Archive for Mexico

BIRS in Granada

Posted in Mountains, pictures, Statistics, Travel, University life with tags , , , , , , , , , , , , , on November 8, 2021 by xi'an

Just heard that a new “branch” of BIRS was going to open in Granada, Spain! This is most exciting, given the (relative) proximity of Granada when compared with Banff and Oaxaca. And given the most enjoyable city, which I visited several times, esp. when George Casella was there for a year. And given the nearby mountain of Mulhacén.

The full IMAG opportunities will be made available through the BIRS call for proposals that will be issued in June 2022 for the 2024 program. However, we are currently planning a BIRS-IMAG pilot program to be hosted in Granada as early as 2023, and the BIRS Scientific Board will consider a limited number of workshops proposals for the 2023 cycle. Please write to the BIRS Scientific Director ( for further information, if you are interested in developing such a workshop.

a ghastly data visualisation

Posted in Books, pictures, Statistics with tags , , , , , , on August 15, 2021 by xi'an

stratified MCMC

Posted in Books, pictures, Statistics with tags , , , , , , , , , , , , on December 3, 2020 by xi'an

When working last week with a student, we came across [the slides of a talk at ICERM by Brian van Koten about] a stratified MCMC method whose core idea is to solve a eigenvector equation z’=z’F associated with the masses of “partition” functions Ψ evaluated at the target. (The arXived paper is also available since 2017 but I did not check it in more details.)Although the “partition” functions need to overlap for the matrix not to be diagonal (actually the only case that does not work is when these functions are truly indicator functions). As in other forms of stratified sampling, the practical difficulty is in picking the functions Ψ so that the evaluation of the terms of the matrix F is not overly impacted by the Monte Carlo error. If spending too much time in estimating these terms, there is not a clear gain in switching to stratified sampling, which may be why it is not particularly developed in the MCMC literature….

As an interesting aside, the illustration in this talk comes from the Mexican stamp thickness data I also used in my earlier mixture papers, concerning the 1872 Hidalgo issue that was printed on different qualities of paper. This makes the number k of components somewhat uncertain, although k=3 is sometimes used as a default. Hence a parameter and simulation space of dimension 8, even though the method is used toward approximating the marginal posteriors on the weights λ¹ and λ².

post-COVID post-conference mood

Posted in Kids, Running, Travel, University life with tags , , , , , , , , , , , , , on August 27, 2020 by xi'an

Nature ran a 4-page comment on the post-COVID future of massive conferences (NeurIPS or JSM style) and on how to make them less carbon greedy. Some of their common-sense suggestions come close to what I had suggested a while ago and some became promptly implemented in these times of COVID-19 travel restrictions, as, e.g., to systematically include virtual attendance option(s), with provisions from one’s institutions for quality time (as if one was indeed away), to add multiple (3?) regional hubs to a single location, which also offers the perk of a round-the-clock meeting, with an optimisation of the three places chosen to minimise (estimated) total flight distances for the potential participants, as in e.g. choosing U.S. central Chicago rather than extremes like Seattle or Miami, and possibly adding Tokyo and Paris, to reduce the frequency of the monster meetings by coordinating with sister societies, to enforce an individual or institutional maximum yearly budget, to have corporate sponsors turning from travel support to improving remote access in less favoured countries.

Obviously, it seems difficult to completely switch to a fully virtual solution, as attending a conference has many academic dimensions to be accounted for, but the “big ones” should be the first to shrink, if only because the most impacting. And also because small, high quality workshops have much more impact research-wise on their attendants. With the above still offering some savings. And also the possibility to bypass financial, personal, visa, political, life-threatening impossibilities to attend a meeting in a specific foreign country. Provided uncensored remote communication tools are allowed or possible from the said  country. (Calling for the question, barring financial difficulties, and once COVID-related restrictions have been lifted, what are the countries where everyone could consider attending?!)

This year, before lockdown forced the cancellation of ABC in Grenoble, we had set a mirror version in Warwick. Which led us to create the One World ABC seminar. The Bernoulli-IMS World congress was postponed by one year but a few dedicated volunteers managed to build within a few weeks a free impressive virtual substitute with more than 600 talks and close to 2000 participants (so far). Remember it is to take place on 24-28 August, on different time zones and with ten live plenaries repeated twice to this effect.

Next year, we still hope to organise an Objective Bayesian workshop at Casa Matemática Oaxaca (CMO) in México and the current sanitary conditions imply a reduction of the physically present participants by two thirds. Meaning for certain a remote component and possibly a mirror location depending on the state of the World in December 2021.

a memory called Empire [book review]

Posted in Books, Kids, pictures, Travel with tags , , , , , , , , , , , on June 6, 2020 by xi'an

A pleasant read for a few afternoon breaks (and vitamin D intake), that I chose as it was nominated for the Hugo and Nebula awards as well as a Not the Booker Prize Guardian choice. But not really worth the hype I think as the novel, A Memory Called Empire, is quite unidimensional (which is unfortunate for a space opera). In that the few characters that populate the book manage to move by themselves the political structure of the interstellar universe quite substantially. Within a few days. These characters are definitely attractive but somewhat too nice to be true and the way they bond and connect with one another is just implausible, even for a science fiction novel

“…no algorithm is innocent of its designersAn algorithm is only as perfect as the person designing it.”

The most interesting part in the story, although somewhat stretched too thin, is the conflict the central character feels between her attraction to the highly sophisticated culture of the Empire and the feeling that she will never be fully incorporated within that culture. Despite mastering the language and the societal codes well-enough to reach the upper spheres of society and impact them.

“…the real inspiration for the number-noun naming system comes from the naming practices of the Mixtec people of Oaxaca…” Arkady Martine

But, beside borrowing a lot to Japanese culture, and a wee bit to Maya or Aztec societies, the universe created by Arkady Martine is quite close to ours in its mundane aspects, including plastic spoons..! With very few truly novel technologies. But with email delivered on USB keys after travelling faster than light between star systems. The threat of an alien invasion is pending, by the end of the book, paving the way for an incoming second volume.To be read…

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