GDBA Revisited: Unleashing the Power of Guided Local Search for Distributed Constraint Optimization

TL;DR

This paper introduces DGLS, an improved guided local search framework for DCOPs, addressing limitations of GDBA, and demonstrating superior empirical performance on various benchmark problems.

Contribution

The paper proposes DGLS with adaptive violation, penalty evaporation, and synchronization, enhancing GDBA's effectiveness for distributed constraint optimization.

Findings

DGLS outperforms state-of-the-art baselines on benchmark problems.

DGLS achieves competitive results on general-valued problems.

DGLS significantly improves anytime performance on structured problems.

Abstract

Local search is an important class of incomplete algorithms for solving Distributed Constraint Optimization Problems (DCOPs) but it often converges to poor local optima. While Generalized Distributed Breakout Algorithm (GDBA) provides a comprehensive rule set to escape premature convergence, its empirical benefits remain marginal on general-valued problems. In this work, we systematically examine GDBA and identify three factors that potentially lead to its inferior performance, i.e., over-aggressive constraint violation conditions, unbounded penalty accumulation, and uncoordinated penalty updates. To address these issues, we propose Distributed Guided Local Search (DGLS), a novel GLS framework for DCOPs that incorporates an adaptive violation condition to selectively penalize constraints with high cost, a penalty evaporation mechanism to control the magnitude of penalization, and a synchronization scheme for coordinated penalty updates. We theoretically show that the penalty values are bounded, and agents play a potential game in DGLS. Extensive empirical results on various benchmarks demonstrate the great superiority of DGLS over state-of-the-art baselines. Compared to Damped Max-sum with high damping factors, our DGLS achieves competitive performance on general-valued problems, and outperforms by significant margins on structured problems in terms of anytime results.