Archive for the Mountains Category

no ISBA 2016 in Banff…

Posted in Mountains, pictures, Statistics, Travel, University life with tags , , , , , , , , , , , , on July 13, 2014 by xi'an

Banff west-northern range from Rundle, Sept. 10, 2010Alas, thrice alas, the bid we made right after the Banff workshop with Scott Schmidler, and Steve Scott for holding the next World ISBA Conference in 2016 in Banff, Canada was unsuccessful. This is a sad and unforeseen item of news as we thought Banff had a heap of enticing features as a dream location for the next meeting… Although I cannot reveal the location of the winner, I can mention it is much more traditional (in the sense of the Valencia meetings), i.e. much more mare than monti… Since it is in addition organised by friends and in a country I love, I do not feel particularly aggravated. Especially when considering we will not have to organise anything then!

voices – strange shores [book reviews]

Posted in Books, Mountains, Travel with tags , , , , , , on July 5, 2014 by xi'an

Following my recent trip to Iceland, I read two more books by Arnaldur Indriðason, Voices (Röddin, 2003) and Strange Shores (Furðustrandir, 2010).

As usual, Indriðason’s books are more about the past (of characters as well as of the whole country) than about current times. Voices does not switch from this pattern, the more because it is one of the earliest Inspector Erlendur’s books. Besides the murder of an hotel employee at the fringe of homelessness, lies the almost constant questioning in Indriðason’s books of the difficult or even impossible relations between parents and children and/or between siblings, and of the long-lasting consequences of this generation gap. The murder iitself is but a pretext to investigations on that theme and the murder resolution is far from the central point of the book. The story itself is thus less compelling than others I have read, maybe because the main character spends so much time closeted in his hotel room. But it nonetheless fits well within the Erlendur series. And although it is unrelated with the story, the cover reminded me very much of the Gullfoss waterfalls.

The second book, Strange Shores, is the farthest to a detective stories in the whole series. Indeed, Erlendur is back to his childhood cottage in Eastern Iceland, looking for a resolution of his childhood trauma, loosing his younger brother during a snowstorm. He also investigates another snowstorm disappearance, interrogating the few survivors and reluctant witnesses from that time. Outside any legal mandate. Sometimes very much outside! While the story is not completely plausible, both in the present and in the past, it remains a striking novel, even on its own. (Although it could read better after the earlier novels in the series.) Not only the resolution of the additional disappearance brings additional pain and no comfort to those involved, but the ending of Erlendur’s own quest is quite ambiguous. As the book reaches its final pages, I could not decide if he had reached redemption and deliverance and the potential to save his own children, or he was beyond redemption, reaching another circle of Hell. As explained by the author in an interview, this is intentional and not not the consequence of my poor understanding: ” Readers of Strange Shores are not quite certain what to make of the ending regarding Erlendur, and I’m quite happy to leave them in the dark!”. If the main character of this series focussing more on missing persons than on detective work, what’s next?!

 

R/Rmetrics in Paris [alas!]

Posted in Mountains, pictures, R, Statistics, Travel, University life with tags , , , , , , , , , , , , , , , , , , , on June 30, 2014 by xi'an

Bernard1Today I gave a talk on Bayesian model choice in a fabulous 13th Century former monastery in the Latin Quarter of Paris… It is the Collège des Bernardins, close to Jussieu and Collège de France, unbelievably hidden to the point I was not aware of its existence despite having studied and worked in Jussieu since 1982… I mixed my earlier San Antonio survey on importance sampling approximations to Bayes factors with an entry to our most recent work on ABC with random forests. This was the first talk of the 8th R/Rmetrics workshop taking place in Paris this year. (Rmetrics is aiming at aggregating R packages with econometrics and finance applications.) And I had a full hour and a half to deliver my lecture to the workshop audience. Nice place, nice people, new faces and topics (and even andouille de Vire for lunch!): why should I complain with an alas in the title?!Bernard2What happened is that the R/Rmetrics meetings have been till this year organised in Meielisalp, Switzerland. Which stands on top of Thuner See and… just next to the most famous peaks of the Bernese Alps! And that I had been invited last year but could not make it… Meaning I lost a genuine opportunity to climb one of my five dream routes, the Mittelegi ridge of the Eiger. As the future R/Rmetrics meetings will not take place there.

