforcement learning: I hope this does not catch! In the afternoon, Dennis Prangle gave us the intuition behind his rare event ABC, which is not estimating rare events by ABC but rather using rare event simulation to improve ABC. [A paper I will a.s. comment here soon as well!] And Scott Sisson concluded the day and the week with his views on ABC for high dimensions.
While being obviously biased as the organiser of the workshop, I nonetheless feel it was a wonderful meeting with just the right number of participants to induce interactions and discussions during and around the talk, as well as preserve some time for pairwise interactions. Like all other workshops I contributed to in BIRS along the years
|07w5079||2007-07-01||Bioinformatics, Genetics and Stochastic Computation: Bridging the Gap|
|10w2170||2010-09-10||Hierarchical Bayesian Methods in Ecology|
|14w5125||2014-03-02||Advances in Scalable Bayesian Computation|
this is certainly a highly profitable one! For a [major] change, the next one [18w5023] will take place in Oaxaca, Mexico, and will see computational statistics meet molecular simulation. [As an aside, here are the first and last slides of Ewan Cameron’s talk, appropriately illustrating beginning and end, for both themes of his talk: epidemiology and astronomy!]
Another great day of talks and discussions at BIRS! Continuing on the themes of the workshop between delving into the further validation of those approximation techniques and the devising of ever more approximate solutions for ever more complex problems. Among the points that came clearer to me through discussion, a realisation that the synthetic likelihood perspective is not that far away from our assumptions in the consistency paper. And that a logistic version of the approach can be constructed as well. A notion I had not met before (or have forgotten I had met) is the one of early rejection ABC, which should actually be investigated more thoroughly as it should bring considerable improvement in computing time (with the caveats of calibrating the acceptance step before producing the learning sample and of characterising the output). Both Jukka Corander and Ewan Cameron reminded us of the case of models that take minutes or hours to produce one single dataset. (In his talk on some challenging applications, Jukka Corander chose to move from socks to boots!) And Jean-Michel Marin produced an illuminating if sobering experiment on the lack of proper Bayesian coverage by ABC solutions. (It appears that Ewan’s video includes a long empty moment when we went out for the traditional group photo, missing the end of his talk.)
My daughter sort of dragged me to watch The Revenant as it just came out in French cinemas and I reluctantly agreed as I had read about magnificent winter and mountain sceneries, shot in an unusually wide format with real light. And indeed the landscape and background of the entire movie are magnificent, mostly shot in the Canadian Rockies, around Kananaskis and Canmore, which is on the way to Banff. (Plus a bit in Squamish rain forest.) The story is however quite a disappointment as it piles up one suspension of disbelief after another. This is a tale of survival (as I presume everyone knows!) but so implausible as to cancel any appreciation of the film. It may be the director Iñárritu is more interested in a sort of new age symbolism than realism, since there are many oniric passages with floating characters and falling meteors, desecrated churches and pyramids of bones, while the soundtrack often brings in surreal sounds, but the impossible survival of Hugh Glass made me focus more and more on the scenery… While the true Hugh Glass did manage to survive on his own, fixing his broken leg, scrawling to a river, and making a raft that brought him to a fort downstream, [warning, potential spoilers ahead!] the central character in the movie takes it to a fantasy level as he escapes hypothermia while swimming in freezing rapids, drowning while wearing a brand new bearskin, toxocariasis while eating raw liver, bullets when fleeing from both Araka Indians and French (from France, Louisiana, or Québec???) trappers, a 30 meter fall from a cliff with not enough snow at the bottom to make a dent on, subzero temperatures while sleeping inside a horse carcass [and getting out of it next morning when it should be frozen solid], massive festering bone-deep wounds, and the deadly Midwestern winter… Not to mention the ability of make fire out of nothing in the worst possible weather conditions or to fire arrows killing men on the spot or to keep a never ending reserve of bullets. And while I am at it, the ability to understand others: I had trouble even with the French speaking characters, despite their rather modern French accent!