New Zealand

We propose and study a general framework for modelling and formal reasoning about multi-agent systems and, in particular, multi-stage games where both quantitative and qualitative objectives and constraints are involved. Our models enrich concurrent game models with payoffs and guards on actions associated with each state of the model. We propose a quantitative extension of the logic ATL* that enables the combination of quantitative and qualitative reasoning. We illustrate the framework with some examples and then consider the model-checking problems arising in our framework and establish some general undecidability and decidability results for them.

AAMAS 2022

Combining quantitative and qualitative reasoning in concurrent multi-player games

quantitative and qualitative reasoning

multi-stage games

logic


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The energy cost of storing and moving data is enormous, and is growing at such a rapid pace that within a few years the power demand may overwhelm some developed nations. Non-volatile memory (NVM) and neuromorphic computing are enabling critical advances in this area, but there are many scientific and technological challenges. This conference will cover the materials challenges of different memory technologies, from the fundamental processes and mechanisms, to industry perspectives on materials specifications and manufacturing.

Materials Challenges for Memory

technical paper

AAMAS (International Conference on Autonomous Agents and Multiagent Systems) is the largest and most influential conference in the area of agents and multiagent systems. The aim of the conference is to bring together researchers and practitioners in all areas of agent technology and to provide a single, high-profile, internationally renowned forum for research in the theory and practice of autonomous agents and multiagent systems. AAMAS is the flagship conference of the non-profit International Foundation for Autonomous Agents and Multiagent Systems (IFAAMAS).

The AAMAS conference series was initiated in 2002 in Bologna, Italy as a joint event comprising the 6th International Conference on Autonomous Agents (AA), the 5th International Conference on Multiagent Systems (ICMAS), and the 9th International Workshop on Agent Theories, Architectures, and Languages (ATAL).

Subsequent AAMAS conferences have been held in Melbourne, Australia (July 2003), New York City, NY, USA (July 2004), Utrecht, The Netherlands (July 2005), Hakodate, Japan (May 2006), Honolulu, Hawaii, USA (May 2007), Estoril, Portugal (May 2008), Budapest, Hungary (May 2009), Toronto, Canada (May 2010), Taipei, Taiwan (May 2011), Valencia, Spain (June 2012), Minnesota, USA (May 2013), Paris, France (May 2014), Istanbul, Turkey (May 2015), Singapore (May 2016), São Paulo (2017) and Stockholm, Sweden (2018), Montreal (May 2019), Auckland (May 2020, Virtual), London (May 2021, Virtual).
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A ticket is required to attend this event, please register using the link below:

https://aamas2022-conference.auckland.ac.nz/attending/registration/

Registration Is Required

AAMAS (International Conference on Autonomous Agents and Multiagent Systems) is the largest and most influential conference in the area of agents and multiagent systems. The aim of the conference is to bring together researchers and practitioners in all areas of agent technology and to provide a single, high-profile, internationally renowned forum for research in the theory and practice of autonomous agents and multiagent systems. AAMAS is the flagship conference of the non-profit International Foundation for Autonomous Agents and Multiagent Systems (IFAAMAS).


We study a cooperative game setting where the grand coalition may change since the initial players can invite more players. We focus on the monotone games, i.e., adding more players to the grand coalition is not harmful. We model the invitation relationship as a directed acyclic graph. Our goal is to design a reward distribution mechanism for this new cooperative game setting such that players are incentivized to invite new players. In this paper, we propose the weighted permission Shapley value (inspired by permission structure and the weighted Shapley value) to achieve the goal. Our solution offers the very first attempt to incentivize players to invite more players to form a larger coalition via their private invitations in cooperative settings.

