Markov Models
tfp.mcmc: Modern Markov Chain Monte Carlo Tools Built for Modern Hardware
Lao, Junpeng, Suter, Christopher, Langmore, Ian, Chimisov, Cyril, Saxena, Ashish, Sountsov, Pavel, Moore, Dave, Saurous, Rif A., Hoffman, Matthew D., Dillon, Joshua V.
Markov chain Monte Carlo (MCMC) is widely regarded as one of the most important algorithms of the 20th century. Its guarantees of asymptotic convergence, stability, and estimator-variance bounds using only unnormalized probability functions make it indispensable to probabilistic programming. In this paper, we introduce the TensorFlow Probability MCMC toolkit, and discuss some of the considerations that motivated its design.
DALC: Distributed Automatic LSTM Customization for Fine-Grained Traffic Speed Prediction
Lee, Ming-Chang, Lin, Jia-Chun
Over the past decade, several approaches have been introduced for short - term traffic prediction. However, providing fine - grained traffic prediction for large - scale transportation networks where numerous detectors are geographically deployed to collect traf fic data is still an open issue. To address this issue, in this paper, we formulate the problem of customizing an LSTM model for a single detector into a finite Markov decision process and then introduce an A utomatic L STM C ustomization (ALC) algorithm to a utomatically customize an LSTM model for a single detector such that the corresponding prediction accuracy can be as satisfactory as possible and the time consumption can be as low as possible. Based on the ALC algorithm, we introduce a distributed approac h called D istributed A utomatic L STM C ustomization (DALC) to customize an LSTM model for every detector in large - scale transportation networks. Our experiment demonstrate s that the DALC provides higher prediction accuracy than several approaches provided by Apache Spark MLlib.
Effectively Trainable Semi-Quantum Restricted Boltzmann Machine
Lyakhova, Ya. S., Polyakov, E. A., Rubtsov, A. N.
We propose a novel quantum model for the restricted Boltzmann machine (RBM), in which the visible units remain classical whereas the hidden units are quantized as noninteracting fermions. The free motion of the fermions is parametrically coupled to the classical signal of the visible units. This model possesses a quantum behaviour such as coherences between the hidden units. Numerical experiments show that this fact makes it more powerful than the classical RBM with the same number of hidden units. At the same time, a significant advantage of the proposed model over the other approaches to the Quantum Boltzmann Machine (QBM) is that it is exactly solvable and efficiently trainable on a classical computer: there is a closed expression for the log-likelihood gradient with respect to its parameters. This fact makes it interesting not only as a model of a hypothetical quantum simulator, but also as a quantum-inspired classical machine-learning algorithm.
Generating Digital Twins with Multiple Sclerosis Using Probabilistic Neural Networks
Walsh, Jonathan R., Smith, Aaron M., Pouliot, Yannick, Li-Bland, David, Loukianov, Anton, Fisher, Charles K.
Multiple Sclerosis (MS) is a neurodegenerative disorder characterized by a complex set of clinical assessments. We use an unsupervised machine learning model called a Conditional Restricted Boltzmann Machine (CRBM) to learn the relationships between covariates commonly used to characterize subjects and their disease progression in MS clinical trials. A CRBM is capable of generating digital twins, which are simulated subjects having the same baseline data as actual subjects. Digital twins allow for subject-level statistical analyses of disease progression. The CRBM is trained using data from 2395 subjects enrolled in the placebo arms of clinical trials across the three primary subtypes of MS. We discuss how CRBMs are trained and show that digital twins generated by the model are statistically indistinguishable from their actual subject counterparts along a number of measures.
Quantifying Hypothesis Space Misspecification in Learning from Human-Robot Demonstrations and Physical Corrections
Bobu, Andreea, Bajcsy, Andrea, Fisac, Jaime F., Deglurkar, Sampada, Dragan, Anca D.
Human input has enabled autonomous systems to improve their capabilities and achieve complex behaviors that are otherwise challenging to generate automatically. Recent work focuses on how robots can use such input - like demonstrations or corrections - to learn intended objectives. These techniques assume that the human's desired objective already exists within the robot's hypothesis space. In reality, this assumption is often inaccurate: there will always be situations where the person might care about aspects of the task that the robot does not know about. Without this knowledge, the robot cannot infer the correct objective. Hence, when the robot's hypothesis space is misspecified, even methods that keep track of uncertainty over the objective fail because they reason about which hypothesis might be correct, and not whether any of the hypotheses are correct. In this paper, we posit that the robot should reason explicitly about how well it can explain human inputs given its hypothesis space and use that situational confidence to inform how it should incorporate human input. We demonstrate our method on a 7 degree-of-freedom robot manipulator in learning from two important types of human input: demonstrations of manipulation tasks, and physical corrections during the robot's task execution.
