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)