Corrected typo in 5th order derivative of Chi in the Gadget-2 trunctation formula.

examples/ZeldovichPancake_3D/zeldovichPancake.yml

@@ -47,6 +47,6 @@ Gravity:
   mesh_side_length:   16
   eta: 0.025
   theta: 0.85
-  r_cut_max: 6.
+  r_cut_max: 5.
   comoving_softening: 0.0001
   max_physical_softening: 0.0001

src/kernel_long_gravity.h

@@ -67,7 +67,7 @@ __attribute__((always_inline)) INLINE static void kernel_long_grav_derivatives(
   derivs->chi_2 = rs_inv2 * u;
   derivs->chi_3 = -rs_inv3 * (u2 - 0.5f);
   derivs->chi_4 = rs_inv4 * (u3 - 1.5f * u);
-  derivs->chi_5 = -rs_inv5 * (u4 - u2 + 0.75f);
+  derivs->chi_5 = -rs_inv5 * (u4 - 3.f * u2 + 0.75f);
 
   const float one_over_sqrt_pi = ((float)(M_2_SQRTPI * 0.5));
   const float common_factor = one_over_sqrt_pi * expf(-u2);