Search Results for author: Christopher Amato

Found 45 papers, 12 papers with code

Vision and Language Navigation in the Real World via Online Visual Language Mapping

no code implementations16 Oct 2023 Chengguang Xu, Hieu T. Nguyen, Christopher Amato, Lawson L. S. Wong

Directly transferring SOTA navigation policies trained in simulation to the real world is challenging due to the visual domain gap and the absence of prior knowledge about unseen environments.

Vision and Language Navigation

On-Robot Bayesian Reinforcement Learning for POMDPs

no code implementations22 Jul 2023 Hai Nguyen, Sammie Katt, Yuchen Xiao, Christopher Amato

Bayesian reinforcement learning (BRL), thanks to its sample efficiency and ability to exploit prior knowledge, is uniquely positioned as such a solution method.

reinforcement-learning

Safe Deep Reinforcement Learning by Verifying Task-Level Properties

no code implementations20 Feb 2023 Enrico Marchesini, Luca Marzari, Alessandro Farinelli, Christopher Amato

In this paper, we investigate an alternative approach that uses domain knowledge to quantify the risk in the proximity of such states by defining a violation metric.

reinforcement-learning Reinforcement Learning (RL)

Improving Deep Policy Gradients with Value Function Search

no code implementations20 Feb 2023 Enrico Marchesini, Christopher Amato

Deep Policy Gradient (PG) algorithms employ value networks to drive the learning of parameterized policies and reduce the variance of the gradient estimates.

Continuous Control Value prediction

Trajectory-Aware Eligibility Traces for Off-Policy Reinforcement Learning

1 code implementation26 Jan 2023 Brett Daley, Martha White, Christopher Amato, Marlos C. Machado

Off-policy learning from multistep returns is crucial for sample-efficient reinforcement learning, but counteracting off-policy bias without exacerbating variance is challenging.

reinforcement-learning Reinforcement Learning (RL)

Asynchronous Actor-Critic for Multi-Agent Reinforcement Learning

no code implementations20 Sep 2022 Yuchen Xiao, Weihao Tan, Christopher Amato

Synchronizing decisions across multiple agents in realistic settings is problematic since it requires agents to wait for other agents to terminate and communicate about termination reliably.

Decision Making Multi-agent Reinforcement Learning +3

Deep Transformer Q-Networks for Partially Observable Reinforcement Learning

1 code implementation2 Jun 2022 Kevin Esslinger, Robert Platt, Christopher Amato

Such tasks typically require some form of memory, where the agent has access to multiple past observations, in order to perform well.

Partially Observable Reinforcement Learning reinforcement-learning +1

BADDr: Bayes-Adaptive Deep Dropout RL for POMDPs

no code implementations17 Feb 2022 Sammie Katt, Hai Nguyen, Frans A. Oliehoek, Christopher Amato

Under this parameterization, in contrast to previous work, the belief over the state and dynamics is a more scalable inference problem.

Reinforcement Learning (RL)

A Deeper Understanding of State-Based Critics in Multi-Agent Reinforcement Learning

no code implementations3 Jan 2022 Xueguang Lyu, Andrea Baisero, Yuchen Xiao, Christopher Amato

Centralized Training for Decentralized Execution, where training is done in a centralized offline fashion, has become a popular solution paradigm in Multi-Agent Reinforcement Learning.

Multi-agent Reinforcement Learning reinforcement-learning +1

Improving the Efficiency of Off-Policy Reinforcement Learning by Accounting for Past Decisions

no code implementations23 Dec 2021 Brett Daley, Christopher Amato

Off-policy learning from multistep returns is crucial for sample-efficient reinforcement learning, particularly in the experience replay setting now commonly used with deep neural networks.

reinforcement-learning Reinforcement Learning (RL)

Virtual Replay Cache

1 code implementation6 Dec 2021 Brett Daley, Christopher Amato

Return caching is a recent strategy that enables efficient minibatch training with multistep estimators (e. g. the {\lambda}-return) for deep reinforcement learning.

Atari Games reinforcement-learning +1

Human-Level Control without Server-Grade Hardware

1 code implementation1 Nov 2021 Brett Daley, Christopher Amato

Deep Q-Network (DQN) marked a major milestone for reinforcement learning, demonstrating for the first time that human-level control policies could be learned directly from raw visual inputs via reward maximization.

Cloud Computing reinforcement-learning +1

Local Advantage Actor-Critic for Robust Multi-Agent Deep Reinforcement Learning

no code implementations16 Oct 2021 Yuchen Xiao, Xueguang Lyu, Christopher Amato

By using this local critic, each agent calculates a baseline to reduce variance on its policy gradient estimation, which results in an expected advantage action-value over other agents' choices that implicitly improves credit assignment.

Multi-agent Reinforcement Learning Policy Gradient Methods +2

Asynchronous Multi-Agent Actor-Critic with Macro-Actions

no code implementations29 Sep 2021 Yuchen Xiao, Weihao Tan, Christopher Amato

Many realistic multi-agent problems naturally require agents to be capable of performing asynchronously without waiting for other agents to terminate (e. g., multi-robot domains).

