sumed;
          the routine only calculates the optimal size of the
          DWORK array, returns this value as the first entry of
          the DWORK array, and no error message related to LDWORK
          is issued by XERBLA.

  ZWORK   COMPLEX*16 array, dimension (LZWORK)
          On exit, if INFO = 0, ZWORK(1) contains the optimal
          LZWORK.
          On exit, if  INFO = -30,  ZWORK(1)  returns the minimum
          value of LZWORK. These values are also set when LZWORK = 0
          on entry,