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A Win-win Deal: Towards Sparse and Robust Pre-trained Language Models
Yuanxin Liu · Fandong Meng · Zheng Lin · Jiangnan Li · Peng Fu · Yanan Cao · Weiping Wang · Jie Zhou

Thu Dec 08 05:00 PM -- 07:00 PM (PST) @

Despite the remarkable success of pre-trained language models (PLMs), they still face two challenges: First, large-scale PLMs are inefficient in terms of memory footprint and computation. Second, on the downstream tasks, PLMs tend to rely on the dataset bias and struggle to generalize to out-of-distribution (OOD) data. In response to the efficiency problem, recent studies show that dense PLMs can be replaced with sparse subnetworks without hurting the performance. Such subnetworks can be found in three scenarios: 1) the fine-tuned PLMs, 2) the raw PLMs and then fine-tuned in isolation, and even inside 3) PLMs without any parameter fine-tuning. However, these results are only obtained in the in-distribution (ID) setting. In this paper, we extend the study on PLMs subnetworks to the OOD setting, investigating whether sparsity and robustness to dataset bias can be achieved simultaneously. To this end, we conduct extensive experiments with the pre-trained BERT model on three natural language understanding (NLU) tasks. Our results demonstrate that \textbf{sparse and robust subnetworks (SRNets) can consistently be found in BERT}, across the aforementioned three scenarios, using different training and compression methods. Furthermore, we explore the upper bound of SRNets using the OOD information and show that \textbf{there exist sparse and almost unbiased BERT subnetworks}. Finally, we present 1) an analytical study that provides insights on how to promote the efficiency of SRNets searching process and 2) a solution to improve subnetworks' performance at high sparsity. The code is available at \url{https://github.com/llyx97/sparse-and-robust-PLM}.

Author Information

Yuanxin Liu (Institute of Information Engineering, Chinese Academy of Sciences; SCS, University of Chinese Academy of Sciences)
Fandong Meng (WeChat AI)
Zheng Lin (Institute of Information Engineering, Chinese Academy of Sciences)
Jiangnan Li (Institute of Information Engineering, Chinese Academy of Sciences)
Peng Fu (Institute of Information Engineering, Chinese Academy of Sciences)
Yanan Cao (Institute of Information Engineering, Chinese Academy of Sciences)
Weiping Wang (Institute of Information Engineering, CAS, China)
Jie Zhou (WeChat AI)

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