When to Forget? Complexity Trade-offs in Machine Unlearning

Fuente: arXiv
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Hauptverfasser: Van Waerebeke, Martin, Lorenzi, Marco, Neglia, Giovanni, Scaman, Kevin
Format: Preprint
Veröffentlicht: 2025
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author Van Waerebeke, Martin
Lorenzi, Marco
Neglia, Giovanni
Scaman, Kevin
author_facet Van Waerebeke, Martin
Lorenzi, Marco
Neglia, Giovanni
Scaman, Kevin
contents Machine Unlearning (MU) aims at removing the influence of specific data points from a trained model, striving to achieve this at a fraction of the cost of full model retraining. In this paper, we analyze the efficiency of unlearning methods and establish the first upper and lower bounds on minimax computation times for this problem, characterizing the performance of the most efficient algorithm against the most difficult objective function. Specifically, for strongly convex objective functions and under the assumption that the forget data is inaccessible to the unlearning method, we provide a phase diagram for the unlearning complexity ratio -- a novel metric that compares the computational cost of the best unlearning method to full model retraining. The phase diagram reveals three distinct regimes: one where unlearning at a reduced cost is infeasible, another where unlearning is trivial because adding noise suffices, and a third where unlearning achieves significant computational advantages over retraining. These findings highlight the critical role of factors such as data dimensionality, the number of samples to forget, and privacy constraints in determining the practical feasibility of unlearning.
format Preprint
id arxiv_https___arxiv_org_abs_2502_17323
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle When to Forget? Complexity Trade-offs in Machine Unlearning
Van Waerebeke, Martin
Lorenzi, Marco
Neglia, Giovanni
Scaman, Kevin
Machine Learning
Optimization and Control
Machine Unlearning (MU) aims at removing the influence of specific data points from a trained model, striving to achieve this at a fraction of the cost of full model retraining. In this paper, we analyze the efficiency of unlearning methods and establish the first upper and lower bounds on minimax computation times for this problem, characterizing the performance of the most efficient algorithm against the most difficult objective function. Specifically, for strongly convex objective functions and under the assumption that the forget data is inaccessible to the unlearning method, we provide a phase diagram for the unlearning complexity ratio -- a novel metric that compares the computational cost of the best unlearning method to full model retraining. The phase diagram reveals three distinct regimes: one where unlearning at a reduced cost is infeasible, another where unlearning is trivial because adding noise suffices, and a third where unlearning achieves significant computational advantages over retraining. These findings highlight the critical role of factors such as data dimensionality, the number of samples to forget, and privacy constraints in determining the practical feasibility of unlearning.
title When to Forget? Complexity Trade-offs in Machine Unlearning
topic Machine Learning
Optimization and Control
url https://arxiv.org/abs/2502.17323