Author

Alex Buna

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#machine learning Preprint Sep 2026

Compute-Optimal Pretrain--Fine-tune in Ridge Gradient Descent

This paper characterise the optimal split under data-dependent evaluation geometries induced by the fine-tuning problem as a compute-split problem under a two-stage pretrain--fine-tune procedure with fixed total optimisation budget, using regularised least squares trained by gradient descent as a tractable setting.

Alex Buna, Fang-Hui Liu, Patrick Rebeschini · 0 citations

Preprint Aug 2026

Minimax Optimal Early-Stopped Gradient Descent for Gaussian Mixture Classification

This work shows that early stopping can overcome suboptimality: in a Gaussian mixture model with label-flipping noise, GD stopped at an appropriate oracle time achieves minimax-optimal excess zero-one risk for covariance spectra with fast and continuous decay, including polynomial and exponential spectral decays.

Alex Buna, S. Liu, Patrick Rebeschini · 0 citations