Yann LeCun on Unsupervised Learning

This is a recent Yann LeCun talk at CMU. Toward the end he discusses recent breakthroughs using GANs (Generative Adversarial Networks, see also Ian Goodfellow here and here). LeCun tells an anecdote about the discovery of backpropagation. The first implementation of the algorithm didn’t work, probably because of a bug in the program. But they convinced …

More

Adventures with TeX Live

Since I use the Linux Mint operating system, the obvious (if not only) choice for a LaTeX distribution is TeX Live. (If you are not familiar with, or are not interested in, the LaTeX typesetting system, you have already read too far in this post.) On Mint, Ubuntu and other Debian-type operating systems, you typically …

More

Another Absolute Value Question

Someone asked whether it is possible to eliminate the absolute value from the constraint \(Lx\le |y| \le Ux\) (where \(L\ge 0\) and \(U>0\) are constants, \(x\) is a binary variable, and \(y\) is a continuous variable). The answer is yes, but what it takes depends on whether \(L=0\) or \(L>0\). The easy case is when …

More

Fischetti on Benders Decomposition

I just came across slides for a presentation that Matteo Fischetti (University of Padova) gave at the Lunteren Conference on the Mathematics of Operations Research a few days ago. Matteo is both expert at and dare I say an advocate of Benders decomposition. I use Benders decomposition (or variants of it) rather extensively in my …

More

Pro Bono Analytics Is Growing Social

Pro Bono Analytics is a program by INFORMS (the Institute for Operations Research and the Management Sciences, for the acronym-averse), “the largest society in the world for professionals in the field of operations research (O.R.), management science, and analytics”. PBA “connects our members and other analytics professionals with nonprofit organizations working in underserved and developing communities”. …

More

AlphaGo (BetaGo?) Returns

Rumors over the summer suggested that AlphaGo had some serious problems that needed to be fixed — i.e., whole lines of play that it pursued poorly, despite its thrashing of one of the world’s top players in a highly publicized match. But tuning a neural net is trickier than tuning, for example, an expert system …

More

Mapping Trackball Buttons

For years, I’ve used a Logitech M570 wireless trackball with my Linux Mint PC. I generally prefer trackballs to mice — no need to lift and reposition after a bunch of movement — and I find that using my thumb, rather than my index finger (or, if I’m in a bad mood, my middle finger) …

More

Mint Upgrade Woes

As I mentioned a couple of months ago, I upgraded a laptop from Linux Mint 17.3 (“Rebecca”) to 18.0 (“Sarah”) with minimal difficulties. My laptop serves as a guinea pig for these things. Once I’m sure things work fine on the laptop, I’ll consider upgrading my desktop as well. A few days ago I finally …

More

MIP Models in R with OMPR

A number of R libraries now exist for formulating and solving various types of mathematical programs in R (or formulating them in R and solving them with external solvers). For a comprehensive listing, see the Optimization and Mathematical Programming task view on CRAN. I decided to experiment with Dirk Schumacher’s OMPR package for R. OMPR …

More

Mint Upgrade Problem Solved

I decided to upgrade first my laptop (the canary in the mine shaft), then my desktop (assuming the canary lived), from Linux Mint 17.3 (“Rebecca”) to 18.0 (“Sarah”). The “old school” approach would be to download the distribution to a CD/DVD, or create a bootable version on a USB stick, test it and then install …

More

AI, Westworld, and Electric Sheep

AI, Westworld, and Electric Sheep I’m holding off on this in favor of a big binge watch. Certain AI-related themes have been treated again and again in movies ranging from Blade Runner to the recent Ex Machina (see also this episode of Black Mirror, with Jon Hamm). These artistic explorations help ordinary people think through …

More

DNS on Home WiFi

DNS on Home WiFi Like a lot of people, I have a home WiFi network, and I recently changed my Internet service provider. That required replacing my cable modem. Both the old and new modems provided a DHCP service that doled out local IP addresses to devices connecting to the home WiFi network. Both modems …

More

Better Estimate, Worse Result

I thought I might use a few graphs to help explain an answer I posted on Quora recently. First, I’ll repeat the question here: In parametric optimization with unknown parameters, does a better estimator of the parameter always lead to better solutions to the actual problem? Here we’re trying to minimize f(x,θ) with respect to …

More

Formatting in a Shiny App

I’ve been updating a Shiny (web-based interactive R) application, during the course of which I needed to make a couple of cosmetic fixes. Both proved to be oddly difficult. Extensive use of Google (I think I melted one of their cloud servers) eventually turned up enough clues to get both done. I’m going to record …

