dlasorte(3)

NAME

DLASORTE - sort eigenpairs so that real eigenpairs are together and complex are together

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 and makes no calls.

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 exit.
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, May 1, 1997