Archive for Warwickshire

free fall [fake]

Posted in Mountains, pictures, Running, Travel with tags , , , , , , , , , , on January 12, 2019 by xi'an

As I was looking for the location of a picture serving as a background image for Windows 10 log-in page, I came across several versions of the above, supposedly showing a climber failing to grab another climber’s hand and as a result falling. Or “falling” as the image is obviously doctored, most likely by removing the ropes securing both climbers. This is fairly ridiculous, from the top climber hanging by his hand to the bottom one carrying quickdraws on his harness, as in the worst climbing movies… Still, I wish the location of the shot was provided on the website. (As an insider joke, I had a fall when running that was definitely not fake during the Xmas vacations, scraping a fair amount of skin on the gritty sidewalk, but with no apparent lasting damage, although I am barred from running by a tendinitis which started in Warwick last month..!)

Venus at dawn

Posted in pictures, Running, Travel with tags , , , , , , , on December 14, 2018 by xi'an

troubling trends in machine learning

Posted in Books, pictures, Running, Statistics, University life with tags , , , , , , , , , , , , , on July 25, 2018 by xi'an

This morning, in Coventry, while having an n-th cup of tea after a very early morning run (light comes early at this time of the year!), I spotted an intriguing title in the arXivals of the day, by Zachary Lipton and Jacob Steinhard. Addressing the academic shortcomings of machine learning papers. While I first thought little of the attempt to address poor scholarship in the machine learning literature, I read it with growing interest and, although I am pessimistic at the chances of inverting the trend, considering the relentless pace and massive production of the community, I consider the exercise worth conducting, if only to launch a debate on the excesses found in the literature.

“…desirable characteristics:  (i) provide intuition to aid the reader’s understanding, but clearly distinguish it from stronger conclusions supported by evidence; (ii) describe empirical investigations that consider and rule out alternative hypotheses; (iii) make clear the relationship between theoretical analysis and intuitive or empirical claims; and (iv) use language to empower the reader, choosing terminology to avoid misleading or unproven connotations, collisions with other definitions, or conflation with other related but distinct concepts”

The points made by the authors are (p.1)

  1. Failure to distinguish between explanation and speculation
  2. Failure to identify the sources of empirical gains
  3. Mathiness
  4. Misuse of language

Again, I had misgiving about point 3., but this is not an anti-maths argument, rather about the recourse to vaguely connected or oversold mathematical results as a way to support a method.

Most interestingly (and living dangerously!), the authors select specific papers to illustrate their point, picking from well-established authors and from their own papers, rather than from junior authors. And also include counter-examples of papers going the(ir) right way. Among the recommendations for emerging from the morass of poor scholarship papers, they suggest favouring critical writing and retrospective surveys (provided authors can be found for these!). And mention open reviews before I can mention these myself. One would think that published anonymous reviews are a step in the right direction, I would actually say that this should be the norm (plus or minus anonymity) for all journals or successors of journals (PCis coming strongly to mind). But requiring more work from the referees implies rewards for said referees, as done in some biology and hydrology journals I refereed for (and PCIs of course).

running by Kenilworth Castle [jatp]

Posted in Kids, pictures, Running, Travel with tags , , , , , , , , , , , , , on May 26, 2018 by xi'an

Last week, while in Warwick, I had a nice warm afternoon run around Kenilworth in the fields with Nick Tawn, who brought us to this view of the castle from the West, by a former shallow lake called The Mere [lexicographically connected with La Mare rather than with La Mer!]. It also exposed the fact that my first and only visit to the castle was in the summer of 1977, with my pen friend from Birmingham. This was also the summer when Star Wars was released in Britain, including Birmingham where we first saw it…

Warwick locks [jatp]

Posted in pictures, Running, Travel with tags , , , , , , , , , , , on May 20, 2018 by xi'an

amber warning

Posted in Statistics with tags , , , , , , on December 10, 2017 by xi'an

Just saw this severe Met warning of snow over Warwickshire and neighbouring counties… The campus is indeed covered with snow, but not that heavily. Yet. (It is comparatively mild in Austin, Texas, even though the icy wind turned my fingers to iciles during my morning run there!)

Amber warning of snow

From: 0810 on Sun 10 December
To: 1800 on Sun 10 December
Updated 6 hours ago Active

A spell of heavy snow is likely over parts of Wales, the Midlands and parts of Northern and Eastern England on Sunday.

Road, rail and air travel delays are likely, as well as stranding of vehicles and public transport cancellations. There is a good chance that some rural communities could become cut off.This is an update to extend the warning area as far south as Gloucestershire, Wiltshire, Oxfordshire, Buckinghamshire, Hertfordshire and Essex.

importance demarginalising

Posted in Books, Kids, pictures, Running, Statistics, Travel, University life with tags , , , , , on November 27, 2017 by xi'an

A question on X validated gave me minor thought fodder for my crisp pre-dawn run in Warwick the other week: if one wants to use importance sampling for a variable Y that has no closed form density, but can be expressed as the transform (marginal) of a vector of variables with closed form densities, then, for Monte Carlo approximations, the problem can be reformulated as the computation of an integral of a transform of the vector itself and the importance ratio is given by the ratio of the true density of the vector over the density of the simulated vector. No Jacobian involved.