Papers › Improving SAM Requires Rethinking its Optimization Formulation

Improving SAM Requires Rethinking its Optimization Formulation

17 Jul 2024arXiv:2407.12993archive 2025-07-28

Wanyun Xie, Fabian Latorre, Kimon Antonakopoulos, Thomas Pethick, Volkan Cevher

This paper rethinks Sharpness-Aware Minimization (SAM), which is originally formulated as a zero-sum game where the weights of a network and a bounded perturbation try to minimize/maximize, respectively, the same differentiable loss. To fundamentally improve this design, we argue that SAM should instead be reformulated using the 0-1 loss. As a continuous relaxation, we follow the simple conventional approach where the minimizing (maximizing) player uses an upper bound (lower bound) surrogate to the 0-1 loss. This leads to a novel formulation of SAM as a bilevel optimization problem, dubbed as BiSAM. BiSAM with newly designed lower-bound surrogate loss indeed constructs stronger perturbation. Through numerical evidence, we show that BiSAM consistently results in improved performance when compared to the original SAM and variants, while enjoying similar computational complexity. Our code is available at https://github.com/LIONS-EPFL/BiSAM.

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LIONS-EPFL/BiSAM officialmentioned in papermentioned on GitHubpytorch report

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1ran · our draft was wrong
2ran · fixture could not drive it
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SAM LIONS-EPFL/BiSAM/utility/sam.py official repository ran MIT (permissive) · aacd1c60e21babdd · report
perturbation_loss_log lions-epfl/bisam/loss_fnc.py official repository ran · fixture could not drive it MIT (permissive) · 83634a07e94d9e91 · report
perturbation_loss_tanh lions-epfl/bisam/loss_fnc.py official repository ran · fixture could not drive it MIT (permissive) · dd73f8d81a55afb2 · report
smooth_crossentropy lions-epfl/bisam/loss_fnc.py official repository ran · our draft was wrong MIT (permissive) · e34a3257087e025a · report

Tasks

Bilevel Optimization

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Methods

SAMSharpness-Aware Minimization

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