Incentives to Invite Others to Form Larger Coalitions


We initiate the study of the social welfare loss caused by corrupt auctioneers, both in single-item and multi-unit auctions. In our model, the auctioneer may collude with the winning bidders by letting them lower their bids in exchange for a (possibly bidder-dependent) fraction \gamma of the surplus. We consider different corruption schemes. In the most basic one, all winning bidders lower their bid to the highest losing bid. We show that this setting is equivalent to a \gamma-hybrid auction in which the payments are a convex combination of first-price and the second-price payments. More generally, we consider corruption schemes that can be related to \gamma-approximate first-price auctions (\gamma-FPA), where the payments recover at least a \gamma-fraction of the first-price payments. Our goal is to obtain a precise understanding of the robust price of anarchy (POA) of such auctions. If no restrictions are imposed on the bids, we prove a bound on the robust POA of \gamma-FPA which is tight (over the entire range of \gamma) for the single-item and the multi-unit auction setting. On the other hand, if the bids satisfy the no-overbidding assumption a more fine-grained landscape of the price of anarchy emerges, depending on the auction setting and the equilibrium notion. Albeit being more challenging, we derive (almost) tight bounds for both auction settings and several equilibrium notions, basically leaving open some (small) gaps for the coarse-correlated price of anarchy only.

Corruption in Auctions: Social Welfare Loss in Hybrid Multi-Unit Auctions


Bargaining can be used to resolve mixed-motive games in multi-agent systems. Although there is an abundance of negotiation strategies implemented in automated negotiating agents, most agents are based on single fixed strategies, while it is widely acknowledged that there is no single best-performing strategy for all negotiation settings.

In this paper, we focus on bargaining settings where opponents are repeatedly encountered, but the bargaining problems change. We introduce a novel method that automatically creates and deploys a portfolio of complementary negotiation strategies using a training set and optimise pay-off in never-before-seen bargaining settings through per-setting strategy selection. Our method relies on the following contributions. We introduce a feature representation that captures characteristics for both the opponent and the bargaining problem. We model the behaviour of an opponent during a negotiation based on its actions, which is indicative of its negotiation strategy, in order to be more effective in future encounters.

Our combination of feature-based methods generalises to new negotiation settings, as in practice, over time, it selects effective counter strategies in future encounters. Our approach is tested in an \gls{anac}-like tournament, and we show that we are capable of winning such a tournament with a \(5.6\% \) increase in pay-off compared to the runner-up agent.

Automated Configuration and Usage of Strategy Portfolios for Bargaining



We study strategic network formation games in which agents at- tempt to form (costly) links in order to maximize their network centrality. Our model derives from Jackson and Wolinsky’s symmetric connection model, but allows for heterogeneity in agent utilities by replacing decay centrality (implicit in the J-W model) by a va- riety of classical centrality measures, as well as game-theoretic measures of centrality. We are primarily interested in characteriz- ing the asymptotically pairwise stable networks, i.e. those networks that are pairwise stable for all sufficiently small, positive edge costs. We uncover a rich typology of stability:

- we give an axiomatic approach to network centrality that allows us to predict the stable network for a rich set of com- bination of centrality utility functions, yielding stable networks with features reminiscent of structural properties such as "core periphery" and "rich club" networks.
- We show that a simple variation on the model renders it universal, i.e. every network may be a stable network.
- We also show that often we can infer a significant amount about agent utilities from the structure of stable networks.

Being Central on the Cheap: Stability in Heterogeneous Multiagent Centrality Games


The potential of reinforcement learning (RL) to deliver aligned and performant agents is partially bottlenecked by the reward engineering problem. One alternative to heuristic trial-and-error is preference-based RL (PbRL), where a reward function is inferred from sparse human feedback. However, prior PbRL methods lack interpretability of the learned reward structure, which hampers the ability to assess robustness and alignment. We propose an online, active preference learning algorithm that constructs reward functions with the intrinsically interpretable, compositional structure of a tree. Using both synthetic and human-provided feedback, we demonstrate sample-efficient learning of tree-structured reward functions in several environments, then harness the enhanced interpretability to explore and debug for alignment.

Interpretable Preference-based Reinforcement Learning with Tree-Structured Reward Functions


Automated Negotiation is attracting more attention from researchers recently
as it is becoming more relevant to industrial and business applications with
increased reliance on automated systems.
Most research in this area assumes either a
single negotiation thread with a well-defined utility function for each
agent involved or a set of concurrent negotiations with an ordering of
outcomes in each local negotiation. In this paper, we consider an agent
engaged in a set of concurrent negotiations with a utility function
defined only for the complete set of agreements in all of them and
no locally defined ordering of outcomes in any negotiation independent from what
happens in the others. We argue that this problem setting is interesting both 
from the academic and the industrial points of view. The paper then
presents an algorithm that allows such agent to maximize its expected
global utility by orchestrating its behavior in all negotiation
threads. The performance of the proposed method is analyzed theoretically
and empirically using simulation in the context of a trading market.

