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 Statistical Learning





Efficient Learning by Directed Acyclic Graph For Resource Constrained Prediction

Neural Information Processing Systems

We study the problem of reducing test-time acquisition costs in classification systems. Our goal is to learn decision rules that adaptively select sensors for each example as necessary to make a confident prediction. We model our system as a directed acyclic graph (DAG) where internal nodes correspond to sensor subsets and decision functions at each node choose whether to acquire a new sensor or classify using the available measurements. This problem can be posed as an empirical risk minimization over training data. Rather than jointly optimizing such a highly coupled and non-convex problem over all decision nodes, we propose an efficient algorithm motivated by dynamic programming. We learn node policies in the DAG by reducing the global objective to a series of cost sensitive learning problems. Our approach is computationally efficient and has proven guarantees of convergence to the optimal system for a fixed architecture. In addition, we present an extension to map other budgeted learning problems with large number of sensors to our DAG architecture and demonstrate empirical performance exceeding state-of-the-art algorithms for data composed of both few and many sensors.



On the Power of Louvain for Graph Clustering Supplementary Material A The Stochastic Block Model and Definitions

Neural Information Processing Systems

In the following, we use X P to denote that the random variable X follows the law P . See Figure 1a for an illustration of such a graph generated by the Stochastic Block Model. Interestingly, Newman [31] has shown that the modularity objective is the maximum likelihood of a variant of the SBM on two communities, with prescribed degree distribution. However, it leaves the natural question open of whether the Louvain heuristic on the SBM with two communities indeed converges to this solution (the hidden partition). Proving the convergence shows that Louvain's local decisions can indeed be powerful enough to reach the global optimum.


On the Power of Louvain in the Stochastic Block Model Vincent Cohen-Addad

Neural Information Processing Systems

A classic problem in machine learning and data analysis is to partition the vertices of a network in such a way that vertices in the same set are densely connected and vertices in different sets are loosely connected. In practice, the most popular approaches rely on local search algorithms; not only for the ease of implementation and the efficiency, but also because of the accuracy of these methods on many real world graphs. For example, the Louvain algorithm - a local search based algorithm - has quickly become the method of choice for clustering in social networks.


Variational Dropout and the Local Reparameterization Trick

Neural Information Processing Systems

We investigate a local reparameterizaton technique for greatly reducing the variance of stochastic gradients for variational Bayesian inference (SGVB) of a posterior over model parameters, while retaining parallelizability. This local repa-rameterization translates uncertainty about global parameters into local noise that is independent across datapoints in the minibatch. Such parameterizations can be trivially parallelized and have variance that is inversely proportional to the mini-batch size, generally leading to much faster convergence. Additionally, we explore a connection with dropout: Gaussian dropout objectives correspond to SGVB with local reparameterization, a scale-invariant prior and proportionally fixed posterior variance. Our method allows inference of more flexibly parameterized posteriors; specifically, we propose variational dropout, a generalization of Gaussian dropout where the dropout rates are learned, often leading to better models. The method is demonstrated through several experiments.