The agent is then given a "reward" r commensurate with how well the extract resembles the gold-standard summary.
as reward function we use mean F 1 of ROUGE-1, ROUGE-2, and ROUGE-L. Unigram and bigram overlap (ROUGE-1 and ROUGE-2) are meant to assess informativeness, whereas the longest common subsequence (ROUGE-L) is meant to assess fluency.