In-context learning (ICL) using large language models for tasks with many labels is challenging due to the limited context window, which makes it difficult to fit a sufficient number of examples in the prompt. In this paper, we use a pre-trained dense retrieval model to bypass this limitation, giving the model only a partial view of the full label space for each inference call. Testing with recent open-source LLMs (OPT, LLaMA), we set new state of the art performance in few-shot settings for three common intent classification datasets, with no finetuning. We also surpass fine-tuned performance on fine-grained sentiment classification in certain cases. We analyze the performance across number of in-context examples and different model scales, showing that larger models are necessary to effectively and consistently make use of larger context lengths for ICL. By running several ablations, we analyze the model's use of: a) the similarity of the in-context examples to the current input, b) the semantic content of the class names, and c) the correct correspondence between examples and labels. We demonstrate that all three are needed to varying degrees depending on the domain, contrary to certain recent works.

利用预训练的密集检索模型，我们在有限样本设置中的常见意图分类数据集上，以及特定情况下的细粒度情感分类中，优于微调性能。通过多个实验，我们分析了模型对于上下文示例和不同模型规模的利用情况，并展示了在不同领域中需要不同程度上下文示例的相似性、类名的语义内容和示例与标签之间的正确对应。

多标签文本分类的上下文学习