Before SIMDization

before.cpp

void
force_sorted_z(void) {
  const int pn = particle_number;
  for (int i = 0; i < pn; i++) {
    const double qx_key = z[i][X];
    const double qy_key = z[i][Y];
    const double qz_key = z[i][Z];
    const int np = number_of_partners[i];
    double pfx = 0;
    double pfy = 0;
    double pfz = 0;
    const int kp = pointer[i];
    for (int k = 0; k < np; k++) {
      const int j = sorted_list[kp + k];
      double dx = z[j][X] - qx_key;
      double dy = z[j][Y] - qy_key;
      double dz = z[j][Z] - qz_key;
      double r2 = (dx * dx + dy * dy + dz * dz);
      double r6 = r2 * r2 * r2;
      double df = ((24.0 * r6 - 48.0) / (r6 * r6 * r2)) * dt;
      if (r2 > CL2) df=0.0; 
      pfx += df * dx;
      pfy += df * dy;
      pfz += df * dz;
      z[j][PX] -= df * dx;
      z[j][PY] -= df * dy;
      z[j][PZ] -= df * dz;
    }
    z[i][PX] += pfx;
    z[i][PY] += pfy;
    z[i][PZ] += pfz;
  }
}