Drop-Upcycling: Training Sparse Mixture of Experts with Partial Re-initialization

Fuente: arXiv
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Auteurs principaux: Nakamura, Taishi, Akiba, Takuya, Fujii, Kazuki, Oda, Yusuke, Yokota, Rio, Suzuki, Jun
Format: Preprint
Publié: 2025
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author Nakamura, Taishi
Akiba, Takuya
Fujii, Kazuki
Oda, Yusuke
Yokota, Rio
Suzuki, Jun
author_facet Nakamura, Taishi
Akiba, Takuya
Fujii, Kazuki
Oda, Yusuke
Yokota, Rio
Suzuki, Jun
contents The Mixture of Experts (MoE) architecture reduces the training and inference cost significantly compared to a dense model of equivalent capacity. Upcycling is an approach that initializes and trains an MoE model using a pre-trained dense model. While upcycling leads to initial performance gains, the training progresses slower than when trained from scratch, leading to suboptimal performance in the long term. We propose Drop-Upcycling - a method that effectively addresses this problem. Drop-Upcycling combines two seemingly contradictory approaches: utilizing the knowledge of pre-trained dense models while statistically re-initializing some parts of the weights. This approach strategically promotes expert specialization, significantly enhancing the MoE model's efficiency in knowledge acquisition. Extensive large-scale experiments demonstrate that Drop-Upcycling significantly outperforms previous MoE construction methods in the long term, specifically when training on hundreds of billions of tokens or more. As a result, our MoE model with 5.9B active parameters achieves comparable performance to a 13B dense model in the same model family, while requiring approximately 1/4 of the training FLOPs. All experimental resources, including source code, training data, model checkpoints and logs, are publicly available to promote reproducibility and future research on MoE.
format Preprint
id arxiv_https___arxiv_org_abs_2502_19261
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Drop-Upcycling: Training Sparse Mixture of Experts with Partial Re-initialization
Nakamura, Taishi
Akiba, Takuya
Fujii, Kazuki
Oda, Yusuke
Yokota, Rio
Suzuki, Jun
Computation and Language
Artificial Intelligence
Machine Learning
The Mixture of Experts (MoE) architecture reduces the training and inference cost significantly compared to a dense model of equivalent capacity. Upcycling is an approach that initializes and trains an MoE model using a pre-trained dense model. While upcycling leads to initial performance gains, the training progresses slower than when trained from scratch, leading to suboptimal performance in the long term. We propose Drop-Upcycling - a method that effectively addresses this problem. Drop-Upcycling combines two seemingly contradictory approaches: utilizing the knowledge of pre-trained dense models while statistically re-initializing some parts of the weights. This approach strategically promotes expert specialization, significantly enhancing the MoE model's efficiency in knowledge acquisition. Extensive large-scale experiments demonstrate that Drop-Upcycling significantly outperforms previous MoE construction methods in the long term, specifically when training on hundreds of billions of tokens or more. As a result, our MoE model with 5.9B active parameters achieves comparable performance to a 13B dense model in the same model family, while requiring approximately 1/4 of the training FLOPs. All experimental resources, including source code, training data, model checkpoints and logs, are publicly available to promote reproducibility and future research on MoE.
title Drop-Upcycling: Training Sparse Mixture of Experts with Partial Re-initialization
topic Computation and Language
Artificial Intelligence
Machine Learning
url https://arxiv.org/abs/2502.19261