DLASORTE(l) ) 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 com‐
plex 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.
ARGUMENTS
S (local input/output) DOUBLE PRECISION array, dimension LDS
On entry, a matrix already in Schur form. On exit, the diago‐
nal 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 ei‐
genvalues 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
ScaLAPACK version 1.7 13 August 2001 DLASORTE(l)
