  Steady progress has been made in abstractive summarization with
attention-based sequence-to-sequence learning models. In this paper, we propose
a new decoder where the output summary is generated by conditioning on both the
input text and the latent topics of the document. The latent topics, identified
by a topic model such as LDA, reveals more global semantic information that can
be used to bias the decoder to generate words. In particular, they enable the
decoder to have access to additional word co-occurrence statistics captured at
document corpus level. We empirically validate the advantage of the proposed
approach on both the CNN/Daily Mail and the WikiHow datasets. Concretely, we
attain strongly improved ROUGE scores when compared to state-of-the-art models.
