Long-Tail Zero and Few-Shot Learning via Contrastive Pretraining on and for Small Data


For natural language processing ‘text-to-text’ tasks, the prevailing approaches heavily rely on pretraining large self-supervised models on increasingly larger ‘task-external’ data. Transfer learning from high-resource pretraining works well, but research has focused on settings with very large data and compute requirements, while the potential of efficient low-resource learning, without large ‘task-external’ pretraining, remains under-explored. In this work, we evaluate against three core challenges for resource efficient learning. Namely, we analyze: (1) pretraining data (X) efficiency; (2) zero to few-shot label (Y) efficiency; and (3) long-tail generalization, since long-tail preservation has been linked to algorithmic fairness and because data in the tail is limited by definition. To address these challenges, we propose a data and compute efficient self-supervised, contrastive text encoder, pretrained on 60MB of ‘task-internal’ text data, and compare it to RoBERTa, which was pretrained on 160GB of ‘task-external’ text. We find our method outperforms RoBERTa, while pretraining and fine-tuning in a 1/5th of RoBERTa’s fine-tuning time.

AAAI Workshop on Artificial Intelligence with Biased or Scarce Data