Meta-Gradient Reinforcement Learning with an Objective Discovered Online (2007.08433v1)

Abstract: Deep reinforcement learning includes a broad family of algorithms that parameterise an internal representation, such as a value function or policy, by a deep neural network. Each algorithm optimises its parameters with respect to an objective, such as Q-learning or policy gradient, that defines its semantics. In this work, we propose an algorithm based on meta-gradient descent that discovers its own objective, flexibly parameterised by a deep neural network, solely from interactive experience with its environment. Over time, this allows the agent to learn how to learn increasingly effectively. Furthermore, because the objective is discovered online, it can adapt to changes over time. We demonstrate that the algorithm discovers how to address several important issues in RL, such as bootstrapping, non-stationarity, and off-policy learning. On the Atari Learning Environment, the meta-gradient algorithm adapts over time to learn with greater efficiency, eventually outperforming the median score of a strong actor-critic baseline.

• The paper introduces a meta-gradient descent technique that dynamically formulates learning objectives from real-time environmental feedback.
• It demonstrates improved performance in the Atari Learning Environment by effectively addressing non-stationarity and off-policy challenges.
• This approach minimizes reliance on static, handcrafted objectives, paving the way for more autonomous and scalable reinforcement learning agents.

Overview of Meta-Gradient Reinforcement Learning

The research paper titled "Meta-Gradient Reinforcement Learning with an Objective Discovered Online" presents an innovative approach to reinforcement learning (RL) by developing a meta-learning algorithm capable of discovering its own learning objectives dynamically from its environment. This work addresses one key limitation of traditional RL, where agents optimize pre-defined objectives crafted by human experts. The proposed solution leverages meta-gradient descent to adapt and refine RL objectives online, promoting improved learning efficiency in varied environments.

Summary of Key Concepts

• Meta-Gradient Descent: The core idea is utilizing meta-gradient descent to inform and adapt the agent’s learning objectives based on real-time interaction with its environment. This technique allows for discovering objectives that address RL challenges such as bootstrapping, non-stationarity, and off-policy learning.
• Dynamic Objective Formulation: Instead of using a static, pre-defined learning objective like Q-learning, the algorithm dynamically learns what works best as the environment changes. This facilitates a "learning to learn" paradigm where the agent continually optimizes its learning process.
• Implementation and Performance: The algorithm was tested on the Atari Learning Environment, where it exhibited adaptability and efficiency, outperforming a strong actor-critic baseline by employing a flexible objective discovered through meta-gradients.

Technical Insights

The paper explores several technical dimensions:

• Update Target Parameterization: The update targets in traditional RL algorithms are parameterized by neural networks in the proposed approach. This allows greater versatility and adaptation of the learning objectives in the face of changing environmental contexts.
• Bootstrapping and Non-stationarity: The algorithm showcases its ability to autonomously handle bootstrapping and non-stationary processes without explicit instructions from human designers, highlighting its robustness and adaptability.
• Off-Policy Learning: Through experiments in a large-scale setting, particularly with Atari games, the authors demonstrate the algorithm's efficacy in mitigating off-policy learning challenges by dynamically adjusting the parameters influencing the update targets.

Implications for AI Development

The implications of this research are multifaceted, encompassing theoretical advancements in understanding meta-learning processes and practical enhancements in developing more autonomous RL agents. Notably, it suggests a potential shift away from handcrafted learning objectives towards self-discovered ones, thereby enabling greater scalability and adaptability in RL applications.

Future Directions

Avenues for further exploration include:

• Expanding the algorithm's capabilities to more complex environments than the Atari domain.
• Enhancing computational efficiency and reducing the computational overhead associated with real-time meta-gradient computation.
• Investigating the possible extension of this approach to other areas of machine learning where objective discovery could be beneficial.

In conclusion, while this paper does not purport to offer revolutionary advancements, it methodically outlines a significant improvement in RL methodologies through the application of meta-gradient learning to algorithm objectives. This approach paves the way for more autonomous learning frameworks capable of adapting to diverse and dynamic tasks.