Consequently, it is critical that RL policies are robust: both to naturally
occurring distribution shift, and to malicious attacks by adversaries.
Unfortunately, we find that RL policies which perform at a high-level in normal
situations can harbor serious vulnerabilities which can be exploited by an
Reinforcement learning has seen a great deal of success in solving complex decision making problems ranging from robotics to games to supply chain management to recommender systems. Despite their success, deep reinforcement learning algorithms can be exceptionally difficult to use, due to unstable training, sensitivity to hyperparameters, and generally unpredictable and poorly understood convergence properties. Multiple explanations, and corresponding solutions, have been proposed for improving the stability of such methods, and we have seen good progress over the last few years on these algorithms. In this blog post, we will dive deep into analyzing a central and underexplored reason behind some of the problems with the class of deep RL algorithms based on dynamic programming, which encompass the popular DQN and soft actor-critic (SAC) algorithms – the detrimental connection between data distributions and learned models.
Look at the images above. If I asked you to bring me a picnic blanket in the
grassy field, would you be able to? Of course. If I asked you to bring over a
cart full of food for a party, would you push the cart along the paved path or
on the grass? Obviously the paved path.
In deep learning, using more compute (e.g., increasing model size, dataset
size, or training steps) often leads to higher accuracy. This is especially
true given the recent success of unsupervised pretraining methods like
BERT, which can scale up training to very large models and datasets.
Unfortunately, large-scale training is very computationally expensive,
especially without the hardware resources of large industry research labs.
Thus, the goal in practice is usually to get high accuracy without exceeding
one’s hardware budget and training time.
For most training budgets, very large models appear impractical. Instead, the
go-to strategy for maximizing training efficiency is to use models with small
hidden sizes or few layers because these models run faster and use less memory.
In this blog post, we share our experiences in developing two critical software
libraries that many BAIR researchers use to execute large-scale AI
experiments: Ray Tune and the Ray Cluster Launcher, both of which now
back many popular open-source AI libraries.
As AI research becomes more compute intensive, many AI researchers have become
squeezed for time and resources. Many researchers now rely on cloud providers
like Amazon Web Services or Google Compute Platform to access the huge amounts
of computational resources necessary for training large models.
All living organisms carve out environmental niches within which they can
maintain relative predictability amidst the ever-increasing entropy around them
Humans, for example, go to great lengths to shield themselves from surprise —
we band together in millions to build cities with homes, supplying water, food,
gas, and electricity to control the deterioration of our bodies and living
spaces amidst heat and cold, wind and storm. The need to discover and maintain
such surprise-free equilibria has driven great resourcefulness and skill in
organisms across very diverse natural habitats. Motivated by this, we ask:
could the motive of preserving order amidst chaos guide the automatic
acquisition of useful behaviors in artificial agents?
People give massive amounts of their personal data to companies every day and
these data are used to generate tremendous business values. Some
argue that people should be paid for their contributions—but the
million-dollar question is: by how much?
This article discusses methods proposed in our recent
VLDB papers that attempt to answer this
question in the machine learning context. This is joint work with David Dao,
Boxin Wang, Frances Ann Hubis, Nezihe Merve Gurel, Nick Hynes, Bo Li, Ce Zhang,
Costas J. Spanos, and Dawn Song, as well as a collaborative effort between UC
Berkeley, ETH Zurich, and UIUC. More information about the work in our group
can be found here.
This work presents AVID, a method that allows a robot to learn a task, such as
making coffee, directly by watching a human perform the task.
One of the most important markers of intelligence is the ability to learn by
watching others. Humans are particularly good at this, often being able to
learn tasks by observing other humans. This is possible because we are not
simply copying the actions that other humans take. Rather, we first imagine
ourselves performing the task, and this provides a starting point for further
practicing the task in the real world.
Robots are not yet adept at learning by watching humans or other robots. Prior
methods for imitation learning, where robots learn from demonstrations of the
task, typically assume that the demonstrations can be given directly through
the robot, using techniques such as kinesthetic
teleoperation. This assumption limits
the applicability of robots in the real world, where robots may be frequently
asked to learn new tasks quickly and without programmers, trained roboticists,
or specialized hardware setups. Can we instead have robots learn directly from
a video of a human demonstration?
Reinforcement learning systems can make decisions in one of two ways. In the model-based approach, a system uses a predictive model of the world to ask questions of the form “what will happen if I do x?” to choose the best x1. In the alternative model-free approach, the modeling step is bypassed altogether in favor of learning a control policy directly. Although in practice the line between these two techniques can become blurred, as a coarse guide it is useful for dividing up the space of algorithmic possibilities.
Predictive models can be used to ask “what if?” questions to guide future decisions.
The natural question to ask after making this distinction is whether to use such a predictive model. The field has grappled with this question for quite a while, and is unlikely to reach a consensus any time soon. However, we have learned enough about designing model-based algorithms that it is possible to draw some general conclusions about best practices and common pitfalls. In this post, we will survey various realizations of model-based reinforcement learning methods. We will then describe some of the tradeoffs that come into play when using a learned predictive model for training a policy and how these considerations motivate a simple but effective strategy for model-based reinforcement learning. The latter half of this post is based on our recent paper on model-based policy optimization, for which code is available here.
One of the primary factors behind the success of machine learning approaches in open world settings, such as image recognition and natural language processing, has been the ability of high-capacity deep neural network function approximators to learn generalizable models from large amounts of data. Deep reinforcement learning methods, however, require active online data collection, where the model actively interacts with its environment. This makes such methods hard to scale to complex real-world problems, where active data collection means that large datasets of experience must be collected for every experiment – this can be expensive and, for systems such as autonomous vehicles or robots, potentially unsafe. In a number of domains of practical interest, such as autonomous driving, robotics, and games, there exist plentiful amounts of previously collected interaction data which, consists of informative behaviours that are a rich source of prior information. Deep RL algorithms that can utilize such prior datasets will not only scale to real-world problems, but will also lead to solutions that generalize substantially better. A data-driven paradigm for reinforcement learning will enable us to pre-train and deploy agents capable of sample-efficient learning in the real-world.
In this work, we ask the following question: Can deep RL algorithms effectively leverage prior collected offline data and learn without interaction with the environment? We refer to this problem statement as fully off-policy RL, previously also called batch RL in literature. A class of deep RL algorithms, known as off-policy RL algorithms can, in principle, learn from previously collected data. Recent off-policy RL algorithms such as Soft Actor-Critic (SAC), QT-Opt, and Rainbow, have demonstrated sample-efficient performance in a number of challenging domains such as robotic manipulation and atari games. However, all of these methods still require online data collection, and their ability to learn from fully off-policy data is limited in practice. In this work, we show why existing deep RL algorithms can fail in the fully off-policy setting. We then propose effective solutions to mitigate these issues.