Torch-Struct: Deep Structured Prediction Library
The literature on structured prediction for NLP describes a rich collection of distributions and algorithms over sequences, segmentations, alignments, and trees; however, these algorithms are difficult to utilize in deep learning frameworks. We introduce Torch-Struct, a library for structured prediction designed to take advantage of and integrate with vectorized, auto-differentiation based frameworks. Torch-Struct includes a broad collection of probabilistic structures accessed through a simple and flexible distribution-based API that connects to any deep learning model. The library utilizes batched, vectorized operations and exploits auto-differentiation to produce readable, fast, and testable code. Internally, we also include a number of general-purpose optimizations to provide cross-algorithm efficiency. Experiments show significant performance gains over fast baselines and case-studies demonstrate the benefits of the library.
Automatic structured variational inference
Ambrogioni, Luca, Hinne, Max, van Gerven, Marcel
The aim of probabilistic programming is to automatize every aspect of probabilistic inference in arbitrary probabilistic models (programs) so that the user can focus her attention on modeling, without dealing with ad-hoc inference methods. Gradient based automatic differentiation stochastic variational inference offers an attractive option as the default method for (differentiable) probabilistic programming as it combines high performance with high computational efficiency. However, the performance of any (parametric) variational approach depends on the choice of an appropriate variational family. Here, we introduced a fully automatic method for constructing structured variational families inspired to the closed-form update in conjugate models. These pseudo-conjugate families incorporate the forward pass of the input probabilistic program and can capture complex statistical dependencies. Pseudo-conjugate families have the same space and time complexity of the input probabilistic program and are therefore tractable in a very large class of models. We validate our automatic variational method on a wide range of high dimensional inference problems including deep learning components.
Deep Learning (Interview With Dong Yu)
Dr. Dong Yu is a principal researcher at Microsoft Research. His research has been focusing on speech recognition and applications of machine learning techniques. He has published two monographs and over 150 papers in these areas and is the inventor/co-inventor of near 60 granted/pending patents. His recent work on the context-dependent deep neural network hidden Markov model (CD-DNN-HMM), which was recognized by the IEEE SPS 2013 best paper award, caused a paradigm shift on large vocabulary speech recognition. Dr. Dong Yu is currently serving as a member of the IEEE Speech and Language Processing Technical Committee (2013-).
Deep Reinforcement Learning for Autonomous Driving: A Survey
Kiran, B Ravi, Sobh, Ibrahim, Talpaert, Victor, Mannion, Patrick, Sallab, Ahmad A. Al, Yogamani, Senthil, Pérez, Patrick
With the development of deep representation learning, the domain of reinforcement learning (RL) has become a powerful learning framework now capable of learning complex policies in high dimensional environments. This review summarises deep reinforcement learning (DRL) algorithms, provides a taxonomy of automated driving tasks where (D)RL methods have been employed, highlights the key challenges algorithmically as well as in terms of deployment of real world autonomous driving agents, the role of simulators in training agents, and finally methods to evaluate, test and robustifying existing solutions in RL and imitation learning.
Regret Minimization in Partially Observable Linear Quadratic Control
Lale, Sahin, Azizzadenesheli, Kamyar, Hassibi, Babak, Anandkumar, Anima
Controlling unknown discrete-time systems is a fundamenta l problem in adaptive control and reinforcement learning. In this problem, an agent interacts w ith an environment, with unknown dynamics, and aims to minimize the overall average regulati ng costs. To achieve this goal, the agent is required to explore the environment to gain a better understanding of the environment dynamics, which is often called system identification. The a gent then utilizes this understanding to design a set of improved controllers that simultaneously reduces the possible future costs and also enables the agent to explore the important and unknown a spects of the system. In recent decades, this challenging problem has been extensively stu died and resulted in a set of foundational steps to study the stability and asymptotic convergence to o ptimal controllers [Lai et al., 1982, Lai and Wei, 1987]. While asymptotic analyses set the ground for the design of optimal control, understanding the finite time behavior of adaptive algorith ms is critical for real-world applications. In practice, one might prefer an algorithm that guarantees b etter performance on a much shorter horizon. Recent developments in the fields of statistics and machine learning along with control theory [Van Der Vaart and Wellner, 1996, Peña et al., 2009, Lai et al., 1982] empowers us to not only advance the study of the asymptotic efficiency of algorithms b ut also to analyze their finite-time behavior [Fiechter, 1997, Abbasi-Yadkori and Szepesvári, 2011]. In partially observable linear quadratic control, if the ag ent, a priori, is handed the system dynamics, the optimal control/policy has a closed-form in t he presence of Gaussian disturbances.