src/test/fractions2.c

    Fractions in marginal cases

    This checks that straight interfaces falling exactly on grid lines give the correct fractions.

    #include "fractions.h"

int main() {

    The origin is set at the center of the domain.

      origin (- 0.5, - 0.5);
  init_grid (4);

    Four fractions are defined:

    • f_x corresponding to the Level Set function x;
    • f_y corresponding to the Level Set function y;
    • f_{-x} corresponding to the Level Set function -x;
    • f_{-y} corresponding to the Level Set function -y.

    All four should correspond to an half space.

      scalar fx[], f_x[], fy[], f_y[];

  fraction (fx, x);
  fraction (fy, y);
  fraction (f_x, -x);
  fraction (f_y, -y);

    The cell grid and values of the fractions are saved.

      output_cells (stdout);

  foreach()
    fprintf (stderr, "%g %g %g %g %g %g \n", x, y, fx[], fy[], f_x[], f_y[]);
}

    Ouputs

     set term @SVG size 100,100
 unset key 
 unset border
 unset tics
 plot 'out' w l, 'log' u 1:2:3 with labels
    Reconstruction of \phi(x, y) = x (script)

    Reconstruction of \phi(x, y) = x (script)

     set term @SVG size 100,100
 unset key
 plot 'out' w l, 'log' u 1:2:4 with labels
    Reconstruction of \phi(x, y) = y (script)

    Reconstruction of \phi(x, y) = y (script)

     set term @SVG size 100,100
 unset key
 plot 'out' w l, 'log' u 1:2:5 with labels
    Reconstruction of \phi(x, y) = -x (script)

    Reconstruction of \phi(x, y) = -x (script)

     set term @SVG size 100,100
 unset key
 plot 'out' w l, 'log' u 1:2:6 with labels
    Reconstruction of \phi(x, y) = -y (script)

    Reconstruction of \phi(x, y) = -y (script)