int calculate_pairwise_origin(double *restrict delta_pos[3],double *restrict pos[Ndim]) { int k = 0; int i,j,l; for(i=0;i<Nbody;i++){ for(j=i+1;j<Nbody;j++){ for(l=0;l<Ndim;l++){ delta_pos[l][k] = pos[l][i] - pos[l][j]; } k = k + 1; } } return 0; }