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 Learning Graphical Models


Reviews: Modeling Dynamic Missingness of Implicit Feedback for Recommendation

Neural Information Processing Systems

This paper presents H4MF model (HMM MF for dynamic Missingness) for implicit feedback data. With implicit data, we only observe positive feedback and the missing entries (zeros) in the data can indicate either negative feedback or users are not exposed of the items. H4MF is based on the previous work on modeling user latent exposure (ExpoMF, Liang et al., Modeling user exposure in recommendation, 2016) -- the basic idea is that for each user-item pair, there is a latent binary variable to represent exposure; if it's 1, it means this user is exposed to the item thus 0 feedback mean true negative, while if it's 0, it means this user have not yet been exposed to this item yet. The difference in H4MF is that H4MF uses a hidden Markov model to capture the temporal dynamics in the user exposure (user intent in this paper). The basic idea is that whether or not a user is exposed to something can be dependent on some other items he/she has been exposed before.


Reviews: A Probabilistic Framework for Nonlinearities in Stochastic Neural Networks

Neural Information Processing Systems

Overview: this paper introduces the Truncated Gaussian (TruG) unit (as per eq 1, and its expectation in eq 2). By adjusting the cutoffs \xi_1 and \xi_2 this can mimic ReLU and sigmoid/tanh units. It can be used as a stochastic unit in RBMs (sec 3), in temporal RBMs (sec 4), and in the TGGM (truncated Gaussian graphical model, sec 5). An old but relevant reference is "Continuous sigmoidal belief networks trained using slice sampling" B. J. Frey, in M. C. Mozer, M. I. Jordan and T. Petsche (eds), Advances in Neural Information Processing Systems 9, 452-459, January 1997. One might criticise this paper by saying that once one has come up with the TruG unit, one simply has to "turn the handle" on the usual derivations to get TruG-RBMs, temporal TruG-RBMs and TruG-TGGMs.


Reviews: Robust and Efficient Transfer Learning with Hidden Parameter Markov Decision Processes

Neural Information Processing Systems

Summary: This paper presents a new transfer learning approach using Bayesian Neural Network in MDPs. They are building on the existing framework of Hidden Parameter MDPs, and replace the Gaussian process with BNNs, thereby also modeling the joint uncertainty in the latent weights and the state space. Overall, this proposed approach is sound, well developed and seems to help scale the inference. The authors have also shown that it works well by applying it to multiple domains. The paper is extremely well written.


Reviews: Policy-Conditioned Uncertainty Sets for Robust Markov Decision Processes

Neural Information Processing Systems

The authors consider distributionally robust finite MDPs over a finite horizon. The transition probabilities conditionally to a state-action pair should remain at L1-bounded distance from a base measure, which is feasible as being generated using a given reference policy. This is a nice idea. A few comments are mentioned next. Related to that question, why the requirement of staying "close" to this policy would be beneficial.


Reviews: Bayesian Model Selection Approach to Boundary Detection with Non-Local Priors

Neural Information Processing Systems

Update: I downgrade my review to 5. The main concern is 1) Some more extensive simulations will make the results more convincing, as the numerical experiment is the only way to assess the performance of the proposed priors. It might take a major revision to reflect such comprehensive comparisons. With that being said, I believe the paper does contain interesting results that are novel and useful to the community. In particular, the theoretical results seem sound, and the paper is fairly readable. But I think there is also room for improvement.


Reviews: Multi-domain Causal Structure Learning in Linear Systems

Neural Information Processing Systems

The authors leverage on data recorded in multiple domains with changing parameters of a linear Gaussian models to learn causal direction and relations beyond Markov equivalence class. The paper is clearly written and includes good synthetic data simulations. The result is theoretically interesting. The method seems to need a lot of samples and domains that may not be available in real cases. The authors present different options to improve the methods in this respect.


Reviews: Inverse Filtering for Hidden Markov Models

Neural Information Processing Systems

The paper addresses recovery of the observation sequence given known posterior state estimates, but unknown observations and/or sensor model and also in an extension, noise-corrupted measurements. There is a nice progression of the problem through IP, LP, and MILP followed by a more careful analytical derivation of the answers in the noise-free case, and a seemingly approximate though empirically effective approach (cf. Honestly, most of the motivations seem to be unrealistic, especially the cyber-physical security setting where one does not observe posteriors, but simply an action based on a presumed argmax w.r.t. The EEG application (while somewhat narrow) seems to be the best motivation, however, the sole example is to compare resconstructed observations to a redundant method of sensing -- is this really a compelling application? Is it actually used in practice?


Reviews: Online Structure Learning for Feed-Forward and Recurrent Sum-Product Networks

Neural Information Processing Systems

This paper proposed an online learning algorithm for static and dynamic sum-product networks (SPNs), a type of probabilistic model with tractable inference. The authors essentially combine local structure search in SPNs with a hard variant of expectation-maximization [1]. The algorithm maintains empirical covariance estimates of product nodes and leverages statistical dependence tests to decide when to replace a product (factorized distribution) with either a new leaf or a mixture (sum node). The algorithm further includes a pruning mechanism in order to trim over-grown structures. The proposed method is called online Structure Learning with Running Average Update (oSLRAU).


Reviews: Learning Others' Intentional Models in Multi-Agent Settings Using Interactive POMDPs

Neural Information Processing Systems

The paper describes a sampling method for learning agent behaviors in interactive POMDPs (I-POMDPs). In general, I-POMDPs are a multi-agent POMDP model which, in addition to a belief about the environment state, the belief space includes nested recursive beliefs about the other agents' models. I-POMDP solutions, including the one proposed in the paper, largely approximate using a finite depth with either intentional models of others (e.g., their nested beliefs, state transitions, optimality criterion, etc.) or subintentional models of others (e.g., essentially "summaries of behavior" such as fictitious play). The proposed approach uses samples of the other agent at a particular depth to compute its values and policy. Related work on an interactive particle filter assumed the full frame was known (b, S, A, Omega, T, R, OC).


Reviews: Bayesian Adversarial Learning

Neural Information Processing Systems

This paper proposes a Bayesian model for adversarial learning problem. Empirical studies on Fashion-MINST and traffic sign recognition show that the proposed methods is slightly better than other adversarial learning baselines. Below I list my concerns about the paper: For modeling, 1. This paper ignore a highly relevant work'Bayesian GAN' [1]. The non-cooperative game between'data generator' and'learner' established in this paper is almost the same as the vanilla GAN.