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 Uncertainty


Neural computation from first principles: Using the maximum entropy method to obtain an optimal bits-per-joule neuron

arXiv.org Machine Learning

Optimization results are one method for understanding neural computation from Nature's perspective and for defining the physical limits on neuron-like engineering. Earlier work looks at individual properties or performance criteria and occasionally a combination of two, such as energy and information. Here we make use of Jaynes' maximum entropy method and combine a larger set of constraints, possibly dimensionally distinct, each expressible as an expectation. The method identifies a likelihood-function and a sufficient statistic arising from each such optimization. This likelihood is a first-hitting time distribution in the exponential class. Particular constraint sets are identified that, from an optimal inference perspective, justify earlier neurocomputational models. Interactions between constraints, mediated through the inferred likelihood, restrict constraint-set parameterizations, e.g., the energy-budget limits estimation performance which, in turn, matches an axonal communication constraint. Such linkages are, for biologists, experimental predictions of the method. In addition to the related likelihood, at least one type of constraint set implies marginal distributions, and in this case, a Shannon bits/joule statement arises.


Deep generative models of genetic variation capture mutation effects

arXiv.org Machine Learning

The functions of proteins and RNAs are determined by a myriad of interactions between their constituent residues, but most quantitative models of how molecular phenotype depends on genotype must approximate this by simple additive effects. While recent models have relaxed this constraint to also account for pairwise interactions, these approaches do not provide a tractable path towards modeling higher-order dependencies. Here, we show how latent variable models with nonlinear dependencies can be applied to capture beyond-pairwise constraints in biomolecules. We present a new probabilistic model for sequence families, DeepSequence, that can predict the effects of mutations across a variety of deep mutational scanning experiments significantly better than site independent or pairwise models that are based on the same evolutionary data. The model, learned in an unsupervised manner solely from sequence information, is grounded with biologically motivated priors, reveals latent organization of sequence families, and can be used to extrapolate to new parts of sequence space.



Taming Wild High Dimensional Text Data with a Fuzzy Lash

arXiv.org Machine Learning

The bag of words (BOW) represents a corpus in a matrix whose elements are the frequency of words. However, each row in the matrix is a very high-dimensional sparse vector. Dimension reduction (DR) is a popular method to address sparsity and high-dimensionality issues. Among different strategies to develop DR method, Unsupervised Feature Transformation (UFT) is a popular strategy to map all words on a new basis to represent BOW. The recent increase of text data and its challenges imply that DR area still needs new perspectives. Although a wide range of methods based on the UFT strategy has been developed, the fuzzy approach has not been considered for DR based on this strategy. This research investigates the application of fuzzy clustering as a DR method based on the UFT strategy to collapse BOW matrix to provide a lower-dimensional representation of documents instead of the words in a corpus. The quantitative evaluation shows that fuzzy clustering produces superior performance and features to Principal Components Analysis (PCA) and Singular Value Decomposition (SVD), two popular DR methods based on the UFT strategy.


Realistic Traffic Generation for Web Robots

arXiv.org Machine Learning

Critical to evaluating the capacity, scalability, and availability of web systems are realistic web traffic generators. Web traffic generation is a classic research problem, no generator accounts for the characteristics of web robots or crawlers that are now the dominant source of traffic to a web server. Administrators are thus unable to test, stress, and evaluate how their systems perform in the face of ever increasing levels of web robot traffic. To resolve this problem, this paper introduces a novel approach to generate synthetic web robot traffic with high fidelity. It generates traffic that accounts for both the temporal and behavioral qualities of robot traffic by statistical and Bayesian models that are fitted to the properties of robot traffic seen in web logs from North America and Europe. We evaluate our traffic generator by comparing the characteristics of generated traffic to those of the original data. We look at session arrival rates, inter-arrival times and session lengths, comparing and contrasting them between generated and real traffic. Finally, we show that our generated traffic affects cache performance similarly to actual traffic, using the common LRU and LFU eviction policies.


Stan vs PyMc3 (vs Edward) – Towards Data Science

@machinelearnbot

The holy trinity when it comes to being Bayesian. I will provide my experience in using the first two packages and my high level opinion of the third (haven't used it in practice). Of course then there is the mad men (old professors who are becoming irrelevant) who actually do their own Gibbs sampling. You specify the generative model for the data. You feed in the data as observations and then it samples from the posterior of the data for you.


Stochastic Particle Gradient Descent for Infinite Ensembles

arXiv.org Machine Learning

The superior performance of ensemble methods with infinite models are well known. Most of these methods are based on optimization problems in infinite-dimensional spaces with some regularization, for instance, boosting methods and convex neural networks use $L^1$-regularization with the non-negative constraint. However, due to the difficulty of handling $L^1$-regularization, these problems require early stopping or a rough approximation to solve it inexactly. In this paper, we propose a new ensemble learning method that performs in a space of probability measures, that is, our method can handle the $L^1$-constraint and the non-negative constraint in a rigorous way. Such an optimization is realized by proposing a general purpose stochastic optimization method for learning probability measures via parameterization using transport maps on base models. As a result of running the method, a transport map to output an infinite ensemble is obtained, which forms a residual-type network. From the perspective of functional gradient methods, we give a convergence rate as fast as that of a stochastic optimization method for finite dimensional nonconvex problems. Moreover, we show an interior optimality property of a local optimality condition used in our analysis.


On Gaussian Markov models for conditional independence

arXiv.org Artificial Intelligence

Markov models, or probabilistic graphical models, explicitly establish a correspondence between statistical independence in a probability distribution and certain separation criteria holding in a graph. They were originated at the interface between statistics, where Markov random fields were predominant [Darroch et al., 1980], and artificial intelligence, with a focus on Bayesian networks [Pearl, 1985, 1986]. These two models are now considered the traditional ones, but still are widely applied and nowadays there is a significant amount of research devoted to them [Daly et al., 2011, Uhler, 2012]. They both share the modelling of conditional independences: Bayesian networks relate them with acyclic directed graphs, whereas in Markov fields they are associated with undirected graphs. However, the models they represent are only equivalent under additional assumptions on the respective graphs.



10 most impressive Research Papers around Artificial Intelligence

@machinelearnbot

Artificial Intelligence research advances are transforming technology as we know it. The AI research community is solving some of the most technology problems related to software and hardware infrastructure, theory and algorithms. Interestingly, the field of AI AI research has drawn acolytes from the non-tech field as well. Case in point -- prolific Hollywood actor Kristen Stewart's highly publicized paper on Artificial Intelligence, originally published at Cornell University library's open access site. Stewart co-authored the paper, titled "Bringing Impressionism to Life with Neural Style Transfer in Come Swim" with the American poet and literary critic David Shapiro and Adobe Research Engineer Bhautik Joshi.