Natural-language prompts have recently been used to coax pretrained language models into performing other AI tasks, using a fill-in-the-blank paradigm (Petroni et al., 2019) or a few-shot extrapolation paradigm (Brown et al., 2020). For example, language models retain factual knowledge from their training corpora that can be extracted by asking them to "fill in the blank" in a sentential prompt. However, where does this prompt come from? We explore the idea of learning prompts by gradient descent -- either fine-tuning prompts taken from previous work, or starting from random initialization. Our prompts consist of "soft words," i.e., continuous vectors that are not necessarily word type embeddings from the language model. Furthermore, for each task, we optimize a mixture of prompts, learning which prompts are most effective and how to ensemble them. Across multiple English LMs and tasks, our approach hugely outperforms previous methods, showing that the implicit factual knowledge in language models was previously underestimated. Moreover, this knowledge is cheap to elicit: random initialization is nearly as good as informed initialization.

本文探讨了使用渐进式的梯度下降机制为先前的预训练语言模型 Fine-Tuning 提供含监听词库的句子造句模式，以从中提取模型对于文本特征的认知，并使用软词向量进行任务综合, 将此方式与传统的任务方法进行对比，显示其在任务中的巨大性能提升，而随机初始化甚至可以代替详细的初始化方式，因此这种知识的提取可以廉价地实现。

学会提问：使用软提示混合查询语言模型