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Transformers Without Tears: Improving the Normalization of Self-Attention (arxiv.org)
2 points by sel1 on Oct 16, 2019 | hide | past | pdf | discuss on HN

In plain words: Three normalization tweaks — before each skip connection, rescaling each layer's output, and fixing word-vector lengths — keep translation training stable without a warmup. On five low-resource pairs they always converged and beat top bilingual systems by 1.1 points on average; pre-normalizing hurt with more data.

Abstract · Transformers without Tears: Improving the Normalization of Self-Attention

We evaluate three simple, normalization-centric changes to improve Transformer training. First, we show that pre-norm residual connections (PreNorm) and smaller initializations enable warmup-free, validation-based training with large learning rates. Second, we propose $\ell_2$ normalization with a single scale parameter (ScaleNorm) for faster training and better performance. Finally, we reaffirm the effectiveness of normalizing word embeddings to a fixed length (FixNorm). On five low-resource translation pairs from TED Talks-based corpora, these changes always converge, giving an average +1.1 BLEU over state-of-the-art bilingual baselines and a new 32.8 BLEU on IWSLT'15 English-Vietnamese. We observe sharper performance curves, more consistent gradient norms, and a linear relationship between activation scaling and decoder depth. Surprisingly, in the high-resource setting (WMT'14 English-German), ScaleNorm and FixNorm remain competitive but PreNorm degrades performance.

Toan Q. Nguyen, Julian Salazar
arXiv:1910.05895 · cs.CL, cs.LG, stat.ML · submitted Oct 14, 2019 · updated Dec 30, 2019
abstract · pdf · html · Accepted to IWSLT 2019 (oral); code is available at https://github.com/tnq177/transformers_without_tears

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