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Optimization Functions in Julia

Update 10/30/2013: Since this post was written, Julia has acquired a large body of optimization tools, which have been grouped under the heading of JuliaOpt. Over the last few weeks, I’ve made a concerted effort to develop a basic suite of optimization algorithms for Julia so that Matlab programmers used to using fminunc() and R programmers used to using optim() can start to transition code over to Julia that requires access to simple optimization algorithms like L-BFGS and the Nelder-Mead method.

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A Gentle Introduction to Optimal Power Flow

In an earlier blog post, we discussed the power flow problem, which serves as the key component of a much more challenging task: the optimal power flow (OPF). OPF is an umbrella term that covers a wide range of constrained optimization problems, the most important ingredients of which are: variables that optimize an objective function, some equality constraints, including the power balance and power flow equations, and inequality constraints, including bounds on the variables. The sets of variables and constraints, as well as the form of the objective, will vary depending on the type of OPF.

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Training a random Gaussian generator

I’ve spent the last couple of months tackling the problem of designing an algorithm to rapidly generate high-quality normally-distributed pseudorandom numbers on a GPU. Whilst this may seem q…

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Relative strength - Wilks, IPF GL and allometry

In powerlifting, formulas are used to assess and compare lifters with different body weights. In this article we evaluate two such formulas: Wilks and IPF GL. Then we generalize them and propose an alternative. We also create a formula that accounts for age and training experience.

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Experiments in Supervised Learning Part 4

This article discusses speeding up ML training loops by caching serialized features to reduce repeated data processing time. It covers loading cached features, memory profiling, and evaluating a Logistic Regression model with performance…

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Convolutional neural networks for artistic style transfer

There’s an amazing app out right now called Prisma that transforms your photos into works of art using the styles of famous artwork and motifs. The app performs this style transfer with the help of a branch of machine learning called convolutional neural networks. In this article we’re going to take a journey through the world of convolutional neural networks from theory to practice, as we systematically reproduce Prisma’s core visual effect.

Anatomy of a Probabilistic Programming Framework

Recently, the PyMC4 developers submitted an abstract to the Program Transformations for Machine Learning NeurIPS workshop. I realized that despite knowing a thing or two about Bayesian modelling, I don’t understand how probabilistic programming frameworks are structured, and therefore couldn’t appreciate the sophisticated design work going into PyMC4. So I trawled through papers, documentation and source code1 of various open-source probabilistic programming frameworks, and this is what I’ve managed to take away from it.

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