  We introduce fastcoref, a python package for fast, accurate, and easy-to-use
English coreference resolution. The package is pip-installable, and allows two
modes: an accurate mode based on the LingMess architecture, providing
state-of-the-art coreference accuracy, and a substantially faster model,
F-coref, which is the focus of this work. F-coref allows to process 2.8K
OntoNotes documents in 25 seconds on a V100 GPU (compared to 6 minutes for the
LingMess model, and to 12 minutes of the popular AllenNLP coreference model)
with only a modest drop in accuracy. The fast speed is achieved through a
combination of distillation of a compact model from the LingMess model, and an
efficient batching implementation using a technique we call leftover batching.
Our code is available at https://github.com/shon-otmazgin/fastcoref
