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Rotational Equilibrium: How Weight Decay Balances Learning Across Neural Networks

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arxiv 2305.17212 v4 pith:2TJ74S6D submitted 2023-05-26 cs.LG

Rotational Equilibrium: How Weight Decay Balances Learning Across Neural Networks

classification cs.LG
keywords weightdecaylearningacrossrotationadamdeepequilibrium
verification ladder T0 review T1 audit T2 compute T3 formal T4 reserved
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This study investigates how weight decay affects the update behavior of individual neurons in deep neural networks through a combination of applied analysis and experimentation. Weight decay can cause the expected magnitude and angular updates of a neuron's weight vector to converge to a steady state we call rotational equilibrium. These states can be highly homogeneous, effectively balancing the average rotation -- a proxy for the effective learning rate -- across different layers and neurons. Our work analyzes these dynamics across optimizers like Adam, Lion, and SGD with momentum, offering a new simple perspective on training that elucidates the efficacy of widely used but poorly understood methods in deep learning. We demonstrate how balanced rotation plays a key role in the effectiveness of normalization like Weight Standardization, as well as that of AdamW over Adam with L2-regularization. Finally, we show that explicitly controlling the rotation provides the benefits of weight decay while substantially reducing the need for learning rate warmup.

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Forward citations

Cited by 9 Pith papers

Reviewed papers in the Pith corpus that reference this work. Sorted by Pith novelty score.

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  2. SOAP, Muon, and Beyond: Pushing LLM Pretraining Scales

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  3. Improving Neural Network Training by Decoupling the Magnitude and Direction of Weight Vectors

    cs.LG 2026-06 unverdicted novelty 6.0

    MD Decoupling factorizes weights into fixed-norm directions and learnable per-row/column magnitudes updated at independent rates, improving Adam and Muon training stability and scale transfer without weight decay or warmup.

  4. Weibull Weight-Scale Parameter Evolution under AdamW Training Dynamics

    cs.LG 2026-06 accept novelty 6.0

    Derives three-force decomposition of squared weight norm under AdamW and validates it on Pythia-70M models, plus spline recovery of alignment force from checkpoints.

  5. Does Weight Decay Enhance Training Stability?

    cs.LG 2026-05 conditional novelty 6.0

    Weight decay slows progressive sharpening at the edge of stability, inducing damped oscillations in CNNs and a phase transition to sub-2/η sharpness in MLPs driven by parameter-sharpness gradient alignment, yielding m...

  6. Demystifying Manifold Constraints in LLM Pre-training

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    Manifold constraints via the new MACRO optimizer independently bound activation scales and enforce rotational equilibrium in LLM pre-training, subsuming RMS normalization and decoupled weight decay while delivering co...

  7. Scale Weight Decay and Train Better

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    Muon with weight decay scaled by η/η_max reaches the same MoE validation loss ~30% faster than constant-decay Muon while preserving asymptotic stationarity of the unregularized objective.

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  9. Neural Network Optimization Reimagined: Decoupled Techniques for Scratch and Fine-Tuning

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