Learning Graphical Models
(When) Is Truth-telling Favored in AI Debate?
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.
Multi-Agent Connected Autonomous Driving using Deep Reinforcement Learning
The capability to learn and adapt to changes in the driving environment is crucial for developing autonomous driving systems that are scalable beyond geo-fenced operational design domains. Deep Reinforcement Learning (RL) provides a promising and scalable framework for developing adaptive learning based solutions. Deep RL methods usually model the problem as a (Partially Observable) Markov Decision Process in which an agent acts in a stationary environment to learn an optimal behavior policy. However, driving involves complex interaction between multiple, intelligent (artificial or human) agents in a highly non-stationary environment. In this paper, we propose the use of Partially Observable Markov Games(POSG) for formulating the connected autonomous driving problems with realistic assumptions. We provide a taxonomy of multi-agent learning environments based on the nature of tasks, nature of agents and the nature of the environment to help in categorizing various autonomous driving problems that can be addressed under the proposed formulation. As our main contributions, we provide MACAD-Gym, a Multi-Agent Connected, Autonomous Driving agent learning platform for furthering research in this direction. Our MACAD-Gym platform provides an extensible set of Connected Autonomous Driving (CAD) simulation environments that enable the research and development of Deep RL- based integrated sensing, perception, planning and control algorithms for CAD systems with unlimited operational design domain under realistic, multi-agent settings. We also share the MACAD-Agents that were trained successfully using the MACAD-Gym platform to learn control policies for multiple vehicle agents in a partially observable, stop-sign controlled, 3-way urban intersection environment with raw (camera) sensor observations.
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.
Modelling Bahdanau Attention using Election methods aided by Q-Learning
Neural Machine Translation has lately gained a lot of "attention" with the advent of more and more sophisticated but drastically improved models. Attention mechanism has proved to be a boon in this direction by providing weights to the input words, making it easy for the decoder to identify words representing the present context. But by and by, as newer attention models with more complexity came into development, they involved large computation, making inference slow. In this paper, we have modelled the attention network using techniques resonating with social choice theory. Along with that, the attention mechanism, being a Markov Decision Process, has been represented by reinforcement learning techniques. Thus, we propose to use an election method ( k -Borda), fine-tuned using Q-learning, as a replacement for attention networks. The inference time for this network is less than a standard Bahdanau translator, and the results of the translation are comparable. This not only experimentally verifies the claims stated above but also helped provide a faster inference.
Bayesian Active Learning for Structured Output Design
Matsui, Kota, Kusakawa, Shunya, Ando, Keisuke, Kutsukake, Kentaro, Ujihara, Toru, Takeuchi, Ichiro
In this paper, we propose an active learning method for an inverse problem that aims to find an input that achieves a desired structured-output. The proposed method provides new acquisition functions for minimizing the error between the desired structured-output and the prediction of a Gaussian process model, by effectively incorporating the correlation between multiple outputs of the underlying multi-valued black box output functions. The effectiveness of the proposed method is verified by applying it to two synthetic shape search problem and real data. In the real data experiment, we tackle the input parameter search which achieves the desired crystal growth rate in silicon carbide (SiC) crystal growth modeling, that is a problem of materials informatics.
Missing Features Reconstruction and Its Impact on Classification Accuracy
Friedjungová, Magda, Vašata, Daniel, Jiřina, Marcel
In real-world applications, we can encounter situations when a well-trained model has to be used to predict from a damaged dataset. The damage caused by missing or corrupted values can be either on the level of individual instances or on the level of entire features. Both situations have a negative impact on the usability of the model on such a dataset. This paper focuses on the scenario where entire features are missing which can be understood as a specific case of transfer learning. Our aim is to experimentally research the influence of various imputation methods on the performance of several classification models. The imputation impact is researched on a combination of traditional methods such as k-NN, linear regression, and MICE compared to modern imputation methods such as multi-layer perceptron (MLP) and gradient boosted trees (XGBT). For linear regression, MLP, and XGBT we also propose two approaches to using them for multiple features imputation. The experiments were performed on both real world and artificial datasets with continuous features where different numbers of features, varying from one feature to 50%, were missing. The results show that MICE and linear regression are generally good imputers regardless of the conditions. On the other hand, the performance of MLP and XGBT is strongly dataset dependent. Their performance is the best in some cases, but more often they perform worse than MICE or linear regression.
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.
Investigation of Error Simulation Techniques for Learning Dialog Policies for Conversational Error Recovery
Fazel-Zarandi, Maryam, Wang, Longshaokan, Tiwari, Aditya, Matsoukas, Spyros
Training dialog policies for speech-based virtual assistants requires a plethora of conversational data. The data collection phase is often expensive and time consuming due to human involvement. To address this issue, a common solution is to build user simulators for data generation. For the successful deployment of the trained policies into real world domains, it is vital that the user simulator mimics realistic conditions. In particular, speech-based assistants are heavily affected by automatic speech recognition and language understanding errors, hence the user simulator should be able to simulate similar errors. In this paper, we review the existing error simulation methods that induce errors at audio, phoneme, text, or semantic level; and conduct detailed comparisons between the audio-level and text-level methods. In the process, we improve the existing text-level method by introducing confidence score prediction and out-of-vocabulary word mapping. We also explore the impact of audio-level and text-level methods on learning a simple clarification dialog policy to recover from errors to provide insight on future improvement for both approaches.
A multiple testing framework for diagnostic accuracy studies with co-primary endpoints
Westphal, Max, Zapf, Antonia, Brannath, Werner
This is indicated, among others, by several review and overview publications (Ching et al., 2018; Jiang et al., 2017; Litjens et al., 2017; Miotto, Wang, Wang, Jiang, & Dudley, 2017). In particular, the capabilities of end-to-end deep learning approaches on such supervised learning tasks are highly promising. For instance, vast advances have been reported in the literature regarding cancer diagnosis with deep neural networks (Hu et al., 2018). End-to-end deep learning refers to a trend involving deep (neural network) model architectures which are able to learn highly complex relationships between predictors and the target variable while having less parameters than traditional (more shallow) models with comparable performance (Goodfellow, Bengio, & Courville, 2016). In the training process, highly complex features are derived automatically by the learning algorithm (LeCun, Bengio, & Hinton, 2015). This framework contrasts the traditional pipeline of domain specific data preprocessing and handcrafted features in combination with simpler prediction models. Despite all the recent success of machine learning, there are still challenges regarding over-optimistic conclusions drawn from finite datasets which may to a large extend be attributed to the following two (broad) categories: 1. Study design and reporting: The most popular recommendation to split data for training, selection and evaluation is frequently employed in practice (Friedman, Hastie, & Tibshirani, 2009; Géron, 2017; Goodfellow et al., 2016; Japkowicz & Shah, 2011; Kuhn & Johnson, 2013; Zheng, 2015). In the ML community, the according datasets are commonly denoted as training, validation and test set.