In this task, you will be presented with a context from an academic paper and a question separated with a
. You have to answer the question based on the context.
Q: 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.
Question: What baseline function is used in REINFORCE algorithm?
A:
baseline for each sampled caption is defined as the average reward of the rest samples