Decision Making Policy Gradient Methods

Investigating Alternatives to the Root Mean Square for Adaptive Gradient Methods

no code implementations10 Jun 2021 Brett Daley, Christopher Amato

Adam is an adaptive gradient method that has experienced widespread adoption due to its fast and reliable training performance.

Reconciling Rewards with Predictive State Representations

1 code implementation7 Jun 2021 Andrea Baisero, Christopher Amato

We show that there is a mismatch between optimal POMDP policies and the optimal PSR policies derived from approximate rewards.

Hierarchical Robot Navigation in Novel Environments using Rough 2-D Maps

no code implementations7 Jun 2021 Chengguang Xu, Christopher Amato, Lawson L. S. Wong

In this work, we propose an approach that leverages a rough 2-D map of the environment to navigate in novel environments without requiring further learning.

Navigate Robot Navigation

Unbiased Asymmetric Reinforcement Learning under Partial Observability

no code implementations25 May 2021 Andrea Baisero, Christopher Amato

In partially observable reinforcement learning, offline training gives access to latent information which is not available during online training and/or execution, such as the system state.

Partially Observable Reinforcement Learning reinforcement-learning +1

Decentralized Reinforcement Learning for Multi-Target Search and Detection by a Team of Drones

no code implementations17 Mar 2021 Roi Yehoshua, Juan Heredia-Juesas, Yushu Wu, Christopher Amato, Jose Martinez-Lorenzo

Targets search and detection encompasses a variety of decision problems such as coverage, surveillance, search, observing and pursuit-evasion along with others.

reinforcement-learning Reinforcement Learning (RL)

Stratified Experience Replay: Correcting Multiplicity Bias in Off-Policy Reinforcement Learning

no code implementations22 Feb 2021 Brett Daley, Cameron Hickert, Christopher Amato

Our theory prescribes a special non-uniform distribution to cancel this effect, and we propose a stratified sampling scheme to efficiently implement it.

reinforcement-learning Reinforcement Learning (RL)

Contrasting Centralized and Decentralized Critics in Multi-Agent Reinforcement Learning

no code implementations8 Feb 2021 Xueguang Lyu, Yuchen Xiao, Brett Daley, Christopher Amato

Centralized Training for Decentralized Execution, where agents are trained offline using centralized information but execute in a decentralized manner online, has gained popularity in the multi-agent reinforcement learning community.

Misconceptions Multi-agent Reinforcement Learning +2

Safe Multi-Agent Reinforcement Learning via Shielding

no code implementations27 Jan 2021 Ingy Elsayed-Aly, Suda Bharadwaj, Christopher Amato, Rüdiger Ehlers, Ufuk Topcu, Lu Feng

Multi-agent reinforcement learning (MARL) has been increasingly used in a wide range of safety-critical applications, which require guaranteed safety (e. g., no unsafe states are ever visited) during the learning process. Unfortunately, current MARL methods do not have safety guarantees.

Multi-agent Reinforcement Learning reinforcement-learning +1

Belief-Grounded Networks for Accelerated Robot Learning under Partial Observability

1 code implementation19 Oct 2020 Hai Nguyen, Brett Daley, Xinchao Song, Christopher Amato, Robert Platt

Many important robotics problems are partially observable in the sense that a single visual or force-feedback measurement is insufficient to reconstruct the state.

Expectigrad: Fast Stochastic Optimization with Robust Convergence Properties

1 code implementation3 Oct 2020 Brett Daley, Christopher Amato

Many popular adaptive gradient methods such as Adam and RMSProp rely on an exponential moving average (EMA) to normalize their stepsizes.

Stochastic Optimization

Macro-Action-Based Deep Multi-Agent Reinforcement Learning

no code implementations18 Apr 2020 Yuchen Xiao, Joshua Hoffman, Christopher Amato

In real-world multi-robot systems, performing high-quality, collaborative behaviors requires robots to asynchronously reason about high-level action selection at varying time durations.

Decision Making Decision Making Under Uncertainty +3

Reconciling λ-Returns with Experience Replay

1 code implementation NeurIPS 2019 Brett Daley, Christopher Amato

Modern deep reinforcement learning methods have departed from the incremental learning required for eligibility traces, rendering the implementation of the λ-return difficult in this context.

Atari Games Incremental Learning

Active Goal Recognition

no code implementations24 Sep 2019 Christopher Amato, Andrea Baisero

We propose to combine goal recognition with other observer tasks in order to obtain \emph{active goal recognition} (AGR).

Learning Multi-Robot Decentralized Macro-Action-Based Policies via a Centralized Q-Net

no code implementations19 Sep 2019 Yuchen Xiao, Joshua Hoffman, Tian Xia, Christopher Amato

In many real-world multi-robot tasks, high-quality solutions often require a team of robots to perform asynchronous actions under decentralized control.

