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Scaling Exponents Across Parameterizations and Optimizers (arxiv.org)
2 points by johnsutor on Jul 31, 2024 | hide | past | pdf | discuss on HN

In plain words: They reworked the math for how learning rates should change as networks widen, without assuming parameters line up with data. In tens of thousands of runs, every parameterization carried settings from small to large, and a per-layer rate rule for the standard setup did best.

Abstract

Robust and effective scaling of models from small to large width typically requires the precise adjustment of many algorithmic and architectural details, such as parameterization and optimizer choices. In this work, we propose a new perspective on parameterization by investigating a key assumption in prior work about the alignment between parameters and data and derive new theoretical results under weaker assumptions and a broader set of optimizers. Our extensive empirical investigation includes tens of thousands of models trained with all combinations of three optimizers, four parameterizations, several alignment assumptions, more than a dozen learning rates, and fourteen model sizes up to 26.8B parameters. We find that the best learning rate scaling prescription would often have been excluded by the assumptions in prior work. Our results show that all parameterizations, not just maximal update parameterization (muP), can achieve hyperparameter transfer; moreover, our novel per-layer learning rate prescription for standard parameterization outperforms muP. Finally, we demonstrate that an overlooked aspect of parameterization, the epsilon parameter in Adam, must be scaled correctly to avoid gradient underflow and propose Adam-atan2, a new numerically stable, scale-invariant version of Adam that eliminates the epsilon hyperparameter entirely.

Katie Everett, Lechao Xiao, Mitchell Wortsman, Alexander A. Alemi, Roman Novak, Peter J. Liu, Izzeddin Gur, Jascha Sohl-Dickstein, Leslie Pack Kaelbling, Jaehoon Lee, Jeffrey Pennington
arXiv:2407.05872 · cs.LG · submitted Jul 8, 2024 · updated Jul 16, 2024
abstract · pdf · html · 63 pages, International Conference on Machine Learning 2024

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