More

Some R Resources

(Should I have spelled the last word in the title “ResouRces” or “resouRces”? The R community has a bit of a fascination about capitalizing the letter “r” as often as possible.) Anyway, getting down to business, I thought I’d post links to a few resources related to the R statistical language/system/ecology that I think may …

More

Connecting Bluetooth Headphones

I recently picked up a pair of Bluetooth headphones (Mixcder ShareMe 7) for use with my laptop (which runs Linux Mint). Getting them to connect properly was a bit of an adventure. After I had things (mostly) sorted out, I decided to script the steps necessary to get them working so that I could just …

More

Finding the Kernel of a Matrix

I’m working on an optimization problem (coding in Java) in which, should various celestial bodies align the wrong way, I may need to compute the rank of a real matrix and, if it’s less than full rank, a basis for its kernel. (Actually, I could get by with just one nonzero vector in the kernel, …

More

Enforcing Simultaneous Arrivals

I’m recapping here an answer to a modeling question that I just posted on a help forum. (Since it will now appear in two different places, let’s hope it’s correct!) The original poster (OP) was working on a routing model, in which vehicles (for which I will use and if needed as indices) are assigned …

More

MathJax Whiplash

Technology is continuously evolving, and for the most part that’s good. Every now and then, though, the evolution starts to look like a random mutation … the kind that results in an apocalyptic virus, or mutants with superpowers, or something else that is much more appealing as a plot device in a movie or TV …

More

Using CLP with Java

The COIN-OR project provides a home to a number of open source software projects useful in operations research, primarily optimization programs and libraries. Possibly the most “senior” of these projects is CLP, a single-threaded linear program solver. Quoting the project description: CLP is a high quality open-source LP solver. Its main strengths are its Dual …

More

Java “Deep Learning” Library

If you are a Java (or Scala) (or maybe Clojure?) programmer interested in analytics, and in particular machine learning, you should take a look at Deeplearning4j (DL4J). Quoting their web site: Deeplearning4j is the first commercial-grade, open-source, distributed deep-learning library written for Java and Scala. Integrated with Hadoop and Spark, DL4J is designed to be …

More

Accessing R Objects By Name

At a recent R user group meeting, the discussion at one point focused on two of the possibly lesser known (or lesser appreciated?) functions in the base package: get and assign. The former takes a string argument and fetches the object whose name is contained in the string. The latter does the opposite, assigning an …

More

The story of the Monte Carlo Algorithm

George Dyson is Freeman’s son. I believe this talk was given at SciFoo or Foo Camp. More Ulam (neither he nor von Neumann were really logicians, at least not primarily). Wikipedia on Monte Carlo Methods. I first learned these in Caltech’s Physics 129: Mathematical Methods, which used the textbook by Mathews and Walker. This book was …

More

SOLVED: Problem with Impressive

I’ve written before (here and here) about using the open-source Impressive program to display PDF presentations. It’s been quite a while since I used it, or any other presentation software for that matter — retired geezers don’t do a lot of presenting — but I’ll be helping the INFORMS Student Chapter at the University of …

More

Tale of the Loose Cable

Friday I used my laptop (Acer Aspire V5-131, Linux Mint 17.3) at a coffee shop with no problems. Saturday it wouldn’t boot. The specific error message was: Broadcom UNDI PXE2.1 v15.0.1 <blah blah blah> PXE-E61: Media test failure, check cable PXE-M0F: Exiting Broadcom PXE ROM No bootable device — insert boot disk and press any …

More

Moore’s Law and AI

By now you’ve probably heard that Moore’s Law is really dead. So dead that the semiconductor industry roadmap for keeping it on track has more or less been abandoned: see, e.g., here, here or here. (Reported on this blog 2 years ago!) What I have not yet seen discussed is how a significantly reduced rate …

More

DeepMind and Demis Hassabis

Recent profile in the Guardian; 15 facts about Hassabis. The mastery of Atari games through reinforcement learning deep neural nets is described here (Nature). See also Deep Neural Nets and Go: AlphaGo beats European champion. Guardian: … “We’re really lucky,” says Hassabis, who compares his company to the Apollo programme and Manhattan Project for both …

More

Oracle Java 8 Update

For quite a while, I was getting security nags from Firefox every time a web site wanted to run a Java applet. Firefox would tell me I needed to upgrade to the latest version of Java. That would have been fine, except that I was already running the latest Java (1.8.0_66 as of this writing). …

More