Learning Graphical Models
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Rebuttal: thank you for your clarifications. I still think that learning kernel (parameters) from multiple realizations of a GP is not very novel in general, but sufficiently novel in your specific context to get discussed at NIPS. The authors use Gaussian processes to learn human function extrapolation behaviour from human sample data. After a comprehensive literature review, they introduce the main idea of the paper: learn the kernel parameters by maximizing the conditional probability of the extrapolation data given the training data. To allow for flexible kernel shapes, they use spectral mixture kernels.
Review for NeurIPS paper: Sample-Efficient Reinforcement Learning of Undercomplete POMDPs
Weaknesses: A few comments that are needed to be addressed: 1) The first comment is about the presentation of the derivations. There are steps in the appendix, and also in the main text that are skipped. Some of them took me a while to rederive, some I couldn't spend more time to rederive. Some steps are also taken as granted in the main text. It is useful to elaborate on them more.
Review for NeurIPS paper: A Matrix Chernoff Bound for Markov Chains and Its Application to Co-occurrence Matrices
Summary and Contributions: This paper establishes a concentration inequality in operator norm for the sample co-occurrence matrix C of a regular finite-state Markov chain. This is the matrix whose (i,j) entry counts the fraction of times states i and j co-occur within a time window of fixed size T, with a potential weighting by the difference of their occurrence times. The probability that C-E[C] exceeds eps is shown to be exponentially small in eps 2 * L, where L is the sample size (i.e. the total length of the chain). This concentration inequality is established as a corollary of a general result for the concentration of sample averages for a bounded symmetric-matrix-valued function applied to samples from an ergodic Markov chain. This general result is of independent interest.
Review for NeurIPS paper: A Matrix Chernoff Bound for Markov Chains and Its Application to Co-occurrence Matrices
This work tackles the problem of estimating the co-occurrence matrix of a Markov chain. The referees were unanimous in the assessment that this is a solid contribution, worthy of being accepted. The only reservations were some missing references in related work, which the authors agreed to discuss in the revision.
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The paper describes tricks to scale Bayesian network structure learning to thousands of variables. This is achieved by developing new heuristics for candidate parent set identification and the subsequent order based structure optimization. In general, the paper is clearly written and easy to read. There are issues in editing and style, but the problems do not affect readability (much). The suggested heuristics feel bit ad-hoc, thus the value of the work is eventually judged by empirical evaluation.
Review for NeurIPS paper: Replica-Exchange Nos\'e-Hoover Dynamics for Bayesian Learning on Large Datasets
Summary and Contributions: The paper considers the problem of sampling from the posterior distribution in Bayesian inference. To be more precise, the paper approaches the question of stochastic sampling that relies only on minibatches of data at each iteration. To achieve rapid mixing between isolated modes, the authors consider parallel tempered chains and introduce replica-exchange steps into the stochastic Nose-Hoover Dynamics. The crux of this approach is the stochastic test for the replica-exchange step. To develop such a test, the authors follow the paper [An efficient minibatch acceptance test for metropolis-hastings], which introduces the concept of correction distribution.
Review for NeurIPS paper: Replica-Exchange Nos\'e-Hoover Dynamics for Bayesian Learning on Large Datasets
The paper proposes a novel MCMC-type algorithm to perform Bayesian inference on large datasets. The paper is a mixture of replica exchange, Nose-Hoover dynamics and non-standard acceptance criterion to deal with mini-batches. All the reviewers participated actively to the discussion after the rebuttal was made available. Although all the ingredients of the proposed method do exist, their combination is original and potentially useful for the ML literature as pointed out by most reviewers. Theorem 2 is also neat and proposes a nice way to propose swaps between replicas using mini-batches.
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Summary: The paper proposes a novel approach to computationally efficient maximum likelihood learning in exponential families. In general, finding the maximum likelihood solution is intractable. From a convex optimization perspective, the sticking point is the need to calculate an integral wrt the currently proposed EF parameter. By assuming that MCMC is fast-mixing for all allowed parameters, the author(s) are able to show that the integrals needed for proximal gradient descent can be calculated with sufficient precision that, when combined with the results of Schmidt et al. (2011), a fully-polynomial randomized approximation scheme for calculating the MLE can be obtained. Both the convex and strongly convex cases are considered, which lead to different types of guarantees: the former on the likelihood error, the latter on the parameter error.
Robust Probabilistic Model Checking with Continuous Reward Domains
Ji, Xiaotong, Wang, Hanchun, Filieri, Antonio, Epifani, Ilenia
Probabilistic model checking traditionally verifies properties on the expected value of a measure of interest. This restriction may fail to capture the quality of service of a significant proportion of a system's runs, especially when the probability distribution of the measure of interest is poorly represented by its expected value due to heavy-tail behaviors or multiple modalities. Recent works inspired by distributional reinforcement learning use discrete histograms to approximate integer reward distribution, but they struggle with continuous reward space and present challenges in balancing accuracy and scalability. We propose a novel method for handling both continuous and discrete reward distributions in Discrete Time Markov Chains using moment matching with Erlang mixtures. By analytically deriving higher-order moments through Moment Generating Functions, our method approximates the reward distribution with theoretically bounded error while preserving the statistical properties of the true distribution. This detailed distributional insight enables the formulation and robust model checking of quality properties based on the entire reward distribution function, rather than restricting to its expected value. We include a theoretical foundation ensuring bounded approximation errors, along with an experimental evaluation demonstrating our method's accuracy and scalability in practical model-checking problems.
Student-t processes as infinite-width limits of posterior Bayesian neural networks
Caporali, Francesco, Favaro, Stefano, Trevisan, Dario
The asymptotic properties of Bayesian Neural Networks (BNNs) have been extensively studied, particularly regarding their approximations by Gaussian processes in the infinite-width limit. We extend these results by showing that posterior BNNs can be approximated by Student-t processes, which offer greater flexibility in modeling uncertainty. Specifically, we show that, if the parameters of a BNN follow a Gaussian prior distribution, and the variance of both the last hidden layer and the Gaussian likelihood function follows an Inverse-Gamma prior distribution, then the resulting posterior BNN converges to a Student-t process in the infinite-width limit. Our proof leverages the Wasserstein metric to establish control over the convergence rate of the Student-t process approximation.