          this array must contain the lower triangular part of the
          matrix Q.                     _
          Matrix Q should correspond to Q in the "reduced" Riccati
          equation (with matrix T, instead of A), if LYAPUN = 'R'.
          See METHOD.

  LDQ     INTEGER
          The leading dimension of the array Q.  LDQ &gt;= max(1,N).

  X       (input) DOUBLE PRECISION array, dimension (LDX,N)
          The leading N-by-N part of this array must contain the
          symmetric solution matr