Revisiting the Architectures like Pointer Networks to Efficiently
  Improve the Next Word Distribution, Summarization Factuality, and Beyond
Haw-Shiuan Chang Zonghai Yao Alolika Gon Hong Yu Andrew McCallum
Is the output softmax layer, which is adopted by most language models (LMs),
always the best way to compute the next word probability? Given so many
attention layers in a modern transformer-based LM, are the pointer networks
redundant nowadays? In this study, we discover that the answers to both
questions are no. This is because the softmax bottleneck sometimes prevents the
LMs from predicting the desired distribution and the pointer networks can be
used to break the bottleneck efficiently. Based on the finding, we propose
several softmax alternatives by simplifying the pointer networks and
accelerating the word-by-word rerankers. In GPT-2, our proposals are
significantly better and more efficient than mixture of softmax, a
state-of-the-art softmax alternative. In summarization experiments, without
significantly decreasing its training/testing speed, our best method based on
T5-Small improves factCC score by 2 points in CNN/DM and XSUM dataset, and
improves MAUVE scores by 30% in BookSum paragraph-level dataset.