fp coeff_dx_m1_m1,
   coeff_dx_0_m1,
   coeff_dx_p1_m1,
   coeff_dx_p2_m1,
   coeff_dx_m1_0,
   coeff_dx_0_0,
   coeff_dx_p1_0,
   coeff_dx_p2_0,
   coeff_dx_m1_p1,
   coeff_dx_0_p1,
   coeff_dx_p1_p1,
   coeff_dx_p2_p1,
   coeff_dx_m1_p2,
   coeff_dx_0_p2,
   coeff_dx_p1_p2,
   coeff_dx_p2_p2;