A Thorough Assessment of the Non-IID Data Impact in Federated Learning

Fuente: arXiv
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Auteurs principaux: Jimenez-Gutierrez, Daniel M., Hassanzadeh, Mehrdad, Anagnostopoulos, Aris, Chatzigiannakis, Ioannis, Vitaletti, Andrea
Format: Preprint
Publié: 2025
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author Jimenez-Gutierrez, Daniel M.
Hassanzadeh, Mehrdad
Anagnostopoulos, Aris
Chatzigiannakis, Ioannis
Vitaletti, Andrea
author_facet Jimenez-Gutierrez, Daniel M.
Hassanzadeh, Mehrdad
Anagnostopoulos, Aris
Chatzigiannakis, Ioannis
Vitaletti, Andrea
contents Federated learning (FL) allows collaborative machine learning (ML) model training among decentralized clients' information, ensuring data privacy. The decentralized nature of FL deals with non-independent and identically distributed (non-IID) data. This open problem has notable consequences, such as decreased model performance and more significant convergence times. Despite its importance, experimental studies systematically addressing all types of data heterogeneity (a.k.a. non-IIDness) remain scarce. We aim to fill this gap by assessing and quantifying the non-IID effect through a thorough empirical analysis. We use the Hellinger Distance (HD) to measure differences in distribution among clients. Our study benchmarks four state-of-the-art strategies for handling non-IID data, including label, feature, quantity, and spatiotemporal skewness, under realistic and controlled conditions. This is the first comprehensive analysis of the spatiotemporal skew effect in FL. Our findings highlight the significant impact of label and spatiotemporal skew non-IID types on FL model performance, with notable performance drops occurring at specific HD thresholds. Additionally, the FL performance is heavily affected mainly when the non-IIDness is extreme. Thus, we provide recommendations for FL research to tackle data heterogeneity effectively. Our work represents the most extensive examination of non-IIDness in FL, offering a robust foundation for future research.
format Preprint
id arxiv_https___arxiv_org_abs_2503_17070
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle A Thorough Assessment of the Non-IID Data Impact in Federated Learning
Jimenez-Gutierrez, Daniel M.
Hassanzadeh, Mehrdad
Anagnostopoulos, Aris
Chatzigiannakis, Ioannis
Vitaletti, Andrea
Machine Learning
Artificial Intelligence
Federated learning (FL) allows collaborative machine learning (ML) model training among decentralized clients' information, ensuring data privacy. The decentralized nature of FL deals with non-independent and identically distributed (non-IID) data. This open problem has notable consequences, such as decreased model performance and more significant convergence times. Despite its importance, experimental studies systematically addressing all types of data heterogeneity (a.k.a. non-IIDness) remain scarce. We aim to fill this gap by assessing and quantifying the non-IID effect through a thorough empirical analysis. We use the Hellinger Distance (HD) to measure differences in distribution among clients. Our study benchmarks four state-of-the-art strategies for handling non-IID data, including label, feature, quantity, and spatiotemporal skewness, under realistic and controlled conditions. This is the first comprehensive analysis of the spatiotemporal skew effect in FL. Our findings highlight the significant impact of label and spatiotemporal skew non-IID types on FL model performance, with notable performance drops occurring at specific HD thresholds. Additionally, the FL performance is heavily affected mainly when the non-IIDness is extreme. Thus, we provide recommendations for FL research to tackle data heterogeneity effectively. Our work represents the most extensive examination of non-IIDness in FL, offering a robust foundation for future research.
title A Thorough Assessment of the Non-IID Data Impact in Federated Learning
topic Machine Learning
Artificial Intelligence
url https://arxiv.org/abs/2503.17070