anchor.diff:          real :: x0,y0,x1,y1
           double precision :: slope, x_line
   
  -        internal_precision = 1e-5
  +        internal_precision = 1e-7
           if (present(precision)) internal_precision = precision
           n = size(poly,2)
   
  
positive.code:             write(*,*) x2, y2
              write(*,*) x3, y3
              write(*,*) w1, w2, w3
              stop "Triangulation is broken"
          endif
          w1=max(0.,w1); w2=max(0.,w2); w3=max(0.,w3);
  
negative.code:         real,intent(in)::yi,y(4),xi,x(4)
          real::x0,y0
          real, dimension(4) ::tri_weights
          real :: test_poly(2,3)
  
          real :: w1,w2,w3,denom
  
  