Multi-agent Reinforcement Learning

Likelihood Quantile Networks for Coordinating Multi-Agent Reinforcement Learning

no code implementations15 Dec 2018 Xueguang Lyu, Christopher Amato

When multiple agents learn in a decentralized manner, the environment appears non-stationary from the perspective of an individual agent due to the exploration and learning of the other agents.

Multi-agent Reinforcement Learning Philosophy +2

Bayesian Reinforcement Learning in Factored POMDPs

no code implementations14 Nov 2018 Sammie Katt, Frans Oliehoek, Christopher Amato

Bayesian approaches provide a principled solution to the exploration-exploitation trade-off in Reinforcement Learning.

reinforcement-learning Reinforcement Learning (RL)

Reconciling $λ$-Returns with Experience Replay

1 code implementation23 Oct 2018 Brett Daley, Christopher Amato

Modern deep reinforcement learning methods have departed from the incremental learning required for eligibility traces, rendering the implementation of the $\lambda$-return difficult in this context.

Atari Games Incremental Learning

Learning in POMDPs with Monte Carlo Tree Search

no code implementations ICML 2017 Sammie Katt, Frans A. Oliehoek, Christopher Amato

The POMDP is a powerful framework for reasoning under outcome and information uncertainty, but constructing an accurate POMDP model is difficult.

Learning to Teach in Cooperative Multiagent Reinforcement Learning

no code implementations20 May 2018 Shayegan Omidshafiei, Dong-Ki Kim, Miao Liu, Gerald Tesauro, Matthew Riemer, Christopher Amato, Murray Campbell, Jonathan P. How

The problem of teaching to improve agent learning has been investigated by prior works, but these approaches make assumptions that prevent application of teaching to general multiagent problems, or require domain expertise for problems they can apply to.

reinforcement-learning Reinforcement Learning (RL)

Near-Optimal Adversarial Policy Switching for Decentralized Asynchronous Multi-Agent Systems

no code implementations17 Oct 2017 Trong Nghia Hoang, Yuchen Xiao, Kavinayan Sivakumar, Christopher Amato, Jonathan How

The practicality of existing works addressing this challenge is limited to only small-scale synchronous decision-making scenarios or a single agent planning its best response against a single adversary with fixed, procedurally characterized strategies.

Decision Making

Learning for Multi-robot Cooperation in Partially Observable Stochastic Environments with Macro-actions

no code implementations24 Jul 2017 Miao Liu, Kavinayan Sivakumar, Shayegan Omidshafiei, Christopher Amato, Jonathan P. How

We implement two variants of multi-robot Search and Rescue (SAR) domains (with and without obstacles) on hardware to demonstrate the learned policies can effectively control a team of distributed robots to cooperate in a partially observable stochastic environment.

Decision Making Decision Making Under Uncertainty

Stick-Breaking Policy Learning in Dec-POMDPs

no code implementations1 May 2015 Miao Liu, Christopher Amato, Xuejun Liao, Lawrence Carin, Jonathan P. How

Expectation maximization (EM) has recently been shown to be an efficient algorithm for learning finite-state controllers (FSCs) in large decentralized POMDPs (Dec-POMDPs).

Decentralized Control of Partially Observable Markov Decision Processes using Belief Space Macro-actions

no code implementations20 Feb 2015 Shayegan Omidshafiei, Ali-akbar Agha-mohammadi, Christopher Amato, Jonathan P. How

To allow for a high-level representation that is natural for multi-robot problems and scalable to large discrete and continuous problems, this paper extends the Dec-POMDP model to the decentralized partially observable semi-Markov decision process (Dec-POSMDP).

Decision Making

Scalable Planning and Learning for Multiagent POMDPs: Extended Version

1 code implementation4 Apr 2014 Christopher Amato, Frans A. Oliehoek

Online, sample-based planning algorithms for POMDPs have shown great promise in scaling to problems with large state spaces, but they become intractable for large action and observation spaces.

reinforcement-learning Reinforcement Learning (RL)

Planning for Decentralized Control of Multiple Robots Under Uncertainty

no code implementations12 Feb 2014 Christopher Amato, George D. Konidaris, Gabriel Cruz, Christopher A. Maynor, Jonathan P. How, Leslie P. Kaelbling

We describe a probabilistic framework for synthesizing control policies for general multi-robot systems, given environment and sensor models and a cost function.

Incremental Clustering and Expansion for Faster Optimal Planning in Dec-POMDPs

no code implementations4 Feb 2014 Frans Adriaan Oliehoek, Matthijs T. J. Spaan, Christopher Amato, Shimon Whiteson

We provide theoretical guarantees that, when a suitable heuristic is used, both incremental clustering and incremental expansion yield algorithms that are both complete and search equivalent.

Clustering

Policy Iteration for Decentralized Control of Markov Decision Processes

no code implementations15 Jan 2014 Daniel S. Bernstein, Christopher Amato, Eric A. Hansen, Shlomo Zilberstein

The main contribution of this paper is an optimal policy iteration algorithm for solving DEC-POMDPs.

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