3,325 research outputs found
Unmasking Clever Hans Predictors and Assessing What Machines Really Learn
Current learning machines have successfully solved hard application problems,
reaching high accuracy and displaying seemingly "intelligent" behavior. Here we
apply recent techniques for explaining decisions of state-of-the-art learning
machines and analyze various tasks from computer vision and arcade games. This
showcases a spectrum of problem-solving behaviors ranging from naive and
short-sighted, to well-informed and strategic. We observe that standard
performance evaluation metrics can be oblivious to distinguishing these diverse
problem solving behaviors. Furthermore, we propose our semi-automated Spectral
Relevance Analysis that provides a practically effective way of characterizing
and validating the behavior of nonlinear learning machines. This helps to
assess whether a learned model indeed delivers reliably for the problem that it
was conceived for. Furthermore, our work intends to add a voice of caution to
the ongoing excitement about machine intelligence and pledges to evaluate and
judge some of these recent successes in a more nuanced manner.Comment: Accepted for publication in Nature Communication
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Towards Informed Exploration for Deep Reinforcement Learning
In this thesis, we discuss various techniques for improving exploration for deep reinforcement learning. We begin with a brief review of reinforcement learning (RL) and the fundamental v.s. exploitation trade-off. Then we review how deep RL has improved upon classical and summarize six categories of the latest exploration methods for deep RL, in the order increasing usage of prior information. We then explore representative works in three categories discuss their strengths and weaknesses. The first category, represented by Soft Q-learning, uses regularization to encourage exploration. The second category, represented by count-based via hashing, maps states to hash codes for counting and assigns higher exploration to less-encountered states. The third category utilizes hierarchy and is represented by modular architecture for RL agents to play StarCraft II. Finally, we conclude that exploration by prior knowledge is a promising research direction and suggest topics of potentially impact
Batch Policy Learning under Constraints
When learning policies for real-world domains, two important questions arise:
(i) how to efficiently use pre-collected off-policy, non-optimal behavior data;
and (ii) how to mediate among different competing objectives and constraints.
We thus study the problem of batch policy learning under multiple constraints,
and offer a systematic solution. We first propose a flexible meta-algorithm
that admits any batch reinforcement learning and online learning procedure as
subroutines. We then present a specific algorithmic instantiation and provide
performance guarantees for the main objective and all constraints. To certify
constraint satisfaction, we propose a new and simple method for off-policy
policy evaluation (OPE) and derive PAC-style bounds. Our algorithm achieves
strong empirical results in different domains, including in a challenging
problem of simulated car driving subject to multiple constraints such as lane
keeping and smooth driving. We also show experimentally that our OPE method
outperforms other popular OPE techniques on a standalone basis, especially in a
high-dimensional setting
Learning to Play General Video-Games via an Object Embedding Network
Deep reinforcement learning (DRL) has proven to be an effective tool for
creating general video-game AI. However most current DRL video-game agents
learn end-to-end from the video-output of the game, which is superfluous for
many applications and creates a number of additional problems. More
importantly, directly working on pixel-based raw video data is substantially
distinct from what a human player does.In this paper, we present a novel method
which enables DRL agents to learn directly from object information. This is
obtained via use of an object embedding network (OEN) that compresses a set of
object feature vectors of different lengths into a single fixed-length unified
feature vector representing the current game-state and fulfills the DRL
simultaneously. We evaluate our OEN-based DRL agent by comparing to several
state-of-the-art approaches on a selection of games from the GVG-AI
Competition. Experimental results suggest that our object-based DRL agent
yields performance comparable to that of those approaches used in our
comparative study.Comment: To appear in IEEE CIG201
Grounding Language for Transfer in Deep Reinforcement Learning
In this paper, we explore the utilization of natural language to drive
transfer for reinforcement learning (RL). Despite the wide-spread application
of deep RL techniques, learning generalized policy representations that work
across domains remains a challenging problem. We demonstrate that textual
descriptions of environments provide a compact intermediate channel to
facilitate effective policy transfer. Specifically, by learning to ground the
meaning of text to the dynamics of the environment such as transitions and
rewards, an autonomous agent can effectively bootstrap policy learning on a new
domain given its description. We employ a model-based RL approach consisting of
a differentiable planning module, a model-free component and a factorized state
representation to effectively use entity descriptions. Our model outperforms
prior work on both transfer and multi-task scenarios in a variety of different
environments. For instance, we achieve up to 14% and 11.5% absolute improvement
over previously existing models in terms of average and initial rewards,
respectively.Comment: JAIR 201
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