We introduce kNN-Prompt, a simple and effective technique to use k-nearest neighbor (kNN) retrieval augmentation (Khandelwal et al., 2021) for zero-shot inference with language models (LMs). Key to our approach is the introduction of fuzzy verbalizers which leverage the sparse kNN distribution for downstream tasks by automatically associating each classification label with a set of natural language tokens. Across eleven diverse end-tasks (spanning text classification, fact retrieval and question answering), using kNN-Prompt with GPT-2 Large yields significant performance boosts over zero-shot baselines (14% absolute improvement over the base LM on average). Extensive experiments show that kNN-Prompt is effective for domain adaptation with no further training, and that the benefits of retrieval increase with the size of the model used for kNN retrieval. Overall, we show that augmenting a language model with retrieval can bring significant gains for zero-shot inference, with the possibility that larger retrieval models may yield even greater benefits.

研究了k-nearest neighbor LM以及kNN-Prompt模型在少数样本和零样本任务准确度上的性能，发现其对于扩展任务特定的模糊单词十分有效，且具有在领域适应中快速提高准确度的优势。

kNN-Prompt: 最近邻零样本推理