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Distributed Random Reshuffling Methods with Improved Convergence Guarantees


Concetti Chiave
The paper proposes two distributed random reshuffling algorithms, Gradient Tracking with Random Reshuffling (GT-RR) and Exact Diffusion with Random Reshuffling (ED-RR), that achieve improved convergence guarantees compared to existing distributed random reshuffling methods.
Sintesi

The paper introduces two new distributed optimization algorithms, GT-RR and ED-RR, that leverage random reshuffling (RR) updates to solve the distributed optimization problem over a connected network. Both algorithms inherit favorable characteristics of centralized RR methods and deliver superior numerical and theoretical performance compared to the state-of-the-art decentralized methods.

Key highlights:

  • GT-RR and ED-RR achieve the same convergence rate as centralized RR method (up to coefficients depending on the mixing matrix) for minimizing smooth nonconvex objective functions.
  • The proposed algorithms enjoy enhanced theoretical guarantees in terms of the sample size m and the spectral gap (1-λ) when compared to the existing D-RR algorithm.
  • Under the Polyak-Łojasiewicz (PL) condition, GT-RR and ED-RR achieve improved convergence rate in terms of (1-λ) compared to D-RR, using both constant and decreasing stepsizes.
  • The analysis is based on a general framework that can be applied to derive convergence results for a wide range of distributed algorithms equipped with RR technique.
  • Numerical experiments corroborate the theoretical improvements of the new algorithms.
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Statistiche
The convergence rate of the proposed GT-RR and ED-RR algorithms for minimizing smooth nonconvex objective functions is O(1/[(1-λ)^(1/3)m^(1/3)T^(2/3)]). Under the Polyak-Łojasiewicz (PL) condition, GT-RR and ED-RR achieve a convergence rate of O(1/[(1-λ)mT^2]) in terms of the averaged expected differences between the agents' function values and the global minimum value.
Citazioni
"Both GT-RR and ED-RR share similar procedures with DSGT and ED, respectively, but achieve enhanced convergence results when higher accuracy is demanded." "Notably, GT-RR and ED-RR enjoy better theoretical guarantees compared to the state-of-the-art method D-RR in [18]."

Approfondimenti chiave tratti da

by Kun Huang,Li... alle arxiv.org 04-18-2024

https://arxiv.org/pdf/2306.12037.pdf
Distributed Random Reshuffling Methods with Improved Convergence

Domande più approfondite

What are the potential applications of the proposed distributed random reshuffling algorithms beyond the distributed optimization problem considered in this paper

The proposed distributed random reshuffling algorithms, GT-RR and ED-RR, have potential applications beyond the specific distributed optimization problem discussed in the paper. One potential application is in the field of distributed machine learning, where large datasets are distributed across multiple nodes in a network. By incorporating random reshuffling techniques, these algorithms can be used to improve the convergence rates and performance of distributed learning tasks. Additionally, in decentralized systems where data is distributed among multiple agents or devices, these algorithms can help in achieving consensus or synchronization among the agents while minimizing communication overhead. Furthermore, in scenarios where data privacy and security are crucial, the random reshuffling methods can enhance the privacy-preserving aspects of distributed computations by introducing randomness in the data access patterns.

How can the analysis techniques developed in this work be extended to handle more general network topologies or communication models

The analysis techniques developed in this work can be extended to handle more general network topologies or communication models by adapting the framework to accommodate different connectivity structures and communication patterns. One approach could be to consider directed graphs or weighted graphs in the network topology, which may require modifications to the analysis to account for asymmetric communication links or varying communication strengths between nodes. Additionally, the analysis can be extended to include dynamic networks where the connectivity or weights of the edges change over time, leading to more complex convergence analysis. By incorporating these variations, the algorithms can be applied to a wider range of distributed systems with diverse communication architectures.

Can the proposed algorithms be further improved by incorporating additional techniques, such as variance reduction or adaptive step sizes, while maintaining the benefits of random reshuffling

The proposed algorithms, GT-RR and ED-RR, can be further improved by incorporating additional techniques such as variance reduction or adaptive step sizes while maintaining the benefits of random reshuffling. Variance reduction techniques, such as stochastic variance reduced gradient (SVRG) or mini-batch variance reduction, can help in reducing the variance of the stochastic gradients, leading to faster convergence and improved performance. By integrating variance reduction methods into the random reshuffling algorithms, the convergence rates can be enhanced, especially for large-scale optimization problems. Additionally, adaptive step sizes, such as learning rate schedules or adaptive gradient methods, can be incorporated to dynamically adjust the step sizes based on the local gradients or the network topology, improving the robustness and convergence properties of the algorithms. By combining these techniques with random reshuffling, the algorithms can achieve even better performance in distributed optimization tasks.
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