Uncertainty
Online Replanning in Belief Space for Partially Observable Task and Motion Problems
Garrett, Caelan Reed, Paxton, Chris, Lozano-Pรฉrez, Tomรกs, Kaelbling, Leslie Pack, Fox, Dieter
-- T o solve multi-step manipulation tasks in the real world, an autonomous robot must take actions to observe its environment and react to unexpected observations. This may require opening a drawer to observe its contents or moving an object out of the way to examine the space behind it. If the robot fails to detect an important object, it must update its belief about the world and compute a new plan of action. Additionally, a robot that acts noisily will never exactly arrive at a desired state. Still, it is important that the robot adjusts accordingly in order to keep making progress towards achieving the goal. In this work, we present an online planning and execution system for robots faced with these kinds of challenges. Our approach is able to efficiently solve partially observable problems both in simulation and in a real-world kitchen. Robots acting autonomously in human environments are faced with a variety of challenges. First, they must make both discrete decisions about what object to manipulate as well as continuous decisions about which motions to execute to achieve a desired interaction. Planning in these large hybrid spaces is the subject of integrated T ask and Motion Planning (T AMP) [1], [2], [3], [4], [5], [6].
(When) Is Truth-telling Favored in AI Debate?
Kovaลรญk, Vojtฤch, Carey, Ryan
For some problems, humans may not be able to accurately judge the goodness of AIproposed solutions. Irving, Christiano, and Amodei (2018) propose that in such cases, we may use a debate between two AI systems to amplify the problem-solving capabilities of a human judge. We introduce a mathematical framework that can model debates of this type and propose that the quality of debate designs should be measured by the accuracy of the most persuasive answer. We describe a simple instance of the debate framework called feature debate and analyze the degree to which such debates track the truth. We argue that despite being ver y simple, feature debates nonetheless capture many aspects o f practical debates such as the incentives to confuse the judg e or stall to prevent losing. We then outline how these models should be generalized to analyze a wider range of debate phenomena.
Accurate Uncertainty Estimation and Decomposition in Ensemble Learning
Liu, Jeremiah Zhe, Paisley, John, Kioumourtzoglou, Marianthi-Anna, Coull, Brent
Ensemble learning is a standard approach to building machine learning systems that capture complex phenomena in real-world data. An important aspect of these systems is the complete and valid quantification of model uncertainty. We introduce a Bayesian nonparametric ensemble (BNE) approach that augments an existing ensemble model to account for different sources of model uncertainty. BNE augments a model's prediction and distribution functions using Bayesian nonparametric machinery. It has a theoretical guarantee in that it robustly estimates the uncertainty patterns in the data distribution, and can decompose its overall predictive uncertainty into distinct components that are due to different sources of noise and error. We show that our method achieves accurate uncertainty estimates under complex observational noise, and illustrate its real-world utility in terms of uncertainty decomposition and model bias detection for an ensemble in predict air pollution exposures in Eastern Massachusetts, USA.
TSK-Streams: Learning TSK Fuzzy Systems on Data Streams
Shaker, Ammar, Hรผllermeier, Eyke
In many practical applications of machine learning and pred ictive modeling, data is produced incrementally in the course of time and observed in the form of a continuous, potentially unbounded stream of observations. Correspond ingly, the problem of learning from data streams has recently received increasing attenti on (Gama, 2012). Algorithms for learning on streams must be able to process the data in a si ngle pass, which implies an incremental mode of learning, and to adapt to changes of the u nderlying data-generating process (Domingos and Hulten, 2003). A popular approach for learning on data streams, both for cla ssification and regression, is rule induction, in the fuzzy logic and computational inte lligence community also known as "evolving fuzzy systems" (Lughofer, 2011). Shaker et al. (2017) proposed a method for regression that builds on a very efficient and effective techniq ue for rule induction, which 1 is inspired by the state-of-the-art machine learning algor ithm AMRules, and combines it with the strengths of fuzzy modeling. Thus, the method induc es a set of fuzzy rules, which, compared to conventional rules with Boolean antecedents, h as the advantage of producing smooth regression functions. The method presented in this p aper, called TSK-Streams, is a revised and improved variant. The main modifications and novel contributions are as follows.
Alleviating Label Switching with Optimal Transport
Monteiller, Pierre, Claici, Sebastian, Chien, Edward, Mirzazadeh, Farzaneh, Solomon, Justin, Yurochkin, Mikhail
Label switching is a phenomenon arising in mixture model posterior inference that prevents one from meaningfully assessing posterior statistics using standard Monte Carlo procedures. This issue arises due to invariance of the posterior under actions of a group; for example, permuting the ordering of mixture components has no effect on the likelihood. We propose a resolution to label switching that leverages machinery from optimal transport. Our algorithm efficiently computes posterior statistics in the quotient space of the symmetry group. We give conditions under which there is a meaningful solution to label switching and demonstrate advantages over alternative approaches on simulated and real data.
