A research paper describing an algorithm for calculating the HOMFLY polynomial of directed knots and links. The algorithm has a better time bound for large links than algorithns that ignore duplicates. Source code is on the site. burtleburtle.net
Research paper on a state-space representation of the HOMFLY polynomial, by B. Bollobás, L. Pebody and D. Weinreich. Links to the paper in pdf,dvi and ps formats. www.gettysburg.edu