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NAME

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

SYNOPSIS

       SUBROUTINE SLASORTE ( S, LDS, J, OUT, INFO )

           INTEGER         INFO, J, LDS

           REAL            OUT( J, * ), S( LDS, * )

PURPOSE

       SLASORTE 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) REAL 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) REAL 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