n exit, if INFO = 0, the leading P-by-M part of this
          array contains the input/output matrix Dr of the reduced
          order system.

  LDD     INTEGER
          The leading dimension of array D.  LDD &gt;= MAX(1,P).

  NS      (output) INTEGER
          The dimension of the ALPHA-stable subsystem.

  HSV     (output) DOUBLE PRECISION array, dimension (N)
          If INFO = 0, the leading NS elements of HSV contain the
          Hankel singular values of the phase system corresponding
          