DLASORTE(l) LAPACK routine (version 1.5) DLASORTE(l)
NAME
DLASORTE - sort eigenpairs so that real eigenpairs are together and complex are together
SYNOPSIS
SUBROUTINE DLASORTE ( S, LDS, J, OUT, INFO )
INTEGER INFO, J, LDS
DOUBLE PRECISION OUT( J, * ), S( LDS, * )
PURPOSE
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.
ARGUMENTS
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
LAPACK version 1.5 12 May 1997 DLASORTE(l)
