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From Lazy to Rich: Exact Learning Dynamics in Deep Linear Networks

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arxiv 2409.14623 v2 pith:PABWDLMH submitted 2024-09-22 cs.LG

classification cs.LG
keywords learningnetworksrepresentationsinitializationlazyneuralrichacross
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Biological and artificial neural networks develop internal representations that enable them to perform complex tasks. In artificial networks, the effectiveness of these models relies on their ability to build task specific representation, a process influenced by interactions among datasets, architectures, initialization strategies, and optimization algorithms. Prior studies highlight that different initializations can place networks in either a lazy regime, where representations remain static, or a rich/feature learning regime, where representations evolve dynamically. Here, we examine how initialization influences learning dynamics in deep linear neural networks, deriving exact solutions for lambda-balanced initializations-defined by the relative scale of weights across layers. These solutions capture the evolution of representations and the Neural Tangent Kernel across the spectrum from the rich to the lazy regimes. Our findings deepen the theoretical understanding of the impact of weight initialization on learning regimes, with implications for continual learning, reversal learning, and transfer learning, relevant to both neuroscience and practical applications.

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Cited by 5 Pith papers

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

  1. How are linear representations learned? Exact solutions to the dynamics of abstraction

    cs.LG 2026-07 conditional novelty 8.0 of 10

    Exact solutions show abstraction is set by input/target geometry, rises with depth, peaks under small init, and is attenuated by nonlinearities—improving LLM probes via GELU ablation.

  2. Deep Linear Network Training Dynamics from Random Initialization: Data, Width, Depth, and Hyperparameter Transfer

    cs.LG 2025-02 conditional novelty 8.0 of 10

    Closed dynamical mean field equations describe train and test loss trajectories of randomly initialized deep linear networks at large width and data, capturing hyperparameter transfer and power-law scaling.

  3. A Theory of How Pretraining Shapes Inductive Bias in Fine-Tuning

    cs.LG 2026-02 conditional novelty 6.0 of 10

    In diagonal linear networks, fine-tuning generalization is governed by a tunable per-dimension penalty whose sparsity and pretraining dependence define four regimes and a trade-off between feature reuse and new-featur...

  4. You Had One Job: Per-Task Quantization Using LLMs' Hidden Representations

    cs.CL 2025-11 reject novelty 6.0 of 10

    TAQ estimates per-layer importance from hidden representations and output sensitivity on task calibration data to allocate mixed precision in a training-free PTQ setting, outperforming task-agnostic baselines on accur...

  5. Feature learning is decoupled from generalization in high capacity neural networks

    cs.LG 2025-07 conditional novelty 4.0 of 10

    Current feature learning measures quantify the magnitude of representation change, which the authors argue is decoupled from the generalization benefit that neural networks show over their neural tangent kernel.

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