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Empowerment -- an Introduction
Salge, Christoph, Glackin, Cornelius, Polani, Daniel
This book chapter is an introduction to and an overview of the information-theoretic, task independent utility function "Empowerment", which is defined as the channel capacity between an agent's actions and an agent's sensors. It quantifies how much influence and control an agent has over the world it can perceive. This book chapter discusses the general idea behind empowerment as an intrinsic motivation and showcases several previous applications of empowerment to demonstrate how empowerment can be applied to different sensor-motor configuration, and how the same formalism can lead to different observed behaviors. Furthermore, we also present a fast approximation for empowerment in the continuous domain.
Distributed Coordinate Descent Method for Learning with Big Data
Richtárik, Peter, Takáč, Martin
In this paper we develop and analyze Hydra: HYbriD cooRdinAte descent method for solving loss minimization problems with big data. We initially partition the coordinates (features) and assign each partition to a different node of a cluster. At every iteration, each node picks a random subset of the coordinates from those it owns, independently from the other computers, and in parallel computes and applies updates to the selected coordinates based on a simple closed-form formula. We give bounds on the number of iterations sufficient to approximately solve the problem with high probability, and show how it depends on the data and on the partitioning. We perform numerical experiments with a LASSO instance described by a 3TB matrix.
Accelerated Proximal Stochastic Dual Coordinate Ascent for Regularized Loss Minimization
Shalev-Shwartz, Shai, Zhang, Tong
We introduce a proximal version of the stochastic dual coordinate ascent method and show how to accelerate the method using an inner-outer iteration procedure. We analyze the runtime of the framework and obtain rates that improve state-of-the-art results for various key machine learning optimization problems including SVM, logistic regression, ridge regression, Lasso, and multiclass SVM. Experiments validate our theoretical findings.
A short note on the axiomatic requirements of uncertainty measure
In this note, we argue that the axiomatic requirement of range to the measure of aggregated total uncertainty (ATU) in Dempster-Shafer theory is not reasonable. Keywords: Dempster-Shafer theory, Uncertainty measure Dempster-Shafer theory [1, 2] is widely applied to uncertainty modeling [3, 4]. Two types of uncertainty, namely nonspecificity and discord, are coexisting in the Dempster-Shafer theory [5, 6]. A justifiable measure to these uncertainty is necessary to describe the essential characters of basic probability assignment function(BPA). To be justifiable, for a measure called as aggregated total uncertainty (ATU), some requirements are necessary.
Double four-bar crank-slider mechanism dynamic balancing by meta-heuristic algorithms
Emdadi, Habib, Yazdanian, Mahsa, Ettefagh, Mir Mohammad, Feizi-Derakhshi, Mohammad-Reza
In this paper, a new method for dynamic balancing of double four-bar crank slider mechanism by meta- heuristic-based optimization algorithms is proposed. For this purpose, a proper objective function which is necessary for balancing of this mechanism and corresponding constraints has been obtained by dynamic modeling of the mechanism. Then PSO, ABC, BGA and HGAPSO algorithms have been applied for minimizing the defined cost function in optimization step. The optimization results have been studied completely by extracting the cost function, fitness, convergence speed and runtime values of applied algorithms. It has been shown that PSO and ABC are more efficient than BGA and HGAPSO in terms of convergence speed and result quality. Also, a laboratory scale experimental doublefour-bar crank-slider mechanism was provided for validating the proposed balancing method practically.
Discriminative Features via Generalized Eigenvectors
Karampatziakis, Nikos, Mineiro, Paul
Representing examples in a way that is compatible with the underlying classifier can greatly enhance the performance of a learning system. In this paper we investigate scalable techniques for inducing discriminative features by taking advantage of simple second order structure in the data. We focus on multiclass classification and show that features extracted from the generalized eigenvectors of the class conditional second moments lead to classifiers with excellent empirical performance. Moreover, these features have attractive theoretical properties, such as inducing representations that are invariant to linear transformations of the input. We evaluate classifiers built from these features on three different tasks, obtaining state of the art results.
Generalized Negative Binomial Processes and the Representation of Cluster Structures
The paper introduces the concept of a cluster structure to define a joint distribution of the sample size and its exchangeable random partitions. The cluster structure allows the probability distribution of the random partitions of a subset of the sample to be dependent on the sample size, a feature not presented in a partition structure. A generalized negative binomial process count-mixture model is proposed to generate a cluster structure, where in the prior the number of clusters is finite and Poisson distributed and the cluster sizes follow a truncated negative binomial distribution. The number and sizes of clusters can be controlled to exhibit distinct asymptotic behaviors. Unique model properties are illustrated with example clustering results using a generalized Polya urn sampling scheme. The paper provides new methods to generate exchangeable random partitions and to control both the cluster-number and cluster-size distributions.
Fast and Robust Recursive Algorithms for Separable Nonnegative Matrix Factorization
Gillis, Nicolas, Vavasis, Stephen A.
A hyperspectral image consists of a set of images taken at different wavelengths. It is acquired by measuring the spectral signature of each pixel present in the scene, that is, by measuring the reflectance (the fraction of the incident electromagnetic power that is reflected by a surface at a given wavelength) of each pixel at different wavelengths. One of the most important tasks in hyperspectral imaging is called unmixing. It requires the identification of the constitutive materials present in the image and estimation of their abundances in each pixel. The most widely used model is the linear mixing model: the spectral signature of each pixel results from the additive linear combination of the spectral signatures of the constitutive materials, called endmembers, where the weights of the linear combination correspond to the abundances of the different endmembers in that pixel.
Laplace approximation for logistic Gaussian process density estimation and regression
Riihimäki, Jaakko, Vehtari, Aki
Logistic Gaussian process (LGP) priors provide a flexible alternative for modelling unknown densities. The smoothness properties of the density estimates can be controlled through the prior covariance structure of the LGP, but the challenge is the analytically intractable inference. In this paper, we present approximate Bayesian inference for LGP density estimation in a grid using Laplace's method to integrate over the non-Gaussian posterior distribution of latent function values and to determine the covariance function parameters with type-II maximum a posteriori (MAP) estimation. We demonstrate that Laplace's method with MAP is sufficiently fast for practical interactive visualisation of 1D and 2D densities. Our experiments with simulated and real 1D data sets show that the estimation accuracy is close to a Markov chain Monte Carlo approximation and state-of-the-art hierarchical infinite Gaussian mixture models. We also construct a reduced-rank approximation to speed up the computations for dense 2D grids, and demonstrate density regression with the proposed Laplace approach.
Bayesian Optimization With Censored Response Data
Hutter, Frank, Hoos, Holger, Leyton-Brown, Kevin
Bayesian optimization (BO) aims to minimize a given blackbox function using a model that is updated whenever new evidence about the function becomes available. Here, we address the problem of BO under partially right-censored response data, where in some evaluations we only obtain a lower bound on the function value. The ability to handle such response data allows us to adaptively censor costly function evaluations in minimization problems where the cost of a function evaluation corresponds to the function value. One important application giving rise to such censored data is the runtime-minimizing variant of the algorithm configuration problem: finding settings of a given parametric algorithm that minimize the runtime required for solving problem instances from a given distribution. We demonstrate that terminating slow algorithm runs prematurely and handling the resulting right-censored observations can substantially improve the state of the art in model-based algorithm configuration.