A lunch discussion at the workshop led me to experiment the compiler library in R, library that I was unaware of. The impact on the running time is obvious: recycling the fowler function from the last Le Monde puzzle,

> bowler=cmpfun(fowler)
> N=20;n=10;system.time(fowler(pred=N))
   user  system elapsed 
 52.647   0.076  56.332 
> N=20;n=10;system.time(bowler(pred=N))
   user  system elapsed 
 51.631   0.004  51.768 
> N=20;n=15;system.time(bowler(pred=N))
   user  system elapsed 
 51.924   0.024  52.429 
> N=20;n=15;system.time(fowler(pred=N))
   user  system elapsed 
 52.919   0.200  61.960 

shows a ten- to twenty-fold gain in system time, if not in elapsed time (re-alas!).

20,000 pink ladies [10k: 37'26", 43rd & 3rd V2]

Posted in Kids, Mountains, pictures, Running, Travel with tags , , , , , , , , on June 22, 2014 by xi'an

caen44

This year was a special year for the races of Les Courants de la Liberté, in Caen, as part of the celebrations of the 70th anniversary of the Allied landing on the nearby D-Day beaches. The number of women running the Rochambelle race/walk against breast cancer was raised this year to 20,000 participants, an impressive pink wave riding the streets of Caen, incl. my wife, mother and mother-in-law! And even one of the 1944 Rochambelle nurses attending the start and finish of the race!

While I had no particular expectation for the 10k race, it went on so well that I ended up with my best time ever on this distance (my previous record was in Ottawa in July…1989!). The weather was perfect, cool and cloudy with a tailwind most of the way. (The low intensity training in Edinburgh and the Highlands may have helped.) I had a bit of an issue at the beginning passing the first rows of runners who were clearly in the wrong league but stuck with a runner most of the race, which helped with the middle hardest k’s (with a maximal 3:58 on the 8th k!), and  finished by motivating another V2 to keep up with, very glad to see my finish time. I actually ended up 3rd V2 just ahead of two other runners from this category, but there is no podium or reward for this in this race, given the large number of races to accommodate (ultra-trail of D-Day beaches, marathon, half-marathon, 10k, rollers, kids,…)

DSC_3848

computational methods for statistical mechanics [day #4]

Posted in Mountains, pictures, Running, Statistics, Travel, University life with tags , , , , , , , , , , , , , , , , on June 7, 2014 by xi'an

Arthur Seat, Edinburgh, Sep. 7, 2011

My last day at this ICMS workshop on molecular simulation started [with a double loop of Arthur's Seat thankfully avoiding the heavy rains of the previous night and then] Chris Chipot‘s magistral entry to molecular simulation for proteins with impressive slides and simulation movies, even though I could not follow the details to really understand the simulation challenges therein, just catching a few connections with earlier talks. A typical example of a cross-disciplinary gap, where the other discipline always seems to be stressing the ‘wrong” aspects. Although this is perfectly unrealistic, it would immensely to prepare talks in pairs for such interdisciplinary workshops! Then Gersende Fort presented results about convergence and efficiency for the Wang-Landau algorithm. The idea is to find the optimal rate for updating the weights of the elements of the partition towards reaching the flat histogram in minimal time. Showing massive gains on toy examples. The next talk went back to molecular biology with Jérôme Hénin‘s presentation on improved adaptive biased sampling. With an exciting notion of orthogonality aiming at finding the slowest directions in the target and putting the computational effort. He also discussed the tension between long single simulations and short repeated ones, echoing a long-going debate in the MCMC community. (He also had a slide with a picture of my first 1983 Apple IIe computer!) Then Antonietta Mira gave a broad perspective on delayed rejection and zero variance estimates. With impressive variance reductions (although some physicists then asked for reduction of order 10¹⁰!). Johannes Zimmer gave a beautiful maths talk on the connection between particle and diffusion limits (PDEs) and Wasserstein geometry and large deviations. (I did not get most of the talk, but it was nonetheless beautiful!) Bert Kappen concluded the day (and the workshop for me) by a nice introduction to control theory. Making connection between optimal control and optimal importance sampling. Which made me idly think of the following problem: what if control cannot be completely… controlled and hence involves a stochastic part? Presumably of little interest as the control would then be on the parameters of the distribution of the control.

“The alanine dipeptide is the fruit fly of molecular simulation.”

The example of this alanine dipeptide molecule was so recurrent during the talks that it justified the above quote by Michael Allen. Not that I am more proficient in the point of studying this protein or using it as a benchmark. Or in identifying the specifics of the challenges of molecular dynamics simulation. Not a criticism of the ICMS workshop obviously, but rather of my congenital difficulty with continuous time processes!!! So I do not return from Edinburgh with a new research collaborative project in molecular dynamics (if with more traditional prospects), albeit with the perception that a minimal effort could bring me to breach the vocabulary barrier. And maybe consider ABC ventures in those (new) domains. (Although I fear my talk on ABC did not impact most of the audience!)

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