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| Main Authors: | , , |
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| Format: | Preprint |
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2024
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| Subjects: | |
| Online Access: | https://arxiv.org/abs/2410.23922 |
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| _version_ | 1866912098270838784 |
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| author | Kosson, Atli Messmer, Bettina Jaggi, Martin |
| author_facet | Kosson, Atli Messmer, Bettina Jaggi, Martin |
| contents | Learning Rate Warmup is a popular heuristic for training neural networks, especially at larger batch sizes, despite limited understanding of its benefits. Warmup decreases the update size $Δ\mathbf{w}_t = η_t \mathbf{u}_t$ early in training by using lower values for the learning rate $η_t$. In this work we argue that warmup benefits training by keeping the overall size of $Δ\mathbf{w}_t$ limited, counteracting large initial values of $\mathbf{u}_t$. Focusing on small-scale GPT training with AdamW/Lion, we explore the following question: Why and by which criteria are early updates $\mathbf{u}_t$ too large? We analyze different metrics for the update size including the $\ell_2$-norm, resulting directional change, and impact on the representations of the network, providing a new perspective on warmup. In particular, we find that warmup helps counteract large angular updates as well as a limited critical batch size early in training. Finally, we show that the need for warmup can be significantly reduced or eliminated by modifying the optimizer to explicitly normalize $\mathbf{u}_t$ based on the aforementioned metrics. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2410_23922 |
| institution | arXiv |
| publishDate | 2024 |
| record_format | arxiv |
| spellingShingle | Analyzing & Reducing the Need for Learning Rate Warmup in GPT Training Kosson, Atli Messmer, Bettina Jaggi, Martin Machine Learning Learning Rate Warmup is a popular heuristic for training neural networks, especially at larger batch sizes, despite limited understanding of its benefits. Warmup decreases the update size $Δ\mathbf{w}_t = η_t \mathbf{u}_t$ early in training by using lower values for the learning rate $η_t$. In this work we argue that warmup benefits training by keeping the overall size of $Δ\mathbf{w}_t$ limited, counteracting large initial values of $\mathbf{u}_t$. Focusing on small-scale GPT training with AdamW/Lion, we explore the following question: Why and by which criteria are early updates $\mathbf{u}_t$ too large? We analyze different metrics for the update size including the $\ell_2$-norm, resulting directional change, and impact on the representations of the network, providing a new perspective on warmup. In particular, we find that warmup helps counteract large angular updates as well as a limited critical batch size early in training. Finally, we show that the need for warmup can be significantly reduced or eliminated by modifying the optimizer to explicitly normalize $\mathbf{u}_t$ based on the aforementioned metrics. |
| title | Analyzing & Reducing the Need for Learning Rate Warmup in GPT Training |
| topic | Machine Learning |
| url | https://arxiv.org/abs/2410.23922 |