In coaching GBN, due to the fact that the input of abstractive summarization X contains more information than the summary target Y ⇤ , directly training the bridge p ⌘ (Y |Y ⇤ ) to understand the generator p ✓ (Y |X) is infeasible.
we re-design the coaching bridge to receive both source and target input X, Y and we enlarge its vocabulary size to 88,883 to encompass more information about the source side.