Teacher:In this task, you will be presented with a context from an academic paper and you have to write an answerable question based on the context. Your questions can be extractive, abstractive, or yes-no questions.
Teacher: Now, understand the problem? Solve this instance: Following BIBREF21, we sample $K$ captions for each image when applying REINFORCE: ${\hat{c}}_1 \ldots {\hat{c}}_K$, ${\hat{c}}_k \sim p_{ heta }(c|I)$,

The baseline for each sampled caption is defined as the average reward of the rest samples.
Student:
What baseline function is used in REINFORCE algorithm?