  By using classical invariant theory, we reduce the $S_{n}$-invariant
F-conjecture to a feasibility problem in polyhedral geometry. We show by
computer that for $n \le 19$, every integral $S_{n}$-invariant F-nef divisor on
the moduli space of genus zero stable pointed curves is semi-ample, over
arbitrary characteristic. Furthermore, for $n \le 16$, we show that for every
integral $S_{n}$-invariant nef (resp. ample) divisor $D$ on the moduli space,
$2D$ is base-point-free (resp. very ample). As applications, we obtain the nef
cone of the moduli space of stable curves without marked points, and the
semi-ample cone that of the moduli space of genus 0 stable maps to Grassmannian
for small numerical values.
