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Statistical Mechanics, Neural Networks, and Machine Learning

Directed vs. Undirected Graphs in NNs: The (Surprising!) Implications

Directed vs. Undirected Graphs in NNs: The (Surprising!) Implications

Most of us don’t always use graph language to describe neural networks, but if we dig into the implications of graph theory language, we get some surprising (and very useful) insights! We probably all know that a typical feedforward neural network can be described as a “directed graph.” Many of us also know that a restricted Boltzmann machine (RBM) is an “undirected graph.” In this little difference of terms, there is a wealth of meaning. Salakhutdinov, Mnih, and Hinton (2007;…

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Book Chapter: Draft Chapter 7 – The Boltzmann Machine

Book Chapter: Draft Chapter 7 – The Boltzmann Machine

Chapter 7: Energy-Based Neural Networks This is the full chapter draft from the book-in-progress, Statistical Mechanics, Neural Networks, and Artificial Intelligence. This chapter draft covers not only the Hopfield neural network (released as an excerpt last week), but also the Boltzmann machine, in both general and restricted forms. It deals with that form-equals-function connection, based on the energy equation. (However, we postpone the full-fledged learning method to a later chapter.) Get the pdf using the pdf link in the citation…

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Book Excerpt: Chapter 7

Book Excerpt: Chapter 7

Chapter 7: Energy-Based Neural Networks This is the first time that I’m sharing an excerpt from the book-in-progress, Statistical Mechanics, Neural Networks, and Artificial Intelligence. This excerpt covers the Hopfield neural network only; I’m still revising / editing / adding-to the remaining sections on the (general and restricted) Boltzmann machine. Get the pdf using the pdf link in the citation below: Maren, A.J. (In progress). Chapter 7: Introduction to Energy-Based Neural Networks: The Hopfield Network and the (Restricted) Boltzmann Machine…

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Book Progress

Book Progress

The Uber-Important Chapter 7 – Introduction to Energy-based Neural Networks:   I tell students that it’s like being on the Oregon Trail. All of the stochastic gradient-descent networks (up to and including Convolutional Neural Networks, or ConvNets, and Long Short-Term Memory networks, or LSTM networks) can be understood using backpropagation. This requires only that first-semester calculus background. Sure, grunting through the chain rule (many, many times) gets tedious. But it’s doable. In contrast, the energy-based networks are the heart and…

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Machine Learning: Multistage Boost Process

Machine Learning: Multistage Boost Process

Three Stages to Orbital Altitude in Machine Learning Several years ago, Regina Dugan (then Director of DARPA) gave a talk in which she showed a clip of epic NASA launch fails. Not just one, but many fails. The theme was that we had to risk failure in order to succeed with innovation. This YouTube vid of rocket launch failures isn’t the exact clip that she showed (the “action” doesn’t kick in for about a minute), but it’s pretty close. For…

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Neg-Log-Sum-Exponent-Neg-Energy – That’s the Easy Part!

Neg-Log-Sum-Exponent-Neg-Energy – That’s the Easy Part!

The Surprising (Hidden) “Gotcha” in This Energy Equation: A couple of days ago, I was doing one of my regular weekly online “Synch” sessions with my Deep Learning students. In a sort of “Beware, here there be dragons!” moment, I showed them this energy equation from the Hinton et al. (2012) Nature review paper on acoustic speech modeling: One of my students pointed out, “That equation looks kind of simple.” Well, he’s right. And I kind of bungled the answer,…

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Notational Frenzy

Notational Frenzy

When the Subtle Art of Mathematical Notation Defeats You (and How to Fight Back)   A couple of years ago, I was teaching Time Series and Forecasting for the first time. I didn’t know the subject – at all – but that didn’t bother me. Hey, it was mathematics, right? Anything that’s mathematical, I can eat for lunch, and then want some dessert-equations afterwards. First week, introducing the subject. That went fine. Second week, Simple Exponential Smoothing (SES). That’s simple….

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Seven Essential Machine Learning Equations: A Cribsheet (Really, the Précis)

Seven Essential Machine Learning Equations: A Cribsheet (Really, the Précis)

Making Machine Learning As Simple As Possible Albert Einstein is credited with saying, Everything should be made as simple as possible, but not simpler. Machine learning is not simple. In fact, once you get beyond the simple “building blocks” approach of stacking things higher and deeper (sometimes made all too easy with advanced deep learning packages), you are in the midst of some complex stuff. However, it does not need to be more complex than it has to be.  …

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A Tale of Two Probabilities

A Tale of Two Probabilities

Probabilities: Statistical Mechanics and Bayesian:   Machine learning fuses several different lines of thought, including statistical mechanics, Bayesian probability theory, and neural networks. There are two different ways of thinking about probability in machine learning; one comes from statistical mechanics, and the other from Bayesian logic. Both are important. They are also very different. While these two different ways of thinking about probability are usually very separate, they come together in some of the more advanced machine learning topics, such…

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The Statistical Mechanics Underpinnings of Machine Learning

The Statistical Mechanics Underpinnings of Machine Learning

Machine Learning Is Different Now:   Actually, machine learning is a continuation of what it always has been, which is deeply rooted in statistical physics (statistical mechanics). It’s just that there’s a culmination of insights that are now a very substantive body of work, with more theoretical rigor behind them than most of us know.     A Lesson from Mom: It takes a lot of time to learn a new discipline. This is something that I learned from my…

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