dimension of array C.  LDC &gt;= MAX(1,P).

  U       (input/output) DOUBLE PRECISION array, dimension (LDU,*)
          On entry, if JOBU = 'U', then the leading N-by-N part of
          this array must contain a given matrix U (e.g. from a
          previous call to another SLICOT routine), and on exit, the
          leading N-by-N part of this array contains the product of
          the input matrix U and the state-space transformation
          matrix which reduces the given pair to observer Hessenberg