Concurrent Negotiations with Global Utility Functions


We introduce a practical and scalable algorithm (PALMA) for solving one of the fundamental problems of multi-agent systems -- finding matches and allocations -- in unboundedly large settings (e.g., resource allocation in urban environments, mobility-on-demand systems, etc.), while providing strong worse-case privacy guarantees. PALMA is decentralized, runs on-device, requires no inter-agent communication, and converges in constant time under reasonable assumptions. We evaluate PALMA in a mobility-on-demand and a paper assignment scenario, using real data in both, and demonstrate that it provides a strong level of privacy (epsilon < 1 and median as low as epsilon = 0.5 across agents) and high quality matchings (up to 86% of the non-private optimal).

A Distributed Differentially Private Algorithm for Resource Allocation in Unboundedly Large Settings


Many real-world scenarios involve teams of agents who have to coordinate their policies to achieve a shared goal. Most previous studies mainly focus on learning decentralized control policies to maximize a common reward and rarely consider the coordinated control policies, which is critical in dynamic, complicated environments. Out of the fully decentralized rules, we propose a graph-based coordination strategy (GCS) which consists of a graph generator and a factored coordination policy. We adopt an encoder-decoder model as the generator to construct a directed acyclic graph (DAG), dynamically representing the underlying decision structure. We also apply the DAGness and depth constrained optimization in the graph generator to balance efficiency and performance. To exploit the underlying decision structure, we investigate the factored coordination policy to obtain the optimally coordinated behaviors among agents. We train the graph generator and the factored coordination policy simultaneously to maximize the discounted return. Empirical evaluations on Collaborative Gaussian Squeeze, Cooperative Navigation, and Google Research Football demonstrate the superiority of the proposed method.

GCS: Graph-Based Coordination Strategy for Multi-Agent Reinforcement Learning


High-performing teams learn intelligent and efficient communication and coordination strategies to maximize their joint utility. These teams implicitly understand the different roles of heterogeneous team members and adapt their communication protocols accordingly. Multi-Agent Reinforcement Learning (MARL) seeks to develop computational methods for synthesizing such coordination strategies, but formulating models for heterogeneous teams with different state, action, and observation spaces has remained an open problem. Without properly modeling agent heterogeneity, as in prior MARL work that leverages homogeneous graph networks, communication becomes less helpful and can even deteriorate the cooperativity and team performance. We propose Heterogeneous Policy Networks (HetNet) to learn efficient and diverse communication models for coordinating cooperative heterogeneous teams. Building on heterogeneous graph-attention networks, we show that HetNet not only facilitates learning heterogeneous collaborative policies per existing agent-class but also enables end-to-end training for learning highly efficient binarized messaging. Our empirical evaluation shows that HetNet sets a new state of the art in learning coordination and communication strategies for heterogeneous multi-agent teams by achieving an 8.1% to 98.7% performance improvement over the next-best baseline across multiple domains while simultaneously achieving a 200x reduction in the required communication bandwidth.

Learning Efficient Diverse Communication for Cooperative Heterogeneous Teaming


In online advertising, search engines sell ad placements for keywords continuously through auctions. This problem can be seen as an infinitely repeated game since the auction is executed whenever a user performs a query with the keyword. As advertisers may frequently change their bids, the game will have a large set of equilibria with potentially complex strategies. In this paper, we propose the use of natural strategies for reasoning in such setting as they are processable by artificial agents with limited memory and/or computational power as well as understandable by humans users. To reach this goal, we introduce a quantitative version of Strategy Logic with natural strategies in the setting of imperfect information. In a first step, we show how to model strategies for repeated keyword auctions and take advantage of the model for proving properties evaluating this game. In a second step, we study the logic in relation to the distinguishable power, expressivity, and model-checking complexity for strategies with and without recall.

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Next from AAMAS 2022

Incentives to Invite Others to Form Larger Coalitions

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Current-driven magnetic domain-wall logic

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