ray, dimension (M)
          On entry, this array must contain information on the
          column echelon form of the unitary transformed matrix E.
          Specifically, ISTAIR(i) must be set to +j if the first
          non-zero element E(i,j) is a corner point and -j
          otherwise, for i = 1,2,...,M.
          On exit, this array contains no useful information.

  NBLCKS  (output) INTEGER
          The number of submatrices having full row rank greater
          than or equal to 0 detected in mat