Periodic Schur decomposition


I am wondering if anybody has implemented, and is willing to share, a periodic Schur decomposition. The first paper mentioning it is

D. Kressner, An efficient and reliable implementation of the periodic qz algorithm IFAC Proceedings Volumes, vol. 34, no. 12, pp. 183–188, 2001.

There seems to be a Fortran code of this algorithm if one asks D. Kressner.

Thank you,

IIRC there are routines for this in SLICOT (a FORTRAN library, under GPL).


Is it based on the code by Kressner?

I think Kressner did contribute to the SLICOT project, but I avoid looking at GPL sources so I’ll let someone else check these particular routines.