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arXiv · 2007.03812

Robust Multi-Agent Multi-Armed Bandits

Daniel Vial·Sanjay Shakkottai·R. Srikant
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Abstract

Recent works have shown that agents facing independent instances of a stochastic $K$-armed bandit can collaborate to decrease regret. However, these works assume that each agent always recommends their individual best-arm estimates to other agents, which is unrealistic in envisioned applications (machine faults in distributed computing or spam in social recommendation systems). Hence, we generalize the setting to include $n$ honest and $m$ malicious agents who recommend best-arm estimates and arbitrary arms, respectively. We first show that even with a single malicious agent, existing collaboration-based algorithms fail to improve regret guarantees over a single-agent baseline. We propose a scheme where honest agents learn who is malicious and dynamically reduce communication with (i.e., "block") them. We show that collaboration indeed decreases regret for this algorithm, assuming $m$ is small compared to $K$ but without assumptions on malicious agents' behavior, thus ensuring that our algorithm is robust against any malicious recommendation strategy.

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Daniel Vial, Sanjay Shakkottai, R. Srikant. 2021-10-10. Robust Multi-Agent Multi-Armed Bandits. https://arxiv.org/abs/2007.03812

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