Uncertainty
Bayesian Inference of Temporal Task Specifications from Demonstrations
When observing task demonstrations, human apprentices are able to identify whether a given task is executed correctly long before they gain expertise in actually performing that task. Prior research into learning from demonstrations (LfD) has failed to capture this notion of the acceptability of an execution; meanwhile, temporal logics provide a flexible language for expressing task specifications. Inspired by this, we present Bayesian specification inference, a probabilistic model for inferring task specification as a temporal logic formula. We incorporate methods from probabilistic programming to define our priors, along with a domain-independent likelihood function to enable sampling-based inference. We demonstrate the efficacy of our model for inferring true specifications with over 90% similarity between the inferred specification and the ground truth, both within a synthetic domain and a real-world table setting task.
Reviews: Model-based Bayesian inference of neural activity and connectivity from all-optical interrogation of a neural circuit
This papers proposes an inference method of (biological) neural connectivity from fluorescence (calcium) traces. The model includes the spiking model (GLM low-rank factor) with an external input (optical stimulation) and a fluorescence model. The inference methods is based on variational Bayes, where the approximate posterior is modeled using a neural network. Novelty and originality: The methods in this paper are adequately novel and original, nicely combining various elements from previous work. Technical issues: My main problem with this paper is that I can't really be sure that the proposed method is actually working well. It is very good that the authors tested their method on real data, but since there is no ground truth, I it is hard to estimate the quality of the inferred weights (see footnote (1) below).
Reviews: Convergence rates of a partition based Bayesian multivariate density estimation method
Note: Below, I use [#M] for references in the main paper and [#S] for references in the supplement, since these are indexed differently. Summary: This paper proposes and analyzes a Bayesian approach to nonparametric density estimation. The proposed method is based on approximation by piecewise-constant functions over a binary partitioning of the unit cube, using a prior that decays with the size of the partition. The posterior distribution of the density is shown to concentrate around the true density f_0, at a rate depending on the smoothness r of f_0, a measure in terms of how well f_0 can be approximated by piecewise-constant functions over binary partitionings. Interestingly, the method automatically adapts to unknown r, and r can be related to more standard measures of smoothness, such as Holder continuity, bounded variation, and decay rate of Haar basis coefficients.
Reviews: A Learning Error Analysis for Structured Prediction with Approximate Inference
This paper is on the important topic of learning with approximate inference. Previous work, e.g., Kulesza and Pereira (2007), has demonstrated the importance of matching parameter update rules and inference approximation methods. This paper presents a new update rule based on PAC Bayes bounds, which is fairly agnostic to the inference algorithm used -- it assumes a multiplicative error bound on model score and supports both over and under approximations. The example given in section 3.2 is a great illustration of how approximation error is more subtle than we might think it is. Sometimes an approximate predictor can fit the training data better because it represents a different family of functions!
Reviews: Differentially private Bayesian learning on distributed data
Title: Differentially private Bayesian learning on distributed data Comments: - This paper develops a method for differential privacy (DP) Bayesian learning in a distributed setting, where data is split up over multiple clients. This differs from the traditional DP Bayesian learning setting, in which a single party has access to the full dataset. The main issue here is that performing DP methods separately on each client would yield too much noise; the goal is then to find a way to add an appropriate amount of noise, without compromising privacy, in this setting. To solve this, the authors introduce a method that combines existing DP Bayesian learning methods with a secure multi-party communication method called the DCA algorithm. Theoretically, this paper shows that the method satisfies differential privacy.
Reviews: Thermostat-assisted continuously-tempered Hamiltonian Monte Carlo for Bayesian learning
This paper presents a sampling method that combines Hamiltonian Monte Carlo (HMC), mini-batches, tempering, and thermostats, to more efficiently explore multimodal target distributions. It is demonstrated on a number of substantial neural network problems using real data sets. This is an interesting method, and the empirical results are quite substantial. Figure 2 does a nice job of demonstrating how the omission of any of the ingredients (e.g. the tempering, or the thermostat) is detrimental to the overall result, which is a nice illustration of how the combination works together well. This is followed by some substantial image classification examples.
Reviews: Inference Aided Reinforcement Learning for Incentive Mechanism Design in Crowdsourcing
Summary: In this paper, the authors explore the problem of data collecting using crowdsourcing. In the setting of the paper, each task is a labeling task with binary labels, and workers are strategic in choosing effort levels and reporting strategies that maximize their utility. The true label for each task and workers' parameters are all unknown to the requester. The requester's goal is to learn how to decide the payment and how to aggregate the collected labels by learning from workers' past answers. The authors' proposed approach is a combination of incentive design, Bayesian inference, and reinforcement learning.
Reviews: Policy Gradient With Value Function Approximation For Collective Multiagent Planning
The paper presents a policy gradient algorithm for a multiagent cooperative problem, modeled in a formalism (CDEC-POMDP) whose dynamics, like congestion games, depend on groups of agents rather than individuals. This paper follows the theme of several similar advances in theis field of complex multiagent planning, using factored models to propose practical/tractable approximations. The novelty here is the use of parameterized policies and training algorithms inspired by reinforcement learning (policy gradients). The work is well-motivated, relevant, and particularly well-presented. The theoretical results are new and important.
Reviews: Bayesian Model-Agnostic Meta-Learning
Summary: Meta-learning is motivated by the promise of being able to transfer knowledge from previous learning experiences to new task settings, such that a new task can be learned more effectively from few observations. Yet, updating highly parametric models with little amounts of data can easily lead to overfitting. A promising avenue towards overcoming this challenge is a Bayesian treatment of meta-learning. This work, builds on top of recent work that provides a Bayesian interpretation of MAML (model-agnostic-meta-learning). This contribution is a direct extension of (Grant et al 2018) - where the task-train posterior was approximated via a Gaussian distribution. Applying SVGD instead allows for a more flexible and (potentially) more accurate approximation of a highly complex posterior.
Reviews: Deep Generative Markov State Models
This paper proposes a novel learning frame-work for Markov State Models of real valued vectors. This model can handle metastable processes i.e. processes that evolve locally in short time-scales but switch between a few clusters after very long periods. The proposed framework is based on a nice idea to decompose the transition from x1 to x2 to the probability that x1 belongs to a long-lived state and a distribution of x2 given the state. The first conditional probability is modeled using a decoding deep network whereas the second one can be represented either using a network that assigns weights to x2 or using a generative neural network. This is a very interesting manuscript.