by sven » Wed Jul 12, 2006 2:41 am
You can use DTREXC to do that. Or use DGEESX from the outset to perform the Schur factorization and reorder the eigenvalues.
There are BLAS routines to generate and apply Givens rotations (DROTG and DROT), as well as some LAPACK auxiliary routines (see Appendix B of the Users' Guide).
Best wishes,
Sven Hammarling.