anchor.diff:           id(2) = j2
            !id(3) = j3
            id(4) = j4
  +         iax = -1+c*(j2-1+b*(j1-1))
  +         ibx = c*(id(k)-1+jd(k)*(id(j)-1+jd(j)*(id(i)-1)))
            do j3 = 1,c
  -          ia = j4+d*(j3-1+c*(j2-1+b*(j1-1)))
  -          ib = j3+c*(id(k)-1+jd(k)*(id(j)-1+jd(j)*(id(i)-1)))
  -          s(ib) = u(ia) * factor
  +          ia = j4+d*(j3+iax)
  +          ib = j3+ibx
  +          s(ib) = u(ia) * f
            enddo
           enddo
          enddo
  
positive.code:       integer id(4),jd(4),ia,ib,j1,j2,j3,j4
        double precision s(a*b*c*d)
        double precision u(a*b*c*d)
        double precision factor
        jd(1) = a
        jd(2) = b
        jd(3) = c
  
negative.code:          id(2) = j2
           id(3) = j3
           id(4) = j4
           ibx = a*(id(k)-1+jd(k)*(id(j)-1+jd(j)*(id(i)-1)))
           do j1 = 1,a
            ia = j4+d*(j3-1+c*(j2-1+b*(j1-1)))
            ib = j1+ibx
            s(ib) = u(ia) * f
           enddo
          enddo
         enddo
  