9,866 research outputs found
A Tutorial on Bayesian Optimization of Expensive Cost Functions, with Application to Active User Modeling and Hierarchical Reinforcement Learning
We present a tutorial on Bayesian optimization, a method of finding the
maximum of expensive cost functions. Bayesian optimization employs the Bayesian
technique of setting a prior over the objective function and combining it with
evidence to get a posterior function. This permits a utility-based selection of
the next observation to make on the objective function, which must take into
account both exploration (sampling from areas of high uncertainty) and
exploitation (sampling areas likely to offer improvement over the current best
observation). We also present two detailed extensions of Bayesian optimization,
with experiments---active user modelling with preferences, and hierarchical
reinforcement learning---and a discussion of the pros and cons of Bayesian
optimization based on our experiences
Bayesian multitask inverse reinforcement learning
We generalise the problem of inverse reinforcement learning to multiple
tasks, from multiple demonstrations. Each one may represent one expert trying
to solve a different task, or as different experts trying to solve the same
task. Our main contribution is to formalise the problem as statistical
preference elicitation, via a number of structured priors, whose form captures
our biases about the relatedness of different tasks or expert policies. In
doing so, we introduce a prior on policy optimality, which is more natural to
specify. We show that our framework allows us not only to learn to efficiently
from multiple experts but to also effectively differentiate between the goals
of each. Possible applications include analysing the intrinsic motivations of
subjects in behavioural experiments and learning from multiple teachers.Comment: Corrected version. 13 pages, 8 figure
VIME: Variational Information Maximizing Exploration
Scalable and effective exploration remains a key challenge in reinforcement
learning (RL). While there are methods with optimality guarantees in the
setting of discrete state and action spaces, these methods cannot be applied in
high-dimensional deep RL scenarios. As such, most contemporary RL relies on
simple heuristics such as epsilon-greedy exploration or adding Gaussian noise
to the controls. This paper introduces Variational Information Maximizing
Exploration (VIME), an exploration strategy based on maximization of
information gain about the agent's belief of environment dynamics. We propose a
practical implementation, using variational inference in Bayesian neural
networks which efficiently handles continuous state and action spaces. VIME
modifies the MDP reward function, and can be applied with several different
underlying RL algorithms. We demonstrate that VIME achieves significantly
better performance compared to heuristic exploration methods across a variety
of continuous control tasks and algorithms, including tasks with very sparse
rewards.Comment: Published in Advances in Neural Information Processing Systems 29
(NIPS), pages 1109-111
Developmental Bayesian Optimization of Black-Box with Visual Similarity-Based Transfer Learning
We present a developmental framework based on a long-term memory and
reasoning mechanisms (Vision Similarity and Bayesian Optimisation). This
architecture allows a robot to optimize autonomously hyper-parameters that need
to be tuned from any action and/or vision module, treated as a black-box. The
learning can take advantage of past experiences (stored in the episodic and
procedural memories) in order to warm-start the exploration using a set of
hyper-parameters previously optimized from objects similar to the new unknown
one (stored in a semantic memory). As example, the system has been used to
optimized 9 continuous hyper-parameters of a professional software (Kamido)
both in simulation and with a real robot (industrial robotic arm Fanuc) with a
total of 13 different objects. The robot is able to find a good object-specific
optimization in 68 (simulation) or 40 (real) trials. In simulation, we
demonstrate the benefit of the transfer learning based on visual similarity, as
opposed to an amnesic learning (i.e. learning from scratch all the time).
Moreover, with the real robot, we show that the method consistently outperforms
the manual optimization from an expert with less than 2 hours of training time
to achieve more than 88% of success
Machine Learning in Wireless Sensor Networks: Algorithms, Strategies, and Applications
Wireless sensor networks monitor dynamic environments that change rapidly
over time. This dynamic behavior is either caused by external factors or
initiated by the system designers themselves. To adapt to such conditions,
sensor networks often adopt machine learning techniques to eliminate the need
for unnecessary redesign. Machine learning also inspires many practical
solutions that maximize resource utilization and prolong the lifespan of the
network. In this paper, we present an extensive literature review over the
period 2002-2013 of machine learning methods that were used to address common
issues in wireless sensor networks (WSNs). The advantages and disadvantages of
each proposed algorithm are evaluated against the corresponding problem. We
also provide a comparative guide to aid WSN designers in developing suitable
machine learning solutions for their specific application challenges.Comment: Accepted for publication in IEEE Communications Surveys and Tutorial
Hierarchical Decomposition of Nonlinear Dynamics and Control for System Identification and Policy Distillation
The control of nonlinear dynamical systems remains a major challenge for
autonomous agents. Current trends in reinforcement learning (RL) focus on
complex representations of dynamics and policies, which have yielded impressive
results in solving a variety of hard control tasks. However, this new
sophistication and extremely over-parameterized models have come with the cost
of an overall reduction in our ability to interpret the resulting policies. In
this paper, we take inspiration from the control community and apply the
principles of hybrid switching systems in order to break down complex dynamics
into simpler components. We exploit the rich representational power of
probabilistic graphical models and derive an expectation-maximization (EM)
algorithm for learning a sequence model to capture the temporal structure of
the data and automatically decompose nonlinear dynamics into stochastic
switching linear dynamical systems. Moreover, we show how this framework of
switching models enables extracting hierarchies of Markovian and
auto-regressive locally linear controllers from nonlinear experts in an
imitation learning scenario.Comment: 2nd Annual Conference on Learning for Dynamics and Contro
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