by Paul Howard and Jeff Vitter. Here’s what they have to say about this paper from the abstract: Our algorithm, related to the PPM method, simplifies the modeling phase by eliminating the escape mechanism, and speeds up coding by using a combination of quasi-arithmetic coding and Rice coding. We provide details of the use of quasi-arithmetic code tables, and analyze their compression performance. Our Fast PPM method is shown experimentally to be almost twice as fast as the PPMC method, while giving comparable compression..

http://www.cs.duke.edu/~jsv/Papers/catalog/node68.html