Understanding Server-Assisted Federated Learning in the Presence of Incomplete Client Participation

Fuente: arXiv
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Main Authors: Yang, Haibo, Qiu, Peiwen, Khanduri, Prashant, Fang, Minghong, Liu, Jia
Format: Preprint
Published: 2024
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_version_ 1866917674490003456
author Yang, Haibo
Qiu, Peiwen
Khanduri, Prashant
Fang, Minghong
Liu, Jia
author_facet Yang, Haibo
Qiu, Peiwen
Khanduri, Prashant
Fang, Minghong
Liu, Jia
contents Existing works in federated learning (FL) often assume an ideal system with either full client or uniformly distributed client participation. However, in practice, it has been observed that some clients may never participate in FL training (aka incomplete client participation) due to a myriad of system heterogeneity factors. A popular approach to mitigate impacts of incomplete client participation is the server-assisted federated learning (SA-FL) framework, where the server is equipped with an auxiliary dataset. However, despite SA-FL has been empirically shown to be effective in addressing the incomplete client participation problem, there remains a lack of theoretical understanding for SA-FL. Meanwhile, the ramifications of incomplete client participation in conventional FL are also poorly understood. These theoretical gaps motivate us to rigorously investigate SA-FL. Toward this end, we first show that conventional FL is {\em not} PAC-learnable under incomplete client participation in the worst case. Then, we show that the PAC-learnability of FL with incomplete client participation can indeed be revived by SA-FL, which theoretically justifies the use of SA-FL for the first time. Lastly, to provide practical guidance for SA-FL training under {\em incomplete client participation}, we propose the $\mathsf{SAFARI}$ (server-assisted federated averaging) algorithm that enjoys the same linear convergence speedup guarantees as classic FL with ideal client participation assumptions, offering the first SA-FL algorithm with convergence guarantee. Extensive experiments on different datasets show $\mathsf{SAFARI}$ significantly improves the performance under incomplete client participation.
format Preprint
id arxiv_https___arxiv_org_abs_2405_02745
institution arXiv
publishDate 2024
record_format arxiv
spellingShingle Understanding Server-Assisted Federated Learning in the Presence of Incomplete Client Participation
Yang, Haibo
Qiu, Peiwen
Khanduri, Prashant
Fang, Minghong
Liu, Jia
Machine Learning
Distributed, Parallel, and Cluster Computing
Existing works in federated learning (FL) often assume an ideal system with either full client or uniformly distributed client participation. However, in practice, it has been observed that some clients may never participate in FL training (aka incomplete client participation) due to a myriad of system heterogeneity factors. A popular approach to mitigate impacts of incomplete client participation is the server-assisted federated learning (SA-FL) framework, where the server is equipped with an auxiliary dataset. However, despite SA-FL has been empirically shown to be effective in addressing the incomplete client participation problem, there remains a lack of theoretical understanding for SA-FL. Meanwhile, the ramifications of incomplete client participation in conventional FL are also poorly understood. These theoretical gaps motivate us to rigorously investigate SA-FL. Toward this end, we first show that conventional FL is {\em not} PAC-learnable under incomplete client participation in the worst case. Then, we show that the PAC-learnability of FL with incomplete client participation can indeed be revived by SA-FL, which theoretically justifies the use of SA-FL for the first time. Lastly, to provide practical guidance for SA-FL training under {\em incomplete client participation}, we propose the $\mathsf{SAFARI}$ (server-assisted federated averaging) algorithm that enjoys the same linear convergence speedup guarantees as classic FL with ideal client participation assumptions, offering the first SA-FL algorithm with convergence guarantee. Extensive experiments on different datasets show $\mathsf{SAFARI}$ significantly improves the performance under incomplete client participation.
title Understanding Server-Assisted Federated Learning in the Presence of Incomplete Client Participation
topic Machine Learning
Distributed, Parallel, and Cluster Computing
url https://arxiv.org/abs/2405.02745