Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: On The Impact of Client Sampling on Federated Learning Convergence   While clients' sampling is a central operation of current state-of-the-art
federated learning (FL) approaches, the impact of this procedure on the
convergence and speed of FL remains to date under-investigated. In this work we
introduce a novel decomposition theorem for the convergence of FL, allowing to
clearly quantify the impact of client sampling on the global model update.
Contrarily to previous convergence analyses, our theorem provides the exact
decomposition of a given convergence step, thus enabling accurate
considerations about the role of client sampling and heterogeneity. First, we
provide a theoretical ground for previously reported results on the
relationship between FL convergence and the variance of the aggregation
weights. Second, we prove for the first time that the quality of FL convergence
is also impacted by the resulting covariance between aggregation weights.
Third, we establish that the sum of the aggregation weights is another source
of slow-down and should be equal to 1 to improve FL convergence speed. Our
theory is general, and is here applied to Multinomial Distribution (MD) and
Uniform sampling, the two default client sampling in FL, and demonstrated
through a series of experiments in non-iid and unbalanced scenarios. Our
results suggest that MD sampling should be used as default sampling scheme, due
to the resilience to the changes in data ratio during the learning process,
while Uniform sampling is superior only in the special case when clients have
the same amount of data.

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The categories of this paper are: quant-ph
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The categories of this paper are: patt-sol
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The categories of this paper are: nucl-ex
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The categories of this paper are: q-alg
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The categories of this paper are: math-ph
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The categories of this paper are: q-fin
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The categories of this paper are: supr-con
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The categories of this paper are: math
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The categories of this paper are: cond-mat
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The categories of this paper are: alg-geom
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The categories of this paper are: plasm-ph
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The categories of this paper are: ao-sci
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The categories of this paper are: dg-ga
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The categories of this paper are: funct-an
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The categories of this paper are: hep-ph
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The categories of this paper are: econ