Predictive Biases in Natural Language Processing Models: A Conceptual Framework and Overview
Shah, Deven, Schwartz, H. Andrew, Hovy, Dirk
An increasing number of works in natural language processing have addressed the effect of bias on the predicted outcomes, introducing mitigation techniques that act on different parts of the standard NLP pipeline (data and models). However, these works have been conducted in isolation, without a unifying framework to organize efforts within the field. This leads to repetitive approaches, and puts an undue focus on the effects of bias, rather than on their origins. Research focused on bias symptoms rather than the underlying origins could limit the development of effective countermeasures. In this paper, we propose a unifying conceptualization: the predictive bias framework for NLP . We summarize the NLP literature and propose a general mathematical definition of predictive bias in NLP along with a conceptual framework, differentiating four main origins of biases: label bias, selection bias, model overamplification, and semantic bias . We discuss how past work has countered each bias origin. Our framework serves to guide an introductory overview of predictive bias in NLP, integrating existing work into a single structure and opening avenues for future research.
Protecting from Malware Obfuscation Attacks through Adversarial Risk Analysis
Redondo, Alberto, Insua, David Rios
Standard algorithms in detection systems perform insufficiently when dealing with malware passed through obfuscation tools. We illustrate this studying in detail an open source metamorphic software, making use of a hybrid framework to obtain the relevant features from binaries. We then provide an improved alternative solution based on adversarial risk analysis which we illustrate describe with an example. KEYWORDS: Adversarial Risk Analysis, Malware Obfuscation, Cybersecurity 1 INTRODUCTION The digital era is bringing along new global threats among which cybersecurity related ones emerge as truly worrisome, see for example the evolution of the Global Risks Map from the World Economic Forum (2017, 2018, 2019). Indeed, the operation of critical cyber infrastructures relies on components which could be cyber attacked, both incidentally and intentionally, suffering major performance degradation, Rao et al. (2016).
Not All Claims are Created Equal: Choosing the Right Approach to Assess Your Hypotheses
Azer, Erfan Sadeqi, Khashabi, Daniel, Sabharwal, Ashish, Roth, Dan
Empirical research in Natural Language Processing (NLP) has adopted a narrow set of principles for assessing hypotheses, relying mainly on p-value computation, which suffers from several known issues. While alternative proposals have been well-debated and adopted in other fields, they remain rarely discussed or used within the NLP community. We address this gap by contrasting various hypothesis assessment techniques, especially those not commonly used in the field (such as evaluations based on Bayesian inference). Since these statistical techniques differ in the hypotheses they can support, we argue that practitioners should first decide their target hypothesis before choosing an assessment method. This is crucial because common fallacies, misconceptions, and misinterpretation surrounding hypothesis assessment methods often stem from a discrepancy between what one would like to claim versus what the method used actually assesses. Our survey reveals that these issues are omnipresent in the NLP research community. As a step forward, we provide best practices and guidelines tailored to NLP research, as well as an easy-to-use package called 'HyBayes' for Bayesian assessment of hypotheses, complementing existing tools.
Maximum a-Posteriori Estimation for the Gaussian Mixture Model via Mixed Integer Nonlinear Programming
Flaherty, Patrick, Wiratchotisatian, Pitchaya, Lee, Ji Ah, Trapp, Andrew C.
We present a global optimization approach for solving the classical maximum a-posteriori (MAP) estimation problem for the Gaussian mixture model. Our approach formulates the MAP estimation problem as a mixed-integer nonlinear optimization problem (MINLP). Our method provides a certificate of global optimality, can accommodate side constraints, and is extendable to other finite mixture models. We propose an approximation to the MINLP hat transforms it into a mixed integer quadratic program (MIQP) which preserves global optimality within desired accuracy and improves computational aspects. Numerical experiments compare our method to standard estimation approaches and show that our method finds the globally optimal MAP for some standard data sets, providing a benchmark for comparing estimation methods.
Confidence Intervals for Policy Evaluation in Adaptive Experiments
Hadad, Vitor, Hirshberg, David A., Zhan, Ruohan, Wager, Stefan, Athey, Susan
Adaptive experiments can result in considerable cost savings in multi-armed trials by enabling analysts to quickly focus on the most promising alternatives. Most existing work on adaptive experiments (which include multi-armed bandits) has focused maximizing the speed at which the analyst can identify the optimal arm and/or minimizing the number of draws from sub-optimal arms. In many scientific settings, however, it is not only of interest to identify the optimal arm, but also to perform a statistical analysis of the data collected from the experiment. Naive approaches to statistical inference with adaptive inference fail because many commonly used statistics (such as sample means or inverse propensity weighting) do not have an asymptotically Gaussian limiting distribution centered on the estimate, and so confidence intervals constructed from these statistics do not have correct coverage. But, as shown in this paper, carefully designed data-adaptive weighting schemes can be used to overcome this issue and restore a relevant central limit theorem, enabling hypothesis testing. We validate the accuracy of the resulting confidence intervals in numerical experiments.