DLASORTE - sort eigenpairs so that real eigenpairs are together and complex are
- SUBROUTINE DLASORTE(
- S, LDS, J, OUT, INFO )
INTEGER INFO, J, LDS DOUBLE PRECISION OUT( J, * ), S( LDS, * )
DLASORTE sorts eigenpairs so that real eigenpairs are together and complex are
together. This way one can employ 2x2 shifts easily since every 2nd
subdiagonal is guaranteed to be zero.
This routine does no parallel work.
- S (local input/output) DOUBLE PRECISION array, dimension LDS
- On entry, a matrix already in Schur form. On exit, the diagonal blocks of
S have been rewritten to pair the eigenvalues. The resulting matrix is no
longer similar to the input.
- LDS (local input) INTEGER
- On entry, the leading dimension of the local array S. Unchanged on
- J (local input) INTEGER
- On entry, the order of the matrix S. Unchanged on exit.
- OUT (local input/output) DOUBLE PRECISION array, dimension Jx2
- This is the work buffer required by this routine.
- INFO (local input) INTEGER
- This is set if the input matrix had an odd number of real eigenvalues and
things couldn't be paired or if the input matrix S was not originally in
Schur form. 0 indicates successful completion.
Implemented by: G. Henry, November 17, 1996