Wapiti is a very fast CRF toolkit (written in C++) for segmenting and labeling items and sequence data written and maintained by Thomas Lavergne; Wapiti was developed within the CroTAL project.

Wapiti's implementation is described in

  • T. Lavergne, O. Cappé, and F. Yvon. Practical Very Large Scale CRFs. In Proc. 48th Annual Meeting Association for Computational Linguistics (ACL), pages 504-513, Uppsala, Sweden, July 2010.

and is based, partly, on

Wapiti is also available from the public evaluation site MLcomp and its performance appears to be very good on the SequenceTagging tasks (best program from the repository on 5 of the 16 datasets as of August 2010).