A library for numerically computing the Pfaffian of a real or complex skew-symmetric matrix. This is based on computing the tridiagonal form of the matrix under unitary congruence transformations.
The theory behind the implementation is explained in ACM Trans. Math. Software 38 30 (2012) (also on arxiv). Please cite this paper if you use the PFAPACK library in your work.

Download the library here: pfapack.tgz.

Update on September, 17th 2014
Update on April, 4th 2011
PFAPACK has seen a major update: